Question

\(N, N\)-Diethyl-m-toluamide (DEET) is the active ingredient in several common insect repellents. Propose a synthesis for DEET from 3 -methylbenzoic acid. CCCCNC(=O)c1cccc(C)c1

Short answer

Question: Outline the steps for synthesizing DEET from 3-methylbenzoic acid. Answer: The synthesis of DEET from 3-methylbenzoic acid involves the following steps: 1. Convert the carboxylic acid into the corresponding acid chloride (3-methylbenzoyl chloride) using thionyl chloride and pyridine. 2. Prepare diethylamine from ethylamine and ethyl bromide via an SN2 reaction. 3. Perform an amide coupling reaction between the acid chloride and the diethylamine to form the desired product, DEET.

Step-by-step solution

Identify the functional groups in starting material and target molecule

In the starting material, 3-methylbenzoic acid, we have a carboxylic acid functional group. In the target molecule, DEET, we have an amide functional group. Our main goal is to transform the carboxylic acid into an amide.

Formation of an acid chloride

To form the amide, we can first convert the carboxylic acid into an acid chloride. This can be done by treating the starting material, 3-methylbenzoic acid, with thionyl chloride (SOCl2) and a base such as pyridine. The reaction produces the corresponding acid chloride, 3-methylbenzoyl chloride. \[ \ce{3-MethylbenzoicAcid + SOCl2 -> 3-MethylbenzoylChloride + SO2 + HCl} \]

Preparation of the amine#for_amide_formation

Our target molecule, DEET, contains a diethylamide group. To form the amide, we need an amine for the amide coupling reaction. The appropriate amine is diethylamine (Et2NH), which can be synthesized from ethylamine and ethyl bromide by an SN2 reaction. \[ \ce{EtNH2 + EtBr -> Et2NH + Br-} \]

Amide coupling reaction

Now that we have our acid chloride (3-methylbenzoyl chloride) and the required amine (diethylamine), we can perform the amide coupling reaction by mixing them together in the presence of a base. This reaction forms the amide bond, giving us the final product - DEET. \[ \ce{3-MethylbenzoylChloride + Et2NH -> DEET + HCl} \] In summary, the synthesis of DEET from 3-methylbenzoic acid involves the following steps: 1. Convert the carboxylic acid into the corresponding acid chloride (3-methylbenzoyl chloride) using thionyl chloride and pyridine. 2. Prepare diethylamine from ethylamine and ethyl bromide via an SN2 reaction. 3. Perform an amide coupling reaction between the acid chloride and the diethylamine to form the desired product, DEET.