Magnetic non-equivalence of the α-methylene protons in alkyl chlorosulphites and the effects of temperature and of pyridinium chloride

Hudson, H. R.; Rees, R.G.; Spinoza, G.Riga De

doi:10.1016/0584-8539(71)80172-1

Cited by 4 publications

(1 citation statement)

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“…Hudson et al reported that neopentyl chlorosulfite shows an ABX9 system in the 1 H NMR spectra. 29 Upon raising the temperature of undiluted neopentyl chlorosulfite to 100 °C, a partial collapse of the AB pattern was observed. This is thought to be due to the onset of chlorinechlorine exchange between molecules, each exchange being accompanied with inversion of configuration at the sulfur tetrahedron and causing loss of asymmetry for the time averaged environment of the protons of the methylene group (see TS-II in Scheme 4).…”

Section: Solvent Effects In Geometries Charges and Energiesmentioning

confidence: 99%

A new mechanism for internal nucleophilic substitution reactions

2018

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A new mechanism for the classic internal nucleophilic substitution reactions Si by means of computational studies in the gas-phase, DCM and acetonitrile is reported. Despite the importance of the Si mechanism, since the mid-1990s this mechanism has remained unexplored. This study focused mainly on the comparison between the mechanisms postulated to date for the Si reactions and a new mechanism suggested by us that fits better the experimental observations. This comparative study has been applied to the conversion of ethyl, neopentyl, isopropyl and tert-butyl chlorosulfites into the corresponding alkyl chlorides. This new mechanism occurs through two transition structures. For primary and secondary substrates, the first transition structure is a 6-center syn-rearrangement of the alkanesulfonyl chloride that produces the corresponding olefin by simultaneous expulsion of HCl and SO. The olefin, HCl and SO form a molecular complex. The final syn-addition of HCl to the olefin leads to alkyl chloride with the retention of configuration. For tertiary substrates, a variation of the previous mechanism is postulated with the intervention of contact ion pairs. It is of great importance to emphasize that this new mechanism is able to explain some experimental observations such as the presence of olefins in these types of reactions and the low reactivity of some systems such as neopentyl chlorosulfite. Our results pave the way to a new mechanistic perspective in similar reactions which will need further studies and validation.

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Section: Solvent Effects In Geometries Charges and Energiesmentioning

confidence: 99%