Aliphatic carboxylic acids include a very wide range of chemicals that perform a diverse range of industrial functions. Many occur naturally and serve an important function in nutrition, and others are intermediates in normal biochemical processes. This chapter is limited to a discussion of the saturated aliphatic mono‐ and polycarboxylic acids. Because of the wide range of uses, the differing circumstances of isolation and often the complexity of structure, many organic acids are described by a variety of names. In this chapter, the names used in the text are usually the trivial or most common names; alternative names are given for reference. A current systematic or Chemical Abstracts acid name is given in the tables that describe physicochemical properties. The commercial and industrial importance of this class of compounds is indicated by recent production figures: formic acid has a production volume in excess of 1 billion lb/year, acetic acid has a production volume in the region of 3.3 billion lb/year, acrylic acid in excess of 1 billion lb/year, and propionic acid on the order of 100 million lb/year. Esters and salts of organic acids are also produced in large volumes. In general, serious physiological concerns for humans do not arise from the acids discussed in this chapter. Occasionally, concerns have been reported for individual acids, but usually with very high experimental or accidental exposures. The low level of concern associated with most of these acids is attested to by many members of this class that are used as food additives, flavoring agents, and stabilizers, or as food materials. The primary adverse effect of exposure to aliphatic carboxylic acids is usually acute arising from their primary irritant effects on skin, eyes, and mucous membranes, particularly of the short‐chain acids. As the molecular weight increases and the water solubility decreases, the irritating capacity of a carboxylic acid generally decreases. In addition, skin sensitization is quite rare with the aliphatic carboxylic acids.

The alkenoic series of carboxylic acids are obtained from such natural sources as animal tallows and greases, and vegetable, coconut, palm, and marine oils. Several have also been produced synthetically from petroleum sources. They are frequently referred to as fatty acids (C 6 –C 24 ) and have important commercial applications in plastics, coating materials, fungicides, food preservatives, lubricants, and perfumes. They have been used as softening agents for rubber and as pharmaceuticals in medicine and dentistry. Acids of this type are unstable and polymerize readily, hence offering important chemical and physical properties for use in producing esters, acid halides, acid amides, and acid anhydrides. As a class, the unsaturated carboxylic acids have been subjected to an extensive battery of studies, including acute, short‐term, and chronic toxicity and carcinogenicity tests and reproductive and developmental toxicity and genotoxicity tests. Overall, these acids have a low level of mammalian toxicity, although they are strong skin and eye irritants in animal tests and are irritating to mucosal membranes in humans. For those acids for which adequate studies have been conducted, there is no evidence that they are reproductive or developmental toxicants or carcinogens. Mutagenicity and clastogenicity studies suggest that this group of acids is devoid of genotoxic activity. The biochemistry of many of these acids can be found in general textbooks. Rapid metabolism to other fatty acids may explain their general low degree of toxicity. The physical properties and acute toxicity of saturated monocarboxylic acids are provided. Dietary trans fatty acids are associated with increased risk of cardiovascular disease and have been implicated in the incidence of obesity and type 2 diabetes mellitus. Trans fatty acids from industrial sources (i.e., partially hydrogenated vegetable oil) have been associated with several chronic human diseases, especially coronary heart disease.