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Experimental And Theoretical Studies Of Intramolecular Hydrogen Bonding In 3-hydroxytetrahydropyran: Beyond Aim Analysis
No full textThe conformational preferences of 3-hydroxytetrahydropyran (1) were evaluated using infrared and nuclear magnetic resonance spectroscopic data in solvents of different polarities. Theoretical calculations in the isolated phase and including the solvent effect were performed, showing that the most stable conformations for compound 1 are those containing the substituent in the axial and equatorial orientations. The axial conformation is more stable in the isolated phase and in a nonpolar solvent, while the equatorial conformation is more stable than the axial in polar media. The occurrence of intramolecular hydrogen-bonded O-H⋯O in the axial conformer was detected from infrared spectra in a nonpolar solvent at different concentrations. Our attempt to evaluate this interaction using population natural bond orbital and topological quantum theory of atoms in molecules analyses failed, but topological noncovalent interaction analysis was capable of characterizing it. © 2014 American Chemical Society.1181527942800Eliel, E.L., Samuel, H.W., Doyle, M.P., (2001) Basic Organic Stereochemistry, , Wiley-Interscience: New YorkCortéz-Guzman, F., Hernández-Trujillo, J., Cuevas, G., The Nonexistence of Repulsive 1,3-diaxial Interactions in Monosubstituted Cyclohexanes (2003) J. Phys. Chem. A, 107, pp. 9253-9256Ribeiro, D.S., Rittner, R., The Role of Hyperconjugation in the Conformational Analysis of Methylcyclohexane and Methylheterocyclohexanes (2003) J. Org. Chem., 68, pp. 6780-6787Taddei, F., Kleinpeter, E., The Anomeric Effect in Substituted Cyclohexanes. I. The Role of Hyperconjugative Interactions and Steric Effect in Monosubstituted Cyclohexanes (2004) J. Mol. 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Effect Of Sulfur Oxidation On The Transmission Mechanism Of4jhh Nmr Coupling Constants In 1,3-dithiane
No full textLong-range 4JHH couplings in 1,3-dithiane derivatives are rationalized in terms of the effects of hyperconjugative interactions involving the S=0 group. Theoretical and experimental studies of 4JHH couplings were carried out in 1,3-dithiane-l-oxide (2), cw-l,3-dithiane-l,3-dioxide (3), l,3-dithiane-l,l,3-trioxide (4), and 1,3-dithiane-1,1,3,3-tetraoxide (5) compounds. Hyperconjugative interactions were studied with the natural bond orbital, NBO, method. Hyperconjugative interactions involving the LP O, oxygen lone pair and σ*C2-S1 and σ*S1-C6 antibonding orbitals yield an increase of 4JHeq-Heq couplings. Long-range 4JHax-Hax couplings were also observed between hydrogen atoms in axial orientation, which are rationalized as originating in hyperconjugative interactions involving the bonding σC6-h axand antibonding σ*S=O orbitals. 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A 1h Nmr And Molecular Modelling Investigation Of Diastereotopic Methylene Hydrogen Atoms
