Tetraalkylammonium salt as photoinitiator of vinyl polymerization in organic and aqueous media: A mechanistic and laser flash photolysis study

A study of the solvolysis of a series of (N-nitrosomethylamino)arylmethyl esters and azides and the products of nucleophilic trapping of the corresponding N-nitrosiminium ion intermediates in aqueous media, 25°C, ionic strength 1 M is reported. Structure-reactivity data for the forward and reverse reactions have been obtained. In three cases, the rate constants for reactions of the cations with nucleophiles have been measured directly by laser flash photolysis. The data allow a comparison of the degree to which the N-methyl-N-nitroso functionality enhances cation stability from a thermodynamic and kinetic perspective. It has been possible to deduce that the carbon basicity of azide ion is less than 1 kcal/mol greater than that of acetate ion.Key words: nitrosiminium ions, α-acetoxynitrosamines, carbocations, iminium ions, nucleophilicity.

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1995 Merck Frosst Award Lecture Quinone methides: relevant intermediates in organic chemistry

Canadian Journal of Chemistry ◽

10.1139/v96-051 ◽

1996 ◽

Vol 74 (4) ◽

pp. 465-475 ◽

Cited By ~ 101

Author(s):

Peter Wan ◽

Beverly Barker ◽

Li Diao ◽

Maike Fischer ◽

Yijian Shi ◽

...

Keyword(s):

Flash Photolysis ◽

Laser Flash Photolysis ◽

Aqueous Media ◽

Laser Flash ◽

Alder Reaction ◽

Quinone Methide ◽

Quinone Methides ◽

Chemical Systems ◽

The One ◽

Chroman Ring

ortho and para-Quinone methides (2-methylene-3,5-cyclohexadien-1-one and 4-methylene-2,5-cyclohexadien-1-one, respectively) are intermediates in a variety of important chemical systems. In particular, o-quinone methides are useful in synthesis for the construction of chroman ring systems. A brief account of the relevance of quinone methide chemistry will be provided. This is followed by a review of recent studies from our laboratory on efficient methods for the photogeneration of quinone methides, concentrating on the use of hydroxy-substituted benzyl alcohols in aqueous media. It is shown that this method is general since it provides access to o-, m-, and p-quinone methide isomers. When appropriately substituted, all of these quinone methide isomers have been spectroscopically characterized by laser flash photolysis, making this technique the one of choice for studying the dynamics of these reactive intermediates. The mechanism of photochemical generation from hydroxybenzyl alcohols and extensions of the reaction to photogeneration of fluorenyl and biphenyl quinone methides will also be presented. Key words: quinone methide, biphenyl quinone methide, carbocation, photosolvolysis, photodehydroxylation, hetero-Diels–Alder reaction.

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Molecular environment effect on O2 binding to lipidporphyrinatoiron(II) complexes in aqueous media

Journal of Porphyrins and Phthalocyanines ◽

10.1002/(sici)1099-1409(200001/02)4:1<81::aid-jpp207>3.0.co;2-u ◽

2000 ◽

Vol 04 (01) ◽

pp. 81-87 ◽

Cited By ~ 2

Author(s):

EISHUN TSUCHIDA ◽

TERUYUKI KOMATSU ◽

TETSUYA YANAGIMOTO

Keyword(s):

Flash Photolysis ◽

Laser Flash Photolysis ◽

Critical Concentration ◽

Aqueous Media ◽

Laser Flash ◽

Fiber Formation ◽

Ionization Mass ◽

Self Organized ◽

Covalently Linked ◽

The Stability

Lipidporphyrinatoiron(II) complexes are tetrakis(o-substituted)phenylporphinatoiron(II) derivatives which can be easily dispersed in water by molecular assembling. The most remarkable aspect of lipidporphyrinatoiron(II) assemblies is their reversible binding of dioxygen under physiological conditions (in aqueous media, pH 7.3, 37 °C) like hemoglobin and myoglobin. In these structures the O 2-binding properties are largely influenced by the molecular environment around the coordination site. Tetrakis(o-pivalamido)phenylporphinatoiron(II) with a covalently linked axial imidazole (lipidporphyrinatoiron(II), 1) is incorporated into recombinant human serum albumin (rHSA), providing a totally synthetic O 2-carrying hemoprotein (rHSA–1). Electrospray ionization mass spectrometry revealed the molecular mass of this non-covalent albumin–porphyrin hybrid. The O 2 rebinding after laser flash photolysis represented a three-phase decay, suggesting that each porphyrin is embedded into different cavities in the albumin structure. On the other hand, amphiphilic lipidporphyrinatoiron(II) with four alkylphosphocholine chains (2) is self-organized in aqueous solution to produce bimolecular fibers with a uniform thickness of 10 nm. This fiber also gave a stable O 2 adduct, and the O 2 rebinding after laser flash irradiation showed monophasic kinetics. Up to 20 vol% of methanol, which is a critical concentration for fiber formation, the morphology was gradually dissociated into spherical micelles, and the stability of the dioxygenated species suddenly decreased to 10% of that of the fibers.

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Two- and Three-Component Visible Light Photoinitiating Systems for Radical Polymerization Based on Onium Salts: An Overview of Mechanistic and Laser Flash Photolysis Studies

International Journal of Photoenergy ◽

10.1155/2012/260728 ◽

2012 ◽

Vol 2012 ◽

pp. 1-9 ◽

Cited By ~ 13

Author(s):

María L. Gómez ◽

Carlos M. Previtali ◽

Hernán A. Montejano

Keyword(s):

Visible Light ◽

Flash Photolysis ◽

Laser Flash Photolysis ◽

Aqueous Media ◽

Laser Flash ◽

Time Resolved ◽

Onium Salt ◽

Onium Salts ◽

Photopolymerization Kinetics ◽

Polymerization Conditions

A review of our work on two- and-three component photoinitiator systems is presented. The emphasis is in on visible light polymerization in aqueous media. The systems discussed comprise a synthetic dye as sensitizer and an onium salt as coinitiator, or a dye-amine-onium salt with the amine as coinitiator and the onium salt as an enhancer of the polymerization efficiency. The effect of the composition of the system on the photopolymerization kinetics was analyzed. To this end, the photophysics and photochemistry of the dye under polymerization conditions was explored by means of stationary and time-resolved spectroscopic methods. Different dyes and onium salts were investigated. The action mechanism of the different photoinitiators systems is discussed.

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