Deuterium isotope effects on the 13C-H coupling constants in acetylene

13C NMR spectra of a mixture of deuterated acetylenes containing 1H13C12C1H, 1H13C12CD, 1H12C13CD and D13C12CD isotopomers have been measured. Saturated solutions of acetylene in acetone were studied. The 13C-D coupling constants were reduced to a 13C-H basis using the relationship J(C,H) = 6.5144.J(C,D). The primary isotope effects on 1J(C,H) and 2J(C,H) were found to be -0.64 +- 0.10 and +0.09 +- 0.13 Hz, and the secondary isotope effects on 1J(C,H) and 2J(C,H) were equal to +0.10 +- 0.05 and +0.25 +-0.05 Hz, respectively. The deuterium isotope effects upon 13C chemical shifts were also determined. The α effect was normal, -0.223 ppm, while the β effect was unusually large, -0.438 ppm. The isotope effects on the 13C-H coupling constants and the 13C chemical shifts were shown to be additive. (author)