Accession Number : AD0647914

Title :   ACID-BASE CHARACTERISTICS OF PHOTOCHROMISM.

Descriptive Note : Contract rept. for 1 Oct 64-30 Sep 66,

Corporate Author : HUGHES RESEARCH LABS MALIBU CALIF CHEMICAL PHYSICS DEPT

Personal Author(s) : Mergerum,J. David

Report Date : 30 SEP 1966

Pagination or Media Count : 75

Abstract : The mechanisms of photochromic reactions are studied in regard to their acid-base characteristics. An intramolecular mechanism, consisting of a six-membered hydrogen transfer from the methylene group in p-nitrobenzyl structures to an o-carboxylate group, is elaborated by kinetic analysis of the flash photolysis intermediates from 2-(4-nitrobenzyl)benzoic acid and other additional model structures. Compounds synthesized for this purpose include 5-nitro-o-toluic acid and 4,4'-dinitrobibenzyl-2,2'-dicarboxylic acid. The spectra of similar short lived aci-anion intermediates are observed in the photodecarboxylation of o- and p-nitrophenylacetic acid derivatives in aqueous base. These are identified by comparison with similar spectra obtained from other reactions of the corresponding nitrotoluene compounds. A ketone model compound, 2-methyl-5-nitrobenzophenone, was synthesized and unexpectedly found to cause efficient oxidation of isopropyl alcohol to acetone, as well as showing several spectral intermediates. The trans to cis photoisomerization of N, N'-dimethylindigo and N, N'-dimethyl-5, 5', 7, 7'-tetrabromoindigo is confirmed, and the cis spectra of these two dyes are calculated using photostationary state techniques. The reverse cis to trans reaction kinetics are studied with flash photolysis and found to be highly acid-catalyzed. The reaction rate is linearly dependent upon the hydrogen ion concentration. Optical saturation effects with helium-neon and with ruby lasers are described. (Author)

Descriptors :   (*PHOTOCHROMISM, PH FACTOR), MOLECULAR ISOMERISM, REACTION KINETICS, STEREOCHEMISTRY, PHOTOCHEMICAL REACTIONS, DYES, LASERS, SYNTHESIS(CHEMISTRY)

Subject Categories : Organic Chemistry
      Radiation and Nuclear Chemistry

Distribution Statement : APPROVED FOR PUBLIC RELEASE