Lcao Mo Calculations on Saturated Hydrocarbons and Their Substituted Derivatives

Abstract

T h e simple semiempirical niolecnlar orbital method was applied t o saturated hytlrocarbons in three different approximations. Electronic charge clistribt~tion diagrams were obtained. Characteristic differences between saturatecl ancl conjugated compounds concerning bond localization and t h e effect of an electronegative sr~hstituent can be interpreted on t h e basis of these diagrams. ?'he 1s electrons of the hydrogens are introcl~tced for the first time in semiempirical molecular orbital calculations.

35Cl Nuclear Quadrupole Resonance of Alkyl Chloroformates, Alkyl Acid Chlorides, and Carbamyl Chlorides

“…frequencies, as previously described (3). (Table 1 ) The frequencies of the n-alkyl chloroformates are approximately constant for R greater than n-C,H,, in agreement with the behavior of the frequencies in the RCl series (4) and with the normal o-inductive effects of organic chemistry in such alkyl molecules (5)(6)(7).…”

Geometric localisation in Möbius π systems

“…The fact that the occupied molecular orbitals of small Mobius annulenes can be partitioned into those of a polyene and a twisted ethene fragment [10] is consistent with the dominance of r factors. The energetic cost of such twisting can be estimated by a modified version of the Sandorfy C model [26] taking explicitly into account 1,3-interactions [27,28].…”

Addition of nucleophile to bent bonds of the carbonyl group

“…2). As already mentioned, non-zero resonance parameters represent pairs of HAOs of the same atom [35][36][37] in contrast to σ and π orbitals. Let the resonance parameter referring Notations ai and bi represent the coefficients at separate HAOs in the final bond orbitals.…”

“…In our context, the most important attractive feature of bent bonds consists in non-zero resonance parameters between respective bond orbitals both inside the double bond and between the latter and other fragments, in contrast to the above-discussed σ, π-model. (Let us recall here that non-zero resonance parameters always arise between pairs of sp 3 -HAOs of the same atom owing to different one-electron energies of 2s and 2p AOs [35][36][37].) Thus, the model of Ad N 2 reactions to be suggested in the present study is based on a certain combination of the semilocalized approach of Refs.…”