Theory of nuclear magnetic resonance of higher spin nuclei. 3. A2B2 systems and many-spin basis sets

1982 ◽  
Vol 86 (1) ◽  
pp. 91-96 ◽  
Author(s):  
T. H. Siddall
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Basis Sets ◽  
Higher Spin ◽  
Spin Basis ◽  
Nuclear Magnetic

1H nuclear magnetic resonance and molecular orbital estimates of the internal rotational barrier in phenylpropynal in solution and in the vapor

1992 ◽  
Vol 70 (9) ◽  
pp. 2365-2369 ◽  
Author(s):  
Ted Schaefer ◽  
Rudy Sebastian ◽  
Robert W. Schurko
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Molecular Orbital ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Basis Sets ◽  
Am1 Calculations ◽  
Internal Barrier ◽  
The One ◽  
Nuclear Magnetic

The 1H nuclear magnetic resonance spectra of phenylpropynal and 1-phenylpropyne are analyzed for CS2/C6D12 and acetone-d6 solutions. The ensuing spin–spin coupling constants over eight formal bonds are used in assessing the conformational dependence of the one in the propynal derivative, as compared to the one over six bonds in benzaldehyde. The eight-bond coupling constant in phenylpropynal implies, via a hindered rotor model, that the twofold barrier to internal rotation is 5.9 ± 1.6 kJ/mol in both solutions. This number is much smaller than that for the internal barrier in benzaldehyde, reflecting the reduced π electron conjugation in phenylpropynal. Molecular orbital computations, with geometry optimization, confirm the essentially purely twofold internal barrier in the free propynal. The theoretical magnitudes are given for AM1 calculations, as well as for abinitio computations with STO-3G, 3-21G, 6-31G, and 6-31G* bases. To within experimental error, the barrier magnitudes from the split-valence basis sets agree with those obtained in solution.

Use of locally dense basis sets for nuclear magnetic resonance shielding calculations

1993 ◽  
Vol 14 (11) ◽  
pp. 1364-1375 ◽  
Author(s):  
D.B. Chesnut ◽  
B.E. Rusiloski ◽  
K.D. Moore ◽  
D.A. Egolf
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Basis Sets ◽  
Dense Basis ◽  
Nuclear Magnetic

An emerging technology: Nuclear magnetic resonance microscopy

1988 ◽  
Vol 46 ◽  
pp. 1000-1001
Author(s):  
M.J. Hennessy ◽  
E. Kwok
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Relaxation Times ◽  
Basic Research ◽  
Local Environment ◽  
Magnetic Resonance Images ◽  
Nmr Microscopy ◽  
Mri Scans ◽  
Temperature Relaxation ◽  
Nuclear Magnetic

Much progress in nuclear magnetic resonance microscope has been made in the last few years as a result of improved instrumentation and techniques being made available through basic research in magnetic resonance imaging (MRI) technologies for medicine. Nuclear magnetic resonance (NMR) was first observed in the hydrogen nucleus in water by Bloch, Purcell and Pound over 40 years ago. Today, in medicine, virtually all commercial MRI scans are made of water bound in tissue. This is also true for NMR microscopy, which has focussed mainly on biological applications. The reason water is the favored molecule for NMR is because water is,the most abundant molecule in biology. It is also the most NMR sensitive having the largest nuclear magnetic moment and having reasonable room temperature relaxation times (from 10 ms to 3 sec). The contrast seen in magnetic resonance images is due mostly to distribution of water relaxation times in sample which are extremely sensitive to the local environment.

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