Radical cations of sterically hindered phenols as intermediates in radiation-induced electron transfer processes

被引:86
作者
Brede, O
Orthner, H
Zubarev, V
Hermann, R
机构
[1] Max Planck Society, Research Unit Time-Resolved Spectroscopy, University of Leipzig, D-04303 Leipzig
关键词
D O I
10.1021/jp953526s
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
The radical cations of several preferably sterically hindered phenols have been observed through the radiation-induced electron transfer from the phenol (ArOH) to the parent cations of nonpolar solvents (n- and iso-butyl chloride, cyclohexane, freon-113). For p-methoxyphenol and its 2,6-di-tert-butyl-substituted derivative, ArOH.+ has been characterized after radiolysis at 77 K by EPR and optical absorption spectroscopies. Their broad optical absorption bands at lambda = 430 and <310 nm agree well with those seen at room temperature after pulse radiolysis of the phenol solutions in n-butyl chloride. Generally, also the other phenols studied show similar absorption spectra, but the bands are not so pronounced as in the case of the p-methoxy-substituted ones. Electron transfer from the phenols to n-butyl chloride radical cation proceeds with a rate constant of (1.5-2.0) x 10(10) dm(3) mol(-1) s(-1) at 293 K. In the case of phenols containing a further functional group distant from the phenol aromatic ring(phenyl acrylate, amine groups), depending on their ionization potential, after the primary ionization intramolecular charge transfer phenomena from or to the phenol unit are observed. ArOH.+ decay under dissociation to phenoxyl radicals (ArO.) and protons. In the 266 nm laser flash photolysis under ionizing conditions (absorption of two. UV photons) in aqueous solutions of the phenols, phenoxyl radicals and solvated electrons are observed, whereas in n-butyl chloride solution ArOH.+ of almost of the studied phenols were found to exist in the nanosecond time range.
引用
收藏
页码:7097 / 7105
页数:9
相关论文
共 44 条
[1]   ROOM-TEMPERATURE POWDER ENDOR SPECTRA OF BETA-PROTONS IN SOME ORGANIC PI-RADICALS [J].
ATHERTON, NM ;
OLIVER, CE .
JOURNAL OF THE CHEMICAL SOCIETY-FARADAY TRANSACTIONS I, 1988, 84 :3257-3262
[2]   PROTON-TRANSFER REACTIONS OF ALKYLAROMATIC CATION RADICALS - THE EFFECT OF ALPHA-SUBSTITUENTS ON THE KINETIC ACIDITY OF P-METHOXYTOLUENE CATION RADICALS [J].
BACIOCCHI, E ;
DEL GIACCO, T ;
ELISEI, F .
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 1993, 115 (26) :12290-12295
[3]   KINETICS OF EXCITATION AND CHARGE-TRANSFER REACTIONS IN NONPOLAR MEDIA [J].
BREDE, O ;
MEHNERT, R ;
NAUMANN, W .
CHEMICAL PHYSICS, 1987, 115 (02) :279-296
[4]   PRIMARY PROCESSES OF STABILIZER ACTION IN RADIATION-INDUCED ALKANE OXIDATION [J].
BREDE, O ;
HERMANN, R ;
MEHNERT, R .
JOURNAL OF THE CHEMICAL SOCIETY-FARADAY TRANSACTIONS I, 1987, 83 :2365-2380
[5]   PHENOL-ASSISTED PHOTOLYTIC AND RADIOLYTIC RADICAL-CATION FORMATION OF A STERICALLY HINDERED TERTIARY AMINE [J].
BREDE, O ;
ORTHNER, H ;
HERMANN, R .
CHEMICAL PHYSICS LETTERS, 1994, 229 (4-5) :571-576
[6]  
BREDE O, 1986, RADIAT PHYS CHEM, V28, P507
[7]  
BREDE O, 1987, RADIAT PHYS CHEM, V29, P369
[9]   PHOTO-INDUCED AND RADIATION-INDUCED CHEMICAL GENERATION AND REACTIONS OF STYRENE RADICAL CATIONS IN POLAR AND NONPOLAR-SOLVENTS [J].
BREDE, O ;
DAVID, F ;
STEENKEN, S .
JOURNAL OF THE CHEMICAL SOCIETY-PERKIN TRANSACTIONS 2, 1995, (01) :23-32
[10]   Charge transfer to a semi-esterified bifunctional phenol [J].
Brede, O ;
Hermann, R ;
Orthner, H .
RADIATION PHYSICS AND CHEMISTRY, 1996, 47 (03) :415-417