Isotopic Effect on X-Nuclei Screening and X–H(D) Scalar Spin-Spin Coupling in XH4 and XO4

1984 ◽  
Vol 39 (9) ◽  
pp. 1230-1235 ◽  
Author(s):  
V. P. Tarasov ◽  
V. I. Privalov ◽  
Yu. A. Buslaev ◽  
U. Eichhoff
Keyword(s):  
Atomic Number ◽  
Chemical Shifts ◽  
Isotopic Effect ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Isotopic Shift ◽  
Coupling Constant ◽  
Screening Constant ◽  
Spin Spin Coupling ◽  
Isotopic Effects

Changes in X-nuclei screening and scalar spin-spin X-H(D) coupling constants induced by the H-D substitutions in isotopomers [XH4-nDn] (X = N, Al, Ga) have been determined by 14,1l5N, 27 AI, 69,71Ga NMR. Isotopic chemical shifts of nuclei 51V, 53Cr, 99Tc induced by the 16O-18O substitution have been measured for tetra-oxo complexes [VO4]3-, [CrO4]2-, and [TcO4]-. The deuterium-induced secondary isotopic effect on the screening constant of the X nuclei and the scalar spin-spin X-H(D) coupling are correlated with the X-H bond length in [XHJ for the row X = N, C, B, Al, Ga, As the internuclear X-H distance increases, the isotopic shift of the X nuclei with respect to the signal from [XHJ rises linearly on H-D substitution from a negative value for [NH4]+, CH4 to a positive value (the downfield shift) for [GaH4]-. When D is substituted for H in [XH4] the X-H spin-spin coupling constant decreases for X = N, C, B, Al, Ga (the secondary isotopic effect). The magnitude and sign of the secondary isotopic effects on the screening constants of the X nuclei in [XH4] and [XO4] depend on the atomic number of the X element. With the increasing atomic number in the period the isotopic shift to high field rises in magnitude, while with the increasing atomic number in the group the isotopic upfield shift drops in the absolute value and can even change sign in the substitution of the ligand light isotope by a heavier isotope.

Reconnaissance of diverse structural and electronic environments in germanium halides by solid-state 73Ge NMR and quantum chemical calculations

2011 ◽  
Vol 89 (9) ◽  
pp. 1118-1129 ◽  
Author(s):  
Brandon J. Greer ◽  
Vladimir K. Michaelis ◽  
Victor V. Terskikh ◽  
Scott Kroeker
Keyword(s):  
Solid State ◽  
Quantum Chemical Calculations ◽  
Quantum Chemical ◽  
Chemical Shifts ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Coupling Constant ◽  
Electronic Environments ◽  
Isotropic Chemical Shifts ◽  
Spin Spin Coupling

Solid-state 73Ge nuclear magnetic resonance (NMR) is an attractive technique for the characterization of solid germanium-containing materials, but experiments can be exceedingly difficult in practice due to the unfavourable NMR properties of the 73Ge nucleus. Presented herein is a series of solid-state 73Ge NMR experiments on germanium halides (GeX4 and GeX2, where X = I, Br, and Cl) conducted at moderate (9.4 and 11.7 T) and ultrahigh (21.1 T) magnetic fields, intended to characterize the 73Ge NMR response in highly symmetric and asymmetric coordination environments. Quadrupole coupling constants range from 0.16 to 35 MHz. Isotropic chemical shifts for the GeX4 series trend with halide electronegativity, as found for the analogous silicon and tin halides. The indirect spin-spin coupling constant 1J(73Ge, 127I) is estimated from 73Ge MAS NMR to be 35 ± 10 Hz in GeI2, with the reduced coupling constant agreeing with those of other group 14 halides. Quantum chemical calculations using GIPAW DFT are in reasonable accord with experimental quadrupole couplings, but fail for chemical shielding. A preliminary NMR crystallographic study of GeI2 and GeCl2 incorporating 127I and 35Cl NMR spectra has led to plausible conclusions reflecting the structural homology of these compounds, although definitive characterization remains elusive.

