Cleavage of the radical cations of alkenes; 1-butene and 4,4-dimethyl-1-pentene. Ab initio calculations on the interaction between the allyl and alkyl radical and carbocation moieties

1991 ◽  
Vol 69 (9) ◽  
pp. 1365-1375 ◽  
Author(s):  
Xinyao Du ◽  
Donald R. Arnold ◽  
Russell J. Boyd ◽  
Zheng Shi
Keyword(s):  
Ab Initio Calculations ◽  
Ab Initio ◽  
Radical Cation ◽  
Alkyl Radical ◽  
Radical Cations ◽  
Molecular Orbital Calculations ◽  
Allyl Radical ◽  
Allyl Cation ◽  
Tert Butyl ◽  
Carbon Carbon Bond

Carbon–carbon bond cleavage of the radical cations of 1-butene [Formula: see text] and 4,4-dimethyl-1-pentene [Formula: see text] will generate the allyl and alkyl radical and carbocation fragments. Alternative bonding arrangements between the allyl and methyl moieties in [Formula: see text] and between the allyl and tert-butyl moieties in [Formula: see text] possible metastable intermediates or transition states preceding complete separation of the fragments, have been investigated by ab initio molecular orbital calculations. Structures were fully optimized at the UHF/6-31G* or UHF/STO-3G levels, and some of the calculations on [Formula: see text] were expanded with single point MP2/6-31G*//UHF/6-31G* computations. The C4H8+ radical cation, having a structure similar to that of 1-butene, is more stable than the separated fragments: 183 kj mol−1 lower in energy than the sum of the energies of the allyl cation and the methyl radical, and 385 kJ mol−1 lower than the sum of the energies of an allyl radical and a methyl cation, at the MP2/6-31G* level. The corresponding values at the UHF/STO-3G level are 276 and 415 kj mol−1, respectively. There is less bonding interaction between the allyl and tert-butyl moieties in [Formula: see text] The summation of the energies of the allyl radical and tert-butyl cation is 123 kj mol−1 lower than the summation of the energies of the allyl cation and tert-butyl radical, and 115 kJ mol−1 higher in energy than the bonded radical cation [Formula: see text] at the UHF/STO-3G level. These calculated values are compared with thermochemical data and with experimental results on the cleavage of these, and related, radical cations. Key words: radical cation, cleavage, ab initio calculations, electron transfer, photochemistry.

The effect of meta- and para-methoxy substitution on the reactivity of the radical cations of arylalkenes and alkanes. Radical ions in photochemistry. Part 26

1991 ◽  
Vol 69 (5) ◽  
pp. 839-852 ◽  
Author(s):  
Donald R. Arnold ◽  
Xinyao Du ◽  
Kerstin M. Henseleit
Keyword(s):  
Electron Transfer ◽  
Radical Cation ◽  
Bond Cleavage ◽  
Cation Radical ◽  
Radical Cations ◽  
Addition Product ◽  
Molecular Orbital Calculations ◽  
Carbon Carbon Bond ◽  
Markovnikov Addition ◽  
Cis And Trans

The effect of meta- and para-methoxy substitution on the reactivity of some radical cations has been determined. The compounds chosen for study were 1-(3-methoxyphenyl)-1-phenylethylene (7), 1-(4-methoxyphenyl)-1-phenylethylene (8), 3-(3-methoxyphenyl)indene (9), 3-(4-methoxyphenyl)indene (10), methyl 2-(3-methoxyphenyl)-2-phenylethyl ether (11), methyl 2-(4-methoxyphenyl)-2-phenylethyl ether (12), cis- and trans-2-methoxy-1-(3-methoxyphenyl)indane (13), and cis- and trans-2-methoxy-1-(4-methoxyphenyl)indane (14). The radical cations of these compounds were generated by photosensitization (electron transfer) using 1,4-dicyanobenzene (3) as the electron acceptor. The three reactions studied were: (1) The addition of nucleophiles (methanol) to the radical cation of the arylalkenes, a reaction that yields the anti-Markovnikov addition product. (2) The carbon–carbon bond cleavage of radical cations, which yields products derived from the radical and carbocation fragments. (3) The deprotonation of the radical cation, a reaction that can be used to invert the configuration at a saturated carbon centre. The mechanisms of these reactions are discussed and the factors that need to be considered in order to predict reactivity are defined. Molecular orbital calculations (UHF/STO-3G) were carried out on the radical cations of the model compounds 3- and 4-vinylanisole and 3- and 4-methylanisole. Key words: photochemistry, photosensitize (electron transfer), radical cation, radical.

The effect of meta- or para-cyano substitution on the reactivity of the radical cations of arylalkenes and alkanes. Radical ions in photochemistry, Part 34

1995 ◽  
Vol 73 (3) ◽  
pp. 307-318 ◽  
Author(s):  
Donald R. Arnold ◽  
Xinyao Du ◽  
Jing Chen
Keyword(s):  
Electron Transfer ◽  
Molecular Orbital ◽  
Radical Cation ◽  
Radical Cations ◽  
Molecular Orbital Calculations ◽  
Single Electron Transfer ◽  
Radical Ions ◽  
Benzylic Carbon ◽  
Carbon Carbon Bond ◽  
Cis And Trans

