N. M. Pozdeev

Structure and internal rotation of methyl ethyl ketone

As a result of an investigation of the microwave spectrum of methyl ethyl ketone (CH~.COCH2CHs), from the triplet fine structure of the transition between the rotational levels of the vibrational ground state which are almost degenerate with respect to K, we have determined the height of the potential barrier to internal rotation V 3 = 795 • i0 cm -I of the methyl group furthest from the carbonyl. We give the rotational constants, the centrifugal distortion constants, and other spectroscopic parameters for methyl ethyl ketone in the first excited state of the torsional vibration of the skeleton. From measurements of the relative intensities of the transitions, we determined the frequency of the torsional vibration of the skeleton ~ = 80.4 • 6 cm -~, and found the height of the potentialbarrier V l ~ 5500 cm -I hindering internal rotation about the central C-C bond, We have observed strong interaction between the torsional vibration and the twisting vibration of the methyl group closest to the carbonyl group. We have concluded that the ground-state isomeric trans form predominates.

Microwave spectra ofs-cis-Glyoxal (CHO−CHO) molecules in excited vibrational states

The microwave spectra of s-cis-glyoxal molecules in the excited states of torsional (vt=1,2) and bending (vbend=1) vibrations have been studied. For the vt=1 state, the rotational constants have been refined and the quartic constants of centrifugal distorition have been determined. For the excited vt=2 and vbend=1 states, the rotational constants have found. For the ground vibrational state, the rotational constants and the quartic constants of centrifugal distortion have been refined. The vibrational frequencies have been determined from the relative intensities of rotational transitions.

Microwave spectrum, centrifugal perturbation, and dipole moment of acetyl chloride

An analysis of the microwave spectrum of acetyl chloride (12CH312C16O35Cl) in the ground vibrational state allowed us to determine the quartic constants of centrifugal distortion and to refine the rotational constants and the constants of quadrupole coupling of35Cl nuclei in this compound. The Stark effect of the 0–111 transition has been measured and analyzed. The components of the dipole moment have been determined: μa=1.047(10) D and μb=2.503(4) D. The total dipole moment of the moment of the molecule is 2.713(8) D.