Saturated fatty acids nomenclature used

A useful convention is to denote fatty acids by the number of carbon atoms and the number of C=C bonds. For example, lauric acid, which has 12 carbon atoms and no C=C bonds, is C12 0. This nomenclature does not specify the position of the C=C bonds, nor whether they are cis or trans. All fats are mixtures of triglycerides (and hence contain a number of different fatty acid residues). The approximate fatty acid composition of some fats is shown in Table 3.4. Butterfat contains a much wider range of fatty acids than the vegetable fats. Coconut oil contains very high levels of saturated fatty acids, particularly lauric acid. 

Methyl esters of saturated fatty acids show one stable crystal form. It was originally termed but according to the nomenclature used here it is a )8 -form. The crystal structure of this form in methyl stearate (Aleby and von Sydow, 1960) is shown in Fig. 8.36. Although the forces between the polar groups must be very weak in an ester the molecules are arranged head-to-head in bilayers. The chain packing is the... 

An overview of important fatty acids with an even number of carbon atoms in the molecule is given in Table 3.1. Besides the systematic names derived from the corresponding hydrocarbons, trivial names are also given, and these are used predominately in routine practice, especially in the nomenclature of common fatty acids. In the Hterature, for brevity, various short designations predominate, such as an N M ratio, where N is the number of carbon atoms in the molecule and M the number of double bonds. The most abundant saturated fatty acids in animal and plant tissues... 

The aliphatic chain is referred to as saturated because all carbon atoms are linked to four other atoms (sp carbons in organic chemistry). When a carbon atom is linked to only three other atoms, one of the chemical bond has to be a double bond to respect the valency of 4, which is characteristic of carbon. In this case, the double bond links two carbons and it is noted C=C. The nomenclature used for saturated fatty acids refers to the number of carbon atoms, and to the lack of double bonds correspondingly, palmitic add, which is the saturated fatty acid with 16 carbons, is noted C16 0 (C16 for the carbon number, 0 for the number of double bond). You can train yourself to write the structure of the following fatty acids C9 0, C14 0, and C18 0. A list of biologically saturated fatty acids can be found in Table 1.2. Note that only the limited piece of information found in the first column is useful to draw the chemical structure of all these lipids. 

The most frequently used systematic nomenclature names the fatty acid after the hydrocarbon with the same number and arrangement of carbon atoms, with -oic being substituted for the final -e (Genevan system). Thus, saturated acids end in -anoic, eg, octanoic acid, and unsaturated acids with double bonds end in -enoic, eg, octadecenoic acid (oleic acid). 

Aliphatic framework molecules most common in organic acids include alkanes (saturated hydrocarbons) and alkenes (unsaturated hydrocarbons). These saturated and unsaturated aliphatic carboxylic acids may be acyclic (straight or branched chains) or alicyclic (aliphatic rings). Acyclic aliphatic monocarboxylic acids are also referred to as fatty acids (Table 1). The first five saturated acids (formic to valeric) of this type are sometimes referred to as short-chain, low-molecular-weight, or volatile fatty acids. Although a nomenclature for these acids has been established by the International Union of Pure and Applied Chemistry (lUPAC), the convention of using the trivial names for the first five saturated acids has remained. Similarly, trivial names are used for the aliphatic dicarboxylic acids (Table 2) that are saturated with two to four carbon atoms (C2-C4) and unsaturated with four carbon atoms (C4). Alicyclic carboxylic acids contain one or more saturated or partially unsaturated rings. These acids most commonly occur... 

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