Photoreduction of Quinones in a Polymer Matrix
Comparison of 2-isopropoxy substituted and 2-methyl substituted 1, 4-naphthoquinones
1982 Volume 45 Issue 2 Pages 85-90
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1982 Volume 45 Issue 2 Pages 85-90
Photochemical behaviors of 2-isopropoxy-1, 4-naphthoquinone (IPNQ) which has an intramolecular hydrogen donor adjacent to one of its carbonyl oxygens, have been investigated in cellulose acetate film, and compared with those of 2-methyl-1, 4-naphthoquinone (MNQ) which has no intramolecular hydrogen donor.
The quantum yield of photoreduction in film increased by addition of benzhydrol which served as a hydrogen donor but leveled off at 0.5 for both IPNQ and MNQ. When no benzhydrol was present, however, the quantum yield was 0.3 for IPNQ, three times larger than that for MNQ. For photographic applications, it dose not seem to be necessary to add hydrogen donors to IPNQ.
Photo-generated reductants from quinones undergo air oxidation. The reaction was pseudounimolecular as to the concentration of reductants, with the rate constants 1.0×10-4 min-1 and 4.8×10-4 min-1, or with the half-lives 115 hr and 24 hr, for IPNQ and MNQ at 20°C, respectively. The activation energy was measured for IPNQ and found to be 12 kcal/mol. The frequency factor was as small as 103, suggesting that the latent image consisting of reductants are relatively stable against the variation of storage temperature.
