<p class="jove_content">Riconoscimento viene dato ai donatori della American Chemical Society petrolio fondo di ricerca supporto parziale di questa ricerca. Siamo grati per la National Science Foundation (-0619275 e-0963165) per le sovvenzioni di ristrutturazione e strumentazione supportata questa ricerca.</p>

<p class="jove_title">1. protocollo standard per la separazione delle aldeidi aromatiche da una miscela. Esempio: Separazione del butirrato benzilico da una miscela di 1:1 con anisaldeide.</p>
<ol><li>Sciogliere 175 μL di anisaldeide e 250 μL di butirrato di benzile in 5 mL di metanolo e trasferire la soluzione in un imbuto separatore.<br>Attenzione: il bisolfuro del sodio può generare gas di biossido di zolfo, così questo protocollo dovrebbe essere svolta con una ventilazione adeguata, come in una cappa aspirante.</li>
	<li>Aggiungere 1 mL di bisolfito di sodio acquoso saturo e agitare energicamente per circa 30 s.</li>
	<li>Aggiungere 25 mL di acqua deionizzata e 25 mL di acetato di etile 10% / esano ed agitare vigorosamente.</li>
	<li>Separare gli strati. Asciugare lo strato organico con solfato di magnesio anidro. Filtrare la soluzione per rimuovere il solfato di magnesio e concentrarsi <em>nel vuoto</em> utilizzando un evaporatore rotante.</li>
</ol><p class="jove_title">2. separazione di alifatiche aldeidi e chetoni da una miscela. Esempio: Separazione del butirrato benzilico da una miscela di 1:1 con Benzylacetone.</p>
<ol><li>Sciogliere 213 μL di Benzilacetone e 250 μL di butirrato di benzile in 10 mL di dimetilformammide e trasferire la soluzione in un imbuto separatore.<br>Attenzione: il bisolfuro del sodio può generare gas di biossido di zolfo, così questo protocollo dovrebbe essere svolta con una ventilazione adeguata, come in una cappa aspirante.</li>
	<li>Aggiungere 25 mL di bisolfito di sodio acquoso saturo e agitare energicamente per circa 30 s.</li>
	<li>Aggiungere 25 mL di acqua deionizzata e 25 mL di acetato di etile 10% / esano ed agitare vigorosamente.</li>
	<li>Separare gli strati. Restituire lo strato acquoso per l'imbuto separatore, aggiungere 25 mL di acetato di etile 10% / esano e agitare energicamente. Lo strato acquoso, lasciando lo strato organico nell'imbuto di scarico. Aggiungere lo strato organico precedente nuovamente l'imbuto separatore.</li>
	<li>Lavare gli strati organici combinati tre volte con acqua deionizzata (10 mL per ogni lavaggio). Asciugare lo strato organico con solfato di magnesio anidro. Filtrare la soluzione per rimuovere il solfato di magnesio e concentrarsi <em>nel vuoto</em> utilizzando un evaporatore rotante.</li>
</ol><p class="jove_title">3. separazione delle aldeidi da una miscela contenente un alchene. Esempio: Separazione del butirrato benzilico da una miscela di 1:1 con Citronellal.</p>
<ol><li>Sciogliere 255 μL di citronellal e 250 μL di butirrato di benzile in 10 mL di dimetilformammide e trasferire la soluzione in un imbuto separatore.<br>Attenzione: il bisolfuro del sodio può generare gas di biossido di zolfo, così questo protocollo dovrebbe essere svolta con una ventilazione adeguata, come in una cappa aspirante.</li>
	<li>Aggiungere 25 mL di bisolfito di sodio acquoso saturo e agitare energicamente per circa 30 s.</li>
	<li>Aggiungere 25 mL di acqua deionizzata e 25 mL di esano ed agitare vigorosamente.</li>
	<li>Separare gli strati. Restituire lo strato acquoso per l'imbuto separatore, aggiungere esano 25 mL e agitare energicamente. Lo strato acquoso, lasciando lo strato organico nell'imbuto di scarico. Aggiungere lo strato organico precedente nuovamente l'imbuto separatore.</li>
	<li>Lavare gli strati organici combinati tre volte con acqua deionizzata (10 mL per ogni lavaggio). Asciugare lo strato organico con solfato di magnesio anidro. Filtrare la soluzione per rimuovere il solfato di magnesio e concentrarsi <em>nel vuoto</em> utilizzando un evaporatore rotante.</li>
</ol><p class="jove_title">4. re-isolamento delle aldeidi da una miscela. Esempio: Separazione di piperonale da una miscela di 1:1 con alcool benzilico butirrato.</p>
<ol><li>Sciogliere 217 mg di piperonale e 250 μL di butirrato di benzile in 5 mL di metanolo e trasferire la soluzione in un imbuto separatore.<br>Attenzione: il bisolfuro del sodio può generare gas di biossido di zolfo, così, questo protocollo dovrebbe essere effettuato con una ventilazione adeguata, come in una cappa.</li>
	<li>Aggiungere 1 mL di bisolfito di sodio acquoso saturo e agitare energicamente per circa 30 s.</li>
	<li>Aggiungere 25 mL di acqua deionizzata e 25 mL di acetato di etile 10% / esano ed agitare vigorosamente.</li>
	<li>Separare gli strati. Lo strato acquoso ritornare l'imbuto separatore.<ol>
<li>Opzionale: Lavare strato acquoso una volta con 25 mL di acetato di etile/esano di 10% per rimuovere la piccola quantità di butirrato di benzile rimanenti.</li>
	</ol>
</li>
	<li>Aggiungere 25 mL di acetato di etile e quindi aggiungere idrossido di sodio 50% fino a una striscia di pH indica che il pH è 12. Agitare vigorosamente.<br>Attenzione: Evoluzione di Gas è stato osservato durante questo passaggio e può causare accumulo di pressione. Assicurarsi di sfiatare correttamente l'imbuto separatore. La scalabilità di questa procedura renderà evoluzione di gas più pronunciati. Usare cautela.</li>
	<li>Separare gli strati. Tornare lo strato acquoso l'imbuto separatore e aggiungere 25 mL di acetato di etile. Agitare vigorosamente.</li>
	<li>Separare gli strati. Combinare lo strato organico con lo strato organico dal passaggio precedente. Asciugare lo strato organico combinato con solfato di magnesio anidro. Filtrare la soluzione per rimuovere il solfato di magnesio e concentrarsi <em>nel vuoto</em> utilizzando un evaporatore rotante.</li>
</ol>

