Title Conformational stability, $r_{0}$ structural parameters, barriers to internal rotation and vibrational assignment of cyclobutylamine Author Durig, James R. Ganguly, Arindam Defrawy, el, Ahmed M. Guirgis, Gamil A. Gounev, Todor K. Herrebout, W.A. van der Veken, B.J. Faculty/Department Faculty of Sciences. Chemistry Publication type article Publication 2009 Amsterdam , 2009 Subject Chemistry Source (journal) Journal of molecular structure. - Amsterdam Volume/pages 918(2009) :1/3 , p. 64-76 ISSN 0022-2860 ISI 000263426100008 Carrier E Target language English (eng) Full text (Publishers DOI) Affiliation University of Antwerp Abstract The infrared spectra (3600100 cm−1) of gaseous and solid cyclobutylamine, c-C4H7NH2 have been recorded, as well as, the infrared (360060 cm−1) spectra in xenon or krypton solutions at variable temperatures. From the latter studies, the enthalpy differences have been determined to be 225 ± 26 cm−1 (2.69 ± 0.31 kJ/mol) between the most stable equatorial-gauche (Eq-g) conformer and the equatorial-trans (Eq-t) form and 417 ± 42 cm−1 (4.99 ± 0.50 kJ/mol) with the axial-trans (Ax-t) conformer. At ambient temperature there is only 13 ± 1% of the Eq-t form present and 5 ± 1% of the Ax-t form. The potential function governing the conformational interchange of the NH2 moiety of the equatorial conformer has been determined with the following potential coefficients (cm−1): V1 = −176 ± 20, V2 = −199 ± 25, V3 = 721 ± 5 and V4 = 65 ± 10 with barriers of 784 cm−1 for gauche to gauche and 834 cm−1 for gauche to trans form. By utilizing previously reported microwave rotational constants for the Eq-g conformer along with the ab initio predicted structural parameters from the MP2(full)/6-311 + G(d,p) calculations, r0 structural parameters have been obtained for this conformer. The determined r0 heavy atom distances in Å are: (C1N) = 1.453(5); (C1C4) = 1.560(5); (C1C5) = 1.547(5); (C4C6) = 1.557(5); (C5C6) = 1.555(5) and the angles in degrees NC1C4 = 122.8(5)°; NC1C5 = 116.8(5)° with the four CCC ranging from 87.5° to 88.1°. A complete vibrational assignment is proposed for the (Eq-g) conformer based on the infrared band contours, infrared intensities, Raman activities and group frequencies which is supported by normal coordinate calculations utilizing the force constants from ab initio MP2(full)/6-31G(d) calculations. Proposed assignments are also made for several fundamentals of the (Eq-t) form and a few for the Ax-t conformer. The results are discussed and compared to the corresponding properties of some similar molecules. E-info http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000263426100008&DestLinkType=RelatedRecords&DestApp=ALL_WOS&UsrCustomerID=ef845e08c439e550330acc77c7d2d848 http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000263426100008&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=ef845e08c439e550330acc77c7d2d848 http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000263426100008&DestLinkType=CitingArticles&DestApp=ALL_WOS&UsrCustomerID=ef845e08c439e550330acc77c7d2d848 Handle