Predict the products of the following reactions.
(a) phenol + acetic anhydride
(b) phenol + acetic formic anhydride
(c) aniline + phthalic anhydride

Verified step by step guidance

1. Step 1: Understand the reactivity of phenol in reaction (a). Phenol contains an -OH group, which is a nucleophile. Acetic anhydride is an electrophile that reacts with nucleophiles to form esters. The reaction involves the nucleophilic attack of the phenol's oxygen atom on one of the carbonyl carbons of acetic anhydride, leading to the formation of phenyl acetate and acetic acid as products.
2. Step 2: Analyze reaction (b) with phenol and acetic formic anhydride. Acetic formic anhydride is a mixed anhydride containing both acetic and formic acid components. Phenol will react similarly to reaction (a), where the -OH group attacks the carbonyl carbon of the acetic group, forming phenyl acetate and formic acid as products.
3. Step 3: Examine the reactivity of aniline in reaction (c). Aniline contains an -NH2 group, which is a nucleophile. Phthalic anhydride is a cyclic anhydride that reacts with nucleophiles. The -NH2 group of aniline will attack one of the carbonyl carbons of phthalic anhydride, leading to the formation of a phthalimide derivative as the product.
4. Step 4: Consider the mechanism for each reaction. For reactions (a) and (b), the mechanism involves nucleophilic acyl substitution, where the nucleophile (phenol) attacks the electrophilic carbonyl carbon, followed by the departure of a leaving group (acetate or formate). For reaction (c), the mechanism involves nucleophilic attack by the -NH2 group on the carbonyl carbon, followed by ring opening and subsequent stabilization to form the phthalimide derivative.
5. Step 5: Verify the products by considering the functional groups involved and the stability of the resulting compounds. For reactions (a) and (b), the ester products (phenyl acetate) are stable. For reaction (c), the phthalimide derivative is a stable cyclic compound due to resonance stabilization within the imide group.

Key Concepts

Acid-Base Reactions

Acid-base reactions are fundamental in organic chemistry, where an acid donates a proton (H+) and a base accepts it. In the context of the reactions involving phenol and anhydrides, phenol acts as a weak acid, and the anhydrides can act as electrophiles, facilitating the formation of esters through nucleophilic acyl substitution.

Nucleophilic Acyl Substitution

Nucleophilic acyl substitution is a key reaction mechanism in organic chemistry where a nucleophile attacks an electrophilic carbonyl carbon, leading to the substitution of a leaving group. In the reactions presented, phenol and aniline act as nucleophiles, attacking the carbonyl carbon of the anhydrides to form ester or amide products.

Reactivity of Anhydrides

Anhydrides are highly reactive compounds that can undergo various reactions, including acylation. They are more reactive than carboxylic acids due to the presence of two carbonyl groups, making them effective acylating agents. Understanding their reactivity is crucial for predicting the products of reactions with nucleophiles like phenol and aniline.