Carboxylic Acids - Carboxyl / Alfa Chemistry

Introduction

Carboxylic acids, characterized by a carboxy group, have the general formula RCOOH (where R is a carbon group or a hydrogen atom), with a carbon atom double bonded to an oxygen atom and single bonded to a hydroxyl group (Fig. 1). Apart from their vital role in biological metabolism, carboxylic acids serve as significant chemical raw materials and intermediates in organic synthesis. Alfa Chemistry, a leading chemical supplier, offers a diverse range of carboxylic acids from grams to kilograms, catering to various applications.

Fig. 1 Structure of carboxylic acid.

Classification of Carboxylic Acids

Except formic acid, carboxylic acids are composed of an alkyl group and a carboxyl group. Carboxylic acids can be classified according to the structure of the alkyl group and the number of carboxyl groups contained in the molecule, as described below.

According to the structure of the alkyl group, carboxylic acids can be divided into aliphatic acids and aromatic acids. Aliphatic acids have an alkyl group bonded to the carboxyl group, which can be further divided into saturated acids and unsaturated acids according to the degree of unsaturation of the alkyl group. Aromatic acids are carboxylic acids with at least one aromatic ring.

Fig. 2 Structures of aliphatic acids and aromatic acids.

According to the number of carboxyl groups contained in their molecules, carboxylic acids can be classified into monocarboxylic acids, dicarboxylic acids and polycarboxylic acids. Carboxylic acids containing one carboxyl group are referred to as monocarboxylic acids, and those that have two carboxyl groups are referred to as dicarboxylic acids. Those containing more than two carboxyl groups are collectively known as polycarboxylic acids.

Representative Reactions

Carboxylic acids participate in a variety of reactions, and the representative reactions include reduction, esterification, and decarboxylation.

Reduction: Reduction reactions of carboxylic acids usually involve the reduction of carboxylic groups (-COOH) to other functional groups, such as alcohols and aldehydes. They can be carried out in a variety of ways, including the use of strong reducing agents such as lithium aluminum hydride, sodium metal or borane. These reactions provide an efficient way to convert carboxylic acids into other functional groups.
Esterification: Another important reaction of carboxylic acids is esterification, where a carboxylic acid reacts with an alcohol in the presence of an acid catalyst to form an ester and water. This reaction is widely used in the synthesis of fragrances, flavorings, and plasticizers.
Decarboxylation: Decarboxylation is a reaction where a carboxylic acid loses a carbon dioxide molecule to form a lower carboxylic acid or an alkane. This reaction is often observed in the biosynthesis of fatty acids and the metabolism of certain organic acids in living organisms.

Applications

Carboxylic acids find numerous applications across different industries, including pharmaceuticals, food, and cosmetics.

In the pharmaceutical industry, carboxylic acids are used as active pharmaceutical ingredients (APIs) in drugs targeting various diseases. For example, ibuprofen, a nonsteroidal anti-inflammatory drug (NSAID), contains a carboxylic acid functional group that is essential for its pharmacological activity.

In the food industry, carboxylic acids are used as preservatives, flavor enhancers, and acidulants. Citric acid, for instance, is widely used as a flavoring agent and acidulant in soft drinks and confectionery products. Lactic acid is used as a preservative and flavoring agent in dairy products and pickled vegetables.

In cosmetics, carboxylic acids such as alpha hydroxy acids (AHAs) are used in skincare products for their exfoliating and anti-aging properties. Glycolic acid, derived from sugar cane, is a popular AHA used in chemical peels and anti-aging creams.

Alfa Chemistry provides various carboxylic acids to our customers from grams to kilograms. We can also customize synthesis according to customers' requirements. Please feel free to contact us for more information.