Knowledge Bank

The microwave spectrum of cyclopentylchloride has been studied in order to determine the stable molecular conformation(s). Extensive measurements have led to the assignment of the $\mathrm{<mrow\; data-mjx-texclass="ORD">35</mrow>}Cl$ and $\mathrm{<mrow\; data-mjx-texclass="ORD">37</mrow>}Cl$ species in the ground vibrational state, and also of at Least four excited states of a low frequency vibrational mode of the $\mathrm{<mrow\; data-mjx-texclass="ORD">35</mrow>}Cl$ species. Structural calculations indicate that the halogen substituent occupies the axial conformation. No spectral evidence for an equatorial species has yet been obtained, although there do exist some unassisted transitions. For the $\mathrm{<mrow\; data-mjx-texclass="ORD">35</mrow>}Cl$ ground state species the observed rotational constants are A = 4547.60 $\pm 0.01,B=2290.13\pm 0.02$, and $C=2073.29\pm 0.01$ MHz. $\mathrm{<mrow\; data-mjx-texclass="ORD">35</mrow>}Cl$ quadrupole coupling constants have been found to have the values $Xaa=-23.6,Xbb=30.6$, and $Xcc=-7.0$ MHz, in agreement with expectations for an axial C-Cl bond having approximately cylindrical symmetry. Preliminary structural calculations indicate a $CS$ structure with a ring dihedral angle of $32\circ$ and a CCl-ring angle of $55\circ$. These and other results will be discussed in detail.""