Carboxylic acids and esters are distinct classes of organic compounds, differing primarily in their functional groups and chemical properties.

Carboxylic acids are characterized by the presence of a carboxyl group, denoted as $-\text{COOH}$, which is attached to a hydrocarbon chain. This functional group imparts acidic properties to carboxylic acids, allowing them to donate a proton (H$^+$) and form a carboxylate ion. Due to the ability to form hydrogen bonds between molecules, carboxylic acids exhibit high solubility in water and possess elevated boiling points. Their polar nature enhances their interaction with water molecules, facilitating solubility.

In contrast, esters contain an ester group, represented as $-\text{COO}-$, bonded to a hydrocarbon chain. Esters are typically synthesized through the reaction of a carboxylic acid with an alcohol, often in the presence of an acid catalyst. Unlike carboxylic acids, esters are less acidic and do not generate carboxylate ions. Consequently, they tend to be less soluble in water and have lower boiling points than their carboxylic acid counterparts. While esters can also form intermolecular hydrogen bonds with water, these interactions are weaker compared to those of carboxylic acids.

The differences between carboxylic acids and esters extend to their applications in industry and daily life. Carboxylic acids are essential in the manufacturing of plastics, detergents, and pharmaceuticals. They are also prevalent in various foods, such as vinegar and citrus fruits. On the other hand, esters are widely used as solvents, fragrances, and flavorings in the food and cosmetic industries, contributing to the distinctive aromas and tastes of many fruits and flowers.