Long-range 13C, 13C spin–spin coupling constants in anisole and some derivatives

1988 ◽  
Vol 66 (7) ◽  
pp. 1635-1640 ◽  
Author(s):  
Ted Schaefer ◽  
Glenn H. Penner
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Methoxy Group ◽  
Chemical Shifts ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Coupling Constant ◽  
Spin Coupling Constants ◽  
Spin Spin Coupling ◽  
Nuclear Magnetic

13C nuclear magnetic resonance chemical shifts and nJ(13C,13C) are reported for anisole and 16 of its derivatives, all enriched with 13C in the methoxyl group. 5J(13C,13C) is directly proportional to sin2θ, where θ is the angle by which the methoxy group twists about the C(1)—O bond. In acetone-d6 solution, 5J(C,C) is not observable for a number of 4-substituted anisoles, except for 1,4-dimethoxybenzene. For the latter, 5J(C,C) is compatible with a twofold barrier of 19.3 ± 1.1 kJ/mol hindering rotation about the C(1)—O bond. However, it is unlikely that the barrier is purely twofold in nature. The observed 5J(C,C) is also compatible with 10.5 and 6.0 kJ/mol for the twofold and fourfold components, respectively, implying a dynamical nuclear magnetic resonance barrier of less than 13 kJ/mol. While phase and solvent effects on the internal barrier in anisole are certainly substantial, it appears that a fourfold component must also be present. The apparent twofold barrier in 2,6-difluoroanisole is 5.4 ± 0.9 kJ/mol, based on 5J(C,C) and 6J(H-4,13C). The latter coupling constant is also reported for 1,2,3-trimethoxybenzene and used to deduce its conformation. The θ dependence of 3J(C,C) and 4J(C,C) is briefly discussed for symmetrical anisole derivatives. Differential 13C, 13C isotope shifts are reported for 1,4-dimethoxybenzene.

31P−15N Coupling Constants and 15N/14N Isotope Effects on 31P NMR Chemical Shifts of 2-Phenylamino-2-oxo(-thioxo, -selenoxo)- 4-methyl-1,3,2-dioxaphosphorinanes and Related Compounds

1983 ◽  
Vol 38 (7) ◽  
pp. 815-818 ◽  
Author(s):  
Willy Gombler ◽  
Ryszard W. Kinas ◽  
Wojciech J. Stec
Keyword(s):  
31P Nmr ◽  
Chemical Shifts ◽  
Isotope Effects ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Coupling Constant ◽  
The Family ◽  
Nuclear Shielding ◽  
Spin Spin Coupling ◽  
Related Compounds

The strong influence of a chalcogen atom (O, S, Se) attached to phosphorus on the spin-spin coupling constant 1J(P-15N) in the family of diastereoisomeric 2-|15N] -phenyl-amino-2X(X = O, S, Se)-4-methyl-l,3,2-dioxaphosphorinanes is demonstrated. The 15N/14N isotope effect on the nuclear shielding of phosphorus-31 is larger for the shorter equatorial than for the longer axial P-N bonds.

A 13 C and 31 P magnetic double resonance study of organo-phosphorus compounds

1968 ◽  
Vol 306 (1485) ◽  
pp. 185-199 ◽  
Keyword(s):  
Phosphorus Atom ◽  
Chemical Shifts ◽  
Double Resonance ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Phosphorus Compounds ◽  
Resonance Spectroscopy ◽  
Coupling Constant ◽  
Spin Coupling Constants ◽  
Spin Spin Coupling

Twenty-two organo-phosphorus compounds of a variety of structural types have been examined by 1 H—{ 13 C} and 1 H—{ 31 P} magnetic double resonance spectroscopy. The signs and magnitudes of the 31 P—H and 31 P— 13 C spin-spin coupling constants are sensitive to the valency of the phosphorus atom, and the nature of the groups attached to it. Parallel behaviour is noted between two types of coupling constant. The 31 P chemical shifts agree with results obtained by conventional 31 P single resonance spectroscopy, and the 13 C chemical shifts depend on the polarizability of the phosphorus atom and its associated groups.

Structural Characterization of Natural Products By Means of Quantum Chemical Calculations of NMR Parameters: New insights

2021 ◽  
Author(s):  
Fabio Luiz Paranhos Costa ◽  
Ana Carolina Ferreira de Albuquerque ◽  
Rodolfo Goetze Fiorot ◽  
Luciano Morais Lião ◽  
Lucas Haidar Martorano ◽  
...  
Keyword(s):  
Natural Products ◽  
Structural Characterization ◽  
Quantum Chemical ◽  
Chemical Shifts ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Nmr Parameters ◽  
Spin Coupling Constants ◽  
Spin Spin Coupling

The calculation of NMR parameters for natural products was pioneered by Bifulco and coworkers in 2002. Since then, modelling 1H and 13C chemical shifts and spin-spin coupling constants for this...

