Fatty shorthand designation

A shorthand designation for fatty acids is used. For example, 18 0 = saturated C g 18 1 = acid with one double bond 18 2 = Cjg acid with two... 

Table 11.1 Systematic and common names of saturated fatty acids together with the shorthand designation and typical occurrence (compiled from Gunstone et al., 1994 Hilditch and Williams, 1964 Perkins, 1993 Robinson, 1982). The shorthand designation denotes Cx n where x is the number of carbon atoms and n is the number of double bonds.

There are two general systems of nomenclature for fatty acids, as well as a few useful shorthand designations. Common names have their origins in history and are frequently used. Several examples are provided in table 18.1. Systematic names derive from the number of carbon atoms in the fatty acid for example, lauric acid is systematically known as dodecanoic acid. The parent hydrocarbon dodecane has 12 carbon atoms as does lauric acid. Several other examples are provided in table 18.1. 

We will use a shorthand designation for fatty acids, i.e., 18 0, stearic acid 18 1, oleic acid etc. The first figure is the number of carbons, the second the number of double bonds. To locate the fatty acids in acyl-glycerols, stereospecific numbering (sn) will be employed. If a glycerol molecule is drawn with the secondary hydroxyl to the left, the hydroxyl above is sn-1 and that below is sn-3. 

To describe the composition of fatty acids it is sometimes useful to use a shorthand designation. In this convention the composition of a fatty acid can be described by two numbers separated by a colon. The first number indicates the number of carbon atoms in the fatty acid chain, the second number indicates the number of double bonds. Thus, 4 0 is short for butyric acid, 16 0 for palmitic acid, 18 1 for oleic acid, etc. The two numbers provide a complete description of a saturated fatty acid. For unsaturated fatty acids, information about the location of double bonds and their stereo isomers can be given as follows oleic acid (the cis isomer) is 18 lc9 elaidic acid (the... 

The following shorthand designation may be used to describe the chemical structure of fatty acids the number of carbon atoms in the chain separated by a colon from the number of unsaturated bonds is followed by a set of parentheses containing the numbers of the double-bond positions and the letters c, t, or a to indicate whether a bond is cis-olefinic, trans-olefinic, or acetylenic. The position of double bonds is numbered from the carboxyl group. 

Glycerol, as a trihydroxylic alcohol, can form triesters with one, two or three different fatty acids. In the first case a triester is formed with three of the same acyl residues (e. g. tripalmitin P3). The mixed esters involve two or three different acyl residues, e. g., dipalmito-olein (P2O) and palmito-oleo-linolein (POL). The rule of this shorthand designation is that the acid with the shorter chain or, in the case of an equal number of carbons in the chain, the chain with fewer double bonds, is mentioned first. The Z number gives the possible different triacylglycerols which can occur in a fat (oil), where n is the number of different fatty acids identified in that fat (oil) ... 

TABLE 9.1 Systematic Names, Trivial Names, and Shorthand Designations of the Most Common Fatty Acids ... 

Shorthand notations have been developed to avoid repetitive systematic names of unsaturated fatty acids. Eor example, linolenic or (7j -9,i7j -12-,i7j -15-octadecatrienoic acid can be represented by 18 3(9, 12, 15 ). The Greek letter A has been used to indicate presence and position of double bonds, eg a fatty acid, but it should never be used in a systematic name. An equally inappropriate but popular designation is derived by counting... 

There is also a shorthand notation to show the number of carbon atoms and the position of any double bonds in the structure. A fatty acid with 18 carbons and no double bonds is designated 18 0, while one with 18 carbons and two double bonds is 18 2. The carbon atoms in fatty acids are numbered from the carboxylic acid residue, and so the position of double bonds can be described using the number of the first carbon involved in the bond (e.g. A9 shows a... 

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