Abstract
When 5% citric acid solution containing citral and ethanol was stored at 40°C, unpleasant odor was produced within several days. After four weeks storage, the deteriorated products of citral were extracted with petroleum ether. The extracts were fractionated by vacuum distillation and each fraction was further separated by chromatography on aluminium oxide-Celite 535 (3: 1) column. p-Cymene and three components (P-3, P-4 and P-9) were isolated. P-3 showed the characteristic odor of the deteriorated citral.
P-3 was identified as 2-p-tolyl-propene by comparing the IR spectrum and the gas chromatogram with those of authentic specimen. P-9 was similarly identified as 2-p-tolyl-2-propanol. P-4 was concluded to be 2-p-tolyl-2-ethoxypropane by IR, MS and NMR spectra.
Among these components, P-4 was not detected in the deteriorated products of citral when the citric acid solution was used without ethanol. While P-3 and P-4 were derived from P-9 in the citric acid solution containing ethanol.
