The photoelectron spectrum of 1,1-difluoroallene. On .pi. electron donation and withdrawal by fluorine

Abstract

The photoelectron spectrum and ab initio 4-31G calculations on 1,1 -difluoroallene provide unique data on the donor and acceptor properties of fluorine operating on the mutually perpendicular orbitals in a single molecule. The spectrum has been assigned by correlative analyses, by analysis of the vibrational structure in the first two bands, and by comparison with ab initio 4-31G calculations on aliene, 1,1 -difluoroallene, and tetrafluoroallene. Because fluorines have only a minor influence on the tv and * orbitals of the double bond to which they are directly attached, but have a profound energy lowering effect on the orbitals with which they "negatively hyperconjugate", 1,1-difluoroallene has one electron-rich and one electron-deficient double bond, and should provide a valuable probe of electronic characteristics and mechanisms of cycloaddition reactions.

Organometallic chemistry of fluorinated propadienes and butadienes

“…During the following years the organic chemistry of fluorinated allenes has been studied in detail mainly by Dolbier [12] The structures of fluoroallene [13] and 1,1-difluoroallene [14] in the gas phase were determined by microwave spectroscopy and the photoelectron spectrum of 1,1-difluoroallene was recorded in 1978 [15]. Tetrafluroallene, first prepared by Jacobs and Bauer [16], is even less studied.…”

Organometallic Chemistry of Fluorinated Allenes

“…During the subsequent years, the organic chemistry of fluorinated allenes has been studied in detail mainly by those workers 11. The structures of fluoroallene12 and 1,1‐difluoroallene13 in the gas phase were determined by microwave spectroscopy, and the photoelectron spectrum of 1,1‐difluoroallene was recorded in 1978 14. Tetrafluroallene, first prepared by Jacobs and Bauer in 1959, has been even less studied 15.…”

1,3‐Dipolar Cycloadditions of 1,1‐Difluoroallene, Nitrones, Nitrile‐Oxides and Carbonyl Ylides

“…It is also expected that the LUMO of OFA (i,e. the C rC3 1T* orbital) is influenced by the "negative hyperconjugative" electron-accepting properties of the low-lying a* CF 2 orbital (see 21 below) [4] such that a significant electron deficiency should be present at C 3 , perhaps even creating electrostatic attraction to the oxygen end of the nitrone dipole in the transition state.…”

“…Such behavior is in dramatic contrast to the general non-regiospecificity of the [2+2] reactions of DFA, where the major adducts are always contrarily those with the CF2 group in the ring [1,2] . to~C .Fl The regiospecificity of the [2+4] reactions of DFA was rationalized in terms of the FMO theory of concerted cyc1oadditions [3,4], recognizing that the LUMO of DFA is its C 2-C 3 1(* orbital [4]. On the other hand, the lack of regiospecificity of its [2+2] reactions, as well as the preferential formation of adducts such as 2 and 3, is totally consistent with the expectation that such reactions should be non-concerted and involve diradical intermediates.…”