CONFORMATIONAL PREFERENCE OF 4-ETHYL- 6-METHYL-1,3-DITHIANES

Interconversion reaction of I ⇔ II conformers of 4-ethyl-6-methyl-1,3-dithiane (METDIT) has been studied by means of ab initio methods on the frame of MO theory. Optimized geometries at HF/6-31G** level correlate well with that found for the parent 1,3-dithianefrom an x-ray diffraction stu...

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Autores principales:	CONTRERAS,J. GUILLERMO, GERLI,LORENA A.
Lenguaje:	English
Publicado:	Sociedad Chilena de Química 2007
Materias:	4-ethyl-6-methyl-1,3-dithiane conformational preference NMR properties
Acceso en línea:	http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072007000300018
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spelling	oai:scielo:S0717-970720070003000182007-11-29CONFORMATIONAL PREFERENCE OF 4-ETHYL- 6-METHYL-1,3-DITHIANESCONTRERAS,J. GUILLERMOGERLI,LORENA A. 4-ethyl-6-methyl-1,3-dithiane conformational preference NMR properties Interconversion reaction of I ⇔ II conformers of 4-ethyl-6-methyl-1,3-dithiane (METDIT) has been studied by means of ab initio methods on the frame of MO theory. Optimized geometries at HF/6-31G** level correlate well with that found for the parent 1,3-dithianefrom an x-ray diffraction study. Both conformers possess similar bond distances, but differ in up 12° in some dihedrals. Conformer I geometry presents the larger distortion from the regular 1,3-dithiane mainly due to difference between angles κ1 and κ2 (ca. 14°). In conformer II this difference is just ca. 3°. The energetics and thermodynamics were obtained with basis sets that include diffuse, polarization functions and electronic correlations at the second-order perturbation Meller Plesset theory. Gas phase thermodynamic predicts II to be in a 98% concentration. Low and medium high polarity solvents seem to exert no influence on the conformers concentrations. Thus the I ⇔ II interconversion reaction is largely displaced to II formation, both in the gas phase and solution. The calculated ¹H-NMR data, i.e., chemical shifts and one-bond C-H spin-spin coupling constants are predicted on the basis of the consistent results obtained for the parent 1,3-dithiane. For both conformers reverse Perlin effect takes place at C2 and C5. The C2 - Hax and C2 - Heq bond distances are similar ( ca. 1.092 Å), whereas the C5- Heq are larger than the axial ones yielding smaller ¹J C-H coupling constantsinfo:eu-repo/semantics/openAccessSociedad Chilena de QuímicaJournal of the Chilean Chemical Society v.52 n.3 20072007-09-01text/htmlhttp://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072007000300018en10.4067/S0717-97072007000300018
institution	Scielo Chile
collection	Scielo Chile
language	English
topic	4-ethyl-6-methyl-1,3-dithiane conformational preference NMR properties
spellingShingle	4-ethyl-6-methyl-1,3-dithiane conformational preference NMR properties CONTRERAS,J. GUILLERMO GERLI,LORENA A. CONFORMATIONAL PREFERENCE OF 4-ETHYL- 6-METHYL-1,3-DITHIANES
description	Interconversion reaction of I ⇔ II conformers of 4-ethyl-6-methyl-1,3-dithiane (METDIT) has been studied by means of ab initio methods on the frame of MO theory. Optimized geometries at HF/6-31G** level correlate well with that found for the parent 1,3-dithianefrom an x-ray diffraction study. Both conformers possess similar bond distances, but differ in up 12° in some dihedrals. Conformer I geometry presents the larger distortion from the regular 1,3-dithiane mainly due to difference between angles κ1 and κ2 (ca. 14°). In conformer II this difference is just ca. 3°. The energetics and thermodynamics were obtained with basis sets that include diffuse, polarization functions and electronic correlations at the second-order perturbation Meller Plesset theory. Gas phase thermodynamic predicts II to be in a 98% concentration. Low and medium high polarity solvents seem to exert no influence on the conformers concentrations. Thus the I ⇔ II interconversion reaction is largely displaced to II formation, both in the gas phase and solution. The calculated ¹H-NMR data, i.e., chemical shifts and one-bond C-H spin-spin coupling constants are predicted on the basis of the consistent results obtained for the parent 1,3-dithiane. For both conformers reverse Perlin effect takes place at C2 and C5. The C2 - Hax and C2 - Heq bond distances are similar ( ca. 1.092 Å), whereas the C5- Heq are larger than the axial ones yielding smaller ¹J C-H coupling constants
author	CONTRERAS,J. GUILLERMO GERLI,LORENA A.
author_facet	CONTRERAS,J. GUILLERMO GERLI,LORENA A.
author_sort	CONTRERAS,J. GUILLERMO
title	CONFORMATIONAL PREFERENCE OF 4-ETHYL- 6-METHYL-1,3-DITHIANES
title_short	CONFORMATIONAL PREFERENCE OF 4-ETHYL- 6-METHYL-1,3-DITHIANES
title_full	CONFORMATIONAL PREFERENCE OF 4-ETHYL- 6-METHYL-1,3-DITHIANES
title_fullStr	CONFORMATIONAL PREFERENCE OF 4-ETHYL- 6-METHYL-1,3-DITHIANES
title_full_unstemmed	CONFORMATIONAL PREFERENCE OF 4-ETHYL- 6-METHYL-1,3-DITHIANES
title_sort	conformational preference of 4-ethyl- 6-methyl-1,3-dithianes
publisher	Sociedad Chilena de Química
publishDate	2007
url	http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072007000300018
work_keys_str_mv	AT contrerasjguillermo conformationalpreferenceof4ethyl6methyl13dithianes AT gerlilorenaa conformationalpreferenceof4ethyl6methyl13dithianes
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CONFORMATIONAL PREFERENCE OF 4-ETHYL- 6-METHYL-1,3-DITHIANES

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