A Method for the Determination of the Structure of Saturated Branched-Chain Fatty Acids

Abstract

A method is described for the determination of the structure of branched-chain fatty acids. It is found that the carbon chain of methyl-branched acids can be readily degraded by potassium permanganate in acetone, to give a series of acids of decreasing carbon number. Where a branch occurs the acid series is interrupted and a methyl ketone, of the same carbon number as a missing acid, is produced. Gas chromatographic examination of the ketone(s) and esterified acids gives clear evidence for the location of the branch(es). The method is illustrated by application to tuberculostearic acid (10-methyl-octadecanoic acid) and C27-phthianoic acid (2,4,6-trimethyltetracosanoic acid). It appears also able to decide the location of the ring in cyclopropane fatty acids.

Studies in Waxes. XXI. The Branched-chain Acids of the Preen Gland Wax of the Goose

“…3, peaks 1, 2, and 3) in the approximate ratio of 100 : 10 : 1 respectively. Accepting Weitzel, Fretzdorff, and Wojahn's (1952) finding that this main acid is a branched tetradecanoic acid (as confirmed * As previously observed with the oxidation of C,,-phthianoic acid (Murray 1959), acids of longer retention time are also present. Evidence which will be discussed in a further paper of this series suggests that these are formed by the oxidation of aldol condensation products of acetone and the main ketone oxidation product (in the above case C,,), producing keto acids of higher molecular weight than the parent acid.…”

“…Column temp. 120 "C. below), and following the general reasoning used previously (Murray 1959), then the retention times of the ketone and acid (as ester) degradation products compared with those of homologous series of n-alkyl methyl ketones and n-methyl esters, give clear evidence that the acid A has four methyl side branches, three of which are in the 2-, 4-, and 6-positions. This conclusion is clearer when the comparison of retention times with those of tho reference compounds are expressed graphically as in Figures 4 and 5.…”

“…i.d., packed with Silicone Elastomer E 301 15% on Celite 60-100 mesh, and heated in an air-bath which was stirred by a high-speed fan. The detector was a gas-density meter (Murray 1959) through which approximately 1/30 of the oolumn effluent was by-passed. At a column temperature of 200 "C, a flow rate of 1 l/min, and with a charge of 1 g, complete separation of the esters of the C,, and CIS acids (of.…”

C-20 Hydrocarbons of butterfat

“…About 3% (with respect to the branched C-18 ketone) of the branched C-13 ketone was also produced in the oxidation of phytol (branching), 85, 71, 58 (second largest peak), and 43 (base peak)]. A trace of this compound is to be expected from the work of Murray (1959) and probably only indicates branching and not a second isomer of phytol.…”

On the Fatty Acids of Brucella abortus and Brucella melitensis

“…No characteristic splitting of the molecule was observed: it is known that mass spectrometry does not allow one to locate directly a cyclopropane ring in a cyclopropane fatty acid [15]. Two different methods were used to determine the localisation of the cyclopropane ring : a ) mild permanganate oxidation according to Murray [16]: all the series of lower homologs of the C,, acid were observed except those with 8 and 9 carbon atoms (see formula 11). Moreover, while compounds higher than C,, still contained a cyclopropane ring, compounds lower thanC, were esters of straightchain acids (according to their retention times in gas chromatography of the methyl esters).…”