Isopropyl alcohol radiolysis

We have demonstrated a particularly clear and simple technique for evaluating the reactions of pyridinyl radicals in water through measurement of the pH changes resulting from radiolysis of pyridinium ions in unbuffered aqueous solutions containing isopropyl alcohol ( ). Radiolysis generates one proton for each pyridinyl radical, as set forth in Eq. 9. ( ). 

The products of reaction of e aq with olefins are carbanions which react with the solvent within less than 10-n sec. (47) to give the corresponding hydrogen adducts >C = C< + e aq(> C = C <)- + H + - > C — CH <. In the case of acetone, the adduct (CH8)2CHO was observed spectrophotometrically by pulse radiolysis and was found to be identical to the radical obtained from isopropyl alcohol by hydrogen abstraction (69). (CH8)2CO- was also detected by electron spin reso-... 

The l-ethyl-4-carbomethoxypyridinyl radical disproportionation products, aside from the pyridinium ion, probably included ethylamine, and a compound thought to be an ester dialdehyde (Eq. 31). The pH changes noted after radiolysis of buffer-free isopropyl alcohol-water solutions of the pyridinium ions revealed that the initial dihydropyridine 4 H) formed from 4 hydrolyzed and consumed another proton, presumably because of ethylamine. 

Warman JM, de Haas MP, Pichat P, Serpone N. (1991) Effect of isopropyl alcohol on the surface localization and recombination of conduction-band electrons in Degussa P25 TiOj. A pulse-radiolysis time-resolved microwave conductivity study. JPhys Chem 95 8858-8861. 

Yields of the Reducing Species in the Vapor-Phase Radiolysis of Isopropyl Alcohol and Water-Isopropyl Alcohol Mixtures... 

In the y-radiolysis of water-isopropyl alcohol mixtures in the vapor phase, the total yields of hydrogen, methane, and carbon monoxide are linear over the whole concentration range, in the presence and absence of electron scavengers. The majority of the hydrogen produced from energy absorption by both water and isopropyl alcohol is formed by H-atom abstraction from isopropyl alcohol. Part of the H-atom yield is formed by electron-positive ion neutralization and part by processes not involving electrons. As far as the formation of H atoms is concerned, both electron-positive ion and ion-ion neutralizations appear to be independent of the composition of the positive ion cluster. A yield of molecular hydrogen is also present in both water and isopropyl alcohol. 

Figure 1. Radiolysis of water-isopropyl alcohol vapor mixtures at 125°C. in the presence and absence of electron scavengers. Dependence of G(H2)t on the fraction of dose absorbed by water (fw) and isopropyl alcohol (fv)...

It therefore seems likely that C3H7OH2+ will be the major positive ion remaining in pure isopropyl alcohol after ion-molecule reactions, though it will be of the clustered form C3H7OH2+(C3H7OH)y, and that neutralization will proceed via Reaction 6. The mercury photosensitized decomposition of isopropyl alcohol shows a high quantum yield of H atoms (21) and a yield of H atoms from dissociation of excited isopropyl alcohol molecules might also be expected in the radiolysis. Hence, as for water vapor, the yield of H atoms from pure isopropyl alcohol will have... 

Assuming that a similar effect occurs in y-radiolysis, that all methyl radicals abstract from isopropyl alcohol... 

In the mass spectrum, about 4.5% of the ions produced are COH+ (16). As discussed earlier, proton transfer from COH+ to isopropyl alcohol is likely and if the same situation applies to y-radiolysis, this could... 

Molecular Hydrogen Formation. In the mass spectrum of isopropyl alcohol vapor with 50 e.v. electrons, about 18% of the total ionization leads to molecular hydrogen as a product (16). Assuming a similar cracking pattern in y-radiolysis, this would account for G— 0.7 in pure isopropyl alcohol. Again, this figure may not strictly apply to the radiolysis, but it appears that about half the molecular yield probably arises from decomposition of excited isopropyl alcohol molecules. Production of molecular hydrogen via... 

Hydrogen, methane, and carbon monoxide yields in the vapor phase radiolysis of water-isopropyl alcohol mixtures at 125°C. are linear over... 

A series of nondissociative electron transfer reactions involving aromatic radical ions produced by electron attachment in isopropyl alcohol solutions, have been studied by pulse radiolysis by Dorfman and co-workers (9). Donor radical anions were derived from diphenyl,... 

In the steady-state radiolysis of aqueous isopropyl alcohol containing N20, electron transfer from the isopropyl alcohol radical ion to N20 has been suggested (38). Since electron transfer from this radical ion to benzophenone is efficient even in N20-saturated solution, transfer to N20, if it occurs, must be slow and unimportant under the conditions of the above pulse experiments. 

Since the submission of this paper, the measurement of a large number of values of kn for H-atoms by a new radiolysis technique has been reported. Neta, Fessenden, and Schuler have studied the alcohols, and they conclude that the published values for ethanol and isopropyl alcohol are correct. However, they point out that these values are not consistent with values for other OH-containing substrates (27). 

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