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We studied the rotational spectra of the adducts of ammonia with several organic molecules, namely \textit{tert}-butanol,, 2008, 463, 330} glycidol,, 2009, 48, 1102} ethyl alcohol, anisol and 1,4-difluorobenzene. The adducts with glycidol and ethanol have been observed for both conformers of the substrate molecule. Based on the rotational and $\mathrm{<mrow\; data-mjx-texclass="ORD">14</mrow>}$N quadrupole coupling constants of the various complexes, we found a considerably different behaviour of ammonia, with respect to water, in its proton donor/acceptor double role. In the interaction with the three alcohol molecules, NH$\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}$ acts as a proton acceptor and the OH groups as a proton donor. However, in the case of glycidol-NH$\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}$, a secundary N-H$\cdots$O interaction occurrs between ammonia and the ether oxygen. This interaction generates a sizable \textit{V}$\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}$ barrier to the internal rotation of the NH$\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}$ moiety, while NH$\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}$ undergoes a free rotation in \textit{tert}-butanol-NH$\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}$ and in ethanol-NH$\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}$. As to the anisole-NH$\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}$ and 1,4-difluorobenzene-NH$\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}$ complexes, the NH$\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}$ group explicits its double proton donor/acceptor role, although through two weak (C-H$\cdots$N and N-H$\cdots \pi$) H-bonds. There is, however, an important difference between the two complexes, because in the first one NH$\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}$ lies out of the aromatic plane, while in the second one it is in the plane of the aromatic ring.