interações de orbitais e seus efeitos nos acoplamentos jch em 1,3,5 ...

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