Internal H-C-C angle dependence of vicinal 1H-1H coupling constants

Barfield, Michael; Smith, William B.

doi:10.1021/ja00031a006

Cited by 86 publications

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“…Second, the coefficient of cos $ is not required to be negative by theory because it is the difference between large terms of opposite signs (16). In fact, for the latest formulating of 3~(~,~) , which takes CCH angles into consideration (16,17), the B term is 0.3 Hz for tetrahedral angles and hence JI8, < JO in the ideal case. Third, the exact values of $ for 1 above are not to be taken too literally; it does appear, however, that $, , > $ , , > $, , .…”

Section: The Pucker Of the Dithiane Tnoietymentioning

confidence: 99%

“…The vicinal coupling constant, 3~(~,~) , is sensitive to the dihedral angle, +, between the protons (14, 15), but also depends on the CCH angles, the s character of the hybrid orbitals at the two carbon atoms in the HCCH fragment, on various overlap integrals, themselves dependent on the C-C distance, and on the effective nuclear charges at the carbon atoms (16,17). It follows that substituents, X, at carbon will also perturb 3~(~,~) , a perturbation whose magnitude may well depend on the dihedral angle between the C-X and the vicinal C-H bonds.…”

Section: The Pucker Of the Dithiane Tnoietymentioning

confidence: 99%

“…The original formulation (14) writes 2~ = Jo cos2+ -0.28 for 0" 5 $ 5 90" and 3~ = 3~, 8 0 cos2$ -0.28 for 90"' + 5 180". This formulation will be used here because there is good reason (16,17) to believe that 3~ is more sensitive to changes in CCH angles and C-C distances at torsion angles greater than 90" than it is for torsion angles less than 90". Accordingly, the smaller 3~ values for 1, corresponding to + < 90°, may well be the more reliable sources of +, , , +, , , and +, , .…”

Section: The Pucker Of the Dithiane Tnoietymentioning

confidence: 99%

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A precise analysis of the ¹H nuclear magnetic resonance spectrum of 2-phenyl-1,3-dithiane. Ring pucker, signs of long-range J(H,H), internal rotational barrier, and van der Waals shifts

Schaefer¹,

Kunkel²,

Schurko³

et al. 1994

Can. J. Chem.

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. Can. J. Chem. 72, 1722Chem. 72, (1994. The 'H nuclear magnetic resonance spectrum of 2-phenyl-l,3-dithiane, as a dilute solution in a CS2-C6D12-TMS solvent mixture at 300 K, is analyzed to yield 8 chemical shifts and 22 distinct coupling constants, "J(H,H), n = 2-6. The coupling constant between H-2 and the para proton indicates, first, that the bisected conformer (phenyl plane perpendicular to the pseudo plane of the dithiane ring) is most stable and, second, that the apparent twofold barrier to rotation about the ~s p~--~s p~ bond is 9.6 kJ/ mol. The AMI, STO-3G, and STO-3G* computations confirm the twofoldedness of the barrier; the AM1 barrier is 9.4 kJ/mol.The empirical equation, 3~(~,~) = 13.36 cos2 + + 9.59 cos + -0.43, reproduces the vicinal coupling constants of the CH2CH2CH2 fragments and implies puckering angles +, , , +, , , and +, , of 54", 61°, and 64", respectively. It is implied that 3~ at + = 0" is larger than at + = 180". This results is discussed in terms of the latest theoretical approach to 3~ in the HCCH fragment.The 4~(~,~) signs and magnitudes for the CH2CH2CH2 fragment agree reasonably well with theory. For the CH2SCH fragment, 4~(~,~) values are positive, in contrast to corresponding numbers in the propanic fragment, perhaps the first experimental values for certain rigid orientations about a heteroatom. INDO MO FFT computations on propane, dimethyl ether, and dimethyl sulfide confirm the experimental trend in 4~(~,~) . 'J(H,H) and 'J(H,H) values are compared to those in related molecules. The striking differential shifts of the axial and equatorial protons are attributed to differential van der Waals interactions with the 3p lone-pair orbital on sulfur. A comparison of the ring proton chemical shifts with those in phenylcyclohexane and isopropylbenzene implies that C-S bonds are weaker net electron donors by hyperconjugation than are C-C bonds. It is also proposed that the ortho protons are deshielded by intramolecular van der Waals interactions with the 3p orbitals on the sulfur atoms.-TED SCHAEFER, JEREMY P. KUNKEL, ROBERT W.J SCHURKO et GUY M. BERNARD Can. J. Chem. 72, 1722Chem. 72, (1994. Le spectre rCsonance magnCtique nucltaire du 'H du 2-phCnyl-l,3-dithiane, dCterminC B 300 K, en solution diluCe dans un milange de solvants form6 de CS,, de C6D12 et de TMS, a Ct C analysi et on en a dtduit 8 dkplacements chimiques et 22 constantes de couplage distinctes, "J(H,H), n = 2 -6. La constante de couplage entre le proton H-2 et le proton en para indique, en premier lieu, que le conformkre avec bissection (dans lequel le plan du phCnyle est perpendiculaire au pseudo plan du noyau dithiane) est le plus stable et, deuxikmement, que la barrikre binaire apparente a la rotation autour de la liaison Csp2-Csp3 est de 9,6 kJlmol. Des calculs AM1, STO-3G et STO-3G* confirment que la barrikre est binaire; les calculs AM 1 indiquent que la barrikre est de 9,4 kJ/mol. L'Cquation empirique, 3~(~,~) = 13,36 cos2 + + 0,519 cos + -0,43, permet de reproduire les constantes de couplage vicinales du fr...

