1H NMR coupling constants

Benzoquinone oximes (30) exhibit sidedness the structures exhibit anomalous 1H-NMR coupling constants (J21 can exceed by 0.6 Hz), and its additions show a syn selectivity.49 The apparent stereoelectronic effect is concluded to be primarily steric in origin. 

For Pt-ssDNA adducts, the H(8) chemical shift order is 5 -G H(8) up-field / 3 -G H(8) downfield, the same order observed for the simple d(G pG ) adduct. Thus, the presence of a base to the 5 or 3 side of the platination site does not change the preferred canting in Pt-ssDNA adducts. In order to relieve some of the strain introduced by platination, the 5 -G sugar pucker becomes N in Pt-ssDNA, while the 3 -G sugar pucker remains mostly S, as deduced from 1H-NMR coupling constant and NOE data [38][57][67] [68][91—93]. This observation is again the same as found for d(G pG ). 

Addition of 3-methylcyclohex-2-enone to C6o afforded four stereoisomers comprising the diastereoisomeric cis- and trans racemates ( )-195 and ( )-196 (ratio 40 60), respectively, which were identified by 1H-NMR coupling constant analysis (Figure 1.44)238 The separation of the enantiomers of... 

The 1H-NMR coupling constants and chemical shifts of 8a-methylperhy-dropyrrolo[l,2-a]pyrimidin-6-one, shown with the structure, are in accordance with conformation (442). Data on l,8a-dimethyl- and 8a-phenyl-substituted derivatives of the same system are also available (71AP774). 

The conformational characteristics of dimethyl esters of dicarboxylic acids are studies by the NMR and dipole moment method. Conformational energies of the internal CH2-CH2 bonds are determined from the observed 1H-1H vicinal coupling constants. Preferred conformations around the C-C bond are elucidated from the RIS analysis of dipble moments. With the RIS parameters thus established, the orientational correlation between the terminal ester groups is examined. The analysis provides the reason why the odd-even effect in the dipole moment is moderate, and attenuates rapidly with n in the ct.co-diester series. 

Figure 13.15 The 1H NMR spectrum of 2-bromopropane. The -CH3 proton signal at 1.71 <5 is split into a doublet, and the -CHBr- proton signal at 4.28 8 is split into a septet. Note that the distance between peaks—the coupling constant—is the same in both multiplets. Note also that the outer two peaks of the septet are so small as to be nearly lost.

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]. 

H and 13C NMR Data. The examples in Scheme 3.3 provide insight into expected proton and carbon chemical shift and coupling constant data for primary alkyl fluorides. It can be seen that the influence on both proton and carbon chemical shifts diminishes rapidly as one moves away from the site of fluorine substitution. 

H and 13C NMR Data. Pertinent proton and carbon NMR data, in addition to those given above, are provided in Scheme 3.9. Again, the increase in one-bond F—C coupling constant observed in the... 

H and13C NMR Data for Halofluoroalkanes. Scheme 3.13 provides some pertinent proton and carbon chemical shift and coupling constant data for fluorochloro- and fluorobromomethanes, whereas Scheme 3.14 contains relevant data for some typical halo fluoroalkanes. There does not appear to be anything unusual going on here. 

H and13C NMR Data. The data given in Scheme 3.39 provide some guidelines for proton and carbon NMR chemical shift and coupling constant data for fluoroalkenes. Notice that in all cases, hydrogens that are cis to the fluorine substituent are deshielded relative to those that are trans. 

H and 13C NMR Data. The H chemical shifts of CF2H protons of difluoromethyl ethers lie between 6.00 and 6.3 ppm, with a significantly enhanced F—H two-bond coupling constant of around... 

H and 13C NMR Data. Typical proton and carbon NMR data for a,(3-unsaturated carbonyl compounds with a terminal vinylic CF2 group are given in Scheme 4.50. The pertinent F—H coupling constants have been given in the previous Scheme 4.49. Conjugation with a carbonyl group deshields the (3-CF2 carbon by 4-5 ppm. 

French workers have studied the 1H- and 13C-NMR parameters of disubstituted selenophenes.37 38 The proton chemical shifts are discussed in terms of magnetic anisotropy and electric field effects of the substituents in order to study the conformational equilibrium of the carbonyl group. The relationship between the H- and 13C-chemical shifts and 7t-electron distribution calculated by the PPP method are examined. Shifts and coupling constants are discussed in additivity terms. 

Table 4 1H NMR chemical shifts (ppm), multiplicity and coupling constants (Hz) for benzotriazol-1 -yl derivatives 27-29...

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