Couphng constant

The couphng constants of O nt used here in the bifurcation analysis are 6 /2r... 

Ruonne NMR data can be collected readily on most spectrometers, requinng only minor adjustments to mstrumentation used to run proton samples The fluonne-19 nucleus is easily detected (relative abundance, 100%, spin, 1/2) and generates a wealth of spectral information to assist in structure elucidation To take full advantage of all the spectral evidence available, H, and chemical shifts and couphng constants should be acquired and correlated... 

Four fluorinated acrylates are presented in Table 4 [66, 67, 68, 69] to supplement the vmyl fluoride data Perfluoroacrylic acid [70] and methyl per-fluoroaciylate [69, 70] are both reported m the literature. The cts and trans isomers of fluoroethylenes are readily distinguished by the magnitude of their couphng constants, with trans typically more than 3 times the magnitude of cis... 

Characterizafion of organometalhc agents through multinuclear analysis by correlating fluonne chemical shifts and fluonne-heteroatom couphng constants... 

Although it is now established that CIDNP has a quite different origin from DNP, the two effects were initially thought to be related. Thus the Overhauser effect, in which saturation of unpaired electron spins leads to polarization of nuclei coupled to the electrons through the hyperfine couphng constant (ajj), can be observed in organic radicals, and CIDNP 3... 

The results of NMR measurements have to be converted into a 3D structure. After establishing the constitution by NMR parameters that are transmitted through bond, i.e. J-coupHng constants, information about the spatial structure is introduced. Here, mainly distances from NOE build-up rates are used to define the configuration and conformation. 

Munzarova, M., Kaupp, M., 1999, A Critical Validation of Density Functional and Coupled Cluster Approaches for the Calculation for EPR Hyperfine Couphng Constants in Transition Metal Complexes , J. Phys. Chem. A, 103, 9966. 

The observation that the isomer shift varies between 0.39 mm s 1 at 4 K and 0.54 mm s-1 at 80 or 298 K only, irrespective of the charge n of the complexes (n = 0, 1,2), immediately implies that all complexes contain an octahedral, high-spin ferric ion (d5, S = ). Furthermore, from the applied-field Mossbauer spectra of [Fem(LBuMet)] (.S t = f), [Fem(LBuMet )]+ (5t = 2), and [Fem(LBuMet )]2+ (5t = ) intrinsic isotropic hyperfine couphng constants, AFe/gNpN, of -21.4, -21.0, -20.8 T, respectively, have been established. These values are also typical of high-spin iron(III). 

The theoretical background for the quadrupole coupling constant was developed already in the 1950s . Direct calculation of quadrupolar couphng constants is stiU not straightforward and depends heavily on the basis set used The quadrupolar coupling constant is thus mainly used as an empirical parameter. Nevertheless, experimental trends can be reproduced quite well with available theoretical methods as shown in Section n.F. 

TABLE 8. NMR chemical shifts and one-bond carbon-hydrogen spin-spin couphng constants of oximes 44-51 measured for saturated solutions in DMSO-de ... 

A similar reversal of the signs of the N—C—H coupling with stereochemistry is not, however, found for the geometric isomer, fi-formanihde (74) and Z-formanilide (75). In both cases, the one- and two-bond reduced couphng constants have been shown to be positive. 

The quadrupole perturbed NMR spectriun of Rb (I = 312) consists of the central hne and two satelUte Unes. In D-RADP-x the nuclear quadrupole couphng constant decreases linearly with x from 9.6 MHz (x = 0) to 6.6 MHz (x = 0.95) [10], whereas the Larmor frequency amounts to 98.163 MHz in a Bo field of 7 T. Due to the substitutional disorder, and the corresponding loss of the translational invariance, the satelHte transitions are inhomogeneously broadened that much, that only the central transition can be directly observed. The position of the corresponding resonance line can be calculated using standard NMR-NQR theory [16], where the second order shift is given by ... 

The ab initio calculation of the transition rate between two electronic states with the emission of p phonons involves a very complicated sum over phonon modes and intermediate states. Due to this complexity, these sums are extremely difficult to compute however, it is just this complexity, which permits a very simple phenomenological theory to be used. There are an extremely large number of ways in which p phonons can be emitted and the sums over phonon modes and intermediate states are essentially a statistical average of matrix elements. In the phenomenological approach it is assumed that the ratio of thep-th and (p - l)-th processes will be given by a couphng constant characteristic of the matrix in which the rare earth is situated and not depending... 

After this preamble we may consider the Chlorine, Bromine and Iodine couphng constants in the tetrahahdes of Group IV Carbon, Silicon, Germanium and Tin. 

Structure Chemical shift Mppm rf (multiplicity), couphng constant J[Hz]f ... 

The fast motion spectrum of the /-PMMA radical consists of 21 lines attributed to three separate isotropic hyperfine coupling constants. There is coupling to the methyl group to form a quartet (22.9 G) that is then split further into a triplet from one set of p-methylene protons (16.4 G) and another triplet from the other set (11.7G). Theoretically, this should lead to 36 lines (4 x 3 x 3), but a fortuitous degeneracy exists because one of the fast motion p-methylene couphng constants is almost exactly... 

The values of couphng constants 7 (t C-t C) in organic compounds are proportional to the C—C bond ordert . In series 4 this constant characterizes the interaction of nuclei of aliphatic (0 ) and aromatic (Ci) carbon atoms. The t7(i3Co.-t Ci) value increases when M changes from M = C to M = Sn, corresponding to an increase of the Car—CH2 bond order, i.e. to the enhancement of the a-7T conjugation as the atomic number of M increases. 

From CIDNP patterns it is possible to derive magnetic properties of free radicals as magnitudes and signs of hyperfine couphng constants, g factors and nuclear relaxation times. 

Here the Heaviside function 6 ensures that the contribution vanishes outside the bands. Sc and w indicate the center and the half width of the band, respectively. We still neglect any dependence of the couphng constants on k and consider an effective value, which is a good approximation for most cases. Then A sJ is proportional to Pe/s J but no more constant can be easily obtained from equation (16). The effect on the density of states of the reactant Pa sJ depends on the relative values of the parameters and w. In Fig. 8b and 8c we show the chemisorption functions for two semielliptic bands with different width, a wide band (Fig. 8b), which can represent a sp band, and a thinner one (Fig. 8c), which can describe a d band. 

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