n-Butyllithium Titration

Przegląd

Source: Vy M. Dong and Diane Le, Department of Chemistry, University of California, Irvine, CA

This experiment will demonstrate a simple technique to titrate and obtain an accurate concentration of the organolithium reagent, n-butyllithium (n-BuLi). Organolithium reagents are extremely air- and moisture-sensitive and proper care must be taken to maintain the quality of the reagent so that it may be used successfully in a reaction. The n-BuLi titration experiments should be performed regularly to obtain accurate concentrations prior to use in a chemical reaction. Subsequently, we will demonstrate the addition of the titrated n-BuLi to benzaldehyde.

Procedura

1. Preparation of Titrant

To a flame-dried round bottom flask equipped with a stir bar under N₂, add diphenylacetic acid (250 mg, 1.18 mmol) and anhydrous THF (5 mL).

2. Titration of n-BuLi

Calculate the approximate amount of n-BuLi solution (in hexanes) needed to consume the diphenylacetic acid. Using a syringe, slowly adda solution of n-BuLi dropwise. The reaction mixture will turn temporarily yellow and back to a colorless

Wyniki

Representative results for the titration of n-BuLi for Procedures 1-3

Procedure Step	Color of reaction mixture
1.1	Colorless
2.1	Yellow, then colorless
2.2	Deep yellow
3.1	1.18 mmol diphenylacetic acid/1 mL n-BuLi Log in or to access full content. Learn more about your institution’s access to JoVE content here Wniosek i Podsumowanie In this experiment, we have demonstrated how to determine the concentration of an n-BuLi solution by using diphenylacetic acid. We have also performed a reaction by adding n-BuLi to benzaldehyde. Accurate concentrations of n-BuLi are important for its successful application in a number of reactions. n-BuLi is commonly used in lithium-halogen exchange reactions to prepare aryllithium or vinyllithium reagents, which can be subsequently used in C-C bond forming Log in or to access full content. Learn more about your institution’s access to JoVE content here Tagi N Butyllithium Titration Organolithium Reagent Strong Base Nucleophile Alkanes Hexane Heptane Degradation Aging Water Exposure Lithium Di isopropylamide Precise Amount Titration Experiments Chemical Reaction Applications Br nsted Base Lithium halogen Exchange Reactions Polymerization Initiator Elastomers Molar Excess Reaction Mixture Incomplete Reaction Side Products Diphenylacetic Acid 1. Preparation of Titrant To a flame-dried round bottom flask equipped with a stir bar under N₂, add diphenylacetic acid (250 mg, 1.18 mmol) and anhydrous THF (5 mL). 2. Titration of n-BuLi Calculate the approximate amount of n-BuLi solution (in hexanes) needed to consume the diphenylacetic acid. Using a syringe, slowly adda solution of n-BuLi dropwise. The reaction mixture will turn temporarily yellow and back to a colorless solution with each drop. Continue adding the solution of n-BuLi dropwise until the reaction mixture continues to stay a deep yellow color. This will be the end point of the reaction. Repeat the titration 3x to obtain an average volume of the n-BuLi used. 3. Calculation of Molarity The moles of n-BuLi used in the titration are equivalent to the moles of diphenylacetic acid used in the reaction. Since the moles of diphenylacetic acid used is known, the calculation of concentration of n-BuLi is given by the following equation: mmol diphenylacetic acid/mL n-BuLi = molarity of n-BuLi solution. 4. Addition of n-BuLi to Benzaldehyde (Figure 2) To a flame-dried round bottom flask equipped with a stir bar under N₂, add anhydrous THF (30 mL) and benzaldehyde (3 mmol, 1 equiv.). Cool the solution to −78 °C. Add n-BuLi (1.1 equiv.) and let the reaction warm to room temperature. Add saturated NH₄Cl (aq., 10 mL) to quench the reaction and extract the aqueous layer with diethyl ether (2 x 25 mL). Wash the combined organic layers with water (2 x 15 mL) and brine (1 x 20 mL). Dry with Na₂SO₄, filter, and concentrate the combined organic layers under reduced pressure to afford the product. Figure 2. Addition of n -BuLi to benzaldehyde. Przejdź do... 0:00 Overview 1:06 Principles of n-Butyllithium 2:11 Titration of n-Butyllithium 3:23 Addition of n-Butyllithium to Benzaldehyde 4:58 Applications 6:33 Summary Filmy z tej kolekcji: Now Playing n-Butyllithium Titration Organic Chemistry II 47.3K Wyświetleń Cleaning Glassware Organic Chemistry II 121.9K Wyświetleń Nucleophilic Substitution Organic Chemistry II 98.5K Wyświetleń Reducing Agents Organic Chemistry II 42.5K Wyświetleń Grignard Reaction Organic Chemistry II 147.9K Wyświetleń Dean-Stark Trap Organic Chemistry II 97.5K Wyświetleń Ozonolysis of Alkenes Organic Chemistry II 66.3K Wyświetleń Organocatalysis Organic Chemistry II 16.5K Wyświetleń Palladium-Catalyzed Cross Coupling Organic Chemistry II 33.3K Wyświetleń Solid Phase Synthesis Organic Chemistry II 40.4K Wyświetleń Hydrogenation Organic Chemistry II 48.5K Wyświetleń Polymerization Organic Chemistry II 90.2K Wyświetleń Melting Point Organic Chemistry II 148.3K Wyświetleń Infrared Spectroscopy Organic Chemistry II 211.4K Wyświetleń Polarimeter Organic Chemistry II 98.2K Wyświetleń Prywatność Warunki Korzystania Zasady Skontaktuj Się z Nami Poleć Bibliotece BIULETYNY JoVE Badania JoVE Journal Methods Collections JoVE Encyclopedia of Experiments Archiwum Edukacja JoVE Core JoVE Business JoVE Science Education JoVE Lab Manual Centrum Zasobów Akademickich Strona Wydziału Autorzy Przegląd Proces Publikacji Rada Redakcyjna Zakres i Zasady Recenzja ekspercka FAQ Prześlij Bibliotekarze Przegląd Referencje Subskrypcje Dostęp Zasoby Biblioteczna Rada Doradcza FAQ O JoVE Przegląd Kierownictwo Blog JoVE Help Center JoVE Sitemap Copyright © 2025 MyJoVE Corporation. Wszelkie prawa zastrzeżone