No full textThe 1H NMR spectra of methyl 3-bromo-2-methylpropionate (1a) and the corresponding chloro compound (2a) show no long-range coupling between the methyl and methylene protons. In contrast, in the analogous dihalocompounds, methyl 2,3-dibromo-2-methylpropionate (1b) and methyl 2,3-dichloro-2-methylpropionate (2b), one of the methylene protons exhibits a large 4JHH coupling (0.8 Hz) to the methyl group, but the other proton shows no observable splitting. This can be explained quantitatively by calculations of the conformational preferences in these compounds combined with the known orientation dependence of the 4JHH couplings. One conformer predominates in the dihalo compounds 1b and 2b, and this is responsible for the 4JHH coupling. In 1a and 2a all three conformers are populated and the 4JHH couplings average to zero. The technique is a potentially general method of unambiguously assigning diastereotopic methylene protons. Copyright © 2002 John Wiley & Sons, Ltd.404279283Ault, A., (1970) J. Chem. Educ., 47, p. 813Sanders, J.K.M., Hunter, B.K., (1993) Modern NMR Spectroscopy - A Guide for Chemists, 2nd Ed., , Oxford University Press: New YorkCookson, D.J., Smith, B.E., (1984) J. Magn. Reson., 56, p. 510Snyder, E.I., (1963) J. Am. Chem. Soc., 85, p. 2624Mislow, K., (1978) J. Am. Chem. Soc., 100, p. 911Waugh, J.S., Cotton, F.A., (1961) J. Phys. Chem., 65, p. 562Abraham, R.J., Rittner, R., Unpublished resultsAbraham, R.J., Tormena, C.F., Rittner, R., (2001) J. Chem. Soc. Perkin Trans. 2, p. 815Abraham, R.J., (1999) Prog. Nucl. Magn. Reson. Spectrosc., 35, p. 85Abraham, R.J., Oliver, W.L., (1971) Org. Magn. Reson., 13, p. 725Abraham, R.J., Fisher, J., Loftus, P., (1988) Introduction to NMR Spectroscopy, , John Wiley & SonsAbraham, R.J., Jones, A.D., Warne, M.A., Rittner, R., Tormena, C.F., (1996) J. Chem. Soc. Perkin Trans. 2, p. 533Abraham, R.J., Tormena, C.F., Rittner, R., (1999) J. Chem. Soc. Perkin Trans. 2, p. 1663Tormena, C.F., Rittner, R., Abraham, R.J., Basso, E.A., Pontes, R.M., (2000) J. Chem. Soc. Perkin Trans. 2, p. 2054PCMODEL, Version 7, , Serena Software: Bloomington, IN, USAFrisch, M.J., Trucks, C.W., Schlegel, H.B., Scuseria, G.E., Robb, M.A., Cheeseman, J.R., Zakrzewski, V.G., Pople, J.A., (1998) Gaussian 98, , Gaussian Inc.: Pittsburgh, PAFurniss, B.S., Hannaford, A.J., Rogers, V., Smith, P.W.G., Tatchell, A.R., (1978) Vogel's Textbook of Practical Organic Chemistry, 4th Ed., , Longman Inc.: New Yor
Theoretical And Experimental Investigation On The Rotational Isomerism In A-fluoroacetophenones
No full textThe geometries involved in the conformational equilibria of α-fluoroacetophenone, p-nitro-α-fluoroacetophe- none, and p-methoxy-α-fluoroacetophenone were investigated. Theoretical calculations showed that cis and gauche forms (F - C - C=0) are their most stable conformers and that in the vapor phase the gauche conformer is predominant. The three compounds were synthesized, and the conformational behavior in solution was estimated from infrared (IR) and nuclear magnetic resonance (NMR) spectra obtained in solvents of different polarity. Their IR spectra showed one carbonyl absorption for the cis and one for the gauche conformer, and that the cis conformer was preferred in the more polar solvents, 1JCF, 2JC(O)F, and 2JHF coupling constants were obtained from their NMR spectra, and they also showed a preference for the cis conformer when more polar solvents were used. The vapor phase calculations showed a conformational preference for the gauche form. However, when the solvent effects were included in the calculations, the