Show how you would use anhydrides to synthesize the following compounds. In each case, explain why an anhydride might be preferable to an acid chloride.
(c) phthalic acid monoamide 
(d) succinic acid monomethyl ester

Verified step by step guidance

1. Step 1: Understand the reactivity of anhydrides compared to acid chlorides. Anhydrides are less reactive than acid chlorides, making them easier to control in reactions. They also avoid the generation of HCl as a byproduct, which can be corrosive and require neutralization.
2. Step 2: For (c) phthalic acid monoamide, start with phthalic anhydride. React phthalic anhydride with one equivalent of ammonia (NH₃). The nucleophilic attack of ammonia on one of the carbonyl groups of the anhydride will result in the formation of phthalic acid monoamide and a carboxylic acid group.
3. Step 3: For (d) succinic acid monomethyl ester, begin with succinic anhydride. React succinic anhydride with one equivalent of methanol (CH₃OH). Methanol will act as a nucleophile, attacking one of the carbonyl groups of the anhydride to form the monomethyl ester and a carboxylic acid group.
4. Step 4: Explain why anhydrides are preferable to acid chlorides in these syntheses. Acid chlorides are highly reactive and can lead to overreaction or side products. Anhydrides provide better control over the reaction, especially when forming mono-substituted products like monoamides or monomethyl esters.
5. Step 5: Highlight the importance of stoichiometry in these reactions. Using one equivalent of the nucleophile (ammonia or methanol) ensures that only one carbonyl group of the anhydride reacts, leaving the other as a carboxylic acid group in the final product.

Key Concepts

Anhydrides in Organic Synthesis

Anhydrides are reactive compounds derived from acids by the removal of water. They are commonly used in organic synthesis due to their ability to acylate nucleophiles, forming new carbon-carbon or carbon-heteroatom bonds. Their reactivity allows for the formation of various functional groups, making them versatile intermediates in the synthesis of complex molecules.

Comparison with Acid Chlorides

Acid chlorides are another class of reactive acylating agents, but they can be more reactive and less selective than anhydrides. While both can be used to synthesize amides and esters, anhydrides are often preferred for their milder reactivity, which can lead to fewer side reactions and better yields in certain reactions, especially when sensitive functional groups are present.

Synthesis of Phthalic Acid Monoamide and Succinic Acid Monomethyl Ester

The synthesis of phthalic acid monoamide and succinic acid monomethyl ester using anhydrides involves nucleophilic attack by amines and alcohols, respectively, on the anhydride. This process allows for the selective formation of the desired products while minimizing by-products. Understanding the specific reactivity of anhydrides in these reactions is crucial for optimizing yields and ensuring the correct functionalization of the target compounds.