Generation, Reactions, and Kinetics of Sterically Congested Triplet Diphenylcarbenes. Effects of Bromine Groups
作者： Hideo Tomioka , Tetsuya Watanabe , Makoto Hattori , Naoki Nomura , Katsuyuki Hirai
DOI: 10.1021/JA010658S
关键词: Chemistry 、 Carbene 、 Photochemistry 、 Kinetics 、 Bromine 、 Benzene 、 Flash photolysis 、 Steric effects 、 Methyl group 、 Irradiation
摘要: A series of polybrominated diphenylcarbenes (DPCs) are generated by irradiation the corresponding precursor diazomethanes, and their reactivities investigated means low-temperature spectroscopies as well laser flash photolysis. Triplet bis(2,4,6-tribromophenyl)carbene was shown to decay undergoing dimerization have a half-life 1 s in degassed benzene solution at room temperature, some 6 orders magnitude longer-lived than parent DPC. Anomalous effects para substituents on stability triplet noted. Thus, while replacement 4-bromine group with methyl resulted sharp decrease lifetime, introduction tert-butyl dramatic increase lifetime; bis(2,6-dibromo-4-tert-butylphenyl)carbene 16 temperature. Attempts these DPCs buttressing m-bromine synergetic effect bromine groups also described.
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