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 Application and Summary 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 Tags N ButyllithiumTitrationOrganolithium ReagentStrong BaseNucleophileAlkanesHexaneHeptaneDegradationAgingWater ExposureLithium Di isopropylamidePrecise AmountTitration ExperimentsChemical ReactionApplicationsBr nsted BaseLithium halogen Exchange ReactionsPolymerization InitiatorElastomersMolar ExcessReaction MixtureIncomplete ReactionSide ProductsDiphenylacetic Acid Skip to... ABOUT JoVE Copyright © 2024 MyJoVE Corporation. All rights reserved |
