Laboratory Detection of the Ring‐Chain Carbenes HC 4 N and HC 6 N

Abstract

The highly polar ring-chain carbenes and formed by substituting either CN or CCCN HC 4 N HC 6 N, for a hydrogen atom in cyclopropenylidene were detected in a supersonic molecular beam with (c-C 3 H 2), a Fourier transform microwave spectrometer. Seven a-and four b-type rotational transitions of HC 4 N and 11 a-type transitions of each with resolved nitrogen nuclear quadrupole hyperÐne structure, HC 6 N, were measured between 6 and 21 GHz, yielding precise values for the three rotational constants, the leading centrifugal distortion constants, and the quadrupole coupling constants. Like the hydrocarbon carbenes and both new molecules have a planar ring-chain structures and singlet C 5 H 2 , C 7 H 2 , C 9 H 2 , electronic ground states. The strongest lines of can be detected with a signal-to-noise ratio HC 4 N exceeding 10 in a total integration time of less than 1 s, but the lines of were nearly 100 times HC 6 N weaker.