Carboxylic Acids, Esters, Amines, and Amides: Structure, Properties, and Nomenclature

Study Guide - Smart Notes

Tailored notes based on your materials, expanded with key definitions, examples, and context.

Carboxylic Acids

Structure and Functional Groups

Carboxylic acids are organic compounds containing a carboxyl group (–COOH), which is composed of a carbonyl group (C=O) and a hydroxyl group (–OH) attached to the same carbon atom. This functional group is responsible for the characteristic properties of carboxylic acids.

Carboxyl group: The combination of a carbonyl and a hydroxyl group on the same carbon atom.
General formula: R–COOH, where R is a hydrocarbon group.

Structure of carboxyl group showing carbonyl and hydroxyl groups

Nomenclature of Carboxylic Acids

Carboxylic acids are named by replacing the -e ending of the parent alkane with -oic acid in IUPAC nomenclature. The carboxyl carbon is always carbon 1.

For aromatic carboxylic acids, such as benzoic acid, substituents are indicated by prefixes (ortho-, meta-, para-) or by numbering the ring.
Examples: Methanoic acid (formic acid), Ethanoic acid (acetic acid), Benzoic acid.

Examples of benzoic acid derivatives with substituents

Carboxylic Acids in Everyday Life

Carboxylic acids and their salts are widely used as preservatives and flavor enhancers in food products, such as soups and instant noodles.

Sodium propionate is a common preservative in bakery items.

Packaged foods containing carboxylate salts as preservatives

Physical Properties of Carboxylic Acids

Carboxylic acids are strongly polar due to the presence of both a carbonyl and a hydroxyl group, which allows them to form hydrogen bonds.

They have higher boiling points than similar alcohols, aldehydes, and ketones.
Carboxylic acids with 1–5 carbon atoms are very soluble in water due to hydrogen bonding.
Solubility decreases as the hydrocarbon chain length increases.

Polarity of carboxylic acids due to two polar groups Hydrogen bonding between acetic acid and water molecules

Acidity of Carboxylic Acids

Carboxylic acids are weak acids that partially dissociate in water to produce carboxylate ions and hydronium ions.

The negative charge on the carboxylate ion is stabilized by resonance between the two oxygen atoms.
General dissociation equation:

Dissociation of ethanoic acid in water

Esters

Structure and Synthesis of Esters

Esters are organic compounds derived from carboxylic acids and alcohols. They are characterized by the functional group –COOR.

Esters are commonly found in fats, oils, and as components responsible for the aroma and flavor of many fruits.
They are synthesized via esterification, a reaction between a carboxylic acid and an alcohol in the presence of an acid catalyst and heat.
This reaction is an equilibrium process:

Willow tree, source of salicin, a precursor to aspirin Esterification: conversion of acetic acid to methyl acetate

Naming Esters

The name of an ester consists of two parts:

The alkyl group from the alcohol (first word).
The carboxylate name from the acid (second word, replacing -ic acid with -ate).

Example: Methyl ethanoate (from methanol and ethanoic acid).

Esters in Nature and Industry

Many esters are responsible for the pleasant aromas and flavors of fruits and flowers. Small esters are volatile and soluble in water, making them detectable by smell and taste.

Esters are also used as solvents in products like nail polish remover (ethyl acetate).

Fruits containing esters responsible for aroma and flavor Grapes containing esters responsible for their odor Ethyl acetate as a solvent in nail polish

Amines

Structure and Classification of Amines

Amines are derivatives of ammonia (NH3) in which one or more hydrogen atoms are replaced by alkyl or aromatic groups.

Primary (1°) amine: One carbon group attached to nitrogen.
Secondary (2°) amine: Two carbon groups attached to nitrogen.
Tertiary (3°) amine: Three carbon groups attached to nitrogen.

Naming Amines

The -e ending of the parent alkane is replaced with -amine.
For amines with substituents on nitrogen, the prefix N- is used for each alkyl group attached to the nitrogen atom.

Properties of Amines

Amines contain polar N–H bonds, allowing primary and secondary amines to form hydrogen bonds with each other and with water. Tertiary amines can only form hydrogen bonds with water.

Hydrogen bonds in amines are weaker than those in alcohols due to the lower electronegativity of nitrogen compared to oxygen.

Hydrogen bonding in primary, secondary, and tertiary amines

Amides

Structure and Preparation of Amides

Amides are derivatives of carboxylic acids in which the hydroxyl group is replaced by an amino group (–NH2, –NHR, or –NR2).

Amides are produced by the reaction of a carboxylic acid with ammonia or a primary/secondary amine, releasing water (amidation or condensation reaction).

Naming Amides

Replace -oic acid (IUPAC) or -ic acid (common) with -amide.
Alkyl groups attached to the nitrogen are named with the prefix N- followed by the alkyl name.
Example: N,N-Dimethylbutanamide (from butanoic acid and dimethylamine).

Structure and naming of N,N-dimethylbutanamide

Applications of Amides

Amides are found in many pharmaceuticals, such as acetaminophen (Tylenol), which acts as a pain and fever reducer. Products containing amides such as acetaminophen *Additional info: The notes above include expanded academic context and examples to ensure completeness and clarity for exam preparation.*