Measurement of Ribose Carbon Chemical Shift Tensors for A-form RNA by Liquid Crystal NMR Spectroscopy

2005 ◽  
Vol 127 (20) ◽  
pp. 7387-7396 ◽  
Author(s):  
David L. Bryce ◽  
Alexander Grishaev ◽  
Ad Bax
Keyword(s):  
Liquid Crystal ◽  
Nmr Spectroscopy ◽  
Chemical Shift ◽  
Chemical Shift Tensors ◽  
Carbon Chemical Shift

A solid-state 13C NMR and theoretical investigation of carbonyl and thiocarbonyl carbon chemical shift tensors

1995 ◽  
Vol 73 (4) ◽  
pp. 604-613 ◽  
Author(s):  
Christopher W. Kirby ◽  
Michael D. Lumsden ◽  
Roderick E. Wasylishen
Keyword(s):  
Solid State ◽  
Chemical Shift ◽  
Ab Initio ◽  
Principal Axis ◽  
Comparative Investigation ◽  
Conclusive Evidence ◽  
Carbon Nucleus ◽  
Chemical Shift Tensors ◽  
Carbon Chemical Shift ◽  
C Nmr

The carbon chemical shift tensors of the carbonyl and thiocarbonyl groups of acetamide, thioacetamide, thioacetanilide, 4′-methoxyacetanilide, and 4′-methoxythioacetanilide have been experimentally determined using dipolar – chemical shift solid-state 13C NMR spectroscopy. The magnitudes of the three principal components of the carbon chemical shift tensors are found to exhibit marked variations between the carbonyl and thiocarbonyl functionalities. However, in contrast to the conclusions of an earlier comparative investigation involving benzophenone and thiobenzophenone, the orientations of the principal axis systems of these chemical shift tensors are found to be similar. These experimental results represent the first complete characterizations of the carbon chemical shift tensor in organic thiocarbonyls. The results of our ab initio GIAO and LORG calculations of carbon chemical shielding tensors in formaldehyde, thioformaldehyde, formamide, and thioformamide as well as in acetamide and thioacetamide are in qualitative agreement with experiment. The findings of the present investigation provide conclusive evidence that the well-known isotropic deshielding of the carbon nucleus in the C=S group relative to C=O is primarily attributable to the decreased energy associated with the σ ↔ π* excitation within the thiocarbonyl fragment. This result is in contrast with the conventional interpretation that the deshielding originates from a red shift in the C=S HOMO–UMO n → π* transition. Keywords: chemical shift tensors, solid-state 13C NMR, carbonyls, thiocarbonyls, ab initio calculations.

Phosphorus Chemical Shift Tensors of Phosphole Derivatives Determined by31P NMR Spectroscopy of Powder Samples

1996 ◽  
Vol 35 (13) ◽  
pp. 3904-3912 ◽  
Author(s):  
Klaus Eichele ◽  
Roderick E. Wasylishen ◽  
Janet M. Kessler ◽  
Ljiljana Solujić ◽  
John H. Nelson
Keyword(s):  
Nmr Spectroscopy ◽  
Chemical Shift ◽  
Chemical Shift Tensors ◽  
Powder Samples

15N Chemical Shift Tensors of Uracil Determined from 15N Powder Pattern and 15N-13C Dipolar NMR Spectroscopy

1995 ◽  
Vol 99 (26) ◽  
pp. 10454-10458 ◽  
Author(s):  
Karen L. Anderson-Altmann ◽  
Cu G. Phung ◽  
Stylianos Mavromoustakos ◽  
Zhiwen Zheng ◽  
Julio C. Facelli ◽  
...  
Keyword(s):  
Nmr Spectroscopy ◽  
Chemical Shift ◽  
Powder Pattern ◽  
Chemical Shift Tensors
Sign in / Sign up

Export Citation Format

Share Document