GC-MS SEPARATION AND IDENTIFICATION OF THE C5H10 ISOMERS - APPLICATION TO THE HG-6((3)P(1)) PHOTOSENSITIZED REACTIONS OF CIS-2-PENTENE, 1-PENTENE AND TRANS-1,2-DIMETHYLCYCLOPROPANE

The analysis (separation and identification) of eleven C5H10 isomers i s performed using coupled GC/MS with a 70 m glass capillary column con taining a 2.5 mum thick film of PS225 as stationary phase. Cryogenic C O2 cooling improves the separations. The total analysis time is less t han 12 minutes. Some mechanistic details on the Hg 6(3P1) (hereafter d enoted by Hg) photosensitization of the title compounds are elucidate d. Thus the Hg photosensitization of cis-2-pentene at 20 Torr yields methylcyclobutane with a quantum yield phi = 0.1, not ethylcyclopropan e as was previously thought. (Ethylcyclopropane is formed in trace qua ntities.) The photostationary state for the Hg sensitization of the 2 -pentenes is confirmed to correspond to the concentration ratio [trans ]/[cis] = 1.00 Trans-1,2-dimethylcyclopropane is a product of the Hg photosensitization of 1-pentene. The major products of the Hg photose nsitization of trans-1,2-dimethylcyclopropane at 80 Torr are 3-methyl- 1-butene, trans- and cis-2-pentene and cis-1,2-dimethylcyclopropane wh ich are all formed with quantum yields near 0.1 and in the ratios 1.04 :1.07:1.00:1.45.