Quantitative analysis of cyclopentadiene compounds

Abstract and SummaryA quantitative color reaction of cyclopentadiene was examined when cyclopentadiene was contained in a mixture of benzene, 1,3‐cyclohexadiene, cyclohexene, cyclohexane, cyclopentene, or cyclopentane. It was found that cyclopentadiene could be determined in the following manner. A sample was weighed to 1.38 x 10‐5 mole in a test tube, while a mixture of 10 ml ethyl alcohol plus 4 ml sulfuric acid was cooled in an ice bath. The mixture was poured into the test tube and the tube was heated in a water bath at 95 C for 30 sec followed by immediate cooling. Then the absorbance at 580 nm was measured and the content of cyclopentadiene was calculated with a calibration curve. The color reaction was tested with ethyl linoleate cyclic monomer (11 cm), ethyl linolenate cyclic monomer (mem), and photoisomerized tung oil fatty acid ethyl ester cyclic monomer (βcm), which were prepared from each purified fatty acid or from photo‐isomerized tung oil by cyclization with sodium hydroxide. It was found that cyclopentadiene compounds were formed from ethyl linolenate, but not from ethyl linoleate or from β‐eleostearate, which was a main component of photo‐isomerized tung oil.