Octynes hydrogen bonding

The H-P bond in hydrogen phosphonates readily adds across a C=C bond [22]. Upon treatment of 1-octyne with dimethyl phosphonate in the presence of a palladium complex in refluxing tetrahydrofuran, the addition reaction proceeds smoothly to afford dimethyl l-octen-2-ylphosphonate (2) regio-and stereo-selectively (Scheme 18). 

Rogers and coworkers did not anticipate conjugative or steric influence on a linear diyne with distant triple bonds and thus one-half of Skinner s value should be equal to the experimental data for 1-octyne. The 2-alkynes for the same groups of compounds have heats of hydrogenation which are 273.81 kJ mol k The bulk of the difference, 16.73 kJ mol", is clearly due to a substituent effect, replacement of a hydrogen by an alkyl. 

The spectrum of 4-octyne is not very helpful. Since there is no acetylenic hydrogen, there is no =C—H stretching absorption around 3300 cm . There is no visible C=C stretching absorption around 2100 to 2200 cm either, because the disubstituted triple bond has a very small dipole moment. This spectrum fails to alert us to the presence of a triple bond. 

The gas phase reactions of [MCX3] (M = Fe, Co X = H, D) with 1-octyne were investigated . The alkyne was shown to undergo interligand C-C bond coupling as well as extensive hydrogen exchange reactions. 

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