PENTAMETHYLDISILANYL-SUBSTITUTED PHENOL AND ACETOPHENONE - ELECTRONIC EFFECTS OF P-PENTAMETHYLDISILANYL GROUP

The chemical shifts of the hydroxyl protons of p-(trimethylsilyl)- and p-(pentamethyldisilanyl) phenol have been measured, and used in the derivation of σ--constants of +0.06 and +0.02, respectively, for the p-Me3Si and p-Me5Si2 group. The carbonyl stretching frequencies of p-(trimethylsilyl)-, p-(pentamethyldisilanyl)-, p-(trimethylsiloxy)-, and p-(pentamethyldisilanoxy)acetophenone have been determined and used to give σ+-constants for p-Me3Si, p-Me5Si2, p-Me3SiO, and p-Me5Si2O of 0.0, -0.23, -0.60, and -0.60, respectively. It is concluded that the p-Me5Si2 group has a larger + I and also a larger - T effect than the p-Me3Si group. © 1969.