Which of the following statements best describes the main purpose of the malonic ester synthesis in organic chemistry?

• A. It is used to prepare substituted ${\mathrm{acetic}}_{\mathrm{acid}}$ derivatives by alkylation and subsequent decarboxylation.
• B. It is a technique for reducing carboxylic acids to primary alcohols using ${\mathrm{LiAlH}}_4$.
• C. It is a method for converting alcohols into aldehydes using ${\mathrm{PCC}}_{}$ as an oxidizing agent.
• D. It is a process for synthesizing alkenes from alkyl halides via elimination reactions.

Answer: (A)

Verified step by step guidance

1. Understand that the malonic ester synthesis is a classical method in organic chemistry used to prepare substituted acetic acid derivatives.
2. Recognize that the process involves the alkylation of a malonic ester, which contains two ester groups adjacent to a methylene group, making the methylene hydrogens acidic and able to be deprotonated by a strong base.
3. After deprotonation, the resulting carbanion can undergo alkylation with an alkyl halide, introducing a substituent at the methylene position.
4. Following alkylation, the compound is subjected to hydrolysis and then decarboxylation, which removes one carboxyl group as carbon dioxide, yielding a substituted acetic acid.
5. Note that this method is distinct from reductions with LiAlH4, oxidations with PCC, or elimination reactions to form alkenes, which are different types of organic transformations.