Reversed substituent effect for the ¹³C NMR chemical shifts in the unsubstituted ring of para‐substituted benzophenones

Abstract

The 13C NMR chemical shifts of the C-1' carbon atom of fifteen para-substituted benzophenones correlate with the 9 and % substituent constants in a reversed manner.

A Very Facile SNAr Reaction with Elimination of Methoxide

“…Reaction of 0.40 g (1.9 mmol) of 4-methoxybenzophenone with KH in ethanol under the conditions described above gave 0.045 g (11%) of 4-ethoxybenzophenone as a yellow oil after chromatography (petroleum ether/ethyl acetate 20:1): 1 H NMR (300 MHz, CDCl 3 ) δ 1.45 (t, J = 7.0 Hz, 3H), 4.11 (q, J = 7.0 Hz, 2H), 6.95 (dd, J = 8.8, 2.6 Hz, 2H), 7.46 (t, J = 7.8 Hz, 2H), 7.54 (m, 1H), 7.75 (dd, J = 7.1, 1.3 Hz, 2H), 7.82 (7.0, J = 1.7 Hz, 2H); 13 C NMR (75.5 MHz, CDCl 3 ) δ 14.6, 63.7, 114.0, 128.1, 129.6, 129.9, 131.8, 132.5, 138.3, 162.6, 195.5; IR (KBr) 1665, 1608 cm -1 ; MS (EI) m / z 226 (88), 197 (15), 149 (100). The 13 C NMR data were consistent with those reported by Frahm and Hambloch …”

Evidence of the Lewis‐Amphoteric Character of Tris(pentafluoroethyl)silanide, [Si(C2F5)3]−

“…In keeping with this, 1 a and 1 b feature a 29 Si NMR chemical shift of −127.5 ppm and −122.8 ppm, respectively. The 13 C NMR chemical shift of the R′PhC moiety shifts from 194.0 ppm in benzaldehyde [30a] to 75.5 ppm in 1 a and from 196.3 ppm in benzophenone [30b] to 78.9 ppm in 1 b . Negative ESI mass spectra reveal the molecular ion peaks of 1 a and 1 b at m / z values of 491 for [Si(C 2 F 3 ) 3 (η 2 ‐CPhHO)] − ( 1 a ) and 567 for [Si(C 2 F 5 ) 3 (η 2 ‐CPh 2 O)] − ( 1 b ).…”

Nachweis des Lewis‐amphoteren Charakters von Tris(pentafluorethyl)silanid, [Si(C2F5)3]−

“…−122.8 ppm auf. Die Verschiebungen der R′PhC‐Einheit in den entsprechenden 13 C‐NMR‐Spektren ändern sich von 194.0 ppm für Benzaldehyd [30a] zu 75.5 ppm für 1 a und von 196.3 ppm für Benzophenon [30b] zu 78.9 ppm für 1 b . In den negativen ESI‐Massenspektren sind die Molekülionenpeaks von 1 a und 1 b bei m / z ‐Werten von 491 für [Si(C 2 F 3 ) 3 (η 2 ‐CPhHO)] − ( 1 a ) und 567 für [Si(C 2 F 5 ) 3 (η 2 ‐CPh 2 O)] − ( 1 b ) zu sehen.…”