Quiz - Carboxylic Acid Derivatives - 1 | Carboxylic Acid Derivatives - Acid Halides, Esters

The correct IUPAC name for CH₃COCl is acetyl chloride. This compound is an acid chloride derivative of acetic acid, where the OH is replaced by a Cl. Acyl chlorides are named by replacing the 'ic acid' suffix with 'yl chloride'.

Carboxylic acid derivatives commonly have the ability to form hydrogen bonds due to the polar carbonyl group which increases their boiling points and, for lower molecular weight derivatives, makes them soluble in water.

Acid chlorides are more reactive than esters in nucleophilic acyl substitution reactions because the chlorine atom is a better leaving group than an alkoxide ion. The electron-withdrawing effect of the chlorine also makes the carbonyl carbon more susceptible to nucleophilic attack.

The reactivity of carboxylic acid derivatives towards nucleophilic acyl substitution is influenced by the ability of the leaving group to leave, electron-donating or withdrawing groups near the acyl carbon, and steric hindrance. Solubility in polar solvents does not directly affect the inherent reactivity of the derivative.

A common method for preparing acid halides from carboxylic acids is treatment with a strong halogenating agent like thionyl chloride (SOCl₂). This reaction replaces the hydroxyl group of the carboxylic acid with a chlorine atom to form the acid chloride.

Acid halides typically undergo nucleophilic acyl substitution with water to form carboxylic acids. The chlorine atom in the acid halide serves as a good leaving group, making the carbonyl carbon susceptible to nucleophilic attack by water.

Carboxylic acids are commonly converted into esters via esterification, which involves reacting the carboxylic acid with an alcohol in the presence of an acid catalyst such as sulfuric acid or hydrochloric acid. The acid catalyst helps to protonate the carbonyl oxygen, increasing the electrophilicity of the carbonyl carbon.

The base-catalyzed hydrolysis of an ester, also known as saponification, results in the formation of a carboxylate salt and an alcohol. The ester carbonyl carbon is attacked by a hydroxide ion, leading to the cleavage of the ester bond and formation of the carboxylate salt. After the reaction is complete, the carboxylate ion is usually protonated in the presence of an acid to form the desired carboxylic acid.

A common pathway for converting an ester into an amide is the treatment with ammonia or an ammonia derivative. This involves nucleophilic acyl substitution where the ester oxygen is replaced by a nitrogen atom from the amine, forming an amide.

In the mechanism for nucleophilic acyl substitution in carboxylic acid derivatives, a distinctive feature is that the acyl carbon undergoes sp³ hybridization during the rate-determining step as the nucleophile attacks and forms a tetrahedral intermediate. This is followed by the expulsion of the leaving group and reformation of the double bond, returning the carbon to sp² hybridization.