Steric effects on nitrogen-15 chemical shifts of 4-aminooxanes (tetrahydropyrans), 4-aminothianes, and the corresponding N,N-dimethyl derivatives. Use of nitrogen-15 shifts as an aid in stereochemical analysis of these heterocyclic systems

1982 ◽  
Vol 47 (10) ◽  
pp. 1933-1935 ◽  
Author(s):  
Pullachipatti K. Subramanian ◽  
Nallappan ChandraSekara ◽  
Kondareddiar Ramalingnam ◽  
Phanviet M. Tan ◽  
George C. Levy ◽  
...  
Keyword(s):  
Chemical Shifts ◽  
Steric Effects ◽  
Stereochemical Analysis

14N-NMR-Untersuchungen an Aminophosphinen / 14N NMR Studies on Aminophosphines

1978 ◽  
Vol 33 (5) ◽  
pp. 515-520 ◽  
Author(s):  
K. Barlos ◽  
H. Nöth ◽  
B. Wrackmeyer
Keyword(s):  
Chemical Shifts ◽  
Steric Effects ◽  
Nmr Studies ◽  
Π Interactions ◽  
Nuclear Shielding ◽  
14N Nmr

Abstract14N chemical shifts of a series of cyclic and noncyclic aminophosphines are reported. The nuclear shielding of nitrogen decreases with increasing number of halogen substituents at phosphorus as well as with increasing number of phosphinyl groups attached to nitrogen. In addition to the influence of electronegativity PN(π)-interactions may account for the observed shielding. Steric effects are discussed.

Semiempirical calculation of 13C nuclear magnetic resonance chemical shifts of acyclic hydrocarbons. Application to the stereochemical analysis of steroidal side chains

1988 ◽  
Vol 66 (1) ◽  
pp. 71-75 ◽  
Author(s):  
Manuel Gonzalez-Sierra ◽  
Daniel A. Bustos ◽  
Edmundo A. Ruveda ◽  
Alejandro C. Olivieri ◽  
Mariano Grasselli
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shifts ◽  
Side Chains ◽  
Stereochemical Analysis ◽  
Microcomputer Program ◽  
Semiempirical Approach ◽  
13C Nuclear Magnetic Resonance ◽  
Acyclic Hydrocarbons ◽  
Nuclear Magnetic

A semiempirical approach for predicting 13C nuclear magnetic resonance chemical shifts of acyclic hydrocarbons has been adapted to a microcomputer program. A series of methyl and dimethyl substituted cholesterols has been studied using this program, and the predicted shifts are in agreement with literature reports. Preferred conformations of the steroidal side chains have been also predicted and agree with previous studies. A simple rule for analyzing the trends in the chemical shift of the carbon C-20, which is sensitive to changes in the configuration at C-22, is also given, not only for hydrocarbon side chains but also for hydroxy substituted compounds.

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