Vinyl protons coupling constant

Bates, P., Cawley, S., Danyluk, S. S. Solvent Dependence of Proton-Proton Coupling Constants in Substituted Vinyl Silanes. J. Chem. Phys. 40, 2415 (1964). 

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... 

Z-Configuration of the initial compounds does not change in the reaction course, as indicated by the coupling constants of the methoxyethenyl group vinyl protons of the triazoles 166 and 167. Adducts of -configuration are present only as admixtures (83DIS). 

I The C2 vinylic proton signal (blue) appears at 6.73 8 and shows an interesting four-line absorption pattern. It is coupled to the two nonequivalent protons at Cl and C3 with two different coupling constants /. 2 6 Hz and /2.3 - 12 Hz. 

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. 

The proton spectrum consists of two signals for the vinylic protons, each a doublet of quartets. The signal for the proton at C2 is centered at 6.53ppm with a trans three-bond H—H coupling constant of 15.8Hz, and a four-bond F—H coupling of 2.0 Hz. That of the proton at C3 is centered at 6.91 ppm, with respective coupling constants of 15.8 and 6.5 Hz. 

The 13C—H coupling constants of methyl (213 Hz23 ) and phenyl (216 Hz55 ) cyclopropenone are in the order of those obtained for cyclopropene vinylic protons (200/201 218 Hz/221 Hz174 ) and reflect an s-contribution of more than 40% in the carbon hybrid orbital of the vinyl C—H bond. 

The coupling constants generally lies between 0 and 20 Hz and depend on the structural relationship between the protons as demonstrated for those of vinyl group. 

Chemical shifts for the azepine ring protons, as might be anticipated from their non-planar, polyene character, lie in the vinyl proton region (5 4.5-6.8 p.p.m.). Chemical shifts and coupling constants of representative examples of azepines and their hydro, oxo, benzo and dibenzo derivatives are listed in Table 2. 

The H-NMR spectra of all 1.1-carbo or l.l-hetero-X -phosphorins show a doublet between 5 = 7,5 and 8 = 8,5 ppm with/p c-c-H = 30 to 50 Hz which is due to the protons at C-3 and C-5 of the phosphorin ring. The low-field signals usually appear somewhat lower than those of X -phosphorins. The position of these signals suggests the existence of a ring current induced by the aromatic X -phosphorin system. However, the vinyl protons of X -phospha-cyclohexadiene -2,5 or -2,4 derivatives also absorb at relative low fields (p. 135). Much more characteristic are the P—H coupling constants, which are about six times as large in X -phosphorins as in X -phosphorins (/p c c-H = 5—7 Hz). Indeed, they provide an excellent help in the identification of X -phosphorins. 

In the Horner-Emmons reaction (Scheme 3), the sulfonylphosphonate carbanion 5 is formed in the presence of NaH and then reacts with an aldehyde to produce the intermediate 6 that undergoes in situ elimination to yield the vinyl sulfones and phosphonate anion. The sulfonyl group can stabilize the anion in the sulfonylphosphonate 5. The vinyl sulfones that are produced by this method using aldehydes as starting materials are exclusively the E (trans) isomers. The E-isomers of the vinyl sulfones are shown in the NMR spectra based on the coupling constants of the vinylic protons. Although strongly basic conditions are used in the Horner-Emmons reaction and a-amino aldehydes are easily racemized, the amino acid vinyl sulfones prepared by this method still show substantial optical activity. However, the enantiomeric purity of these compounds has not been determined. 5 ... 

We would expect that the spectrum of the latter compound would consist of two signals a two-proton triplet in the vinyl region and a four-proton doublet in the allylic region. This is because the coupling constant, / 3 is zero. It if were not zero, then a more complicated spectrum would result. Thus magnetic nonequivalence can lead to much more complicated spectra. 

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