<ol><li>Boucher, M. M., Furigay, M. H., Quach, P. K., Brindle, C. S. <a target="_blank" href="http://pubs.acs.org/doi/abs/10.1021/acs.oprd.7b00231">Liquid-Liquid Extraction Protocol for the Removal of Aldehydes and Highly Reactive Ketones from Mixtures.</a> <em>Org. Process Res. Dev</em>. <strong>21</strong> (9), 1394-1403 (2017).</li>
<li>Separation of Aldehydes and Ketones. , US2552513 A (1951).</li>
<li>Hsu, W. L. <em><a target="_blank" href="http://scholar.google.com/scholar?hl=en&safe=off&q=author%3aHsu%2C+WL+%22Separation+of+Aldehydes+from+Ketones+via+Acid-Catalyzed+Cyclotrimerization+of+the+Aldehyde%22">Separation of Aldehydes from Ketones via Acid-Catalyzed Cyclotrimerization of the Aldehyde</a></em>. , October 4701561(1987).</li>
<li>Process for Separating Aldehydes and Ketones. , US2295760 A (1942).</li>
<li>Separation of Aldehyde-Ketone Mixtures. , US2355140 A (1944).</li>
<li>Masilamani, D., Manahan, E. H., Vitrone, J., Rogic, M. M. <a target="_blank" href="http://pubs.acs.org/doi/abs/10.1021/jo00173a028">Organic Reactions of Sulfur Dioxide. Reactions with Nucleophilic Double Bonds Leading to the Isomerization, Aromatization, Selective Hydrogen-Deuterium Exchange, and Electron-Transfer Proceses.</a> <em>J. Org. Chem</em>. <strong>48</strong> (25), 4918-4931 (1983).</li>
<li>Masilamani, D., Rogic, M. M. <a target="_blank" href="http://pubs.acs.org/doi/abs/10.1021/ja00482a072">Organic Reactions of Sulfur Dioxide. 4. A Facile Regiospecific Hydrogen-Deuterium Exchange in Olefins. Consequence of the Intermediacy of Allylic Sulfinic Acids in the Ene Reaction of Sulfur Dioxide with Double Bonds.</a> <em>J. Am. Chem. Soc</em>. <strong>100</strong> (14), 4634-4635 (1978).</li>
<li>Makitra, R. G., Kal'muk, S. D., Bryk, D. V., Polyuzhin, I. P. <a target="_blank" href="https://link.springer.com/article/10.1134/S0036023610080310">Factors Controlling Sulfur Dioxide Solubilities in Organic Solvents.</a> <em>Russ. J. Inorg. Chem</em>. <strong>55</strong> (8), 1322-1329 (2010).</li>
<li>van Dam, M. H. H., Lamine, A. S., Roizard, D., Lochon, P., Roizard, C. <a target="_blank" href="http://pubs.acs.org/doi/abs/10.1021/ie970111f">Selective Sulfur Dioxide Removal Using Organic Solvents.</a> <em>Ind. Eng. Chem. Res</em>. <strong>36</strong> (11), 4628-4637 (1997).</li>
<li>Li, H., Jiao, X., Chen, W. <a target="_blank" href="http://www.tandfonline.com/doi/abs/10.1080/00319104.2013.830720">Solubility of Sulphur Dioxide in Polar Organic Solvents.</a> <em>Phys. Chem. Liq</em>. <strong>52</strong> (2), 349-353 (2014).</li>
<li>Trost, B. M., Brindle, C. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((The+Direct+Catalytic+Asymmetric+Aldol+Reaction%5BTitle%5D)+AND+%22Chem.+Soc.+Rev%22%5BJournal%5D)">The Direct Catalytic Asymmetric Aldol Reaction.</a> <em>Chem. Soc. Rev</em>. <strong>39</strong> (5), 1600(2010).</li>
</ol>

<p class="jove_content">Gli autori non hanno nulla a rivelare.</p>

<p class="jove_content">I tentativi iniziali di utilizzare la reazione di bisolfito come un metodo per rimuovere aldeidi utilizzando un'estrazione bifase tipica portato a livelli molto bassi di rimozione. Abbiamo supposto che la reazione non era abbastanza veloce per verificarsi durante il tempo molto limitato che i due strati erano in contatto. Per aumentare il contatto tra i reagenti, abbiamo sviluppato un protocollo di estrazione a due fasi in cui un solvente miscibile in acqua viene utilizzato inizialmente per consentire sufficiente miscela...

<p class="jove_content">La separazione dei componenti di miscele uno da altro è essenziale per la preparazione di materiali puri. Il metodo descritto nel presente documento consente la facile separazione delle aldeidi e stericamente unhindered ciclico e metil chetoni da altre molecole organiche<sup class="xref">1</sup>. La tecnica si basa sulla reattività di bisolfito con il gruppo carbonilico per creare una carica del complesso che può essere suddiviso in uno strato acquoso, mentre altri componenti separano in uno strato organico immiscibile. La chiave per raggiungere reattività tra bisolfito e il carbonile è l'uso di un solvente miscibile, che permette la reazione che si terrà prima della separazione in fasi distinte. Senza l'aggiunta della separazione minima solvente miscibile è ottenuta, presumibilmente a causa di scarso contatto fra il bisolfito idrofila ed i prodotti organici idrofobici.</p>
<p class="jove_content">Il vantaggio di questo metodo di separazione per la purificazione è la facilità del protocollo. Estrazione liquido-liquido è un'operazione semplice da eseguire e può essere effettuata su larga scala. Tecniche di depurazione alternativo, ad esempio di cromatografia a colonna, sono molto più costoso, richiede tempo e difficile da eseguire su larga scala e richiedono sufficiente differenziazione dei componenti in termini di polarità. Purificazione di ricristallizzazione o distillazione richiede sufficiente differenziazione tra la solubilità o punti di ebollizione dei componenti della miscela, rispettivamente. Perché estrazione bisolfito si basa sulla differenza di reattività del gruppo carbonilico di aldeidi e chetoni, composti con solubilità simili, punti di ebollizione o polarità possono essere separati in modo efficace. Esistono altri metodi di separazione chimica per la separazione selettiva di aldeidi e chetoni da miscele, ad esempio, la formazione selettiva di ossime<sup class="xref">2</sup>, acetali ciclici<sup class="xref">3</sup>o mercaptal<sup class="xref">4</sup> formazione. Questi metodi richiedono un ulteriore passaggio per separare le specie formate dalla miscela, perché il prodotto non è solubile in acqua e pertanto non può essere separato da un protocollo di estrazione semplice. Ossidazione dell'aldeide per formare acidi carbossilici rimovibili è un altro segnalato tecnica<sup class="xref">5</sup>, ma il passo di ossidazione richiesto è meno chemoselective rispetto alle condizioni di lieve bisolfito descritti nel presente documento e richiede l'utilizzo di gas di ossigeno e un catalizzatore di cobalto.</p>
<p class="jove_content">Questo metodo è applicabile alla separazione delle aldeidi (<strong>Figura 1</strong>) e stericamente unhindered chetoni ciclici e metile (<strong>Figura 2</strong>) da molecole che non contengono questi gruppi funzionali. Chetoni particolarmente reattivi, come α-cheto esteri vengono rimossi anche utilizzando questo processo. Alcani, alcheni, dieni, alchini, esteri, ammidi, acidi carbossilici, alogenuri alchilici, alcoli, fenoli, nitrili, cloruri di benzile, epossidi, ammine aromatiche, acetali, e leggermente ostacolato, α, β-insaturi, o arilici chetoni sono tutti non reattivo alle condizioni e può essere separato dall'aldeide o il chetone reattiva componente della miscela (<strong>figure 2</strong> e <strong>Figura 3</strong>). Etile chetoni o α-sostituiti chetoni ciclici, ad esempio, sono sufficientemente ostacolati e pertanto sono separabili da aldeidi e chetoni più reattive. Quando si utilizza alcheni, esano è raccomandato come il solvente immiscibile per prevenire la decomposizione indesiderate a causa di anidride solforosa presente nella soluzione di bisolfito. La compatibilità di gruppo funzionale del protocollo estrazione bisolfito è estremamente ampia e pertanto è applicabile a una gamma estremamente ampia di separazioni, se il contaminante del carbonilico di essere separati dalla miscela è un'aldeide o un senza ostacoli metile o chetone ciclico. Chetoni meno reattivi non reagiscono con bisolfito in queste condizioni e pertanto non vengono rimossi.</p>