An estimate of the spin–spin coupling constant, 1J(1H,13C), in gaseous benzene

1996 ◽  
Vol 74 (8) ◽  
pp. 1524-1525 ◽  
Author(s):  
Ted Schaefer ◽  
Guy M. Bernard ◽  
Frank E. Hruska
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Dielectric Constant ◽  
Magnetic Resonance ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Coupling Constant ◽  
Spin Coupling Constant ◽  
Spin Coupling Constants ◽  
Spin Spin Coupling ◽  
Gaseous Benzene

An excellent linear correlation (r = 0.9999) exists between the spin–spin coupling constants 1J(1H,13C), in benzene dissolved in four solvents (R. Laatikainen et al. J. Am. Chem. Soc. 117, 11006 (1995)) and Ando's solvation dielectric function, ε/(ε – 1). The solvents are cyclohexane, carbon disulfide, pyridine, and acetone. 1J(1H,13C)for gaseous benzene is predicted to be 156.99(2) Hz at 300 K. Key words: spin–spin coupling constants, 1J(1H,13C) for benzene in the vapor phase; spin–spin coupling constants, solvent dielectric constant dependence of 1J(1H,13C) in benzene; benzene, estimate of 1J(1H,13C) in the vapor; nuclear magnetic resonance, estimate of 1J(1H,13C) in gaseous benzene.

Internal motion in benzylidene diacetate and its 2,6-dibromo derivative by DNMR and the J method

1989 ◽  
Vol 67 (6) ◽  
pp. 1022-1026 ◽  
Author(s):  
Ted Schaefer ◽  
Craig S. Takeguchi
Keyword(s):  
Double Resonance ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Maximum Magnitude ◽  
Coupling Constant ◽  
Spectral Parameters ◽  
Proton Proton ◽  
Ether Solution ◽  
Spin Spin Coupling ◽  
Dibromo Derivative

The 1H nuclear magnetic resonance spectral parameters are reported for benzylidene diacetate in CS2 and acetone-d6 solutions. The long-range spin–spin coupling constant over six formal bonds, 6J, is used to derive apparent twofold barriers to rotation about the exocyclic C(1)—C bond in the two solutions. The conformation of lowest energy has the α. C—H bond in the benzene plane. The barrier is higher in CS2 than in acetone-d6 solution, in contrast to a molecule like benzyl chloride. In the 2,6-dibromo derivative, the free energy of activation for reorientation about the bond in question is 36 kJ/mol at 165 K in dimethyl ether solution. Such a high barrier implies a very small six-bond proton–proton coupling constant for this derivative because 6J is proportional to the expectation value of sin2θ. The angle θ is zero when the α C—H bond lies in the benzene plane. 6J is −0.051 Hz in acetone-d6 solutions; its sign is determined by double resonance experiments. The question of an angle-independent component of 6J, that is, whether 6J is finite at θ = 0°, is addressed. A maximum magnitude of 0.02 Hz may be present at θ = 0° for the 2,6-dibromo derivative, although a zero magnitude is also compatible with the experimental data. In a compound with a higher internal barrier, α,α,2,6-tetrachlorotoluene, the experimental results are best in accord with a negligibly small 6J at θ = 0°. Keywords: 1H NMR of benzylidene diacetate, spin–spin coupling constants for benzylidene diacetate, DNMR, 2,6-dibromobenzylidene diacetate.

The planar conformation of 2-methylthiobenzaldehyde in solution

1983 ◽  
Vol 61 (1) ◽  
pp. 26-28
Author(s):  
Ted Schaefer ◽  
Rudy Sebastian
Keyword(s):  
Chemical Shifts ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Spectral Parameters ◽  
H Nmr ◽  
Heavy Atoms ◽  
Planar Conformation ◽  
Spin Coupling Constants ◽  
Spin Spin Coupling ◽  
Infrared Data

The 1H nmr spectral parameters are extracted for a 4 mol% solution of 2-methylthiobenzaldehyde in CCl4 at 305 K. The long-range spin–spin coupling constants involving the aldehydic and methyl protons are consistent only with a preferred conformation in which all heavy atoms are coplanar, as are the chemical shifts of the ring and methyl protons. This conclusion contradicts previous interpretations of the dipole moment, the nmr parameters, and of the infrared data for CCl4 solutions. The present data show that the O-syn and O-anti forms of the compound are present in roughly equal proportions.

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