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Section: The Pucker Of the Dithiane Tnoietymentioning

confidence: 99%

Section: The Pucker Of the Dithiane Tnoietymentioning

confidence: 99%

Section: The Pucker Of the Dithiane Tnoietymentioning

confidence: 99%

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A precise analysis of the ¹H nuclear magnetic resonance spectrum of 2-phenyl-1,3-dithiane. Ring pucker, signs of long-range J(H,H), internal rotational barrier, and van der Waals shifts

Schaefer¹,

Kunkel²,

Schurko³

et al. 1994

Can. J. Chem.

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“…Because HTOs can be written in terms of internal and dihedral angles, it is often possible to relate the matrix elements and, therefore, coupling constants to angles and internuclear separations. Such models have been used in these laboratories to obtain explicit expressions in terms of the structural factors such as the H-C-C internal angle dependence of 3 J H,H 0 ; 32 the dependence of long range coupling 4 J H,H 0 over four bonds on dihedral angle and internal angles; 33 and the relationships of trans H-bonding J-coupling to H-bond geometries in nucleic acids and proteins. 28,29 In the next sections, an LCAO-MO/SOS analysis will be used to examine the structural dependencies of 2 J H,H 0 in a CH 2 moiety, Figure 1.…”

Section: Analysis Of Fc Terms Via a Lcao-mo Sum-over-states Modelmentioning

confidence: 99%

DFT studies of the conformational/structural dependencies of geminal ¹H,¹H scalar coupling ²J(H,H′) in substituted methanes

Barfield¹

2007

Magnetic Reson in Chemistry

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A study is presented of the structural dependencies for scalar, interproton J-coupling across two bonds in a series of substituted methanes. The coupled perturbed, density functional theory method with a B3PW91 functional and aug-cc-pVTZ-J basis sets is used to examine coupling between geminal protons (2)J(H,H') in methane and a series of substituted compounds CH(3)X (X = CH3, CH(2)CH(3), CH=CH2, CH=O, and NH2) as functions of the dihedral angle phi measured about the C1-X2 bonds. All four contributions are obtained but all conformational effects are dominated by the Fermi contact term. Simple linear combination of atomic orbitals (LCAO)-molecular orbital (MO) sum-over-states methods are used to examine the relationships of the coupling constants with dihedral angles as well as internal H-C-H and H-C1-X2 angles. This study explores some novel aspects of geminal H-H coupling including an analysis of the asymmetry in the conformational dependencies arising from non-next-nearest neighbor interactions. For each of the substituted methanes, explicit trigonometric/exponential expressions are given and these accurately reproduce the (2)J(H,H') structural dependencies with standard deviations usually less than 0.03 Hz. The molecular structures for representative bicyclic molecules were fully optimized, and DFT results for (2)J(H,H') reproduce all the trends in the experimental data. A discussion is given on the applicability of the equations for H--H coupling in the substituted methanes to coupling in the bicyclic molecules.

