No abstract

ANILINE may be considered to be a member of comparable intensity. This observation strongly a class of molecules of general type NH,X in which suggests that the molecule is non-planar and that X is an unsaturated system which may act as an we are observing rotational transitions due to electron sink. In a valence-bond picture, the molecules in O+ and 0inversion states. Both

Rotational constants have been measured for three isotopic forms of fluorine cyanide, six isotopic forms of fluoroacetylene, and for the species 35ClC15N, 37ClC15N, IClsN, 35C113CCH and 35ClC13CH. Accurate bond-distances have been computed for all the halogen cyanides and for fluoro-and chloroacetylene, by the method of isotopic substitution at all atoms (except I; and I). The CF bonds in these compounds are the shortest yet found. The CN distance is virtually constant at 1.159 A.The nuclear quadrupole coupling constant for nitrogen-14 in fluorine cyanide, -2.67 Mc/sec, is the lowest yet measured for a cyanide grouping. The dipole moments of fluorine cyanide and fluoroacetylene, from Stark effects, are 217 D and 0.73 D respectively. Rotation spectra of molecules in excited bending vibrational states are analyzed for fluorine cyanide, fluoroacetylene and cyanoacetylene.

Microwave spectra have been measured for the planar molecules 4H-pyran-4-one (I), 4H-pyran-4thione (11), 4H-thiapyran-4-one (111) and 4H-thiapyran-4-thione (IV). Extensive isotopic data for I, I1 and IV enable precise, complete structures to be calculated. There is little structural evidence for enhanced aromaticity in these molecules.The high, almost constant, values for the dipole moments near 4 D, previously indicated from solution measurements on I, I1 and IV, have been confirmed and the values more closely defined.Vibrational satellite spectra indicate the lowest frequency fundamentals in these molecules to be out-of-plane motions near 100 cm-'.

The ultraviolet absorption spectrum of HCP has been observed from 4100 Å to about 2350 Å, and seven electronic transitions have been identified. Three of these transitions involve excited singlet states and four of them involve excited triplet states. The symmetries, energies, and equilibrium conformations of these states are listed below:[Formula: see text]Some observations have also been made on the vibration–rotation energy levels of the ground electronic state, [Formula: see text], of HCP. The fundamental vibration frequencies (in cm−1) are ν1 = 3216.9, ν2 = 674.7, and ν3 = 1278.4.