Show how you would accomplish the following syntheses. Some of these conversions may require more than one step.
(b) 3-ethylpentanoic acid → 3-ethylpentanenitrile

Verified step by step guidance

1. Step 1: Begin by identifying the functional group transformation required. In this case, you need to convert a carboxylic acid (-COOH) group in 3-ethylpentanoic acid to a nitrile (-CN) group in 3-ethylpentanenitrile.
2. Step 2: Recognize that carboxylic acids can be converted to nitriles through an intermediate step involving the formation of an amide. First, react 3-ethylpentanoic acid with ammonia (NH₃) to form 3-ethylpentanamide. This reaction typically requires heating and may use a dehydrating agent.
3. Step 3: Once the amide is formed, dehydrate the amide to form the nitrile. This can be accomplished using a dehydrating agent such as phosphorus pentoxide (P₂O₅) or thionyl chloride (SOCl₂). The dehydration reaction removes water and converts the amide (-CONH₂) to the nitrile (-CN).
4. Step 4: Ensure proper reaction conditions, such as temperature and solvent, to optimize the yield of 3-ethylpentanenitrile. For example, the dehydration step may require heating under reflux.
5. Step 5: Verify the product by analyzing its structure using techniques such as infrared spectroscopy (IR) to confirm the presence of the nitrile group (sharp peak around 2200 cm⁻¹) and ensure the conversion is complete.

Key Concepts

Functional Groups

Understanding functional groups is essential in organic chemistry as they determine the chemical reactivity and properties of molecules. In this synthesis, we are converting a carboxylic acid (3-ethylpentanoic acid) into a nitrile (3-ethylpentanenitrile), which involves recognizing the functional groups involved and their transformations.

Nucleophilic Substitution Reactions

Nucleophilic substitution reactions are key mechanisms in organic synthesis where a nucleophile replaces a leaving group in a molecule. In this case, converting the carboxylic acid to a nitrile may involve a nucleophilic substitution step, where a suitable reagent can facilitate the transformation by replacing the -OH group of the acid.

Reagents and Reaction Conditions

Different reagents and reaction conditions are crucial for achieving specific transformations in organic synthesis. For the conversion of 3-ethylpentanoic acid to 3-ethylpentanenitrile, one might use reagents like thionyl chloride (SOCl2) to convert the acid to an acid chloride, followed by reaction with a nitrile source, highlighting the importance of selecting appropriate reagents.