Studies on the mechanism of the hydrazine reduction reaction: Applications to selected monoethylenic, diethylenic and triethylenic fatty acids ofcis configurations

Abstract

The hydrazine reduction of cis ethylenic bonds has been studied using a number of Cle, Cls, and C20 monoethylenic, Cls diethylenic, and Cls plus C20 triethylenic fatty acids. Relative reduction rates were determined and correlated with the positions of the ethylenic bonds in the fatty acids. The terminal ethylenic bond was the most reactive and among the others, reactivity was greater nearer the ends of the chain than in the center. Also, the ethylenic bonds closer to the carboxyl group showed greater reactivity than those closer to the methyl end of the chain. Differences in reactivity among the centrally located double bonds were not significant. These reactivity trends are consistent with a mechanism involving protonated diimide as an intermediate in the reduction process. In diethylenic fatty acids, the non-methylene-interrupted dienes showed slightly lower reactivity than the methylene-interrupted counterparts, which indicated that both the position of ethylenic bonds and the relative distance between two ethylenic bonds in the diene influence the rate of reaction. The information obtained from the rate studies should be useful for predicting the product distribution from partial hydrazine reductions of long-chain polyethylenic compounds.KEY WORDS: Diimide reductions, fatty acids, hydrazine reduction, reduction of unsaturated fatty acids, structure determinations.

Geometry of conjugated double bonds of CLA isomers in a commercial mixture and in their hepatic 20∶4 metabolites

“…This method consists of partial reduction of the dienoic acid to give a mixture of saturates, monoenes, and unreacted dienes. Hydrazine reduction takes place without modification of either the position or the geometry of the ethylenic bonds, so the position(s) and geometry of the ethylenic bonds in the resulting monoenes represent those of the parent molecule (31). The resulting mixture (Fig.…”

“…Hydrazine reduction of 18:2 and 20:4 conjugated isomers. The CLA mixture (42 mg; Sigma) was dissolved in 30 mL of 96% ethanol in a round-bottom flask fitted with a condenser and a magnetic stirrer (31) and immersed in a water bath at 40°C. A 95% hydrazine solution (1 mL) was added, and oxygen was passed over the stirred solution for 3 h. After addition of water, the fatty acids were extracted with diethyl ether and then converted to methyl esters with BF 3 -MeOH at 95°C for 5 min (32).…”

Separation Behavior of Octadecadienoic Acid Isomers and Identification of cis‐ and trans‐Isomers Using Gas Chromatography

“…FAME were dissolved in n-hexane (1 mL) and poured into the Discovery DSCSi SPE Tube for purification. FAME were eluted with 5 % ether/n-hexane (10 mL), and evaporated to dryness under a nitrogen stream at 40 °C and n-hexane (2 mL) was then added to produce a partially reduced FAME/n-hexane solution [26][27][28][29][30][31][32]. The partially reduced FAME/n-hexane solution was added to the Ag-ION SPE column which had been conditioned as mentioned previously.…”

“…The 24 isomers were obtained by performing cis-to trans-isomerization of six regioisomers [33]. Using partial reduction with hydrazine to decrease the number of double bonds [26][27][28][29][30][31][32], we prepared five di-cis-octadecadienoic acid methyl ester (C18:2ME) isomers by the partial reduction of methyl α-linolenate and methyl γ-linolenate C18 trienoic acids with different double bond positions. This enabled the preparation of a sample of di-cis-C18:2ME containing (c5, c9), (c6, c9), (c6, c12), (c9, c12), (c9, c15), (c12, c15) where the (c5, c9) was prepared from a raw constituent FAME sample extracted from Japanese yew seed.…”

Occurrence of all-cis-5,8,11,14,17,20,23-hexacosaheptaenoic acid (26:7n-3) in roughscale sole Clidoderma asperrimum flesh lipids

“…Derivatization for structural analysis Partial hydrogenation of the polyunsaturated fatty acids was carried out using hydrazine hydrate [30,31]. A mixture of 5 mg free fatty acids and 10% (v/v) hydrazine hydrate in methanol (5 ml) was stirred at 50°C for 7 h with aeration.…”