Fatty Acid Isopropylidene Hydrazides - A Novel Class of Derivatives for Analysis of Fatty Acids

  • V. P. Agrawal Royal Nepal Academy of Science and Technology, G.PO.Box 3323, Kathmandu


Treatment of Q acyl lipids with hydrazine hydrate at 60oC (hydrazinolysis) converts constituent fatty acids in corresponding hydrazides (R-CO-NH-NH2) which upon heating with acetone (acetonization) yield fatty acid isopropylidene hydrazides , R-CO-NH-N=(CH3)2 (FAIH). These compounds represent a new class of fatty acid derivatives and are named N'- isopropylidenealkanohydrazides. These derivatives can be converted into free fatty acids by refluxing with 3N HCl in 90% ethanol. Fatty acid isopropylidene hydrazides strongly absorb ultraviolet radiation in 220-240 nrn range. The value of molar absorptivity of FAIH is l0,l00 M-1 cm-1 at 229 nm . Proton resonance spectrum of FAIH is characterized by the presence of two sharp singlets at  d = 1.815 and 1.995 ppm caused by the non-equivalent nature of the two methyl groups of the isopropylidene moiety The mass spectrum of FAIH contains, in addition to mass ions for all the expected fragments m/z 72 for 3,3-dimethyldiazirdinium ion, as the base peak and a McLafferty ion m/z 114. FAIHs can be separated by thin layer chromatography on silica gel using chloroform as the developing solvent and resolved by gas liquid chromatography at 210 C on 3% Silar 10 C column and by reverse phase high performance liquid chromatography using octadecasilyl (RP=18) column and methanol-water (85: 15, v/v) as eluant.