Monocarboxylic fatty acid content

This study reports the monocarboxylic fatty acid content of a series of brown coal lithotypes from the Latrobe Valley, Victoria, Australia. We have looked both at the solvent-extractable, or free, fatty acids (which include those extractable as esters or intact lipids) and at those that are released upon hydrolysis (saponification) of the residue after solvent extraction. The latter are presumably bound chemically to the coal matrix (kerogen) and are therefore designated as bound acids. The total acids are taken as the sum of the free and bound acids. 

Although the number of fatty acids detected in plant tissues approaches 300, most of them only occur in a few plant species (Hitchcock and Nichols, 1971). The major fatty acids are all saturated or unsaturated monocarboxylic acids with an unbranched even-numbered carbon chain. The saturated fatty acids, lauric (dodecanoic), myristic (tetradecanoic), palmitic (hexadeca-noic), and stearic (octadecanoic), and the unsaturated fatty acids, oleic (cis-9-octadecenoic), linoleic (c/5 -9,cw-12-octadecadienoic), and linolenic (all-cij-9,12,15-octadecatrienoic (Table I), together account for almost all of the fatty acid content of higher plants. For example, about 94% of the total fatty acids of commercial oils and 89-97% of leaf fatty acids consist of these seven structures alone. It will be noted that the unsaturated acids all contain a cis-9 double bond and that the polyunsaturated acids contain a methylene-interrupted structure. The four saturated fatty acids differ from each other by two carbons. These structural relationships are due to the principal pathways of fatty acid biosynthesis in plants (see Stumpf, this volume. Chapter 7). 

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