Bindungssystem der N-acyl-sulfilimine—II: Ir spektroskopische untersuchung der N-Dihalogenacetyl-sulfilimine

Abstract

N-Dihaloacetyl-sulphilimines (RR′SNCOQ; R,R′ = aliphatic or aromatic groups, Q = CHCl 2, CHBr 2) can be prepared from dihalogeno acetamide and thioether by a slightly modified Mann-Pope condensation. In the IR spectra of these compounds the ν SN and ν CO band may be found at 820-780 cm −1 and at 1640-1600 cm −1 respectively. The ν SN and ν CO values depend on the kind of halogen atoms of the Q group, but they are independent of the character of the R and R′ groups. On the basis of these facts, the bonding system of N-dihaloacetyl-sulphilimines shows a strong conjugative effect, but this is limited to the SNCO bonding system. As a result of the conjugation the SN and CO bonds are strongly polar, the first one having nearly single bond character, and consequently the SN dπ bond is very weak. The relative lability of sulphilimines containing the N-carboacyl group is due to their highly polar structure. In the case of N-dihaloacetyl-sulphilimines the —I effect of the Q group represents a stability-enhancing factor.