Show how you would use an acid chloride as an intermediate to synthesize (b) phenyl propionate (CH3CH2COOPh) from propionic acid and phenol.

Verified step by step guidance

1. Identify the starting materials and the desired product: You are starting with propionic acid (CH3CH2COOH) and phenol (C6H5OH), and you want to synthesize phenyl propionate (CH3CH2COOPh).
2. Convert propionic acid to its acid chloride: React propionic acid with thionyl chloride (SOCl2) to form propionyl chloride (CH3CH2COCl). This reaction typically involves heating the acid with SOCl2 and then distilling off the excess SOCl2 and by-products like SO2 and HCl.
3. Prepare the phenol to react: Ensure that the phenol (C6H5OH) is in a form that can react with the acid chloride. This might involve having it in a solution, possibly with a base like pyridine to act as a catalyst and to absorb the HCl formed in the next step.
4. Perform the nucleophilic acyl substitution: React the propionyl chloride with the phenol. The oxygen of the phenol will attack the carbonyl carbon of the propionyl chloride, leading to the formation of phenyl propionate and the release of HCl.
5. Purify the product: Use techniques such as extraction, washing, and recrystallization to purify the phenyl propionate. Verify the structure and purity of the product using methods like NMR or IR spectroscopy.

Key Concepts

Acid Chlorides

Acid chlorides, also known as acyl chlorides, are derivatives of carboxylic acids where the hydroxyl group is replaced by a chlorine atom. They are highly reactive compounds that can be used as intermediates in organic synthesis, particularly in the formation of esters and amides. Their reactivity allows them to easily react with alcohols or phenols to form esters, making them valuable in synthetic pathways.

Esterification Reaction

Esterification is a chemical reaction that forms an ester from an alcohol and a carboxylic acid, typically in the presence of an acid catalyst. In this context, the reaction between an acid chloride and phenol leads to the formation of an ester, specifically phenyl propionate. This reaction is characterized by the nucleophilic attack of the alcohol on the carbonyl carbon of the acid chloride, resulting in the release of hydrochloric acid.

Nucleophilic Acyl Substitution

Nucleophilic acyl substitution is a fundamental reaction mechanism in organic chemistry where a nucleophile attacks the electrophilic carbon of a carbonyl group, leading to the substitution of a leaving group. In the case of acid chlorides, the chlorine atom acts as a good leaving group, facilitating the formation of new carbon-oxygen bonds. This mechanism is crucial for understanding how acid chlorides can be transformed into esters, such as phenyl propionate, through the reaction with nucleophiles like phenol.