Fatty acids (FA) differ widely in a number of chemical features.
General features:
(1) carboxylic acid at one end
(2) aliphatic tail or chain
Descriptors:
(1) total number of carbon molecules
(2) number of carbons in aliphatic side chain (tail)
(3) number of double bonds
(4) configuration relative to a double bond (isomers)
|
Number of Carbons in Aliphatic Tail |
Term |
|
< 6 |
short chain (SCFA) |
|
6 to 12 |
medium chain (MCFA) |
|
13 to 21 |
long chain (LCFA) |
|
> 21 |
very long chain (VLCFA) |
The total number of carbons should be length of the aliphatic tail plus 1 for the carboxylic moiety at the end.
|
Number of Double Bonds |
Saturation |
Term |
|
none |
saturated |
anoic |
|
1 |
monounsaturated |
enoic |
|
2 or more |
polyunsaturated |
dienoic (2), trienoic (3), etc |
|
Configuration |
Hydrogen Atoms |
Occurrence |
|
cis |
same side of the double bond |
usual form in natural sources |
|
trans |
opposite side of double bond |
may occur during partial chemical hydrogenation |
