ISSN:
0749-1581
Keywords:
13C NMR
;
1H NMR Olefins
;
Substituent effects
;
Substituent-induced chenical shifts (SCS)
;
Chemistry
;
Analytical Chemistry and Spectroscopy
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
1H and 13C NMR signals were assigned and CH coupling constants (1J, 2J, 3J) determined for a series of α-mono-and α,α-disubstituted (1,1,3,3-tetramethyl-2-indanylidene)methanes with the following α-substituents: (mesityl)2B, n-propyl, phenyl, tert-butyl-C(=NH), cyano, (tert-butyl)2C(OH), pivaloyl, H2N-CO, PhNH-CO, carboxy, ritro, acetoxy, Me3SiO, Me3Si, PhS, PhSMe+, PhSO, PhSO2, bromo and trimethylstannyl. The 1J couplings with the olefinic proton span the range 124.3-193.7 Hz. Substituent-induced chemical shifts (SCS) of most of the nuclei with respect to the α-unsubstituted olefin obey simple additivity in the α,α-disubstituted compounds and are very similar to the SCS values along the C=N double bond in the isoelectronic (1,1,3,3-tetramethyl-2-indanylidene)amines within the error limits. The exceptions concern nuclei in the immediate vicinity of the perturbing substituent. A dominant mechanistic contribution of electric field effects appears likely for the more distant aromatic part of the indanylidene moiety. The chemical shifts of two (2,2,5,5-tetramethylcyclopentylidene)methanes are shown to be compatible with the SCS parameters from the indanylidene series.
Additional Material:
2 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/mrc.1260310608
Permalink
