Experimental Structures of the Carbon Chains HC7N, HC9N, and HC11N by Isotopic Substitution

✍ Scribed by M.C. McCarthy; E.S. Levine; A.J. Apponi; P. Thaddeus

• Publisher: Elsevier Science
• Year: 2000
• Tongue: English
• Weight: 211 KB
• Volume: 203
• Category: Article
• ISSN: 0022-2852
• DOI: 10.1006/jmsp.2000.8149

✦ Synopsis

The effective structures (r 0 ) of the three linear cyanopolyynes HC 7 N, HC 9 N, and HC 11 N have been determined to high accuracy by isotopic substitution, following detection in a supersonic molecular beam with a Fourier transform microwave spectrometer of all of the singly substituted rare isotopic species. For each chain, the lengths of the individual bonds have been determined to an accuracy of 0.001 Å or 0.1% toward the end of the chain and to 0.01 Å or 1.0% toward the center. The experimental structures are in excellent agreement with recent high-level theoretical calculations, or, in the case of HC 11 N, with extrapolation from HC 9 N. The three polyynes studied here represent the largest reactive carbon chain molecules for which accurate structures have been derived empirically. For HC 7 N and HC 9 N, it has been possible to resolve at high-resolution nitrogen hyperfine structure in the lower rotational transitions and determine eQq for all of the singly substituted isotopic species of HC 7 N and for normal HC 9 N.