Deuteron Quadrupole Coupling Constants in Deuterocarbons

The dependence of the deuteron quadrupole coupling constant (DQCC) on the nature of hybridization of carbon in deuterocarbons is examined in detail. A simple molecular orbital description of the C–D fragment, with various effective nuclear charges on carbon, is used. The calculated values are shown to be comparable to experimental results and other theoretical models which treat the entire molecules rather than simply the C–D fragment. It is shown that $\mathrm{DQCC}\mathrm{(sp)\hspace{0.17em}>\hspace{0.17em}}\mathrm{DQCC}{\mathrm{(sp}}^2\mathrm{)\hspace{0.17em}>\hspace{0.17em}}\mathrm{DQCC}{\mathrm{(sp}}^3)$ which may be attributed to the fact that the nuclear contribution to the electric field gradient decreases faster than the electronic part in the series ${\mathrm{sp,\; sp}}^2{\mathrm{,\; sp}}^3$ . A collection of experimental data, establishing the same trend obtained theoretically, is presented including new deuterium NMR results on phenylacetylene‐d and ferrocene‐d₁₀.