<table><tbody><tr><td>sodium bisulfite</td><td>Fisher</td><td>AC419440010&amp;nbsp;</td><td>1 kg</td></tr><tr><td>benzyl butyrate</td><td>Fisher</td><td>AAB2424130&amp;nbsp;</td><td>250 g</td></tr><tr><td>anisaldehyde</td><td>Fisher</td><td>AC104801000&amp;nbsp;</td><td>100 mL</td></tr><tr><td>magnesium sulfate</td><td>Fisher</td><td>M65-500&amp;nbsp;</td><td>500 g</td></tr><tr><td>ethyl acetate</td><td>Fisher</td><td>E195-4&amp;nbsp;</td><td>4 L</td></tr><tr><td>hexanes</td><td>Fisher</td><td>H292-4&amp;nbsp;</td><td>4 L</td></tr><tr><td>methanol&amp;nbsp;</td><td>Fisher</td><td>A456-1&amp;nbsp;</td><td>1 L</td></tr><tr><td>dimethylformamide</td><td>Fisher</td><td>D119-1&amp;nbsp;</td><td>1 L</td></tr><tr><td>citronellal</td><td>Fisher</td><td>AAL15753AE&amp;nbsp;</td><td>100 mL</td></tr><tr><td>benzylacetone&amp;nbsp;</td><td>Fisher</td><td>AC105832500&amp;nbsp;</td><td>250 mL</td></tr><tr><td>deionized water</td><td>Fisher</td><td>BP28194&amp;nbsp;</td><td>4 L</td></tr><tr><td>piperonal&amp;nbsp;</td><td>Sigma-Aldrich</td><td>P49104-25G</td><td>25 G</td></tr><tr><td>sodium hydroxide</td><td>Fisher</td><td>S318-1&amp;nbsp;</td><td>1 kg</td></tr><tr><td>separatory funnel with cap</td><td>Fisher</td><td>10-437-5B&amp;nbsp;</td><td>125 mL</td></tr><tr><td>ring stand</td><td>Fisher</td><td>03-422-215</td><td>3 aluminum rods</td></tr><tr><td>ring clamp</td><td>Fisher</td><td>12-000-104&amp;nbsp;</td><td>5 cm</td></tr><tr><td>cork ring</td><td>Fisher</td><td>07-835AA&amp;nbsp;</td><td>8 cm outer dimension</td></tr><tr><td>round bottom flask</td><td>Fisher</td><td>31-501-107&amp;nbsp;</td><td>100 mL</td></tr><tr><td>rotary evaporator with accessories</td><td>Fisher</td><td>05-000-461&amp;nbsp;</td><td>cold trap bondenser</td></tr><tr><td>bump trap 14/20 joint</td><td>Fisher</td><td>CG132201</td><td>14/20 joint</td></tr><tr><td>funnel</td><td>Fisher</td><td>05-555-6&amp;nbsp;</td><td>organic solvent compatible</td></tr><tr><td>cotton</td><td>Fisher</td><td>22-456-881</td><td>non-sterile</td></tr><tr><td>glass pipets</td><td>Fisher</td><td>13-678-20A&amp;nbsp;</td><td>borosilicate 5.75&quot;</td></tr><tr><td>two 250 microliter syringes</td><td>Fisher</td><td>14-813-69&amp;nbsp;</td><td></td></tr><tr><td>4 erlenmeyer flasks</td><td>Fisher</td><td>10-040D&amp;nbsp;</td><td>125 mL</td></tr><tr><td>fume hood&amp;nbsp;</td><td>Fisher</td><td>13-118-370&amp;nbsp;</td><td></td></tr><tr><td>nitrile gloves</td><td>Fisher</td><td>19-149-863B&amp;nbsp;</td><td>medium</td></tr><tr><td>safety goggles</td><td>Fisher</td><td>17-377-403&amp;nbsp;</td><td></td></tr><tr><td>spatula</td><td>Fisher</td><td>14-357Q</td><td></td></tr><tr><td>balance</td><td>Fisher</td><td>01-912-403&amp;nbsp;</td><td>120 g capacity</td></tr></tbody></table>

separation of aldehydes and reactive ketones from mixtures using a bisulfite extraction protocol

<p class="jove_content">La purificazione dei composti organici è una componente essenziale delle operazioni di routine sintetiche. La possibilità di rimuovere i contaminanti in un strato acquoso generando una struttura carica offre l'opportunità di utilizzare estrazione come una tecnica di purificazione semplice. Combinando l'uso di un solvente organico miscibile con bisolfito di sodio satura, aldeidi e chetoni reattive può essere trasformato con successo in carico bisolfito addotti che possono poi essere separati da altri componenti organici di una miscela della introduzione di uno strato organico immiscibile. Qui, descriviamo un semplice protocollo per la rimozione delle aldeidi, tra cui stericamente impedito neopentilica aldeidi e alcuni chetoni, da miscele di sostanze chimiche. Chetoni possono essere separati se essi sono stericamente unhindered ciclico o metil chetoni. Per alifatiche aldeidi e chetoni, dimetilformammide è utilizzato come solvente miscibile per migliorare i tassi di rimozione. La reazione di addizione di bisolfito può essere invertita di basificazione dello strato acquoso, consentendo per il re-isolamento del componente di una miscela carbonilici reattivi.</p>

<p class="jove_content" fo:keep-together.within-page="1">Procedura <strong>1</strong> per la rimozione di aldeide è usato per aldeidi aromatiche. Procedura <strong>2</strong>, in cui la dimetilformammide è utilizzato come solvente miscibile, deve essere utilizzato per chetoni e aldeidi alifatiche. Procedura <strong>2</strong> deve essere utilizzato anche per le miscele che non sono completamente solubili in metanolo. Il materiale ottenuto da ciascuno dei protocolli viene analizzato per purezza utilizzando <sup>1</sup>H NMR integrazione analis...

Watch this Scientific Journal Video about Separation of Aldehydes and Reactive Ketones from Mixtures Using a Bisulfite Extraction Protocol at JoVE.com

Separation of Aldehydes and Reactive Ketones from Mixtures Using a Bisulfite Extraction Protocol

Separazione di aldeidi e chetoni reattive da miscele utilizzando un protocollo di estrazione di bisolfito

<p class="jove_content">Qui, presentiamo un protocollo per rimuovere aldeidi e chetoni reattive da miscele di un protocollo di estrazione liquido-liquido direttamente con bisolfito di sodio satura in un solvente miscibile. Questo protocollo combinato è rapida e facile da eseguire. L'aldeide o un chetone può essere ri-isolato tramite la basificazione dello strato acquoso.</p>

The purification of organic compounds is an essential component of routine synthetic operations. The ability to remove contaminants into an aqueous layer ...