results were in complete agreement with the experimental data (NMR and IR), the cis conformer being the most stable one. © 2009 American Chemical Society.1131229062913Moss, S.J., Murphy, C.D., Hamilton, J.T.G., McRoberts, W.C., O'Hagan, D., Schaffrath, C., Harper, D.B., (2000) Chem. Commun, p. 2281O'Hagan, D., Harper, D.B.J., (1999) Fluor. Chem, 100, p. 127Purser, S., Moore, P.R., Swallow, S., Gouverneur, V., (2008) Chem. Soc. Rev, 37, p. 320O'Hagan, D., (2008) Chem. Soc. Rev, 37, p. 308Phan, H.V., Durig, J.R., (1990) J. Mol. Struct. (THEOCHEM), 209, p. 333Pontes, R.M., Fiorin, B.C., Basso, E.A., (2004) Chem. Phys. Lett, 395, p. 205Abraham, R.J., Tormena, C.F., Rittner, R., (1999) J. Chem. Soc, Perkin Trans, 2, p. 1663Abraham, R.J., Jones, A.D., Warne, M.A., Rittner, R., Tormena, C.F., (1996) J. Chem. Soc, Perkin Trans. 2, p. 533Abraham, R.J., Tormena, C.F., Rittner, R., (2001) J. Chem. Soc, Perkin Trans. 2, p. 815van der Veken, B.J., Truyen, S., Herrebout, W.A., Watkins, G., (1993) J. Mol. Struct, 293, p. 55Tormena, C.F., Rittner, R., Abraham, R.J., Basso, E.A., Pontes, R.M., (2000) J. Chem. Soc, Perkin Trans, 2, p. 2054Tormena, C.F., Amadeu, N.S., Rittner, R., Abraham, R.J., (2002) J. Chem Soc, Perkin Trans. 2, p. 773Olivato, P.R., Guerrero, S., Hase, Y., Rittner, R., (1990) J. Chem. Soc, Perkin Trans. 2, p. 465Catalano, D., Celebre, G., Emsley, J.W., Longeri, M., Luca, G.D., Veracini, C.A., (1998) J. Chem. Soc, Perkin Trans. 2, p. 1823Rodriguez, A.M., Giannini, F.A., Baldoni, H.A., Santagata, L.N., Zamora, M.A., Zacchino, S., Sosa, C.P., Csizmadia, I.G., (1999) J. Mol. Struct, 463, p. 271Frisch, M.J., (2003) Gaussian 03, , Gaussian Inc, Pittsburgh, PAHehre, W.J., (2003) A Guide to Molecular Mechanics and Quantum Chemical Calculations, , Wavefunction Inc: Irvine, CAFliikiger, P., Liithi, H.P., Portmann, S., Weber, J., (2000) Molekel 4.3, , Swiss Center for Scientific Computing: Manno, Switzerland;Portmann, S., Liithi, H.P., (2000) CHIMIA, 54, p. 766Tomasi, J., Scrocco, E., Miertus, S., (1981) Chem. Phys, 55, p. 117Bridge, C.F., O'Hagan, D.J., (1997) Fluor. Chem, 82, p. 21Yoshinaga, F., Tormena, C.F., Freitas, M.P., Rittner, R., Abraham, R.J., (2002) J. Chem. Soc, Perkin Trans. 2, p. 1494Eliel, E.L., Wilen, S.H., Mander, L.N., (1994) Stereochemistry of Organic Compounds, , Wiley: New Yor
1,5-stereoinduction In Boron-mediated Aldol Reactions Of β,δ-bisalkoxy Methylketones Containing Cyclic Protecting Groups
No full textFigure Persented: A study of the aldol reactions of boron enolates from methylketones that are protected with dimethylacetonide or di-tert-butylsilyl groups and that possess a trans or cis relationship between the chiral centers is presented. The main objective of this work was to evaluate the influence of the relative stereochemistry between the chiral centers and the steric and electronic influences of the cyclic protecting groups on the aldol reactions. The aldol adducts were obtained with moderate to high 1,5-anti stereoselectivity that was dependent on both the identity of the protecting group on the β,δ-oxygen stereocenters and the relative stereochemistry between the β and δ chiral centers. A theoretical analysis of the transition states involving these aldol reactions was performed utilizing DFT (density functional theory). © 2012 American Chemical Society.77837663792Dias, L.C., Aguilar, A.M., (2008) Chem. Soc. 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Conformational Analysis Of Trans-2-halocyclohexanols And Their Methyl Ethers: A 1h Nmr, Theoretical And Solvation Approach
