Knowledge Bank

Rotational spectra of \emph{p}-, \emph{m}-, and \emph{o}-cyanophenol have been measured in the range of 10.5 - 21 GHz and fit using Watson's A-reduction Hamiltonian coupled with nuclear quadrupole coupling interaction terms for the $\mathrm{<mrow\; data-mjx-texclass="ORD">14</mrow>}$N nuclei. Ab initio calculations at the MP2/6-311++G** level predict the \emph{cis} conformers of \emph{m}- and \emph{o}-cyanophenol to be more stable due to the intramolecular hydrogen bonding interaction between the hydroxyl hydrogen and the cyano nitrogen. We recorded 14 $a$- and $b$-type rotational transitions for \emph{cis m}-cyanophenol and 16 $a$- and $b$-type rotational transitions for \emph{trans m}-cyanophenol. The rotational constants are $A=3408.9200(2)$ MHz, $B=1205.8269(2)$ MHz, and $C=890.6672(1)$ MHz and $A=3403.1196(3)$ MHz, $B=1208.4903(2)$ MHz, and $C=891.7241(2)$ MHz for the \emph{cis} and \emph{trans} species respectivly. We recorded 25 $a$- and $b$-type rotational transitions for \emph{cis o}-cyanophenol; the rotational constants are $A=3053.758(2)$ MHz, $B=1511.2760(3)$ MHz, and $C=1010.7989(2)$ MHz. The \emph{trans} conformer of \emph{o}-cyanophenol was not observed. Rotational transitions of the \emph{p}-cyanophenol monomer are split due to the symmetric internal rotation of the hydroxyl group with respect to the aromatic ring. We recorded 25 $a$- and $b$-type rotational transitions for \emph{p}-cyanophenol; the $b$-type transitions are split by 40 MHz. The rotational constants are $A=5612.96(2)$ MHz, $B=990.4283(6)$ MHz, and $C=841.9364(6)$ MHz and the ground state spitting $\Delta E$ is 20.1608(6) MHz.