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34.0K Views.  Trinity College. Qui, presentiamo un protocollo per rimuovere aldeidi e chetoni reattive da miscele di un protocollo di estrazione liquido-liquido direttamente con bisolfito di sodio satura in un solvente miscibile. Questo protocollo combinato è rapida e facile da eseguire. L'aldeide o un chetone può essere ri-isolato tramite la basificazione dello strato acquoso.

Video: Separation of Aldehydes and Reactive Ketones from Mixtures Using a Bisulfite Extraction Protocol

Enzymatic Cascade Reactions for the Synthesis of Chiral Amino Alcohols from L-lysine

<p class="jove_content">Amino alcohols are versatile compounds with a wide range of applications. For instance, they have been used as chiral scaffolds in organic synthesis. Their synthesis by conventional organic chemistry often requires tedious multi-step synthesis processes, with difficult control of the stereochemical outcome. We present a protocol to enzymatically synthetize amino alcohols starting from the readily available L-lysine in 48 h. This protocol combines two chemical reactions that are very difficult to conduct by conventional organic synthesis. In the first step, the regio- and diastereoselective oxidation of an unactivated C-H bond of the lysine side-chain is catalyzed by a dioxygenase; a second regio- and diastereoselective oxidation catalyzed by a regiodivergent dioxygenase can lead to the formation of the 1,2-diols. In the last step, the carboxylic group of the alpha amino acid is cleaved by a pyridoxal-phosphate (PLP) decarboxylase (DC). This decarboxylative step only affects the alpha carbon of the amino acid, retaining the hydroxy-substituted stereogenic center in a beta/gamma position. The resulting amino alcohols are therefore optically enriched. The protocol was successfully applied to the semipreparative-scale synthesis of four amino alcohols. Monitoring of the reactions was conducted by high performance liquid chromatography (HPLC) after derivatization by 1-fluoro-2,4-dinitrobenzene. Straightforward purification by solid-phase extraction (SPE) afforded the amino alcohols with excellent yields (93% to &#62;95%).</p>

<p class="jove_content">Chiral amino alcohols are versatile molecules for use as scaffolds in organic synthesis. Starting from L-lysine, we synthesize amino alcohols by an enzymatic cascade reaction combining diastereoselective C-H oxidation catalyzed by dioxygenase followed by cleavage of the carboxylic acid moiety of the corresponding hydroxyl amino acid by a decarboxylase.</p>

Reazioni a cascata enzimatica per la sintesi di Amino alcoli chirali da L-lisina

Amino alcohols are versatile compounds with a wide range of applications. For instance, they have been used as chiral scaffolds in organic synthesis. ...

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A Two-Step Protocol for Umpolung Functionalization of Ketones Via Enolonium Species

<p class="jove_content">&#945;-Functionalization of ketones via umpolung of enolates by hypervalent iodine reagents is an important concept in synthetic organic chemistry. Recently, we have developed a two-step strategy for ketone enolate umpolung that has enabled the development of methods for chlorination, azidation, and amination using azoles. In addition, we have developed C-C bond&#8211;forming arylation and allylation reactions. At the heart of these methods is the preparation of the intermediate and highly reactive enolonium species prior to addition of a reactive nucleophile. This strategy is thus reminiscent of the preparation and use of metal enolates in classical synthetic chemistry. This strategy allows the use of nucleophiles that would otherwise be incompatible with the strongly oxidizing hypervalent iodine reagents. In this paper we present a detailed protocol for chlorination, azidation, N-heteroarylation, arylation, and allylation. The products include motifs prevalent in medicinally active products. This article will greatly assist others in using these methods.</p>

<p class="jove_content">A two step one-pot protocol for the umpolung of ketone enolates to enolonium species and addition of a nucleophile to the &#945;-position is described. Nucleophiles include chloride, azide, azoles, allyl-silanes, and aromatic compounds.</p>

Un protocollo in due fasi per Umpolung funzionalizzazione di chetoni Via Enolonium le specie

&#945;-Functionalization of ketones via umpolung of enolates by hypervalent iodine reagents is an important concept in synthetic organic chemistry. ...

Synthesis of Esters Via a Greener Steglich Esterification in Acetonitrile

<p class="jove_content">The Steglich esterification is a widely-used reaction for the synthesis of esters from carboxylic acids and alcohols. While efficient and mild, the reaction is commonly performed using chlorinated or amide solvent systems, which are hazardous to human health and the environment. Our methodology utilizes acetonitrile as a greener and less hazardous solvent system. This protocol exhibits rates and yields that are comparable to traditional solvent systems and employs an extraction and wash sequence that eliminates the need for the purification of the ester product via column chromatography. This general method can be used to couple a variety of carboxylic acids with 1&#176; and 2&#176; aliphatic alcohols, benzylic and allylic alcohols, and phenols to obtain pure esters in high yields. The goal of the protocol detailed here is to provide a greener alternative to a common esterification reaction, which could serve useful for ester synthesis in both academic and industrial applications.</p>

<p class="jove_content">A modified Steglich esterification reaction was used to synthesize a small library of ester derivatives with primary and secondary alcohols. The methodology uses a non-halogenated and greener solvent, acetonitrile, and enables product isolation in high yields without the need for chromatographic purification.</p>

Sintesi degli esteri tramite un'esterificazione Steglich più verde in Acetonitrile

The Steglich esterification is a widely-used reaction for the synthesis of esters from carboxylic acids and alcohols. While efficient and mild, the ...

Reducing Agents

<p class="jove_content">Source: Vy M. Dong and Daniel Kim, Department of Chemistry, University of California, Irvine, CA</p>
<p class="jove_content">Controlling the reactivity and selectivity during the synthesis of a molecule is very important criteria for chemists. This has led to the development of many reagents that allow chemists to pick and choose reagents suitable for a given task. Quite often, a balance between reactivity and selectivity needs to be achieved. This experiment will use IR spectroscopy to monitor the reaction and to understand the reactivity of carbonyl compounds as well as the reactivity of hydride-reducing reagents.</p>

Reduction of Carbonyl Compounds

Agenti riducenti

Source: Vy M. Dong and Daniel Kim, Department of Chemistry, University of California, Irvine, CA
Controlling the reactivity and selectivity during the ...

