Int. J. Mol. Sci. 2003, 4(4), 231-248; doi:10.3390/i4040231
Article

The Effect of Substituents on Indirect Nuclear Spin-Spin Coupling Constants: Methan- and Ethanimine, Methanal- and Ethanaloxime

1 Department of Physics, Northeastern University, Av. Libertad 5500, W 3404 AAS Corrientes, Argentina 2 Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen Ø, Denmark
* Author to whom correspondence should be addressed.
Received: 28 October 2002; Accepted: 17 February 2003 / Published: 4 April 2003
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Abstract: Ab initio calculations of the spin-spin coupling constants have been carried out for methan- and ethanimine, methanal- and ethanaloxime at the level of the second order polarization propagator approximation with coupled cluster singles and doubles amplitudes (SOPPA(CCSD)) using the aug-cc-pVTZ-J basis sets. Previously we have shown that this method can reproduce quantitatively the coupling constants for methanimine; our new results for methanal- and ethanaloxime agree also very well with the measured couplings. A study of both purely geometrical and substituent effects on all coupling constants in the title compounds is presented. Analyzing the four contributions to the coupling constants we find that the stereoelectronic effect of the nitrogen lone pair on the one-bond C-H and C-C couplings as well as the corresponding effect for the geminal N-H and N-C couplings is affected strongly by the -OH substituent. For the one-bond C-N couplings we observe that the orbital paramagnetic (OP) contribution is comparable to the Fermi Contact (FC) contribution but opposite in sign and that the spin-dipolar (SD) term amounts to between 40% and 85% of the total coupling constants. Changes in the total one-bond C-N couplings caused by the -OH substituent are also almost entirely due to SD contribution.
Keywords: Ab Initio; NMR; indirect nuclear spin-spin coupling constants; SOPPA(CCSD); methanimine; ethanimine; methanaloxime; ethanaloxime

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MDPI and ACS Style

Provasi, P.F.; Aucar, G.A.; Sauer, S.P.A. The Effect of Substituents on Indirect Nuclear Spin-Spin Coupling Constants: Methan- and Ethanimine, Methanal- and Ethanaloxime. Int. J. Mol. Sci. 2003, 4, 231-248.

AMA Style

Provasi PF, Aucar GA, Sauer SPA. The Effect of Substituents on Indirect Nuclear Spin-Spin Coupling Constants: Methan- and Ethanimine, Methanal- and Ethanaloxime. International Journal of Molecular Sciences. 2003; 4(4):231-248.

Chicago/Turabian Style

Provasi, Patricio F.; Aucar, Gustavo A.; Sauer, Stephan P.A. 2003. "The Effect of Substituents on Indirect Nuclear Spin-Spin Coupling Constants: Methan- and Ethanimine, Methanal- and Ethanaloxime." Int. J. Mol. Sci. 4, no. 4: 231-248.

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