Chapter 15
α-Carbon Chemistry: Enols, Enolates, and Enamines
תגובתיות של אנולים
Enols are a class of compounds where a hydroxyl group is attached to a carbon–carbon double bond, which implies that it is a vinyl alcohol. A ...
תגובתיות של יוני אנולט
Enolate ions are formed by the acid–base reaction of a carbonyl compound with a base. This leads to deprotonation of the α hydrogen atom, ...
סוגי אנולים ואנולטים
Aldehydes and ketones form enols, although only about 1% of the enol is present at the equilibrium for simple monocarbonyl compounds. The enol form is ...
מוסכמות מנגנון Enolate
When a carbonyl compound is treated with a strong base, the α position gets deprotonated to give a resonance-stabilized intermediate called an ...
היווצרות רגיוסלקטיבית של אנולטים
As depicted in the figure below, the unsymmetrical ketones can form two possible enolates: less substituted or more substituted enolates. Usually, ...
השפעות סטריאוכימיות של אנוליזציה
The chiral α-carbon of the carbonyl compound is the stereocenter of the molecule. As shown in the figure below, when such a carbonyl compound ...
α-הלוגנציה מזורזת חומצה של אלדהידים וקטונים
By replacing an α-hydrogen with a halogen, acid-catalyzed α-halogenation of aldehydes or ketones yields a monohalogenated product
In the first ...
α-הלוגנציה מקודמת בסיס של אלדהידים וקטונים
α-Halogenation of aldehydes and ketones is a reaction involving the substitution of α hydrogens with halogens in the presence of a base. ...
הלוגנציה מרובה של קטונים מתיל: תגובת הלופורם
A method involving the transformation of methyl ketones to carboxylic acids using excess base and halogen is called the haloform reaction. It begins with ...
α-הלוגנציה של נגזרות חומצה קרבוקסילית: סקירה כללית
Unlike aldehydes and ketones, carboxylic acids do not readily participate in α halogenation reactions via enols or enolate intermediates. However, ...
α-ברום של חומצות קרבוקסיליות: תגובת גיהנום-וולהרד-זלינסקי
The method to achieve α-brominated carboxylic acids using a mixture of phosphorus tribromide and bromine is known as the ...
תגובות של תרכובות α-Halocarbonyl: החלפה נוקלאופילית
Nucleophilic substitution in α-halocarbonyl compounds can be achieved via an SN2 pathway. The reaction in α-haloketones is generally carried out ...
ניטרוזיציה של אנולים
The nitrosation reaction is one of the methods of preparing 1,2-diketones. The enol tautomer of the starting ketone reacts with sodium nitrite in ...
היווצרות אג"ח C-C: סקירה כללית של עיבוי Aldol
Aldol condensation is an important route in synthetic organic chemistry used to generate a new carbon–carbon bond under basic or acidic conditions. ...
תגובת תוספת Aldol בקטליזציה בסיסית
As depicted in Figure 1, base-catalyzed aldol addition involves adding two carbonyl compounds in aqueous sodium hydroxide to form a β-hydroxy ...
תגובת תוספת Aldol מזורזת חומצה
The aldol reaction of a ketone under acidic conditions successfully forms an unsaturated carbonyl as the final product instead of an aldol. The ...
התייבשות של Aldols לאנלים: עיבוי Aldol זרז בסיס
This lesson delves into the aldol condensation catalyzed by bases, where aldols undergo dehydration to enals. As shown in Figure 1, the β-hydroxy ...
התייבשות של Aldols כדי Enones: עיבוי Aldol זרז חומצה
As shown in Figure 1, under acidic conditions, the β-hydroxy ketone undergoes dehydration via an E1 elimination reaction to form an enone.
Figure 1. ...
תגובת אלדול תוך-מולקולרית
Intramolecular aldol reaction occurs in dicarbonyl compounds such as dialdehydes, diketones, and keto-aldehydes. The dicarbonyl compounds possess more ...
מחשוף אג"ח C-C: תגובת רטרו-אלדול
The reverse of the aldol addition reaction is called the retro-aldol reaction. Here, the carbon–carbon bond in the aldol product is cleaved under ...
תגובות Aldol חצויות: סקירה כללית
Crossed aldol addition is the reaction between two different carbonyl compounds under acidic or basic conditions. Here, both the carbonyl compounds ...
