A multinuclear NMR study of N-(chlorodimethylsilylmethyl) amides
Abstract
A series of N-(chlorodimethylsilylmethyl) amides of the type RCONR′(CH Si(CH ) Cl), where R=H, R′=CH ; R = CH , R′ = CH ; R = H, R′ = C H ; and R = CH , R′ = p-XC H (X = H, OCH , Cl, Br, CF , NO ) were prepared by amination or transsilyation. The H, C, N, O, and Si NMR spectra were obtained and used t to determine the structure of the compounds. The N and O shifts are indicative of the amide structure reported previously. The O and Si shifts can be related to the extent of dative interaction between the carbonyl oxygen and the silicon and correlate with the carbonyl stretching frequencies. The H spectra of most of the acetanilides in CDCl contain a broad peak for the Si(CH ) protons. At lower temperatures this peak separates into two sharp peaks of unequal intensities. The two peaks can be attributed to rotamers, with the large peak at higher frequencies being due to the rotamer with the CH Si(CH ) Cl group cis to the carbonyl oxygen. In toluene, CH Cl and THF, the Si(CH ) protons appear as a sharp peak which does not broaden upon heating to the boiling point of the solvent. The free energies of activation for rotation about the carbon-nitrogen bond were determined by the approximate method of Shanan-Atidi and Bar-Eli and show a rough correlation with the sigma constant of the substituent. © 1995. 2 3 2 3 3 3 6 5 3 6 4 3 3 2 3 3 2 2 3 2 2 2 3 2 1 13 14 17 29 14 17 17 29 1
