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On intramolecular migration of alkyl radicals produced in rigid n-alkane diols by γ-irradiation
Radiat. Phys. Chem. Vol. 27, No. 5, p. 411, 1986 Int. Jnl. Radiat. Applic. lnstrum., Part C Printed in Great Britain.
0146--5724/86 $3.00 + .00 © 1986 Pergamon Press Ltd.
SHORT COMMUNICATION ON INTRAMOLECULAR MIGRATION OF ALKYL RADICALS PRODUCED IN RIGID n-ALKANE DIOLS BY "y-IRRADIATION YOSHIMASA H A M A
Science and Engineering Research Laboratory, Waseda University, Shinjuku, Tokyo 160, Japan
duced directly by v-irradiation at 77 K is different from that of the same kind of radical produced by conversion from the alcohol radical by UV irradiation after v-irradiation. This resulted from different distribution of the alkyl radical on the main chain. The kinetics of this radical decay was treated by computer simulation based on a model of radical (l) migration. --CH2--CH--CH2-- ~ --CH2--CH--OH. We have concluded that the mutual conversion as shown by eqn (1) should be attributed to the inradical I radical II tramolecular migration because of the following reasons. Below we describe the summary of our study on (a) If the intermolecular migration such as hythe alkyl radical migration in n-alkane diols, todrogen abstraction by the radical or radical hopping gether with the results obtained recently. is possible, the alkyl radicals may decay gradually Four kinds of n-alkane diols, 1,6-hexane diol, by the recombination reaction. 1,8-octane diol, 1,10-decane diol, and 1,12-dode(b) The mutual conversion occurring without cane diol were used. When the n-alkane diols in change of the total intensity of ESR spectrum suppolycrystalline state were irradiated at 77 K by Vports the intramolecular migration process. rays, alkyl radicals (radical I) and alcohol type rad(c) The activation energy of 7 kcal/mol supports icals (radical II) were produced. In the 1,6-hexane the intramolecular migration. diol, however, the production of the alkyl radicals In our recent work, we found that the mixture was very slight compared with other samples. of 1,6-hexane diol and 1,8-octane diol is made in On heat treatment above 203 K for 1,8-octane glassy state by cooling rapidly the melted mixture. diol, the radical converts gradually to the alcoholThe mutual radical conversion as described above type radical. On heat treatment above 263 K, only was observed at a temperature below 173 K also in alcohol-type radicals were observed. The total inthe glassy mixture. In this mixture, however, all tensity of radicals did not change through the conradicals disappear on heat treatment at 200 K. The version process. This alcohol radical is stable at activation energy for the decay process of alkyl radroom temperature. When the alcohol radical was ical in the glassy mixture was determined to be 4.7 illuminated at 77 K by UV light below 350 nm, 40% kcal/mol. Moreover, in the glassy mixture, the forof the radical converted to the alkyl radical, without mation of the acyl radical was observed on UV ilchanging the total intensity. The mutual conversion lumination at 77 K. It is suggested that the photoof eqn (I) was observed in 1,10-decane diol and chemical reaction different from that in the 1,12-dodecane diol. polycrystalline sample occurs in a glassy one. The activation energy for the decay process of the alkyl radical was found to be about 7 kcal/mol for all samples from the isothermal decay experiREFERENCE ment of the alkyl radical. Moreover, it was found that the isothermal decay of the alkyl radical proI. Y. HAMA,Radiat. Phys. Chem. 1979, 13, 13-19.
WE HAVEreported on ESR studies of n-alkane diols irradiated by v-rays. ~1~ In the report, we obtained the results that in v-irradiated n-alkane diols the following mutual conversion occurs thermally and optically in the intramolecule:
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0146--5724/86 $3.00 + .00 © 1986 Pergamon Press Ltd.
SHORT COMMUNICATION ON INTRAMOLECULAR MIGRATION OF ALKYL RADICALS PRODUCED IN RIGID n-ALKANE DIOLS BY "y-IRRADIATION YOSHIMASA H A M A
Science and Engineering Research Laboratory, Waseda University, Shinjuku, Tokyo 160, Japan
duced directly by v-irradiation at 77 K is different from that of the same kind of radical produced by conversion from the alcohol radical by UV irradiation after v-irradiation. This resulted from different distribution of the alkyl radical on the main chain. The kinetics of this radical decay was treated by computer simulation based on a model of radical (l) migration. --CH2--CH--CH2-- ~ --CH2--CH--OH. We have concluded that the mutual conversion as shown by eqn (1) should be attributed to the inradical I radical II tramolecular migration because of the following reasons. Below we describe the summary of our study on (a) If the intermolecular migration such as hythe alkyl radical migration in n-alkane diols, todrogen abstraction by the radical or radical hopping gether with the results obtained recently. is possible, the alkyl radicals may decay gradually Four kinds of n-alkane diols, 1,6-hexane diol, by the recombination reaction. 1,8-octane diol, 1,10-decane diol, and 1,12-dode(b) The mutual conversion occurring without cane diol were used. When the n-alkane diols in change of the total intensity of ESR spectrum suppolycrystalline state were irradiated at 77 K by Vports the intramolecular migration process. rays, alkyl radicals (radical I) and alcohol type rad(c) The activation energy of 7 kcal/mol supports icals (radical II) were produced. In the 1,6-hexane the intramolecular migration. diol, however, the production of the alkyl radicals In our recent work, we found that the mixture was very slight compared with other samples. of 1,6-hexane diol and 1,8-octane diol is made in On heat treatment above 203 K for 1,8-octane glassy state by cooling rapidly the melted mixture. diol, the radical converts gradually to the alcoholThe mutual radical conversion as described above type radical. On heat treatment above 263 K, only was observed at a temperature below 173 K also in alcohol-type radicals were observed. The total inthe glassy mixture. In this mixture, however, all tensity of radicals did not change through the conradicals disappear on heat treatment at 200 K. The version process. This alcohol radical is stable at activation energy for the decay process of alkyl radroom temperature. When the alcohol radical was ical in the glassy mixture was determined to be 4.7 illuminated at 77 K by UV light below 350 nm, 40% kcal/mol. Moreover, in the glassy mixture, the forof the radical converted to the alkyl radical, without mation of the acyl radical was observed on UV ilchanging the total intensity. The mutual conversion lumination at 77 K. It is suggested that the photoof eqn (I) was observed in 1,10-decane diol and chemical reaction different from that in the 1,12-dodecane diol. polycrystalline sample occurs in a glassy one. The activation energy for the decay process of the alkyl radical was found to be about 7 kcal/mol for all samples from the isothermal decay experiREFERENCE ment of the alkyl radical. Moreover, it was found that the isothermal decay of the alkyl radical proI. Y. HAMA,Radiat. Phys. Chem. 1979, 13, 13-19.
WE HAVEreported on ESR studies of n-alkane diols irradiated by v-rays. ~1~ In the report, we obtained the results that in v-irradiated n-alkane diols the following mutual conversion occurs thermally and optically in the intramolecule:
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