Cycloheptatrienes radiolysis

OH radicals react very fast (almost in a diffusion-controlled rate) with simple alkenes (k = 7.0 x 109 for 1-butene or cyclopentene and 8.8 x 109 M 1 s 1 for cyclohexene) and there is almost no change for 1,3- or 1,4-cyclohexadiene. Cycloheptatriene reacts very fast with all the three radicals formed in the radiolysis of water k = 6 x 109 with eaq, 8 x 109 with H atoms and 1 x 101CI M 1 s 1 with hydroxyl radicals13. 

It is worth mentioning that cis-trans isomerization can also be achieved radiolytically. Attainment of a photoequilibrium of 4,4 -NMS in benzene under y-radiation is promoted by terphenyl as scintillator [455]. Dainton et al. [456] have ascribed a 100-ns transient, produced by pulse radiolysis of trans-stilbene at room temperature, to the trans triplet state. Pulse radiolysis was applied to determine the triplet state of cycloheptatriene (tt = 6 s) which was used to mimic energy transfer to ds-stilbene [457]. 

Figure I. Radiolysis/EPR results for a) 1,3,5-cycloheptatriene and b) 2,3-dimethyl-2-pentene on HZSM5 and NaZSMS. The radical cations of catalytic products, toluene and tetramethylethylene, were observed only on the acidic zeolite and not on Na2SM5.

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