Didattica

JoVE Science Education

Chimica organica II

Identification of Unknown Aldehydes and Ketones

<p>Source: Lara Al Hariri and Ahmed Basabrain at the University of Massachusetts Amherst, MA, USA</p>
<ol class="note-items">
	<li data-note-item="1" data-parent-collapse="">DNPH Test for Aromatic Aldehydes and Ketones<button class="expand">Expand</button>
	<p>In this lab, you&#39;ll use the DNPH test, the Tollens&#39; test, and the iodoform test to identify two unknown aldehydes or ketones. You&#39;ll use butanone and benzaldehyde as known compounds to confirm that the tests are working as expected.</p>
	<p>You&#39;ll start the lab with the DNPH test, which relies on the reaction between 2,4-dinitrophenylhydrazine, or DNPH, and aldehydes and ketones. When you combine DNPH and an aldehyde or ketone in an acidic environment, they undergo a condensation reaction to form the corresponding hydrazone. The hydrazone then precipitates from solution. If the precipitate is red to orange, the aldehyde or ketone was aromatic. If it&#39;s orange to yellow, the aldehyde or ketone was non-aromatic or aliphatic.</p>
	<ul class="lab-items">
		<li data-sub-note-item="1-3">
		<div class="lab-step">Put on a lab coat, safety glasses, and nitrile gloves.<strong> Note: </strong>Many chemicals in this lab are toxic, corrosive, or flammable, so you will perform this lab in a fume hood. Change your gloves if you get any chemicals on them.</div>
		</li>
		<li data-sub-note-item="1-4">
		<div class="lab-step">Get a vial of each known compound and choose two unknown compounds to analyze. Write the codes for your unknowns in your lab notebook.</div>
		</li>
		<li data-sub-note-item="1-5">
		<div class="lab-step">Label a 250-mL beaker for aqueous waste and a 600-mL beaker for used pipettes. Put several clean Pasteur pipettes in another beaker and get more whenever you need them.</div>
		</li>
		<li data-sub-note-item="1-6">
		<div class="lab-step">Obtain four small test tubes in a rack and label them with the four compound names, or codes, and the name of the first test.</div>
		</li>
		<li data-sub-note-item="1-7">
		<div class="lab-step">Bring a 50-mL beaker and a graduated cylinder to the reagent hood and obtain 8 mL of the DNPH solution.</div>
		</li>
		<li data-sub-note-item="1-8">
		<div class="lab-step">Use four Pasteur pipettes to place 3 &#8211; 4 drops of each compound into its test tube. <strong>Note:</strong> Don&#39;t reuse pipettes during this lab because cross-contamination will invalidate the test results.</div>
		</li>
		<li data-sub-note-item="1-9">
		<div class="lab-step">Add 2 mL of the DNPH solution to one of the test tubes and mix it well with a glass rod. Thoroughly rinse the glass rod with deionized water over your aqueous waste beaker to remove all traces of the ketone or aldehyde.</div>
		</li>
		<li data-sub-note-item="1-10">
		<div class="lab-step">Add 2 mL of the DNPH solution to each of the other three test tubes in the same way. Make sure to thoroughly clean the glass rod after each one. When you&#39;re finished, let the solution sit for 15 min.</div>
		</li>
		<li data-sub-note-item="1-11">
		<div class="lab-step">While you wait, set up for vacuum filtration and fill a 250-mL beaker with deionized water.</div>
		</li>
		<li data-sub-note-item="1-12">
		<div class="lab-step">After 15 minutes, inspect the precipitates in the test tubes. <strong>Note:</strong> Benzaldehyde has an aromatic group, so you should see a red to orange solid in its test tube. Butanone is aliphatic, so you should see an orange to yellow solid in its test tube. Record the results in your lab notebook.
		<h4><strong>Table 1: DNPH, Tollens&#39;, and Iodoform Results</strong></h4>
		<table align="center" height="224" style="border-collapse: collapse; font-size: 17px; line-height: 24px;">
			<tbody>
				<tr>
					<td style="border: 1px solid; padding: 0px; text-align: center;"><strong>Compound</strong></td>
					<td style="border: 1px solid; padding: 0px; text-align: center;"><strong>DNPH </strong></td>
					<td style="border: 1px solid; padding: 0px; text-align: center;"><strong>Tollens&#39; </strong></td>
					<td style="border: 1px solid; padding: 0px; text-align: center;"><strong>Iodoform </strong></td>
					<td style="border: 1px solid; padding: 0px; text-align: center;"><strong>Solubility in water </strong></td>
					<td style="border: 1px solid; padding: 0px; text-align: center;"><strong>Hydrazone m.p. </strong></td>
				</tr>
				<tr>
					<td style="border: 1px solid; padding: 0px;">Butanone</td>
					<td style="border: 1px solid; padding: 0px;"></td>
					<td style="border: 1px solid; padding: 0px;"></td>
					<td style="border: 1px solid; padding: 0px;"></td>
					<td style="border: 1px solid; padding: 0px;"></td>
					<td style="border: 1px solid; padding: 0px;"></td>
				</tr>
				<tr>
					<td style="border: 1px solid; padding: 0px;">Benzaldehyde</td>
					<td style="border: 1px solid; padding: 0px;"></td>
					<td style="border: 1px solid; padding: 0px;"></td>
					<td style="border: 1px solid; padding: 0px;"></td>
					<td style="border: 1px solid; padding: 0px;"></td>
					<td style="border: 1px solid; padding: 0px;"></td>
				</tr>
				<tr>
					<td style="border: 1px solid; padding: 0px;">&#160; &#160;</td>
					<td style="border: 1px solid; padding: 0px;"></td>
					<td style="border: 1px solid; padding: 0px;"></td>
					<td style="border: 1px solid; padding: 0px;"></td>
					<td style="border: 1px solid; padding: 0px;"></td>
					<td style="border: 1px solid; padding: 0px;"></td>
				</tr>
				<tr>
					<td style="border: 1px solid; padding: 0px;">&#160; &#160;</td>
					<td style="border: 1px solid; padding: 0px;"></td>
					<td style="border: 1px solid; padding: 0px;"></td>
					<td style="border: 1px solid; padding: 0px;"></td>
					<td style="border: 1px solid; padding: 0px;"></td>
					<td style="border: 1px solid; padding: 0px;"></td>
				</tr>
			</tbody>
		</table>
		<a href="https://www.jove.com/CDNSource/lm/labs/69/Table_1._DNPH,_Tollens_,_and_Iodoform_results.xlsx" target="_blank">Click Here to download Table 1</a></div>
		</li>
		<li data-sub-note-item="1-13">
		<div class="lab-step">Compare the solids from the unknown compounds to the known compounds. For each unknown, record whether this solid was more red-orange, like benzaldehyde, or more orange-yellow, like butanone.</div>
		</li>
		<li data-sub-note-item="1-14">
		<div class="lab-step">Use a clean Pasteur pipette to wet the filter paper of the vacuum filtration setup with deionized water and collect the solid from one of your unknowns by vacuum filtration. Rinse out any solid left in the tube with deionized water.</div>
		</li>
		<li data-sub-note-item="1-15">
		<div class="lab-step">Wash the solid on the filter paper with 10 mL of deionized water.</div>
		</li>
		<li data-sub-note-item="1-16">
		<div class="lab-step">Pick up a tiny amount of the solid with a clean glass rod and smear it on pH paper. If the pH is below 6.5, rinse the solid with another 10 mL of deionized water. Keep rinsing the solid and checking its pH until it is between 6.5 and 7.</div>
		</li>
		<li data-sub-note-item="1-17">
		<div class="lab-step">Label a small watch glass for the unknown and carefully transfer the filter paper and solid to the watch glass to dry.</div>
		</li>
		<li data-sub-note-item="1-18">
		<div class="lab-step">Thoroughly rinse the B&#252;chner funnel with deionized water, dispose of the filtrate in the DNPH solution waste, and reassemble the vacuum filtration setup with a new piece of filter paper.</div>
		</li>
		<li data-sub-note-item="1-19">
		<div class="lab-step">Collect and wash the solids from the second unknown compound and from the two known compounds in the same way.</div>
		</li>
		<li data-sub-note-item="1-20">
		<div class="lab-step">Leave the four solids in your fume hood to dry (1 h).</div>
		</li>
	</ul>
	</li>
	<li data-note-item="2" data-parent-collapse="">The Tollens&#8217; Test<button class="expand">Expand</button>
	<p>When you combine an aldehyde with diammine silver(I), or Tollens&#39; reagent, the reagent is reduced to metallic silver and ammonia. The silver either coats the inside of the reaction vessel or precipitates as a black solid, so it&#39;s easy to see that the reaction happened.</p>
	<p>Most ketones are harder to oxidize than aldehydes and therefore don&#39;t react with the Tollens&#39; reagent. For this lab, you can assume that if silver appears, the compound is an aldehyde. If silver does not appear, the compound is a ketone.</p>
	<p>The Tollens&#39; reagent solution contains a strong base and must be disposed of specially to avoid forming an explosive decomposition product. Handle it carefully and remember to put the Tollens&#39; test waste in the designated container.</p>
	<ul class="lab-items">
		<li data-sub-note-item="2-4">
		<div class="lab-step">Place your used test tubes in a beaker and label four new tubes with the compound names or codes and Tollens&#39; test.</div>
		</li>
		<li data-sub-note-item="2-5">
		<div class="lab-step">Bring a clean 50-mL beaker and a 5-mL graduated cylinder to the reagent hood and obtain 4 mL of Tollens&#39; reagent.</div>
		</li>
		<li data-sub-note-item="2-6">
