Ab initio calculations on the ring opening of cyclopropane radical cation. Trimethylene radical cation is not a stable intermediate

1988 ◽  
Vol 110 (11) ◽  
pp. 3405-3412 ◽  
Author(s):  
Ping. Du ◽  
David A. Hrovat ◽  
Weston Thatcher. Borden
Keyword(s):  
Ab Initio Calculations ◽  
Ab Initio ◽  
Radical Cation ◽  
Ring Opening ◽  
Stable Intermediate

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.

An SCF MO Treatment of the Conformations of the 1,3,Dimethyl Allyl Carbonium Ion

1974 ◽  
Vol 29 (12) ◽  
pp. 1791-1796 ◽  
Author(s):  
Muthana Shanshal
Keyword(s):  
Ab Initio Calculations ◽  
Ab Initio ◽  
Heat Of Formation ◽  
Trans Conformation ◽  
Molecular Plane ◽  
Carbonium Ion ◽  
Stable Intermediate

The geometry and heat of formation are calculated by means of the MINDO/2 method for the following six conformations of the 1,3,dimethyl allyl carbonium ion: the cis,cis conformation (I), the perpendicular, endo conformation (II), the cis,trans conformation (III), the perpendicular, exo conformation (IV), the trans,trans conformation (V), and the coplanar cis,cis,conformation (VI). Conformation I is predicted to be a stable intermediate, having both CH3 groups 20° oppositelytwisted out of the molecular plane. The order of stability of the planar conformations is V>III>I⪢VI. Utilizing the MINDO/2 calculated geometry, ab Initio calculations were done for all the six conformations. The ab Initio predicted order of stability is similar to that obtained with the MINDO/2 method. It is found that the ab Initio calculations yield rotation barriers that are too high, the MINDO/2 method yields values that are too low, compared with the experimentally determined barriers.

Sign in / Sign up

Export Citation Format

Share Document