Identification by GC—MS of cymene isomers and 3,7,7-trimethylcyclohepta-1,3,5-triene in essential oils
作者:E. P. Romanenko、A. V. Tkachev
DOI:10.1007/s10600-006-0256-6
日期:2006.11
Retention indices of cymene isomers published in popular GC—MS atlases were found to be erroneous by analyzing synthetic samples. The following retention indices (RI) were found using a nonpolar phase (diphenyl: dimethylpolysiloxane, 5:95) for four essential-oil components with indistinguishable mass spectra: 3,7,7-trimethylcyclohepta-1,3,5-triene (RI = 970), m-cymene (RI = 1022), p-cymene (RI = 1024), and o-cymene (RI = 1039). The relative distributions of these compounds were evaluated based on the analysis of about 1000 essential oils. Simple methods were given for preparing standard mixtures of isomeric compounds for identification by GC—MS.
1-Methyl-1,2-epoxycycloheptane, 2α,3α-epoxypinane and 3α,4α-epoxycarane are shown to undergo typical carboniumionrearrangements in contact with active silica gel. Humulene epoxide-II and caryophyllene oxide did not undergo any transformation under these conditions. All these results are in complete contrast to their behaviour on exposure to alumina.
Reactions of Coordinated cyclic polyolefins. The synthesis and cycloaddition reactions of tricarbonyl[(1,2,3,4-η)-3,7,7-trimethylcycloheptatriene]iron
作者:Zeev Goldschmidt、Shlomo Antebi
DOI:10.1016/0022-328x(83)85162-6
日期:1983.12
regiospecificity of the reactions is considered in terms of frontier molecular orbitals. Complex III reacts with tetracyanoethylene to form a mixture of 1,3- and 1,6-cycloadducts in 4/1 ratio. Diphenylketene (DPK) forms a 2 + 2 adduct with III at room temperature. At 80°C an acylated addition product is obtained. In general, steric hindrance increases the yield of products formed via bipolar reactions at the expense