Microwave Spectrum, Molecular Structure, and Quadrupole Coupling Constants of 2-Chloropropane

Abstract

The microwave spectra of (CH3)2CHCl35, (CH3)2CHCl37, (CH3)2CDCl35, (CH3)2C13HCl35, C13H3CHCl35CH3, CH2DCl35CH3 (3 species), and CD3CDCl35CH3 have been examined and a complete structure has been obtained by the substitution method. The parameters obtained are as follows: r(CC) = 1.522 Å, r(CCl) = 1.798 Å, r(CHsec) = 1.091 Å, r(CHmethyl) = 1.092 Å, ∠CCC = 112.7°, ∠CCCl = 109.4°, ∠CCHsec = 109.9°, ∠CCHα = 110.9°, ∠CCHβ,γ = 109.7°. The quadrupole coupling constants in the principal axis system of (CH3)2CHCl35 have been determined to be χaa = —61.49 Mc/sec, χbb = 34.81 Mc/sec, and χcc = 26.68 Mc/sec. These values are consistent with χzz = —69.61 Mc/sec assuming a cylindrical charge distribution near the Cl nucleus, or with χzz = —67.82 Mc/sec and η = 0.0275 assuming that the z axis and the CCl internuclear line coincide. From the absence of observable splitting in certain high J transitions in CD3CDCl35CH3, it has been concluded that the potential barrier hindering internal rotation of the methyl groups is greater than 3450 cal/mole.