		<div class="lab-step">Use clean pipettes to place 3 &#8211; 4 drops of each compound in its test tube.</div>
		</li>
		<li data-sub-note-item="2-7">
		<div class="lab-step">Add 1 mL of Tollens&#39; reagent to each test tube and mix the solutions well with a clean glass rod, thoroughly rinsing the rod with deionized water between tubes. Set the rack of tubes to the side and let it sit for 10 min.</div>
		</li>
		<li data-sub-note-item="2-8">
		<div class="lab-step">While you wait, get about 100 mL of water in a 150-mL beaker and set it on a hotplate. Position a small 3-prong clamp above the beaker.</div>
		</li>
		<li data-sub-note-item="2-9">
		<div class="lab-step">Check the benzaldehyde tube after 10 min.<strong> Note:</strong> Benzaldehyde should have a positive result, as indicated by a silver film or precipitate. If you don&#39;t see a positive result in the benzaldehyde tube, secure a thermometer to the test tube and heat in the water bath at 35 &#176;C for 5 min. The silver film, or precipitate, should then appear. Record this result in your lab notebook.</div>
		</li>
		<li data-sub-note-item="2-10">
		<div class="lab-step">Butanone won&#39;t react with Tollens&#39; reagent. <strong>Note: </strong>The butanone tube is an example of a negative Tollens&#39; test result. Record this in your lab notebook.</div>
		</li>
		<li data-sub-note-item="2-11">
		<div class="lab-step">Check the tubes of your unknowns. If you see a silver mirror or precipitate, record a positive Tollens&#39; test result for that unknown. If you don&#39;t, heat the tube in the water bath for 5 min and check again. If the test is still negative, record that result in your lab notebook.</div>
		</li>
		<li data-sub-note-item="2-12">
		<div class="lab-step">When you&#39;re done, turn off the hotplate and dispose of the Tollens&#39; test solutions in the appropriate waste container. Put silver-coated tubes in the collection box for acid cleaning and put the rest in your beaker.</div>
		</li>
	</ul>
	</li>
	<li data-note-item="3" data-parent-collapse="">Iodoform Test for Methyl Ketones<button class="expand">Expand</button>
	<p>When you combine iodine and a methyl ketone in aqueous base, iodine replaces the alpha methyl&#39;s hydrogens. An addition-elimination reaction followed by proton transfer yields iodoform and a carboxylate anion. Iodoform is insoluble in water, so you&#39;ll see a yellow precipitate if the compound that you&#39;re testing is a methyl ketone. If it is not a methyl ketone, the test solution will eventually turn brown because of the unreacted iodine.</p>
	<ul class="lab-items">
		<li data-sub-note-item="3-2">
		<div class="lab-step">Before the iodoform test, check the solubility of all four compounds in water. Label four clean test tubes with the compound names or codes and H<sub>2</sub>O. Label another four test tubes with the compound names and CHI<sub>3</sub>.</div>
		</li>
		<li data-sub-note-item="3-3">
		<div class="lab-step">Use clean Pasteur pipettes to place 3 &#8211; 4 drops of each compound in its test tube.</div>
		</li>
		<li data-sub-note-item="3-4">
		<div class="lab-step">Add 2 mL of deionized water to each labeled tube. Mix well with a clean glass rod. Thoroughly clean the rod with deionized water between tubes.</div>
		</li>
		<li data-sub-note-item="3-5">
		<div class="lab-step">Wait a few minutes for the liquids to settle before evaluating them. <strong>Note:</strong> Butanone is moderately soluble in water, so you should see little to no separation. Benzaldehyde is sparingly soluble in water, and its density is a little higher than water&#39;s. You should see a small layer at the bottom of the tube.</div>
		</li>
		<li data-sub-note-item="3-6">
		<div class="lab-step">Inspect your unknowns for liquid layers and record the results for all four compounds in your lab notebook.</div>
		</li>
		<li data-sub-note-item="3-7">
		<div class="lab-step">Add 2 mL of deionized water to the butanone tube and any water-soluble ketones and mix them well with a clean glass rod. <strong>Note: </strong>If you have an unknown ketone that is insoluble in water, instead add 2 mL of 1,2-dimethoxyethane and mix it well with a clean glass rod.</div>
		</li>
		<li data-sub-note-item="3-8">
		<div class="lab-step">Now, perform the iodoform test, which is for ketones only. Use a clean 50-mL beaker and a small graduated cylinder to obtain 4 or 6 mL of 3 M NaOH, depending on whether you have two or three ketones to test.</div>
		</li>
		<li data-sub-note-item="3-9">
		<div class="lab-step">Pour ~10 mL of iodoform reagent into another 50-mL beaker.</div>
		</li>
		<li data-sub-note-item="3-10">
		<div class="lab-step">Add 2 mL of 3 M NaOH to each ketone tube and mix well, thoroughly cleaning the glass rod with deionized water between each tube.</div>
		</li>
		<li data-sub-note-item="3-11">
		<div class="lab-step">Obtain a clean Pasteur pipette and add the iodoform reagent dropwise to the butanone tube, frequently stirring until you see a yellow precipitate. <strong>Note:</strong> Butanone is a methyl ketone, so it will produce a positive result.</div>
		</li>
		<li data-sub-note-item="3-12">
		<div class="lab-step">Rinse the glass rod with deionized water and start adding the iodoform reagent dropwise to your first, or only, unknown ketone, while stirring frequently. Continue adding the reagent until either yellow iodoform precipitates, like you saw with butanone, or the solution stays brown, even after you stir it well. <strong>Note: </strong>The latter is a negative result.</div>
		</li>
		<li data-sub-note-item="3-13">
		<div class="lab-step">If you have another unknown ketone, clean the glass rod well and repeat the test with your second ketone.</div>
		</li>
		<li data-sub-note-item="3-14">
		<div class="lab-step">When you&#39;re finished, dispose of your iodine-containing solutions in the appropriate waste container.</div>
		</li>
		<li data-sub-note-item="3-15">
		<div class="lab-step">Once the solids from the DNPH test are dry, measure the melting point of each solid and record them in your lab notebook. Put the remaining solutes in the waste container for solid DNPH derivatives.</div>
		</li>
		<li data-sub-note-item="3-16">
		<div class="lab-step">Dispose of the leftover organic liquids and the aqueous aldehyde mixtures in the usual waste containers.</div>
		</li>
		<li data-sub-note-item="3-17">
		<div class="lab-step">Rinse the Pasteur pipettes used for the aldehydes and ketones with acetone before putting them in the glass waste. Pour your aqueous waste down the drain with running tap water. Clean your glassware, put away your lab equipment, and collect and throw out any trash in your fume hood before you leave.</div>
		</li>
	</ul>
	</li>
	<li data-note-item="4" data-parent-collapse="">Results<button class="expand">Expand</button>
	<ul class="lab-items">
		<li data-sub-note-item="4-1">
		<div class="lab-step">Identify your unknown compounds. There are six options: acetophenone, butanal, 3-methyl-2-butanone, pentanal, 2-pentanone, and 3-pentanone.</div>
		</li>
		<li data-sub-note-item="4-2">
		<div class="lab-step">Look at the DNPH results. If the precipitate was red to orange, the unknown aldehyde or ketone is aromatic. If it was yellow, the unknown is aliphatic. <strong>Note:</strong> Since only one possible compound is aromatic, red precipitate means that the unknown was acetophenone. As confirmation, you should also have seen a negative Tollens&#39; test and a positive iodoform test.</div>
		</li>
		<li data-sub-note-item="4-3">
		<div class="lab-step">A yellow precipitate in the DNPH test means that the unknown could be any of the other five compounds.</div>
		</li>
		<li data-sub-note-item="4-4">
		<div class="lab-step">Look at the results of the Tollens&#39; test. If you saw a silver mirror or silver-gray precipitate in the test tube, the unknown compound is an aldehyde. If you didn&#39;t see any change, then the unknown compound is a ketone. If your unknown is an aldehyde, it could be pentanal or butanal.</div>
		</li>
		<li data-sub-note-item="4-5">
		<div class="lab-step">Compare the melting point of the unknown&#39;s hydrazone derivative to literature values for each aldehyde to figure out which one it was.</div>
		</li>
		<li data-sub-note-item="4-6">
		<div class="lab-step">If Tollens&#39; test was negative and the DNPH test showed an aliphatic compound, the unknown could be 3-methyl-2-butanone, 2-pentanone, or 3-pentanone.</div>
		</li>
		<li data-sub-note-item="4-7">
		<div class="lab-step">Check the results of the iodoform test to narrow it down. If you saw solid yellow iodoform, the compound was a methyl ketone. If you saw a brown solution, it was not a methyl ketone.</div>
		</li>
		<li data-sub-note-item="4-8">
		<div class="lab-step">Only one of the aliphatic ketones is not a methyl ketone, so if you saw a brown solution, the unknown was 3-pentanone. If you saw yellow iodoform precipitate from solution and the DNPH test also had yellow precipitate, then the unknown is 3-methyl-2-butanone or 2-pentanone.</div>
		</li>
		<li data-sub-note-item="4-9">
		<div class="lab-step">Use the melting point of the unknown&#39;s hydrazone derivative to figure out which methyl ketone you had.</div>
		</li>
	</ul>
	</li>
</ol>

