Propose a mechanism for the reaction of benzyl alcohol with acetyl chloride to give benzyl acetate.

Verified step by step guidance

1. Step 1: Identify the reactants and the product. Benzyl alcohol (C6H5CH2OH) reacts with acetyl chloride (CH3COCl) to form benzyl acetate (C6H5CH2OCOCH3). This is an esterification reaction where the hydroxyl group (-OH) of benzyl alcohol is replaced by an acetyl group (-COCH3).
2. Step 2: Recognize the role of acetyl chloride as an acylating agent. Acetyl chloride is highly reactive due to the presence of the carbonyl group (C=O) and the chlorine atom, which makes the carbonyl carbon electrophilic and susceptible to nucleophilic attack.
3. Step 3: Mechanism initiation: The lone pair of electrons on the oxygen atom of benzyl alcohol attacks the electrophilic carbonyl carbon of acetyl chloride. This forms a tetrahedral intermediate, and the chlorine atom is still attached to the carbonyl carbon.
4. Step 4: Collapse of the tetrahedral intermediate: The intermediate collapses, expelling the chloride ion (Cl⁻) as a leaving group. This results in the formation of the ester bond between the benzyl alcohol and the acetyl group.
5. Step 5: Final step: The chloride ion (Cl⁻) may react with a proton (H⁺) from the reaction medium to form HCl as a byproduct. The final product is benzyl acetate (C6H5CH2OCOCH3), an ester.

Key Concepts

Nucleophilic Acyl Substitution

Nucleophilic acyl substitution is a fundamental reaction mechanism in organic chemistry where a nucleophile attacks an electrophilic carbonyl carbon, leading to the substitution of a leaving group. In this case, benzyl alcohol acts as the nucleophile, attacking the carbonyl carbon of acetyl chloride, which is a reactive acyl chloride. This mechanism is crucial for understanding how esters, like benzyl acetate, are formed from alcohols and acyl chlorides.

Role of Leaving Groups

In organic reactions, leaving groups are atoms or groups that can depart with a pair of electrons, facilitating the formation of new bonds. In the reaction between benzyl alcohol and acetyl chloride, the chloride ion (Cl-) is the leaving group. A good leaving group is essential for the reaction to proceed efficiently, as it stabilizes the transition state and allows the nucleophile to bond with the electrophile.

Formation of Esters

The formation of esters is a key reaction in organic chemistry, typically involving the reaction of an alcohol with a carboxylic acid or an acyl chloride. In this case, benzyl alcohol reacts with acetyl chloride to produce benzyl acetate. This reaction is significant in both synthetic organic chemistry and industrial applications, as esters are widely used in fragrances, flavorings, and as solvents.