Hydrazine reduction in the gas liquid chromatographic analysis of the methyl esters of cyclopropenoic fatty acids

Conway, J.; Ratnayake, W. M. N.; Ackman, R. G.

doi:10.1007/bf02545954

Cited by 14 publications

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References 19 publications

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“…The method has suffered from poor reproducibility and a systematic study of the hydrazine reduction reaction for fatty acids with double bonds in various positions has never been reported. It has however been successful in determining the structures of both novel polyenoic fatty acids (15,16,22), those resulting from commercial hydrogenation of fats and oils (23,24), and in the analysis of naturally occurring cyclopropenoic fatty acids (25). More widespread application requires a study of the general principles relating ethylenic bond positions, their interactions, and their relative reduction rates.…”

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

Ratnayake

Grossert

Ackman

1990

J Americ Oil Chem Soc

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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.

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confidence: 99%

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

Ratnayake

Grossert

Ackman

1990

J Americ Oil Chem Soc

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Reduction with Diimide

1991

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The reduction of a double bond in the presence of hydrazine appears to have been first observed in 1905 during the reaction of glyceryl oleate, which produced stearic hydrazide. That hydrazine could act as a reagent for the reduction of a carboncarbon double bond was firmly established much later, at which point it was shown that oleic acid could be reduced to stearic acid by treatment with hydrazine, or with hydrazine and sulfur. In 1941 it was reported that vinyl groups in chlorins and porphyrins are selectively reduced to ethyl groups by hydrazine under mild conditions. The synthetic potential of this type of reduction was not recognized until the early 1960s when results from several independent laboratories implicated diimide (HNNH) as the actual reducing agent. Evidence for the existence of diimide (diimine and diazene) was first obtained in 1892 in the decarboxylation of dipotassium azodicarboxylate, which produced equimolar quantities of nitrogen and hydrazine by the proposed disproportionation of diimide. In 1910 it was proposed that diimide was formed in the reaction of benzenesulfonylhydrazide with hot alkali. Following the proposal that diimide is the reactive intermediate in these reduction reactions, numerous experimental and theoretical studies were launched to find other methods for the synthesis of diimide and to determine the structure(s) of the reactive intermediate(s) and the mechanism of the reduction reaction. An excellent review has appeared which covers the literature on the structure and molecular properties, spectral characterization, and gas‐phase reactions of diimide. In this chapter only highlights of such areas are covered. Two reviews covering reductions with diimide appeared in 1965, but none since that time. Most organic texts describe diimide reductions, but not in significant detail. There are three potential structures for diimide: cis ‐ and trans ‐diimide and 1,1‐diimide (aminonitrene). trans ‐Diimide can be generated and trapped at low temperature by a gas‐phase electric discharge in hydrazine and by the thermal decomposition of metal salts of p ‐toluenesulfonylhydrazide. Recently, 1,1‐diimide has been generated and trapped by the low temperature photochemical decomposition of carbamoyl azide. Although cis ‐diimide must be formed as a reactive intermediate in many systems, it has not yet been unambiguously characterized. The diimide system has been subjected to several theoretical studies at many different basis set levels. The results of stereochemical studies on the reduction of alkenes and alkynes have led to the suggestion that cis ‐diimide is the reactive hydrogen‐transfer reagent. These results support the suggestion that cis ‐diimide is the active hydrogen‐transfer reagent. The fact that cis ‐diimide has not been observed and that the calculated inversion and rotation barriers are too large to provide a rate of isomerization of trans ‐ to cis ‐diimide that would be sufficiently high to account for the observed rate of reduction provides for a mechanistic dilemma. In gas‐phase reactions isomerization of trans ‐ to cis ‐diimide has been proposed to be the rate‐limiting step. In solution, however, the isomerization in all probability occurs via a catalyzed process, probably involving a rapid protonation–deprotonation sequence. In this chapter the use of the term “diimide” implies cis ‐diimide as the reducing agent. The energy barriers for the disproportionation of cis ‐ with cis ‐, and cis ‐ with trans ‐diimide are calculated to be 19.3 and 23.8 kcal per mole, considerably smaller than the barriers for hydrogen transfer to a carboncarbon double bond. From a practical point of view, this competing disproportionation requires the use of considerable excesses of the diimide precursors in the reduction reactions.

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Lipids

Gordon¹

1990

Principles and Applications of Gas Chromatography in Food Analysis

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Hydrazine reduction in the gas liquid chromatographic analysis of the methyl esters of cyclopropenoic fatty acids

Cited by 14 publications

References 19 publications

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

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

Reduction with Diimide

Lipids

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