Microwave Spectra of Nitrogen-Containing Molecules. IV. Conformation, Dipole Moment, and Quadrupole Coupling Constants of Cyclopropylamine

The microwave spectra of three isotopic species of cyclopropylamine have been investigated. The $A$ , $B$ , and $C$ rotational constants in megahertz for C₃H₅NH₂ are, respectively, 16269.95, 6723.00, and 5795.33; for C₃H₅NHD they are 15957.12, 6382.01, and 5504.06; and for C₃H₅ND₂ they are 15592.62, 6091.39, and 5246.56. Quadrupole coupling constants have been measured and have the values ${\chi }_{\mathrm{aa}}\text{\hspace{0.17em}=\hspace{0.17em}2.288}$ , ${\chi }_{\mathrm{bb}}\text{\hspace{0.17em}=\hspace{0.17em}1.841}$ , and ${\chi }_{\mathrm{cc}}\text{\hspace{0.17em}=\hspace{0.17em}−4.129 MHz}$ for the normal isotopic species. The dipole‐moment components are found to be ${\mu }_a\text{\hspace{0.17em}=\hspace{0.17em}0.43 D}$ and ${\mu }_c\text{\hspace{0.17em}=\hspace{0.17em}1.11 D}$ which lead to a total moment of 1.19 D. The molecular structure of cyclopropylamine has been discussed, and in addition to other structural parameters, we have found C–C = 1.520, C–N = 1.428, and amino H···H = 1.631 Å.