Q25E - Organic Chemistry (Mcmurry)

Question

Acid-catalyzed hydrolysis of a nitrile to give a carboxylic acid occurs by initial protonation of the nitrogen atom, followed by nucleophilic addition of water. Review the mechanism of base-catalyzed nitrile hydrolysis in Section 20-7 and then predict the products for each reaction below and write all of the steps involved in the acid-catalyzed  reaction, using curved arrows to represent electron flow in each step.

Step-by-Step Solution

Answer

The products  formed in each reaction and its steps of acid catalyzed reactions  are explained as follows

Step 1: Production prediction for (a)

At the initial step, 2,2-dimethylbutane nitrile can be protonated by HCl. The nucleophilic attack  of water on protonated nitrile yields the protonated aminoketone. In the Next step, the nucleophilic attack on carbonyl carbon gives yield of proton with protonated diol intermediate. This will eliminates ammonia and proton in upcoming steps. The product are ammonia and 2,2-dimethylbutanoic acid.

The mechanism of formation can be explained as follows,

Step 2: Production prediction for (b)

At the initial step, p-methyl benzonitrile is  protonated by HCl. The nucleophilic attack of water  on protonated nitrile  yields the protonated aminoketone. In the next step, the nucleophilic attack on carbonyl carbon will give yield of proton with protonated diol  as intermediate. This will eliminate ammonia and proton in upcoming steps. The products formed are ammonia and para-methyl benzoic acid.

The mechanism of its formation can be shown below  as,

Step 3: Production prediction for (c)

At the initial step, 2-methylbutane can be protonated by HCl. The  nucleophilic attack of water on protonated nitrile can yield the protonated aminoketone. In the Next step, the nucleophilic attack on carbonyl carbon   gives yield of proton with protonated diol  as intermediate. This will eliminates ammonia and proton in upcoming steps. The products formed  are ammonia and 2-methylbutanoic acid.

Step 4: Production prediction for (d)

At the initial step, cyclopentane nitrile can be protonated by HCl. The nucleophilic attack  of water on protonated nitrile yields the protonated aminoketone. In the Next step, the nucleophilic attack on carbonyl carbon gives the yield of proton with protonated amino diol as intermediate. This will eliminates ammonia and proton in upcoming steps. The product formed  are ammonia and cyclopentane carboxylic acid.

The mechanism of the product formation is shown below