Photochemistry of phenoxybenzyl alcohols in aqueous solution: photosolvolysis vs. photorearrangement to 6H-dibenzo[b,d]pyrans
作者:C. G. Huang、Peter Wan
DOI:10.1021/jo00016a009
日期:1991.8
The photochemistry of three phenoxybenzyl alcohols (1-3) has been studied in MeOH, CH3CN, and in aqueous solution. It was found that both of the ortho-substituted phenoxybenzyl alcohols 1 and 2 gave the corresponding 6H-dibenzo[b,d]pyrans 6 and 10, via a mechanism believed to involve initial aryl C-O bond homolysis followed by rearrangement to give a 2-(2'-hydroxyphenyl)benzyl alcohol (biphenyl) derivative, which subsequently undergoes a photocyclization reaction to the corresponding 6H-dibenzo[b,d]pyran. The quantum yield for formation of 6 (from 1) was 0.0073 in neutral 6:4 H2O-CH3CN. Lower quantum yields for formation of 6 were observed on photolysis in pure organic solvents (PHI = 0.0015 in 100% CH3CN). The meta-substituted isomer 3 did not give any reaction via a similar photocyclization process: its photochemistry involves initial aryl C-O bond homolysis followed by simple radical recoupling to give isomeric hydroxybiphenyls, as well as products derived from radical escape. In aqueous sulfuric acid solution (pH < 2), a competing acid-catalyzed photosolvolysis reaction was observed for all of these compounds (i.e., C-OH bond heterolysis with assistance of hydronium ion); it was the only observed reaction in moderately concentrated sulfuric acid solution.
FLÜSSIGKRISTALLANZEIGE
申请人:Merck Patent GmbH
公开号:EP2181173A1
公开(公告)日:2010-05-05
[DE] FLÜSSIGKRISTALLANZEIGE<br/>[EN] LIQUID CRYSTAL DISPLAY<br/>[FR] AFFICHAGE À CRISTAUX LIQUIDES
申请人:MERCK PATENT GMBH
公开号:WO2009030329A1
公开(公告)日:2009-03-12
Die vorliegende Erfindung betrifft eine Flüssigkristall (FK)-Anzeige des PS- (polymer stabilized) oder PSA- (polymer sustained alignment) Typs, sowie polymerisierbare Verbindungen und FK-Medien zur Verwendung in PS- (polymer stabilized) und PSA-Anzeigen.
Charge polarization in photoexcited alkoxy-substituted biphenyls: formation of biphenyl quinone methides
作者:Yijian Shi、Peter Wan
DOI:10.1039/c39950001217
日期:——
Alkoxy-substituted biphenyls are highly polarized in S1, with the negative charge residing on the ring not possessing the alkoxy group, enabling the photogeneration of spectrophotometrically observable transient biphenyl quinone methides by laser flash photolysis.
Solvolysis and ring closure of quinone methides photogenerated from biaryl systems
作者:Yijian Shi、Peter Wan
DOI:10.1139/v05-138
日期:2005.9.1
A variety of biaryl quinone methides have been photogenerated with a range of efficiencies from biaryl precursors 46 and 8, 10, and 11, all having hydroxyl and hydroxymethyl substituents on altern...