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Photodimers of N-alkyl-3,4-dimethylmaleimides—Product ratios and reaction mechanism

Paper ID Volume ID Publish Year Pages File Format Full-Text
28654 44084 2008 11 PDF Available
Title
Photodimers of N-alkyl-3,4-dimethylmaleimides—Product ratios and reaction mechanism
Abstract

The photodimerization of three N-alkyl-3,4-dimethylmaleimides (DMI) – frequently used to form crosslinks in polymers – was examined. N-Isobutyl-3,4-dimethylmaleimide, N-(2-acetamido)ethyl-3,4-dimethylmaleimide, N-(3-propionic acid)-3,4-dimethylmaleimide were studied by steady-state and time-resolved photolysis in various solvents. Unexpectedly, under all conditions a single-bonded dimer distinct from the well-known cyclobutane fused cyclic dimer was identified. Depending on the solvent the single-bonded dimer amounts to 5–50% of the product yield, allowing for considerable selectivity. Dimerization quantum yields, Φdim, range from 0.01 to 0.5. Results from time-resolved experiments establish the involvement of the triplet state in the photodimerization mechanism, the quantum yield of singlet molecular oxygen formation accounts for the Φdim values. Electron transfer and hydrogen abstraction reactions of DMI in polar and protic solvents, in contrast to N-alkylmaleimides, are inefficient processes.

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Keywords
Photodimerization; Photo-cross-linking; Flash photolysis; Triplet state; Reaction mechanism; Selectivity
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Publisher
Database: Elsevier - ScienceDirect
Journal: Journal of Photochemistry and Photobiology A: Chemistry - Volume 198, Issue 1, 5 July 2008, Pages 34–44
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
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