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“…It is thus conceivable that for spatially proximate bonds all of the off-diagonal elements in the numerator of Eqn (4) could be large, whereas hh 0 and J HH 0 in Eqn (1) could be very small! To examine the conformational dependence of Jcoupling, it is often convenient to write the hybrid orbitals t and t 0 in terms of the dihedral and internal angles 37,38 t…”

Section: Analysis Of Fc Coupling In Ch· · ·Oh and Oh· · ·Oh Fragmentsmentioning

confidence: 99%

Density functional theory studies of transannular1H?1HJ-coupling in half-cage alcohols and rigid 1,3- and 1,4-diols: conformational dependencies and implications for intramolecular hydrogen bond detection in carbohydrates

Barfield¹,

Bergset²,

O’Leary³

2001

Magn. Reson. Chem.

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Density functional theory (DFT) methods were used to investigate the conformational dependence of transannular H-H coupling constants in half-cage alcohols and cage diols. Finite perturbation theory (FPT) was used to obtain the Fermi contact (FC) contributions to scalar coupling constants in three halfcage alcohols and the OH· · ·OH coupling between hydroxyl groups sharing 1,4-and 1,3-intramolecular hydrogen bonds. Transannular CH· · ·OH coupling constants in the half-cage alcohols (inner OH) were obtained as a function of the dihedral angle defining the OH orientation. In comparison with the parent compound, chlorine substituents substantially modify the conformational dependence of the transannular H-H coupling and lead to observable coupling in the hexachloro compound. This is an unusual case, wherein the conformationally averaged coupling constants are quite different than those for the minimumenergy conformations. A −1.0 Hz scalar coupling is predicted between the very crowded protons in the half-cage acetate (outer OAc) in comparison with the experimental magnitude <1 Hz. In model 1,4-and 1,3-diols the coupling constants were obtained as functions of the analogous dihedral angles. The primary effects of hydrogen bonding are the stabilization of conformations in which the positive and negative contributions effectively cancel, thereby leading to small, observed values (e.g. ≤0.3 Hz). The DFT/FPT data for transannular coupling constants are consistent with a sum-over-states analysis for the direct mechanisms involving the two bonds containing the coupled nuclei rather than indirect mechanisms associated with oxygen lone pairs. Discussed here are the prospects of using OH· · ·OH scalar coupling for structural studies of carbohydrates.

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Internal H-C-C angle dependence of vicinal 1H-1H coupling constants

Cited by 86 publications

References 3 publications

A precise analysis of the ¹H nuclear magnetic resonance spectrum of 2-phenyl-1,3-dithiane. Ring pucker, signs of long-range J(H,H), internal rotational barrier, and van der Waals shifts

A precise analysis of the ¹H nuclear magnetic resonance spectrum of 2-phenyl-1,3-dithiane. Ring pucker, signs of long-range J(H,H), internal rotational barrier, and van der Waals shifts

DFT studies of the conformational/structural dependencies of geminal ¹H,¹H scalar coupling ²J(H,H′) in substituted methanes

Density functional theory studies of transannular1H?1HJ-coupling in half-cage alcohols and rigid 1,3- and 1,4-diols: conformational dependencies and implications for intramolecular hydrogen bond detection in carbohydrates

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Internal H-C-C angle dependence of vicinal 1H-1H coupling constants

Cited by 86 publications

References 3 publications

A precise analysis of the 1H nuclear magnetic resonance spectrum of 2-phenyl-1,3-dithiane. Ring pucker, signs of long-range J(H,H), internal rotational barrier, and van der Waals shifts

A precise analysis of the 1H nuclear magnetic resonance spectrum of 2-phenyl-1,3-dithiane. Ring pucker, signs of long-range J(H,H), internal rotational barrier, and van der Waals shifts

DFT studies of the conformational/structural dependencies of geminal 1H,1H scalar coupling 2J(H,H′) in substituted methanes

Density functional theory studies of transannular1H?1HJ-coupling in half-cage alcohols and rigid 1,3- and 1,4-diols: conformational dependencies and implications for intramolecular hydrogen bond detection in carbohydrates

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A precise analysis of the ¹H nuclear magnetic resonance spectrum of 2-phenyl-1,3-dithiane. Ring pucker, signs of long-range J(H,H), internal rotational barrier, and van der Waals shifts

A precise analysis of the ¹H nuclear magnetic resonance spectrum of 2-phenyl-1,3-dithiane. Ring pucker, signs of long-range J(H,H), internal rotational barrier, and van der Waals shifts

DFT studies of the conformational/structural dependencies of geminal ¹H,¹H scalar coupling ²J(H,H′) in substituted methanes