Coupling Constants between

IVR in tlie example of the CH clnomophore in CHF is thus at the origin of a redistribution process which is, despite its coherent nature, of a statistical character. In CHD, the dynamics after excitation of the stretching manifold reveals a less complete redistribution process in the same time interval [97]. The reason for this is a smaller effective coupling constant between the Fenni modes of CHD (by a factor of four) when... 

Figure 13 20 there are two other vinylic protons Assuming that the coupling constant between the two geminal protons in ArCH=CH2 is 2 Hz and the vicinal coupling constants are 12 Hz (cis) and 16 Hz (trans) describe the splitting pattern for each of these other two vinylic hydrogens... 

Jp-H coupling constant between the phosphoms and hydrogen atoms. 

Fig. 7.5 Coupling constants between the spins of an elementary plaquette of the triangular lattice used in defining the Ising Hamiltonian appearing in equation 7.65.

It has recently been shown that 1H NMR spectra can distinguish between cis- and trans-isomers of this type. The 3J(Pt-H) coupling constants between platinum and the a-hydrogen of the pyridines are slightly higher for the cw-isomers therefore for ct s-Ptpy2Cl2 3/(Pt-H) is 42 Hz while 3/(Pt-H) is 34 Hz for the trans-isomer [83]. 

First order multiplet First order multiplets are those in which the difference in chemical shifts of the coupled protons, in hertz (Hz), divided by the coupling constant between them is about 8 or more (Av/y>8). These multiplets have a symmetrical disposition of the lines about their midpoints. The distance between the two outermost peaks of a first order multiplet is the sum of each of the coupling constants. 

A third useful example is provided by aromatic residues, where the coupling constant between ortho protons is large (xx-xx Hz), while that between meta protons is much smaller (1-3 Hz). The coupling between para protons is often of the same magnitude as the Hnewidth. 

First of all we have three problems where the structure is known. Here you are asked to calculate coupling constants between phosphorus and carbon or hydrogen (Problem 36) and relaxation times T for carbon nuclei (Problem 37) and phosphorus nuclei (Problems 38a and 38b). Note that the equation you will require for Tj calculations can be found in Fig. 10 on p. 19... 

One should also note the significant 7.5 Hz F—H coupling constant between the methyl hydrogens of the 8-methyl-l-fluoronaphthalene and its fluorine substituent. This likely derives, at least in part, from through-space F—H coupling (see Chapter 2, Section 2.3.1). 

Vicinal coupling constants between fluorine and hydrogen are generally between 18-20 Hz for both primary and secondary CF2 groups. On the other hand, H—H coupling constants between vicinal hydrogens are much smaller in these compounds, between 4 and 8 Hz. 

In all recorded spectra the 3Jee coupling constants between the olefinic protons are on the order of 11-12 Hz, proving the all-E configuration of the investigated carotenoids. Minor differences between the reported chemical shifts and literature data are due to the effect of different solvent compositions. 

In the first, quantum mechanics can be used to calculate the NMR coupling constant between two nuclear spins in the molecular environment or the NMR shielding constant. Jensen [8] in Chapter 10 of the reference provides a comprehensive introduction to the methods for calculating these molecular properties. The NMR coupling constant, KAB, is related to the second derivative of the energy with respect to the internal magnetic moments, /u, arising from the nuclear spin of the two atoms, A and B. 

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