תגובת אלדול מוצלבת באמצעות בסיסים חלשים
This lesson deals with the crossed aldol reaction using weak bases. The self-condensation of an aldehyde having α hydrogen is prevented by adding it ...
קטונים עם אלדהידים ארומטיים שאינם ניתנים לשינוי: עיבוי קלייסן-שמידט
Benzaldehyde, like formaldehyde, lacks an α hydrogen and cannot enolize to form an enolate. Hence, the reaction of benzaldehyde with a ketone in the ...
תגובת אלדול מוצלבת באמצעות בסיסים חזקים: תגובת אלדול מכוונת
The reaction between two different carbonyl compounds comprising α hydrogen in the presence of a strong base like lithium diisopropylamide (LDA) to ...
עיבוי Aldol עם β-Diesters: עיבוי Knoevenagel
The Knoevenagel condensation is an aldol-type reaction involving the condensation of aldehydes or ketones with active methylene compounds such as ...
אסטרים ל β-Ketoesters: Claisen Condensation סקירה כללית
Regular Claisen condensation is a base-promoted reaction involving identical esters with two α hydrogens, condensing to produce β-ketoesters. It ...
אסטרים ל-β-קטוסטרים: מנגנון עיבוי קלייזן
Regular Claisen condensation involves the synthesis of β-ketoesters by combining identical ester molecules bearing two α hydrogens in the ...
עיבוי אלדול מול עיבוי קלייזן
Aldol condensation is an acid or base-catalyzed condensation between aldehydes or ketones to give an α,ꞵ-unsaturated carbonyl compound. A ...
עיבוי קלייזן תוך-מולקולרי של אסטרים דיקרבוקסילים: ציקליזציה של דיקמן
Dieckmann cyclization is an intramolecular Claisen condensation of diesters. The reaction occurs in the presence of a base and generates a cyclic ...
תרכובות β-דיקרבוניל באמצעות עיבוי קלייזן מוצלב
Crossed Claisen condensations are base-promoted reactions between two different ester molecules producing β-dicarbonyl compounds. The reaction ...
α-אלקילציה של קטונים באמצעות יוני אנולאט
Ketones with α protons are deprotonated by strong bases like lithium diisopropylamide (LDA) to form enolate ions. The anion is stabilized by ...
גורמים המשפיעים על α-אלקילציה של קטונים: בחירת הבסיס
α-Alkylation of ketones is achieved in the presence of alkyl halides and a base. The reaction proceeds via the formation of an enolate ion followed ...
אלקילציה של β-Ketoester Enolates: סינתזת אסטר אצטואצטית
Acetoacetic ester synthesis is a method to obtain ketones from alkyl halides and β-keto esters. The reaction occurs in the presence of an alkoxide ...
אלקילציה של β-Diester Enolates: סינתזת אסתר מלונית
Malonic ester synthesis is a method to obtain α substituted carboxylic acids from ꞵ-diesters such as diethyl malonate and alkyl halides.
The ...
תוספת מצומדת לתרכובות קרבוניל בלתי רוויות α,β
α,β-Unsaturated carbonyl compounds are molecules bearing a carbonyl and alkene functionality in conjugation with each other. The conjugation in ...
תוספת מצומדת (תוספת 1,4) לעומת תוספת ישירה (תוספת 1,2)
α,β-Unsaturated carbonyl compounds with two electrophilic sites, the carbonyl carbon, and the β carbon, are susceptible to nucleophilic ...
תוספת מצומדת של אנולטים: תוספת מיכאל
The attack of a nucleophile at the β carbon of an α,β-unsaturated carbonyl compound is called conjugate addition. Conjugate addition ...
Cyclohexenones באמצעות Michael Addition ו- Aldol Condensation: The Robinson Annulation
Robinson annulation is a base-catalyzed reaction for the synthesis of 2-cyclohexenone derivatives from 1,3-dicarbonyl donors (such as cyclic diketones, ...
סינתזה של תרכובות קרבוניל תחליפיות α: תגובת החסידה לאנמין
α-Substituted ketones or aldehydes can be synthesized from enamines by the Stork enamine reaction, named after its pioneer Gilbert Stork. Enamines ...
אלדהידים בלתי ניתנים להכלאה לחומצות ואלכוהולים: תגובת הקניזרו
The Cannizzaro reaction is a base-promoted redox reaction producing a primary alcohol and a carboxylic acid from two molecules of a nonenolizable ...
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