130878-35-2Relevant academic research and scientific papers
PROXIMITY AND CONFORMATION EFFECTS IN 29Si AND 13C NMR SPECTRA OF DI-Ortho SUBSTITUTED TRIMETHYLSILOXYBENZENES
Schraml, Jan,Brezny, Robert,Cermak, Jan
, p. 2027 - 2032 (2007/10/02)
29Si and 13C NMR spectra of five 4-substituted 2,6-dimetoxytrimethylsiloxybenzenes were studied with the aim to elucidate the nature of the deshielding proximity effects observed in the spectra of ortho substitued trimethylsiloxybenzenes.The sensitivity of 29Si chemical shifts to para substitution is in the studied compounds essentially the same as in mono ortho methoxy-trimethylsiloxybenzenes.The deshielding proximity effect of the "second' methoxy group is somewhat smaller than that of the 'first' group.The present results indicate that the two methoxy groups assume coplanar conformations with the benzene ring and are turned away from the trimethylsiloxy group which is not in the benzene plane.It is argued that in mono ortho methoxytrimethylsiloxybenzenes the two substituent groups adopt the same conformations as in the compounds studied here.