No full textThe conformational equilibria of trans-1-methoxy-2-chloro- (1), trans-1-methoxy-2-bromo- (2) and trans-1-methoxy-2-iodocyclohexane (3), and their corresponding alcohols (4-6), were studied through a combined method of NMR, theoretical calculations and solvation theory. They can be described in terms of the axial-axial and equatorial-equatorial conformations, taking into account the main rotamers of each of these conformations. From the NMR experiments at 183 K in CD2Cl2-CS2, it was possible to observe proton H2 in the ax-ax and eq-eq conformers separately for 1 and 2, but not for 3, which gave directly their populations and conformer energies. In the alcohols the proportion of the ax-ax conformer was too low to be detected by NMR under these conditions. Those HH couplings together with the values at room temperature, in a variety of solvents allowed the determination of the solvent dependence of the conformer energies and hence the vapor state energy difference. The ΔE (Eax-Eeq) values in the vapor state for 1, 2 and 3 are -0.05, 0.20 and 0.55 kcal mol-1, respectively, increasing to 1.10, 1.22 and 1.41 kcal mol-1 in CD3CN solution (1 kcal = 4.184 kJ). For 4-6 the eq-eq conformation is always much more stable in both non-polar and polar solvents, with energy differences ranging from 1.78, 1.94 and 1.86 kcal mol-1 (in CCl4) to 1.27, 1.49 and 1.54 kcal mol-1 (in DMSO), respectively. Comparison of the hydroxy and methoxy compounds gives the intramolecular hydrogen bonding energy for the alcohols as 1.40, 1.36 and 1.00 kcal mol-1 (in CCl4) for 4, 5 and 6, respectively. Copyright © 2002 John Wiley & Sons, Ltd.1612733Zefirov, N.S., Samoshin, V.V., Subbotin, A.O., Baranenkov, V.I., (1978) Tetrahedron, 34, p. 2953Carreño, M.C., Carretero, J.C., Ruano, J.L., Rodriguez, J.H., (1990) Tetrahedron, 46, p. 5649Rockwell, G.D., Grindley, T.B., (1996) Aust. J. Chem., 49, p. 379Kay, J.B., Robinson, J.B., Cox, B., Polkonja, D., (1970) J. Pharm. Pharmacol., 22, p. 214Collins, P., Ferrier, R., (1995) Monosaccharides-Their Chemistry and Their Roles in Natural Products, , Wiley: New YorkBervelt, J.P., Ottinger, R., Peters, P.A., Reisse, J., Chiurdoglu, G., (1968) Spectrochim. Acta, Part A, 24, p. 1411Allinger, J., Allinger, N.L., (1958) Tetrahedron, 2, p. 64Allinger, N.L., Allinger, J., (1958) J. Am. Chem. Soc., 80, p. 5476Basso, E.A., Kaiser, C., Rittner, R., Lambert, J.B., (1993) J. Org. Chem., 58, p. 7865Bodot, H., Dicko, D.D., Gounelle, Y., (1967) Bull. Soc. Chim. Fr., p. 870Freitas, M.P., Tormena, C.F., Rittner, R., (2001) J. Mol. Struct., 570, p. 175Wolfe, S.J., Campbell, R., (1967) J. Chem. Soc., Chem. Commum., p. 872Abraham, R.J., Bretschneider, E., (1974) Internal Rotation in Molecules, , Academic Press: London, chapt. 