72390-16-0Relevant academic research and scientific papers
Formation of self-assembled monolayers of π-conjugated molecules on TiO2 surfaces by thermal grafting of aryl and benzyl halides
English, Caroline R.,Bishop, Lee M.,Chen, Jixin,Hamers, Robert J.
, p. 6866 - 6876 (2012)
We demonstrate the formation of molecular monolayers of π-conjugated organic molecules on nanocrystalline TiO2 surfaces through the thermal grafting of benzyl and aryl halides. X-ray photoelectron spectroscopy and Fourier-transform infrared spectroscopy were used to characterize the reactivity of aryl and benzyl chlorides, bromides, and iodides with TiO 2 surfaces, along with controls consisting of nonhalogenated compounds. Our results show that benzyl and aryl halides follow a similar reactivity trend (I > Br > Cl ? H). While the ability to graft benzyl halides is consistent with the well-known Williamson ether synthesis, the grafting of aryl halides has no similar precedent. The unique reactivity of the TiO2 surface is demonstrated using nuclear magnetic resonance spectroscopy to compare the surface reactions with the liquid-phase interactions of benzyl and aryl iodides with tert-butanol and -butoxide anion. While the aryl iodides show no detectable reactivity with a tert-butanol/tert-butoxide mixture, they react with TiO2 within 2 h at 50 °C. Atomic force microscopy studies show that grafting of 4-iodo-1-(trifluoromethyl)benzene onto the rutile TiO2(110) surface leads to a very uniform, homogeneous molecular layer with a thickness of ～0.45 nm, demonstrating formation of a self-terminating molecular monolayer. Thermal grafting of aryl iodides provides a facile route to link π-conjugated molecules to TiO2 surfaces with the shortest possible linkage between the conjugated electron system and the TiO2.
Photochemistry of phosphate esters: An efficient method for the generation of electrophiles
Givens, Richard S.,Matuszewski, Bogdan,Athey, Phillip S.,Robert Stoner
, p. 6016 - 6021 (2007/10/02)
The photochemical cleavage of benzyl diethyl phosphates, 1a-g, has been examined in tert-butyl alcohol, which produces the corresponding benzyl tert-butyl ether as the major solvolysis product upon direct irradiation. The multiplicity of the reactive excited state has been established as the singlet state. Evidence favoring an intermediate benzyl cation-phosphate ion pair formed from photofragmentation includes oxygen-18 scrambling, racemization of chiral benzyl phosphates, and substituent effects on the rate of reaction. The existence of an electrophilic intermediate is further supported by a linear free energy relationship for the rate of disappearance of 1, kdis, with Hammett σ, which gave a ρ value of -0.90 and for the rate of appearance of 2, kapp, a Hammett ρ value of -0.97. Possible mechanisms including an electron transfer either before or after homolysis or simple heterolysis of the ester bond are evaluated.
Photochemical Transformations. 26. Sensitized and Unsensitized Photoreactions of Some Benzyl Chlorides in tert-Butyl Alcohol
Cristol, Stanley J.,Bindel, Thomas H.
, p. 951 - 957 (2007/10/02)
Benzyl chloride and a variety of meta- and para-substituted derivatives have been irradiated in tert-butylalcohol at 254 nm or in acetone-tert-butyl alcohol mixtures at 300 nm.Quantum and chemical yields of photosolvolysis products (benzyl tert-butyl ether and/or benzyl alcohol), photohomolysis products (bibenzyl and 4-phenyl-2-methyl-2-butanol), and corresponding products from substituted benzylchlorides have been measured as functions of substrate concentration and medium composition.Sensitized reactions favor bond heterolysis, but direct irradiations favor homolysis, although reactions are not clean in either case.There is no correlation between quantum yields for photosolvolysis and Hammett ? or Brown ?+ constants, and no salt effects of added lithium perchlorate were observed, in either direct or sensitized reactions.
