Substituent effects on the N.M.R. spectra of carboxylic acid derivatives. II. 3H N.M.R. spectra of substituted benzamides and N-alkylbenzamides

1981 ◽  
Vol 34 (11) ◽  
pp. 2297 ◽  
Author(s):  
CJ O'Conner ◽  
RW Martin ◽  
DJ Calvert
Keyword(s):  
Carboxylic Acid ◽  
Chemical Shifts ◽  
Substituent Effects ◽  
Substituted Benzamides ◽  
Nitrogen Bond

The tritium n.m.r. spectra of 12 substituted benzamides and five series of N-alkylbenzamides have been measured, after tritiation of the amides, and the chemical shifts, δN3H, have been compared with δNH. The values correlate well when σR(BA) is substituted in the Taft DSP equation. Good correlations are also obtained with the Hammett σ parameter. The non-equivalence of the two amido protons of benzamides, arising from the barrier to rotation round the carbon-nitrogen bond, has been confirmed by use of triton n.m.r. spectroscopy.

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

1978 ◽  
Vol 31 (12) ◽  
pp. 2623 ◽  
Author(s):  
CW Fong ◽  
SF Lincoln ◽  
EH Williams
Keyword(s):  
Carbonyl Group ◽  
Steric Effect ◽  
Chemical Shifts ◽  
Resonance Effect ◽  
Substituent Effects ◽  
Parameter Method ◽  
Methyl Groups ◽  
Rotational Barriers ◽  
Effect Parameter ◽  
Nitrogen Bond

The barriers to rotation about the carbon-nitrogen bond and the carbon- 13 N.M.R. chemical shifts of a series of 2-substituted N,N- dimethylbenzamides have been measured. The substituent effects have been examined by a multi-substituent parameter method incorporating a steric effect parameter. The barriers to rotation are subject to a large steric effect, whilst the carbon-13 chemical shifts of the carbonyl group and the methyl groups are dominated by the resonance effect.

Substituent Effects on the 1H N.M.R. Spectra of Substituted Benzamides and N-Alkylbenzamides

1979 ◽  
Vol 32 (2) ◽  
pp. 337 ◽  
Author(s):  
DJ Calvert ◽  
CJ O'Conner
Keyword(s):  
Chemical Shift ◽  
Chemical Shifts ◽  
Substituent Effects ◽  
Substituent Constant ◽  
Substituted Benzamides ◽  
Proton Chemical Shifts

The proton chemical shifts (δNH and δCH) of 60 substituted benzamides and N-alkylbenzamides and δCH of seven substituted N,N-dialkylbenzamides have been reported and compared with sub- stituent effects. The chemical shifts (δNH and δCH of H3,5) of N-alkylbenzamides correlate well with Hammett σ values. The chemical shift δNH also correlates well with the Taft substituent constant Es. All other chemical shifts are independent of substituent effects.

Chemometric Analysis of Substituent Effects. VII. Inductive Effect as a Basic Substituent Effect. Isoeffect Substituent Constant

1995 ◽  
Vol 60 (8) ◽  
pp. 1316-1332 ◽  
Author(s):  
Oldřich Pytela ◽  
Aleš Halama
Keyword(s):  
Inductive Effect ◽  
Chemical Shifts ◽  
Quantitative Description ◽  
Substituent Effects ◽  
Intersection Point ◽  
Chemometric Analysis ◽  
Reaction Centre ◽  
Substituent Constant ◽  
Modified Method ◽  
Substituted Benzoic Acids

The paper deals with chemometric analysis of the inductive effect. The notion of inductive effect is discussed, and unambiguous definitions are given for the notions of triad: reaction centre-basic skeleton-substituent, and the therewith connected definitions of inductive effect. For a quantitative description of inductive effect 7 types of chemical models were selected including noncyclic compounds, cyclic, and bicyclic compounds, derivatives of quinuclidine, 3-substituted benzoic acids, sulfonamides and pyridines. Altogether 139 sets of experimental data from literature have been used including altogether 1 294 points (9.3 points per set, 5 points at least) reflecting substituent effects of 34 substituents. It has been found that for a standard model the dissociation of substituted bicycloalkanecarboxylic acids only is satisfactory, all the other models reflecting also the mesomeric effects to variable extent (up to 10%). A distinctly different substitution behaviour was observed with 19F and 13C NMR chemical shifts of 4-substituted 1-fluoro- or 1-methylbicyclo[2.2.2]octanes. The earlier suggested model of substituent effects based on different way of transmission of substituent effects (3 classes) has been used for separating the inductive and mesomeric effects: it is mathematically presented as a set of straight lines with the intersection point at the so-called isoeffect substituent constant. Using the modified method of conjugated deviations a chemometric scale has been created for the inductive effect which agrees very well with the conventional scales given in literature; the only differences were observed for F and CH=O substituents (which are overestimated and underestimated, respectively, in literature). In the context given the inductive effect appears as a fundamental quantity forming a basis for quantitative description of other effects transferred by electrons.

Nuclear Magnetic Resonance Chemical Shifts of some Monosubstituted Isothiazoles

1975 ◽  
Vol 53 (4) ◽  
pp. 596-603 ◽  
Author(s):  
Roderick E. Wasylishen ◽  
Thomas R. Clem ◽  
Edwin D. Becker
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shifts ◽  
Substituent Effects ◽  
Charge Densities ◽  
Monosubstituted Benzenes ◽  
Proton Chemical Shifts ◽  
Nuclear Magnetic

Carbon-13 and proton chemical shifts have been measured for several monosubstituted isothiazoles. Substituent effects upon these chemical shifts are compared with those observed for monosubstituted benzenes, pyridines, and thiophenes. In general the observed substituent effects in the isothiazoles and thiophenes closely parallel one another. Correlations between the observed carbon-13 Chemical shifts and CNDO/2 calculated charge densities are examined.

6-Methylergoline-8-carboxylic acid esters as serotonin antagonists: N1-substituent effects on 5HT2 receptor affinity

1987 ◽  
Vol 30 (10) ◽  
pp. 1823-1826 ◽  
Author(s):  
Gifford Marzoni ◽  
William L. Garbrecht ◽  
Pawel Fludzinski ◽  
Marlene L. Cohen
Keyword(s):  
Carboxylic Acid ◽  
Substituent Effects ◽  
Serotonin Antagonists ◽  
Receptor Affinity ◽  
5Ht2 Receptor ◽  
Acid Esters
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