13Abraham, R.J., Jones, A.D., Warne, M.A., Rittner, R., Tormena, C.F., (1996) J. Chem. Soc., Perkin Trans., 2, p. 533Abraham, R.J., Tormena, C.F., Rittner, R., (1999) J. Chem. Soc., Perkin Trans., 2, p. 1663Tormena, C.F., Rittner, R., Abraham, R.J., Basso, E.A., Pontes, R.M., (2000) J. Chem. Soc., Perkin Trans., 2, p. 2054Freitas, M.P., Rittner, R., Tormena, C.F., Abraham, R.J., (2001) J. Phys. Org. Chem, 14, p. 317Abraham, R.J., Smith, T.A.D., Thomas, W.A., (1996) J. Chem. Soc., Perkin Trans., 2, p. 1949Frisch, M.J., Trucks, C.W., Schlegel, H.B., Scuseria, G.E., Robb, M.A., Cheeseman, J.R., Zakrzewski, V.G., Pople, J.A., (1998) Gaussian 98, , Gaussian: Pittsburgh, PAAbraham, R.J., Grant, G.H., Haworth, I.S., Smith, P.E., (1991) J. Comput.-Aided Mol. Des., 5, p. 21Zefirov, N.S., Gurvich, L.G., Shashkov, A.S., Krimer, M.Z., Vorob'eva, E.A., (1976) Tetrahedron, 32, p. 1211Epiotis, N.D., (1973) J. Am. Chem. Soc., 95, p. 3087Craig, N.C., Chen, A., Suh, K.H., Klee, S., Mellau, G.C., Winnewisser, B.P., Winnewisser, M., (1997) J. Am. Chem. Soc., 119, p. 4789Senderowitz, H., Fuchs, B., (1997) J. Mol. Struct. (Theochem), 395-396, p. 123Rablen, P.R., Hoffmann, R.W., Hrovat, D.A., Borden, W.T., (1999) J. Chem. Soc., Perkin Trans., 2, p. 1719Ganguly, B., Fuchs, B., (2000) J. Org. Chem., 65, p. 558Li, Z., Fan, K., Wong, M.W., (2001) J. Phys. Chem. A, 105, p. 10890Wiberg, K.B., Murcko, M.A., Laidig, K.E., Macdougall, P.J., (1990) J. Phys. Chem., 94, p. 6956Lagowski, J.J., (1976) The Chemistry of Nonaqueous Solvents, 3. , Academic Press: New YorkJones, D.C., (1928) J. Chem. Soc., p. 1193Guss, C.O., Rosenthal, R., (1955) J. Am. Chem. Soc., 77, p. 2549Sosnovskii, G.M., Astapovich, I.V., (1990) Zh. Org. Khim., 26, p. 911Bajwa, J.S., Anderson, R.C., (1991) Tetrahedron Lett., 32, p. 302
Conformational Analysis Of Fluoroacetoxime And Of Its O-methyl Ether By 1h, 13c And 15n Nmr And Theoretical Calculations
No full textThe solvent dependence of the 1H, 13C and 15N NMR spectra of (E)-fluoroacetoxime [(E)-FAO] and of (E)-fluoroacetoxime 0-methyl ether [(E)-FAOME], was examined and the HF, CF and NF couplings are reported. Density functional theory (DFT) at the B3LYP/6-311++g(2df,2p) level with ZPE (zero point energy) correction was used to obtain the rotamer geometries. In both (E)-FAO and (E)-FAOME the DFT method gave two energy minima corresponding to the cis (F - C - C=N, 0°) and gauche (F - C - C=N, 124.1°) rotamers. In contrast, in (Z)-FAO the DFT method gave only one energy minimum corrsponding to the trans rotamer. The 4JHF and 1JCF couplings in (E)-FAO were analyzed by solvation theory assuming the cis and gauche forms to give Ecis - Egauche = 3.3 kcal mol-1 in the vapor phase, decreasing to 1.54 kcal mol-1 in CCl4 and - 1.19 kcal mol-1 in DMSO (1 kcal = 4.184kJ. In (E)-FAOME the observed couplings, when analysed similarly by solvation theory, gave Ecis - Egauche = 2.2 kcal mol-1 in the vapor phase, 0.91 kcal mol-1 in CCl4 and - 1.18 kcal mol-1 in DMSO. The 3JNF coupling was independent of the molecular conformation, as it did not change with the solvent polarity. Copyright © 2003 John Wiley & Sons, Ltd.1714248McCarty, C.G., (1970) The Chemistry of the Carbon-nitrogen Double Bond, , Patai S (ed). Wiley: Chichester, chap. 2Fry, A.J., Reed, R.G., (1977) The Chemistry of Double Bonded Functional Groups, Supplement A, , Patai S (ed.). Wiley: Chichester, chap. 11Goda, H., Sato, M., Ihara, H., Hirayama, C., (1992) Synthesis, p. 849(1972) CIBA Symposium, Carbon-fluorine Compounds, Chemistry, Biochemistry and Biological Activities, , Association of Scientific