Nitrogen and Deuterium Hyperfine Structure in the Rotational Spectrum of Piperidine

Abstract

We reinvestigated by microwave Fourier transform spectroscopy the rotational spectra of the axial and equatorial isotopomers of piperidine and N-deutero piperidine. The rotational, centrifugal, and nitrogen quadrupole coupling constants were improved, the deuterium quadrupole coupling constants were determined. The principal coupling tensor elements for nitrogen were estimated.

Accurate Equilibrium Structures for Piperidine and Cyclohexane

“… a Transitions were deperturbed for 14 N and 2 H quadrupole coupling. b From ref , 14 N quadrupole coupling constants. …”

“…Another consideration is that isotopic substitution in oblate tops may cause significant rotation of the PAS and consequent problems with structure fitting . On the favorable side, a full set of ground state (GS) rotational constants is now available for all the heavy atom isotopologues of piperidine and the ND variant from microwave (MW) spectroscopy. − New MW observations reported in this paper improve this set of GS rotational constants. The structure of piperidine has been investigated by gas-phase electron diffraction (GED) by Gundersen and Rankin …”

Thermodynamic and Thermophysical Properties of Organic Nitrogen Compounds. Part II. 1- and 2-Butanamine, 2-Methyl-1-Propanamine, 2-Methyl-2-Propanamine, Pyrrole, 1-,2-, and 3-Methylpyrrole, Pyridine, 2-,3-, and 4-Methylpyridine, Pyrrolidine, Piperidine, Indole, Quinoline, Isoquinoline, Acridine, Carbazole, Phenanthridine, 1- and 2-Naphthalenamine, and 9-Methylcarbazole

“…The low temperature dielectric relaxation study of Gilchrist et al (1988-837) also indicates an envelope structure for pyrrolidine. They reported the pseudo-rotational potential parameters, VI = 4.06 kJ'mol-1 and V2 = 4.69 kJ•mol-l • The microwave studies of Pf~fferott et al (1985Pf~fferott et al ( -1415 and Ehrlichmann et al (1989Ehrlichmann et al ( -1058 reported the existence of only one conformer, the envelope form with the imino H in the axial position. Pfafferott et al comment, that if the equatorial conformer exists, its rotational spectrum is very weak and the energy difference between the two isomers could nul be estimated.…”

“…In this work we assume the existence of only axial conformer. The rotational constants reported by Ehrlichmann et al (1989Ehrlichmann et al ( -1058 were used to calculate the moments of inertia (Table 23). The symmetry number of external rotation is one.…”

“…The pos-sibiJity of the existence of a boat form (1971-343) and twist-boat form (1974-320) has been reported. From the structural studies reported in the literature (1968-297, 1969-334, 1976-134, 1981-200, 1983-184 and 1989-1059), we have selected the rotational constants reported by Ehrlichmann et al (1989Ehrlichmann et al ( -1059 to obtain the moments of inertia of the equatorial and axial chair conformers. The twist-boat conformers with three NH orientations were assumed to be present in the equilibrium mixture.…”