Show how you would convert the following starting materials to the indicated nitriles:
(a) phenylacetic acid → phenylacetonitrile

검증된 단계별 안내

Identify the functional group in the starting material, phenylacetic acid. It contains a carboxylic acid group (-COOH) attached to a benzyl group (C6H5-CH2-). The goal is to replace the carboxylic acid group with a nitrile group (-CN).

Recall that carboxylic acids can be converted to nitriles through a two-step process: (1) conversion of the carboxylic acid to an amide intermediate, and (2) dehydration of the amide to form the nitrile.

In the first step, react phenylacetic acid with a reagent like thionyl chloride (SOCl2) to convert the carboxylic acid into an acid chloride (phenylacetyl chloride). This step activates the carboxylic acid for further reaction.

In the second step, react the acid chloride with ammonia (NH3) to form the corresponding amide, phenylacetamide. This occurs via nucleophilic substitution, where ammonia attacks the carbonyl carbon of the acid chloride.

Finally, dehydrate the amide using a dehydrating agent such as phosphorus pentoxide (P2O5) or thionyl chloride (SOCl2) to form phenylacetonitrile. This step removes water from the amide, resulting in the nitrile group (-CN).

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주요 개념

질문에 올바르게 답하기 위해 반드시 이해해야 하는 핵심 개념들은 다음과 같습니다.

Nitrile Synthesis

Nitriles are organic compounds containing a cyano group (-C≡N). One common method to synthesize nitriles is through the conversion of carboxylic acids or their derivatives. In this case, phenylacetic acid can be converted to phenylacetonitrile via a dehydration reaction, often using reagents like thionyl chloride or phosphorus pentoxide to facilitate the transformation.

Carboxylic Acid Derivatives

Carboxylic acids can be transformed into various derivatives, such as acid chlorides, esters, and amides, which can further react to form nitriles. Understanding these derivatives is crucial for predicting reaction pathways. For phenylacetic acid, converting it to an acid chloride is a key step before further reaction to yield the desired nitrile.

Reagents and Reaction Conditions

The choice of reagents and reaction conditions is vital in organic synthesis. For the conversion of phenylacetic acid to phenylacetonitrile, reagents like thionyl chloride (SOCl2) or phosphorus oxychloride (POCl3) are commonly used to create the acid chloride intermediate. The subsequent reaction with a suitable nucleophile, such as sodium cyanide, leads to the formation of the nitrile.

Show how you would convert the following starting materials to the indicated nitriles:(a) phenylacetic acid → phenylacetonitrile