Transient phenomena in the pulse radiolysis of retinyl polyenes. 2. Protonation kinetics

Journal Article · Fri Jan 01 00:00:00 EST 1982 · J. Am. Chem. Soc.; (United States)

DOI:https://doi.org/10.1021/ja00370a043· OSTI ID:5225259

Bobrowski, K; Das, P K

The results of a study are presented concerning the kinetics of reactions of various retinyl derivatives with hydrogen ions released pulse radiolytically in aerated 2-propanol containing 0.5 M acetone and 0.2 M carbon tetrachloride. For retinal and polyene Schiff bases, their protonated forms absorb at much longer wavelengths than the unprotonated substrates and are monitored by kinetic spectrophotometry. In the cases of retinol and retinyl acetate, the initial H/sup +/ adduct undergoes loss of water and acetic acid, respectively, producing the retinyl carbonium ion (lambda/sub max/585 nm), which, in turn, decays with first-order kinetics (t/sub 1///sub 2/ = 10 +/- 3 ..mu..s). The rate constants for protonation are in the range 1 x 10/sup 7/ - 4 x 10/sup 9/ M/sup -1/ s/sup -1/. In the cases of polyene Schiff bases, the protonation rate constant increases slightly with increasing polyene chain length and is higher for 11-cis-retinal Schiff base than for its all-trans counterpart. The absorption spectral maxima of protonated polyene Schiff bases observed in the early stages of protonation in the pulse radiolysis are red-shifted by approx. 10 nm relative to those of the protonated forms obtained by adding dilute hydrochloric acid to Schiff base solutions in 2-propanol. This is explained by the lack of ion pairing in the protonated species seen in the pulse radiolysis.

• Research Organization: Univ. of Notre Dame, IN
• OSTI ID: 5225259
• Journal Information: J. Am. Chem. Soc.; (United States), Vol. 104:6
• Country of Publication: United States
• Language: English

Related Subjects

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY
37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
POLYENES
CHEMICAL REACTIONS
RADIOLYSIS
SCHIFF BASES
SOLVATED ELECTRONS
CATIONS
CHEMICAL REACTION KINETICS
DECAY
EXPERIMENTAL DATA
GROUND STATES
PROTON REACTIONS
QUANTITATIVE CHEMICAL ANALYSIS
SCATTERPLOTS
SPECTRA
STRUCTURAL CHEMICAL ANALYSIS
BARYON REACTIONS
CHARGED PARTICLES
CHARGED-PARTICLE REACTIONS
CHEMICAL ANALYSIS
CHEMICAL RADIATION EFFECTS
CHEMISTRY
DATA
DECOMPOSITION
DIAGRAMS
ELECTRONS
ELEMENTARY PARTICLES
ENERGY LEVELS
FERMIONS
HADRON REACTIONS
HYDROCARBONS
IMINES
INFORMATION
IONS
KINETICS
LEPTONS
NUCLEAR REACTIONS
NUCLEON REACTIONS
NUMERICAL DATA
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
RADIATION CHEMISTRY
RADIATION EFFECTS
REACTION KINETICS
400600* - Radiation Chemistry
400301 - Organic Chemistry- Chemical & Physicochemical Properties- (-1987)