Ethyl carbocation, molecular orbital

Figure 6.12 Stabilization of the ethyl carbocation, CH3CH2+, through hyperconjugation. Interaction of neighboring C H

Ethyl carbocation, electrostatic potential map of, 196 molecular orbital of, 196... 

Single determinant ab initio LCAO-SCF molecular orbital theory is used throughout this study (6,7), Molecular geometries were optimized with the minimal STO-3G basis set (8,9), and where possible the energy of the final structure was recalculated with the extended 4-31G basis set (9,10), Such a procedure has been shown to provide a reasonable description of the structures and energies of neutral organic molecules (11) and carbocations (12), The potential surface for the concerted elimination of hydrogen chloride from ethyl chloride also has been studied successfully (13) with this technique. 

Abbreviations PAH, polycyclic aromatic hydrocarbon DE, diol epoxide PAHDE, polycyclic aromatic hydrocarbon diol epoxide PAHTC, polycyclic aromatic hydrocarbon triol carbocation TC, triol carbocation BaP, benzo[a]pyrene BeP, benzo[e]pyrene BA, benz[a]anthracene DBA, dibenz[a,h]anthracene BcPh, benzo[c)phenanthrene Ch, chrysene MCh, methylchrysene MBA, 7-methyl benz[a]anthracene DMBA, 7,12-dimethyl benz[a]anthracene EBA, 7-ethyl benz[a]anthracene DB(a,l)P, dibenzo[a,l]pyrene MSCR, mechanism-based structure-carcinogenicity relationship PMO, Perturbational molecular orbital method dA, deoxyadenosine dC, deoxycytosine dG, deoxyguanosine MOS, monoxygenase enzyme system EH, epoxide hydrolase enzyme system N2(G), exocyclic nitrogen of guanine C, electrophilic centre of PAHTC K, intercalation constant CD, circular dichroism LD, linear dichroism. 

Carbocations can also be stabilized by a heteroatom that bears a lone pair of electrons able to donate into the empty p orbital (Figure 5.24). Thus, in mass spectrometry, the fragmentation generally occurs such that the cation formed can be stabilized by the heteroatom. The mass spectrum of 2-methyl-2-butanol (Figure 5.25) illustrates. The molecular ion (M would be 88) is not seen as there are good routes to stable cations. The peaks at m/z 73 and 59 represent the loss of methyl and ethyl radicals to give cations stabilized by lone pair... 

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