Publishers: AmsterdamTaylor, N.F., (1988) Fluorinated Carbohydrates, Chemical and Biochemical Aspects. ACS Symposium Series, 374. , American Chemical Society: Washington, DCO'Hagan, D., Rzepa, H.S., (1997) Chem. Commun., p. 645Saegebarth, E., Krishner, L.C., (1970) J. Chem. Phys., 52, p. 3555Durig, J.R., Hardin, J.A., Phan, H.V., Little, T.S., (1989) Spectrochim. Acta, Part A, 45, p. 1239Abraham, R.J., Jones, A.D., Warne, M.A., Rittner, R., Tormena, C.F., (1996) J. Chem. Soc., Perkin Trans. 2, p. 533Olivato, P.R., Ribeiro, D.S., Rittner, R., Hase, Y., Del Pra, D., Bombieri, G., (1995) Spectrochim. Acta, Part A, 51, p. 1479Dal Colle, M., Distefano, G., Modelli, A., Jones, D., Guerra, M., Olivato, P.R., Ribeiro, D.S., (1998) J. Phys. Chem. A, 102, p. 8037Ribeiro, D.S., Abraham, R.J., (2002) Magn. Reson. Chem., 40, p. 49Olivato, P.R., Ribeiro, D.S., Zukerman-Schpector, J., Bombieri, G., (2001) Acta Crystallogr., Sect. B, 57, p. 705Abraham, R.J., Fisher, J., Loftus, P., (1988) Introduction to NMR Spectroscopy, , Wiley: New YorkAbraham, R.J., Bretschneider, E., (1974) Internal Rotation in Molecules, , W. J. Orville-Thomas (ed.). Wiley: London, chap. 13Frisch, M.J., Trucks, C.W., Schlegel, H.B., Scuseria, G.E., Robb, M.A., Cheeseman, J.R., Zakrzewski, V.G., Pople, J.A., (1998) Gaussian 98, Revision A.7, , Gaussian: Pittsburgh, PAAbraham, R.J., Tormena, C.F., Rittner, R., (1999) J. Chem. Soc., Perkin Trans. 2, p. 1663Tormena, C.F., Rittner, R., Abraham, R.J., Basso, E.A., Pontes, R.M., (2000) J. Chem. Soc., Perkin Trans. 2, p. 2054Abraham, R.J., Tormena, C.F., Rittner, R., (2001) J. Chem. Soc., Perkin Trans. 2, p. 815Tormena, C.F., Rittner, R., Abraham, R.J., (2002) J. Phys. Org. Chem., 15, p. 211Tormena, C.F., Amadeu, N.S., Rittner, R., Abraham, R.J., (2002) J. Chem. Soc., Perkin Trans. 2, p. 773Abraham, R.J., (1999) Prog. Nucl. Magn. Reson. Spectrosc., 35, p. 85Abraham, R.J., Leonard, P., Smith, T.A.D., Thomas, W.A., (1996) Magn. Reson. Chem., 34, p. 71Hirota, E., (1970) J. Chem. Phys., 42, p. 2071Enevoldsen, T., Oddershede, J., Sauer, S.P.A., (1998) Theor. Chem. Acc., 100, p. 275Peralta, J.E., Barone, V., Contreras, R.H., (2001) J. Am. Chem. Soc., 123, p. 9162Peralta, J.E., Barone, V., Azua, M.C.R., Contreras, R.H., (2001) Mol. Phys., 99, p. 655Barone, V., Peralta, J.E., Contreras, R.H., (2001) J. Comput. Chem., 22, p. 1615Krivdin, L.B., Sauer, S.P.A., Peralta, J.E., Contreras, R.H., (2002) Magn. Reson. Chem., 40, p. 187Freitas, M.P., Rittner, R., Tormena, C.F., Abraham, R.J., (2001) J. Phys. Org. Chem., 14, p. 317Contreras, R.H., Peralta, J.E., (2000) Prog. Nucl. Magn. Reson. Spectrosc., 37, p. 321Braun, S., Kalinowski, H.O., Berger, S., (1996) 100 and More Basic NMR Experiments, , VCH: Weinhei
Conformational Preferences For N,n-dimethyl-2-haloacetamides (halo=f, Cl, Br And I) Through Theoretical And Experimental Studies: An Unexpected Orbital Interaction
