112929-90-5Relevant articles and documents
Generation, reactions, and kinetics of di(naphthyl)carbenes: Effects of the methyl group
Koshiyama, Tomoki,Hirai, Katsuyuki,Tomioka, Hideo
, p. 10261 - 10274 (2002)
A series of di(naphthyl)carbenes (DNCs) having methyl groups on aromatic rings were generated by photolysis of the corresponding diazo precursors and studied not only by product analysis, but also by spectroscopic means. "Parent" triplet α-DNC was shown to have a half-life of 70 ms, which is some 30 times larger than that of triplet diphenylcarbene (3DPC), whereas parent triplet β-DNC was 2 orders of magnitude shorter-lived than the α-isomer. The lifetimes of triplet DNCs were significantly increased by introducing methyl groups near the carbene center. Thus, 3α-DNC, which has four methyl groups at 2,2′,4,4′-positions, was shown to have a half-life of 100 ms, and the replacement of the two methyl groups at the 2,2′-positions of this carbene with tri(deuterio)methyl groups resulted in an increase of the lifetime by approximately 3 times by quenching the intramolecular H transfer from the methyl groups to the carbene center leading to o-quinoid compounds. The results are discussed in terms of the counteracting effects of electronic properties stabilizing the singlet state and steric factors favoring the triplet and compared with similar studies with 3DPCs.
Substituent effects on homolytic versus heterolytic photocleavage of (1-naphthylmethyl)trimethylammonium chlorides
Foster, B.,Gaillard, B.,Mathur, N.,Pincock, A. L.,Pincock, J. A.,Sehmbey, C.
, p. 1599 - 1607 (2007/10/02)
Singlet escited state rate constants have been measured for both the heterolytic and homolytic photocleavage of 3- and 4-methoxy and 3- and 4-cyano (1-naphthylmethyl)trimethylammonium chlorides, 6-10.The results are interpreted in terms of the meta effect or changes in charge distribution upon excitation and the competition between bond cleavage, electron transfer, and hydrogen atom transfer in the contact pairs resulting from the two types of cleavage.