Test for Aldehydes and Ketones: DNPH, Tollen's Test, and Iodoform Test - Procedure

Identificazione di aldeidi e chetoni sconosciuti

Source: Lara Al Hariri and Ahmed Basabrain at the University of Massachusetts Amherst, MA, USA

	DNPH Test for Aromatic Aldehydes and KetonesExpand
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JoVE Lab Manual

Lab Manual Sub Articles

Alcohols from Carbonyl Compounds: Reduction

<p>Reduction is a simple strategy to convert a carbonyl group to a hydroxyl group. The three major pathways to reduce carbonyls to alcohols are catalytic hydrogenation, hydride reduction, and borane reduction.</p>
<p><strong>Catalytic hydrogenation</strong> is similar to the reduction of an alkene or alkyne by adding H<sub>2</sub> across the pi bond in the presence of transition metal catalysts like Raney Ni, Pd–C, Pt, or Ru. Aldehydes and ketones can be reduced by this method, often under mild to moderate heat (25–100°C) and pressure (1–5 atm H<sub>2</sub>), to yield 1° and 2° alcohols, respectively.</p>
<p style="text-align: center"><img alt="Hydrogenation reaction diagram; cyclohexanone to cyclohexanol using H₂/Pt, Pd, Ni catalyst, 90–95% yield." src="/files/ftp_upload/11925/11925_PT_Figure_1.svg" style="text-align: center; height: 90px;" data-altupdatedat="1747908711000" data-alt="Figure1"></p>
<p align="center"><strong>Figure 1.</strong> Catalytic hydrogenation can be suitable for industrial applications when harsh conditions are not required, but unsaturated carbon–carbon bonds are also reduced.</p>
<p><strong>Hydride reduction</strong> can be achieved by hydride transfer reagents, like sodium borohydride (NaBH<sub>4</sub>) and lithium aluminum hydride (LiAlH<sub>4</sub>, or LAH), as nucleophilic attack by a free hydride ion, <strong><img alt="Lewis structure of hydride ion, H⁻, showing a hydrogen atom with a lone pair and a negative charge." src="/files/ftp_upload/11925/11925_PT_Figure_2.svg" style="height: 18px;" data-altupdatedat="1747908711000" data-alt="Figure2"></strong>, is almost unknown for NaH salts due to its high charge density, making it a strong base. The hydrogen atoms of LAH and NaBH<sub>4</sub>, being covalently bonded to boron and aluminum atoms, have partial negative charges, thereby enhancing their nucleophilicity at the cost of basicity. The first step of nucleophilic addition leads to the formation of alkoxide ions. The byproduct alkoxyborohydride or alkoxyaluminate reduces three more carbonyl molecules, successively transferring all their hydrogen atoms. Since hydride is a poor leaving group, the hydride transfer steps are irreversible, and therefore the reaction proceeds to completion. Lastly, the reaction mixture is worked up with solvent (i.e., water or alcohol in the case of NaBH<sub>4</sub> and dilute acid in the case of LAH).</p>
<p style="text-align: center"><img alt="Chemical reaction diagram: ester reduction by LiAlH4 to form alcohols, showcasing reduction process." src="/files/ftp_upload/11925/11925_PT_Figure_3.svg" style="text-align: center; height:55px;" data-altupdatedat="1747908711000" data-alt="Figure3"></p>
<p align="center"><strong>Figure 2.</strong> Aldehydes and symmetrical esters produce one 1° alcohol product. Unsymmetrical esters produce a mixture of 1° alcohols.</p>
<p>LAH, NaBH<sub>4</sub>, and their derivatives are highly useful in the reduction of aldehydes and ketones. LAH, a powerful reducing agent, can also reduce carbonyl compounds like acids, esters, acyl chlorides, and amides. LAH reacts violently with water and other protic solvents, liberating hydrogen gas and forming metal hydroxides/alkoxides. Hence, LAH reductions are typically carried out in aprotic solvents like anhydrous diethyl ether and THF.</p>
<p style="text-align: center"><img alt="Organic reduction reaction equation, LiBH4/EtOH, carboxylic acid to alcohol conversion, chemical synthesis." src="/files/ftp_upload/11925/11925_PT_Figure_4.svg" style="text-align: center; height: 45px;" data-altupdatedat="1747908711000" data-alt="Figure4"></p>
<p align="center"><strong>Figure 3.</strong> An alcoholic solution of lithium borohydride is a non-hazardous alternative to LAH in selectively reducing esters over acids.</p>
<p>On the other hand, NaBH<sub>4</sub> is of a milder nature and generally reduces only in protic solvents like ethanol or methanol. Therefore, NaBH<sub>4</sub> can be used to reduce aldehydes and ketones in the presence of functional groups like alkyl halides, esters, alkyl tosylates, and nitro groups. Diisobutylaluminum hydride (DIBAL-H) can also convert carbonyls to alcohols at room temperature by two successive additions of hydride ions. However, when reacted with esters at low temperatures, this reaction can be stopped at the aldehyde stage by adding only one equivalent of hydride ion.</p>
<p><strong>Borane reduction</strong> uses a borane (BH<sub>3</sub>) solution in diethyl ether, THF, or Me<sub>2</sub>S to selectively reduce electron-rich carbonyl groups like carboxylic acids in the presence of other reducible functional groups such as esters and even ketones.</p>
<p style="text-align: center"><img alt="Hydroboration-oxidation reaction equation; organic chemistry; synthesis of alcohols; reaction diagram." src="/files/ftp_upload/11925/11925_PT_Figure_5.svg" style="text-align: center; height: 65px;" data-altupdatedat="1747908711000" data-alt="Figure5"></p>
<p align="center"><strong>Figure 4.</strong> The formation of a reactive triacylborate intermediate with a more electrophilic carbonyl group than the starting ester molecule drives the reduction reaction forward.</p>
<p>For living organisms, reduced coenzyme NADH or its phosphoester NADPH is equivalent to laboratory hydride reagents in enzyme catalysis of similar biological reductions.</p>