No full textConformational preferences and orbital interactions of N,N-dimethyl-2- fluoroacetamide (1), N,N-dimethyl-2-chloroacetamide (2), N,N-dimethyl-2- bromoacetamide (3) and N,N-dimethyl-2-iodoacetamide (4) were analyzed using experimental infra-red data, theoretical calculations and NBO analysis. The conformational equilibria of compounds 1-4 can be represented by their cis and gauche rotamers. The gauche form of 1 is stable in the vapor phase and in a non-polar solvent, but the cis is predominant in a polar solvent. For 2-4 the gauche form is more stable than the cis, in both the vapor and liquid phases. These conformational preferences were attributed to the orbital interaction between two antibonding orbitals, π* C=O→σ*C-X. This unexpected interaction was possibly due to the high (0.3) electron density on π* C=O, which results from the interaction between one nitrogen lone pair and π*C=O. © 2005 Elsevier B.V. All rights reserved.7281-37984Vassilev, N.G., Dimitrov, S., (1999) J. Mol. Struct., 484, p. 39Lehninger, A.L., Nelson, D.L., Cox, M.M., (1993) Principles of Biochemistry, , Worth New YorkGreenberg Breneman, C.M.A., Liebman, J.F., (2002) The Amide Linkage: Structural Significance in Chemistry, Biochemistry and Materials Science, , Wiley New YorkWiberg, K.B., Breneman, C.M., (1992) J. Am. Chem. Soc., 114, p. 831Vargas, R., Garza, J., Dixon, D., Hay, B.P., (2001) J. Phys. Chem. a, 105, p. 774Sandrone, G., Dixon, D.A., Hay, B.P., (1999) J. Phys. Chem. a, 103, p. 893Rogers, M.T., Woodbrey, J.C., (1962) J. Phys. Chem., 66, p. 540Drakenberg, T., Dahlqvist, K., Forsen, S., (1972) J. Phys. Chem., 76, p. 2178Hobson, R.F., Reeves, L.W., (1973) J. Phys. Chem., 77, p. 419Wunderlich, M.D., Leung, L.K., Sandberg, J.A., Meyer, K.D., Yoder, C.H., (1978) J. Am. Chem. Soc., 100, p. 1500Ross, B.D., Wong, L.T., True, N.S., (1985) J. Phys. Chem., 89, p. 836Jackowski, K., Les, A., (1995) J. Mol. Struct., 331, p. 295Suarez, C., Tafazzoli, M., True, N.S., Gerrard, S., Lemaster, C.B., Lemaster, C.L., (1995) J. Phys. Chem., 99, p. 8170Yamada, S., (1996) J. Org. Chem., 61, p. 941Crawford, S.M.N., Taha, A.N., True, N.S., Lemaster, C.B., (1997) J. Phys. Chem., 101, p. 4699Basso, E.A., Pontes, R.M., (2002) J. Mol. Struct. (Theochem), 594, p. 199Briggs, R.S., O'Hagan, D., Howard, J.A.K., Yufit, D.S., (2003) J. Fluorine Chem., 119, p. 9Tormena, C.F., Rittner, R., Abraham, R.J., Basso, E.A., Pontes, R.M., (2000) J. Chem. Soc. Perkin Trans., 2, p. 2054Tormena, C.F., Amadeu, N.S., Rittner, R., Abraham, R.J., (2002) J. Chem. Soc. Perkin Trans., 2, p. 773Olivato, P.R., Guerrero, S.A., Yreijo, M.H., Rittner, R., Tormena, C.F., (2002) J. Mol. Struct., 607, p. 87Martins, M.A.P., Rittner, R., Olivato, P.R., (1981) Spectrosc. Lett., p. 505Klapstein, D., Olivato, P.R., Oike, F., Martins, M.A.P., Rittner, R., (1988) Can. J. Spectrosc., 33, p. 161Frisch, M.J., Trucks, G.W., Schlegel, H.B., Scuseria, G.E., Robb, M.A., Cheeseman, J.R., Zakrzewski, V.G., Pople, J.A., (1998) Gaussian 98, Revision A.7, , Gaussian, PittsburghPeterson, K.A., Figgen, D., Goll, E., Stoll, H., Dolg, M., (2003) J. Chem. Phys., 119, p. 11113Extensible Computational Chemistry Environment Basis Set Database, Version 02/25/04, , http://www.emsl.pnl.gov/forms/basisform.htmlGlendening, E.D., Reed, A.E., Carpenter, J.E., Weinhold, F., NBO Version 3.1, , (Included in the Gaussian 98 package of programsRef. [23])Brunck, T.K., Weinhold, F., (1979) J. Am. Chem. Soc., 101, p. 1700Goodman, L., Gu, H., Pophristic, V., (2005) J. Phys. Chem., 109, p. 1223Weinhold, F., (2001) Nature, 411, p. 539Tormena, C.F., Freitas, M.P., Rittner, R., Abraham, R.J., (2004) J. Phys. Chem. a, 108, p. 5161Freitas, M.P., Tormena, C.F., Rittner, R., Abraham, R.J., (2003) Spectrochim. Acta a, 59, p. 1783Bodot, H., Dicko, D.D., Gounelle, Y., (1967) Bull. Soc. Chim. Fr., p. 870Olivato, P.R., Rittner, R., (1996) Rev. Heteroat. Chem., 15, p. 11
