Spectroscopic studies onN,N-dimethylamides—IV An NMR total line shape study of substituent effects and medium effects on amide-rotational barriers ofN,N-dimethylbenzamides and -cinnamamides

1971 ◽  
Vol 3 (5) ◽  
pp. 615-625 ◽  
Author(s):  
K. Spaargaren ◽  
P. K. Korver ◽  
P. J. Der Van Haak ◽  
Th. J. de Boer
Keyword(s):  
Line Shape ◽  
Substituent Effects ◽  
Spectroscopic Studies ◽  
Medium Effects ◽  
Rotational Barriers

Carbon-13 N.M.R. chemical shifts and rotational barriers of para-substituted N,N-dimethylbenzamides

1978 ◽  
Vol 31 (12) ◽  
pp. 2615 ◽  
Author(s):  
CW Fong ◽  
SF Lincoln ◽  
EH Williams
Keyword(s):  
Chemical Shift ◽  
Chemical Shifts ◽  
Substituent Effects ◽  
Rotational Barrier ◽  
Rotational Barriers

The carbon-13 N.M.R. chemical shifts for a series of para-substituted N,N-dimethylbenzamides have been measured. The substituent induced 13C shifts have been examined by a dual substituent parameter (DSP) method using Hammett-type constants. The barriers to rotation have also been correlated with Hammett-type constants by the DSP method and related to 13C substituent induced shifts. Substituent effects of the bromomethyl, dibromomethyl and tribromomethyl groups have been examined by using the chemical shift and rotational barrier probes.

A theoretical approach to substituent effects. Stabilities and rotational barriers of β-substituted ethyl anions

1980 ◽  
Vol 33 (2) ◽  
pp. 241 ◽  
Author(s):  
A Pross ◽  
L Radom
Keyword(s):  
Ab Initio ◽  
Molecular Orbital ◽  
Theoretical Approach ◽  
Substituent Effects ◽  
Molecular Orbital Theory ◽  
Orbital Theory ◽  
Rotational Barriers

Ab initio molecular orbital theory is used to study substituent effects in a series of substituted ethyl anions, XCH2CH2- (X = Li, BeH, BH2, CH3, NH2, OH and F). All substituents stabilize the anion relative to the corresponding neutral ethane. For electronegative substituents (NH2, OH and F) as well as CH3, this stabilization is achieved through enhanced hyperconjugative donation from the occupied 2p(C-) orbital to a vacant π*(CH2X) or π*(CH2) orbital; electropositive groups (Li, BeH and BH2) stabilize the anion primarily by 1,3-overlap between the occupied 2p(C-) orbital and the vacant 2p(X) orbital where such an interaction is possible. The importance of 1,3-interactions contrasts with the situation for cations XCH2CH2+ in which hyperconjugative interactions appear to be dominant.

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