interações de orbitais e seus efeitos nos acoplamentos jch em 1,3,5 ...
interações de orbitais e seus efeitos nos acoplamentos jch em 1,3,5 ...
interações de orbitais e seus efeitos nos acoplamentos jch em 1,3,5 ...
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Abstract:<br />
Orbital Interactions and their effects on 2 JHH e 1 JCH Coupling<br />
Constants in 1,3,5-trioxane, 1,3,5-trithiane and 2-substituted 1,3,5<br />
–trithianes: Experimental and Theoretical Study<br />
Keywords: hyperconjugative interactions, coupling constants<br />
The present work reports the NMR data and theoretical calculations of orbital<br />
interactions and their effects on 2 JHH e 1 JCH coupling constants in 1,3,5-trioxane, 1,3,5-<br />
trithiane and 2-substituted 1,3,5-trithianes, where the substitutents are fluorine, chlorine,<br />
bromine and methyl.<br />
The calculations were carried out with the Gaussian 98 and 03 package of<br />
programs. The aug-cc-pVTZ basis sets were <strong>em</strong>ployed for geometries optimizations at<br />
level MP2. The energies of hyperconjugative interactions were calculated with the NBO<br />
program. The coupling constants were evaluated within the CP-DFT perturbative<br />
approach.<br />
The 1 H and 13 C spectra were recor<strong>de</strong>d for all compounds at room and low<br />
t<strong>em</strong>perature, for obtained the <strong>de</strong>termination of coupling constants.<br />
The experimental results and those from theoretical calculations showed the<br />
influence of hyperconjugative interactions nx→σ*C–Heq, nx→σ*C–Hax e nx→σ*C–X, where X<br />
is oxygen or sulfur atoms, on 1 JCHax, 1 JCheq and 2 JHH coupling constants in 1,3,5-trioxane<br />
and 1,3,5-trithiane.<br />
The experimental results and those from theoretical calculations showed the<br />
influence of electrostatic effects for 1 JCHax coupling constant in 2-substituted 1,3,5-<br />
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