A 1h Nmr And Theoretical Investigation Of The Conformations Of Some Monosubstituted Cyclobutanes
No full textThe complete analysis of the complex 1H NMR spectra of some monosubstituted cyclobutanes was achieved to give all the 1H chemical shifts and nJHH (n = 2, 3 and 4) coupling constants in these molecules. The substituent chemical shifts of the substituents in the cyclobutane ring differ significantly from those in acyclic systems. For example, the OH and the NH2 groups in cyclobutanol and cyclobutylamine produce a large shielding of the hydrogens of the opposite CH2 group of the ring compared with little effect on the comparable methylene protons of butane. These effects and the other 1H shifts in the cyclobutanes were modelled successfully in the CHARGE program. The RMS error (calculated vs observed shifts) for the 34 1H shifts recorded was 0.053 ppm. The conformational equilibrium in these compounds between the axial and the equatorial conformers was obtained by comparing the observed and the calculated 4JHH couplings. These couplings in cyclobutanes, in contrast to the corresponding 3JHH couplings, show a pronounced orientation dependence; 4J eq-eq is ca 5 Hz and 4Jax-ax ca 0 Hz. The couplings in the individual conformers were calculated at the B3LYP/EPR-III level. The conformer energy differences ΔGax-eq vary from 1.1 kcal mol-1 for OH to 0.2 kcal mol-1 for the CH 2OH substituent. The values of the conformer energy differences are compared with the previous IR data and the corresponding theoretical values from molecular mechanics (MM) and DFT theory. Generally, good agreement is observed although both the MM and the DFT calculations deviate significantly from the observed values for some substituents. Copyright © 2010 John Wiley & Sons, Ltd.4912329Cotton, F.A., Frenz, B.A., (1974) Tetrahedron, 30, p. 1587Eliel, E.L., Wilen, S.H., (1994) Stereochemistry of Carbon Compounds, , John Wiley & Sons: New YorkDurig, J.R., Lee, M.J., Zhao, W.Y., Little, T.S., (1992) Struct. 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Spectrosc., 35, p. 85Abraham, R.J., Mobli, M., (2008) Modelling 1H NMR Spectra of Organic Compounds, p. 380. , John Wiley & Sons: ChichesterAbraham, R.J., Byrne, J.J., Griffiths, L., (2008) Magn. Reson. Chem., 46, p. 667McConnell, H.M., (1957) J. Chem. Phys., 27, p. 226(2010) NMRpredict, , Modgraph Ltd, Modgraph Ltd, Welwyn, HertsCastellano, S.M., Bothner-By, A.A., (1964) J. Chem. Phys., 41, p. 3863P. H. M. Budlezaar, Dept of Chemistry, University of Manitoba, Winnopeg, Canada. gNMR/gNMR.html(2003) PC Model 9.0 Serena Software, , Bloomington, INMøller, C., Plesset, M.S., (1934) Phys. Rev., 46, p. 618Dunning, T.H., Peterson, K.A., Wonn, D.E., (1998) Encyclopedia of Computational Chemistry, 1, p. 88. , Wiley: New YorkFrisch, M.J., Trucks, G.W., Schlegel, H.B., Scuseria, G.E., Robb, M.A., Cheeseman, J.R., Montgomery Jr., J.A., Pople, J.A., (2004) Revision E.01, , Gaussian, Wallingford, CTSychrovshý, V., Gräfenstein, J., Cremer, D., (2000) J. Chem. Phys., 113, p. 3530Barone, V., (1994) J. 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