n-Butyllithium Titration

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.

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

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 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 N-butyllithium, abbreviated n-BuLi, is an organolithium reagent that is frequently used as a strong base or as a nucleophile. N-butyllithium is commercially available as a solution in alkanes such as hexane or heptane. These solutions are stable when properly stored, but still degrade upon aging and exposure to water or oxygen. When using an n-butyllithium solution to prepare lithium di-isopropylamide, another type of strong base, it is essential that a precise amount is used in the reaction. For this reason, titration experiment Log in or to access full content. Learn more about your institution’s access to JoVE content here Explore More Videos 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 Privacy Terms of Use Policies Contact Us Recommend to library JoVE NEWSLETTERS Research JoVE Journal Methods Collections JoVE Encyclopedia of Experiments Archive Education JoVE Core JoVE Business JoVE Science Education JoVE Lab Manual Faculty Resource Center Faculty Site Authors Overview Publishing Process Editorial Board Scope and Policies Peer Review FAQ Submit Librarians Overview Testimonials Subscriptions Access Resources Library Advisory Board FAQ ABOUT JoVE Overview Leadership Blog Copyright © 2024 MyJoVE Corporation. All rights reserved