Orbital Phase Control of the Preferential Branching of Chain Molecules

Abstract

The orbital phase theory was applied to the stabilities of the branched isomers (1) of E(4)H(10) (E = C, Si, Ge, Sn) relative to the normal ones (2). The orbital phase prediction was confirmed by ab initio molecular orbital (MO) and density functional theory (DFT) calculations as well as by some experimental results. Further applications to the relative stabilities of other alkane and alkene isomers lead to the preference of the branched to the normal isomers, the neopentane-type to isobutane-type branching, the terminal to inner methyl branching, and the methyl to ethyl inner substitution in the longer alkanes, as well as the preference of isobutene to 2-butene moieties. The preferential stabilization of the branched isomers was shown to be general and controlled by the orbital phase.

Group 14 inorganic hydrocarbon analogues

“…56 This procedure involves exposing cyclo-Si 5 H 10 to 450 nm light which induces ring-opening/ oligomerization to yield a viscous liquid, containing silane oligomers up to M n = 2600 g mol À1 , that can either spin-coated or ink jet printed onto a substrate. 60,61 This parallels what is observed amongst the lighter hydrocarbon analogues 62 and this property has been traced, with the aid of computations, to enhanced E-H s -E-E s* hyperconjugation. 56 Besides avoiding complicated gas-phase deposition methods, this route affords a-Si with much lower hydrogen contents (o0.3 wt%) versus a-Si made by traditional CVD methods (5-20%).…”

An Orbital Phase Theory

“…The branched butene is more stable than the linear isomer. The preferential branching in the heavier congeners (E=Si, Ge, and Sn) was confirmed by the ab initio MO and DFT calculations [41].…”

“…Gronert [42] and Schleyer [43] are not aware of our theory [41]. Branched alkanes are stabilized by the C-C bond polarization by two antiperiplanar C-H bonds.…”

“…Five years after our theory of the branching [41], Gronert [42] fit the experimental atomization energies of numerous alkanes within five parameters involving the C-H and C-C bond energies as well as the repulsive geminal bond (C-C-C, C-C-H, H-C-H) interaction energies, and reproduced the effect of branching on the stability of alkanes. Wodrich and Schleyer [43] put forward alternative fits with different parameters including geminal attraction terms.…”

“…The effect of branching on the stability of alkanes has lacked a compelling explanation in the past, though many attempts [36][37][38][39][40] were made. Here, the orbital phase theory is applied to branching effects on the relative stabilities of isomeric alkanes [41].…”