Coupling constants homoallylic

For stereochemical dependencies of 1H,13C coupling constants through one bond and of allylic and homoallylic H. H couplings, see Section 4.1.1.2.. 

Hz and H absorbs in the range d 1.2-1.75. A rather smaller coupling Vh h = 0.8 Hz was determined for the enol acetate 142 (X = OAc). The homoallylic coupling constants, h = 0.7 Hz for 142 (X = I) and 1.2 Hz for 141 are in accord with earlier cited work on related compounds. The effect on the chemical shift of a vinyl proton brought about by the introduction of a cis or trans cyclopropyl ring has been found to be rather smalF" ... 

In acyclic systems, Jlcisoid l itransoid usually holds. Large homoallylic coupling constants are generally observed in cyclic systems ... 

Unlike the situation for homoallylic coupling in most acyclic alkenes, homopropargylic coupling is almost always observed in the H NMR spectra of internal alkynes. As we saw above, essentially all conformations of the C—H trbond on the carbon a to the triple bond allow for partial overlap with the /r system of the alkyne, resulting in coupling constants significantly larger than those observed for... 

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