Fast interannular proton transfer in gaseous protonated α,ω-diphenylalkanes: stereocontrol by the cyclohexane-1,4-diyl unit
作者:Dietmar Kuck、Detlef Thölmann、Hans-Friedrich Grützmacher
DOI:10.1039/p29900000251
日期:——
The fast ring-to-ring proton transfer in protonated 1,4-bis(ω-phenylalkyl)cyclohexanes [(5a)+ H]+, [(5b+ H)]+, and [(6)+ H]+ has been studied by chemical ionization mass spectrometry. The cyclohexane-1,4-diyl unit exerts a distinct stereocontrol upon the rate of proton exchange. Complete proton equilibration is found for protonated cis-dibenzylcyclohexane [(5a)+ H]+, whereas in the trans isomer [(5b)+
在质子化的1,4-双(ω-苯基烷基)环己烷[(5a)+ H] +,[(5b + H)] +和[(6)+ H] +中快速的环对环质子转移具有通过化学电离质谱法进行了研究。环己烷-1,4-二基单元对质子交换速率具有独特的立体控制。发现质子化的顺式-二苄基环己烷[(5a)+ H] +的完全质子平衡,而在反式异构体[(5b)+ H] +中,环间质子转移被强烈减速。的反式-双(β-苯基乙基)同系物[(发现6)+ H] +代表中间情况。通过与较简单的质子化二苯烷进行比较,估计亚稳态离子[(5b)+ H] +和[(6)+ H] +的环内质子转移速率处于5×10 5和10 6 s –1的范围内。