Preparation Of N-Diethyl-M-Toluamide Lab Report

Preparation of N,N-Diethyl-m-toluamide (DEET) and its Identification by IR and NMR Spectroscopy

Eim A. Chemist
CHEM 304
July 10, 2005

INTRODUCTION

N,N-Diethyl-m-toluamide (DEET) is the active ingredient in many insect repellants.1 In this experiment, DEET will be prepared from m-toluic acid through the intermediate acid chloride and then identified by its IR and proton NMR spectra. The overall reaction is a series of two acyl substitutions and is shown in Scheme 1 below:

[pic]

Scheme 1

Carboxylic acids can be converted to acid chlorides by treatment with a compound such as phosphorus trichloride (PCl3) or thionyl chloride (SOCl2).2 The reactive acid chloride can then be treated with a primary or secondary amine to
The 10-mL reaction flask was charged with 0.275 g of m-toluic acid (0.0020 mol) and 0.30 mL of thionyl chloride (0.492 g, 0.0041 mol). The condenser water was started, and the mixture was gently heated with stirring on an aluminum block (block temp ~ 90 oC) until boiling started. The reaction mixture was then gently boiled for about 15 minutes. After the boiling period was finished, the reaction mixture was cooled to room temperature. 4.0 mL of anhydrous ether were added, and the mixture was stirred at room temperature until a homogeneous mixture was obtained. To this solution was added (dropwise over a 15 minute period) a solution of 0.66 mL of cold (0 oC) diethylamine (0.462 g, 0.0063 mol) in 1.33 mL of anhydrous ether. During the addition, a thick white cloud of diethylamine hydrochloride was formed. After complete addition, the reaction mixture was stirred at room temperature for about 10 minutes. 10% aqueous sodium hydroxide (2 mL) was then added, and the reaction mixture was stirred for an additional 15 minutes at room temperature, then poured into a separatory funnel and allowed to separate. The aqueous layer was discarded, and the organic layer was washed with an additional portion of 10% aqueous sodium hydroxide (2 mL), followed by a portion of 10% hydrochloric acid (2 mL). The organic layer was washed with water (2 mL), dried (Na2SO4) and evaporated to yield crude N,N-diethyl-m-toluamide as dark brown
There were no spills or other abnormal physical losses, so it is doubtful that this procedure can be improved much further without a significant amount of effort.

SUMMARY AND CONCLUSIONS

In this experiment, it was shown that N,N-diethyl-m-toluamide (DEET) could be produced from m-toluic acid by treatment with thionyl chloride followed by reaction of the intermediate acid chloride with diethylamine in an overall yield of 88.1%. That the product synthesized was, in fact, N,N-diethyl-m-toluamide was demonstrated by its IR and 1H-NMR spectra.

REFERENCES

1. Pavia, D. L.; Lampman, G. M.; Kriz, G. S.; Engel, R. G. Introduction to Organic Laboratory Techniques, A Microscale Approach; 3rd ed.; Brooks/Cole: Pacific Grove, CA, 1999; p. 373.
2. Bruice, P. L. Organic Chemistry; 4th ed.; Prentice Hall: Upper Saddle River, NJ, 2004; p.