The effect of electron-withdrawing substituents, meta- or para-cyano, on the reactivity of the radical cation of arylalkenes and alkanes has been determined. The radical cations were generated by single electron transfer (set) to an electron-accepting photosensitizer. Three reactions were studied: (i) the addition of nucleophile to the radical cation of arylalkenes, (ii) cleavage of the benzylic carbon–carbon bond of the radical cation of arylalkanes; and (iii) the deprotonation of the benzylic carbon–hydrogen bond of the radical cation of arylalkanes. The radical cations of 4-(1-phenylethenyl)benzonitrile (1b), 3-(1-phenylethenyl)benzonitrile (1c), 4-(2-methoxy-1-phenylethyl)benzonitrile (2b), 3-(2-methoxy-1-phenylethyl)benzonitrile (2c), cis- and trans-5-cyano-2-methoxy-1-phenylindane (6b-cis and -trans), and 6-cyano-3-phenylindene (7b) were generated, by single electron transfer to the lowest excited singlet state of 1,4-dicyanobenzene (3), in acetonitrile–methanol. The radical cations of 1b, 1c, and 7b react with methanol to yield the anti-Markovnikov adducts (2b, 2c, and 6b-cis and 6b-trans). The radical cations of 2b, 2c, and 6b-trans cleave at the benzylic carbon–carbon bond to give products derived from the radical and carbocation fragments. The radical cation of 6b-cis deprotonates from the benzylic position with subsequent formation of the diastereomer, 6b-trans. This behaviour can be explained/predicted on the basis of the proposed mechanisms for these reactions. Molecular orbital calculations (AM1) support the conclusions. Keywords: photosensitized, electron transfer, radical ions, radicals, molecular orbital calculations (AM1).

scholarly journals Das Methylviologen-Radikalkation. Synthese, Kristallstruktur und ab initio-Rechnungen von N,N′-Dimethyl-4,4′ -bipyridinium-chlorid-dihydrat / The Methylviologen Radical Cation. Synthesis, Crystal Structure and ab initio Calculations of N,N′ -Dimethyl-4,4′ -bipyridinium Chloride Dihydrate

1993 ◽  
Vol 48 (10) ◽  
pp. 1341-1347 ◽  
Author(s):  
Hans Wolkers ◽  
Ralf Stegmann ◽  
Gernot Frenking ◽  
Kurt Dehnicke ◽  
Dieter Fenske ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Ab Initio Calculations ◽  
Ab Initio ◽  
Radical Cation ◽  
Structural Parameters ◽  
Ion Pairs ◽  
Radical Cations ◽  
Chloride Ions ◽  
Chloride Dihydrate ◽  
Deep Blue

The title compound has been prepared by the reduction of N,N′-dimethyl-4,4′-bipyridinium dichloride with dilithium tritelluride in dimethylformamide solution. It forms deep blue crystal needles, which were characterized by a crystal structure determination. Space group Pna 21,Z = 8,3450 observed unique reflections, R = 0.045. Lattice dimensions at -70°C: a =1707.6(8), b = 2323.9(11), c = 664.6(3) pm. The N,N′-dimethyl-4,4′-bipyridinium radical cations are planar and form ion pairs in the lattice. The chloride ions together with the water molecules form an infinite network of hydrogen bridges along the crystallographic a-axis. The structural parameters of the radical cation are in excellent agreement with ab initio calculations.

1,n-Radical ions. Photosensitized (electron transfer) carbon–carbon bond cleavage. Formation of 1,6-radical cations

1991 ◽  
Vol 69 (2) ◽  
pp. 225-233 ◽  
Author(s):  
Donald R. Arnold ◽  
Laurie J. Lamont ◽  
Allyson L. Perrott
Keyword(s):  
Electron Transfer ◽  
Radical Cation ◽  
Bond Cleavage ◽  
Radical Cations ◽  
Dimethyl Acetal ◽  
Mercury Vapour ◽  
Carbon Bond ◽  
Carbon Carbon Bond ◽  
Mercury Vapour Lamp ◽  
Mm2 Calculations

The reactivity of the radical cations of methyl 2,2-diphenylcyclohexyl ether (7), 6,6-diphenyl-1,4-dioxaspiro[4.5]decane (8), methyl cis- and trans-2-phenylcyclohexyl ether (9cis and trans), and 6-phenyl-1,4-dioxaspiro[4.5]decane (10), generated by photosensitized (electron transfer) irradiation, has been studied. Solutions of the ethers and acetals in acetonitrile–methanol (3:1), with 1,4-dicyanobenzene (2) serving as the electron acceptor, were irradiated with a medium-pressure mercury vapour lamp through Pyrex. The diphenyl derivatives 7 and 8 were reactive; 7 gave 6,6-diphenylhexanal dimethyl acetal (11) and 8 gave 2-methoxy-2-(5,5-diphenylpentyl)-1,3-dioxolane (12). These are the products expected from the intermediate 1,6-radical cation, formed upon carbon–carbon bond cleavage of the cyclic radical cation. The monophenyl derivatives 9cis and trans and 10 were stable under these irradiation conditions. The mechanism for the carbon–carbon bond cleavage and for the cis–trans isomerization is discussed. An explanation, based upon conformation, is offered for the lack of reactivity of 9 and 10. Molecular mechanics (MM2) calculations were used to determine the preferred conformation of 9cis and trans, and 10. Key words: photosensitization, electron transfer, radical cation, carbon–carbon bond cleavage, conformation.

The structure of diphosphaallenic radical cations as evidenced by EPR experiments and ab initio calculations

1997 ◽  
pp. 921-926 ◽  
Author(s):  
Mostafa Chentit ◽  
Helena Sidorenkova ◽  
Abdelaziz Jouaiti ◽  
Gustavo Terron ◽  
Michel Geoffroy ◽  
...  
Keyword(s):  
Ab Initio Calculations ◽  
Ab Initio ◽  
Radical Cations ◽  
Epr Experiments
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