Alcoli da composti carbonilici: riduzione

Reduction is a simple strategy to convert a carbonyl group to a hydroxyl group. The three major pathways to reduce carbonyls to alcohols are catalytic ...

Chimica Organica

Unità 1

Alcoli e fenoli

TERMINI E CONCETTI CHIAVE

Preparation of Aldehydes and Ketones from Alcohols, Alkenes, and Alkynes

<p>Aldehydes and ketones are prepared from alcohols, alkenes, and alkynes via different reaction pathways. Alcohols are the most commonly used substrates for synthesizing aldehydes and ketones. The conversion of alcohol to aldehyde, which involves the oxidation process, depends on the class of the alcohol used and the strength of the oxidizing agent. For instance, primary alcohol will form an aldehyde when treated with a weak oxidizing agent; however, it gets over-oxidized to a carboxylic acid in the presence of a strong oxidizing agent. Hence, a mild oxidant like pyridinium chlorochromate is used to convert primary alcohols to aldehydes.</p>
<p>Similarly, Swern and Dess&#8211;Martin oxidations, which employ weaker oxidizing agents, convert primary alcohols to aldehydes. The strength of the oxidizing agent is irrelevant when converting secondary alcohol to a ketone. Both mild and strong oxidants give ketones from secondary alcohols.</p>
<p>Unsaturated hydrocarbons like alkenes undergo an ozonolysis reaction to give aldehydes and ketones. The product formed depends on the substitution present across the double bond in an alkene. A monosubstituted alkene forms formaldehyde and another aldehyde molecule. However, disubstitution gives rise to two cases. A 1,1-disubstituted alkene upon ozonolysis forms a mixture of formaldehyde and ketone, while a 1,2-disubstituted alkene yields a mixture of aldehydes. Both aldehydes and ketones are formed when trisubstituted alkenes undergo ozonolysis, while tetrasubstituted alkenes form ketones exclusively.</p>
<p>Alkynes&#160;also form aldehydes and ketones under hydroboration-oxidation and acid-catalyzed hydration reaction conditions. The hydroboration-oxidation reaction favors anti-Markovnikov&#8217;s addition. Hence terminal alkynes form aldehydes, and internal alkynes&#160;yield ketones. On the other hand, the acid-catalyzed hydration reaction follows Markonikov&#8217;s addition, and thus both terminal and internal alkynes generate&#160;ketones.</p>

Preparazione di Aldeidi e Chetoni da Alcoli, Alcheni e Alchini

Aldehydes and ketones are prepared from alcohols, alkenes, and alkynes via different reaction pathways. Alcohols are the most commonly used substrates for ...

Aldehydes and Ketones

Preparazione di aldeidi e chetoni da alcoli, alcheni e alchini

Preparation of Aldehydes and Ketones from Nitriles and Carboxylic Acids

<p>Although it is possible to reduce a carboxylic acid to an aldehyde, strong reducing agents, like lithium aluminum hydride (LAH), prohibit a controlled reduction, instead causing the generated aldehyde to instantly over-reduce to a primary alcohol.</p>
<p>Reducing carboxylic acid derivatives like acyl chlorides (RCOCl), esters (RCO<sub>2</sub>R&prime;), and nitriles (RCN) using milder aluminum hydride agents like lithium tri-<span style="font-style:italic">tert</span>-butoxyaluminum hydride [LiAlH(O-<span style="font-style:italic">t</span>-Bu)<sub>3</sub>] and diisobutylaluminum hydride [DIBAL-H] allows the easy conversion of the derivative to the corresponding aldehyde. This is because alkylaluminum hydrides are less reactive than LAH, as the former is more sterically hindered.</p>
<p>According to recent studies, a reductant like diphenylsilane in combination with an air-stable Ni precatalyst and dimethyl dicarbonate as an activator converts most of the carboxylic acid to the aldehyde without causing any over-reduction.</p>
<p>In other studies, a hydrosilane through visible light photoredox catalysis efficiently reduces carboxylic acids to aldehydes.</p>
<p>Ketones, unlike aldehydes, can be directly prepared from carboxylic acids using organolithium reagents. The acid rapidly reacts with two equivalents of an organolithium reagent to form a dianion. This dianion gets protonated to form the corresponding hydrate, which loses a water molecule to give a ketone.</p>
<p>Both aldehydes and ketones can be prepared from nitriles using suitable reducing agents. Aldehydes are formed by the partial reduction of nitriles in the presence of DIBAL-H. The nitrile first forms an aluminum complex, which later, on hydrolysis, yields the corresponding aldehyde. Nitriles can be reduced to ketones via imine intermediates using Grignard or organolithium reagents.</p>

Preparazione di aldeidi e chetoni da nitrili e acidi carbossilici

Although it is possible to reduce a carboxylic acid to an aldehyde, strong reducing agents, like lithium aluminum hydride (LAH), prohibit a controlled ...

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Preparazione di Aldeidi e Chetoni da Alcoli, Alcheni e Alchini

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