Conformational stabilities of 1-methoxy-2-(methylthio)ethane and relevant intramolecular CH⋯O interaction studied by matrix-isolation infrared spectroscopy and density functional calculations

• Published in: Chemical physics letters Vol. 362; no. 5; pp. 453 - 460
• Main Authors: Harada, Takanori, Yoshida, Hiroshi, Ohno, Keiichi, Matsuura, Hiroatsu
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 26.08.2002
• ISSN: 0009-2614; 1873-4448
• DOI: 10.1016/S0009-2614(02)01139-9

Conformational stabilities of 1-methoxy-2-(methylthio)ethane were studied by matrix-isolation infrared spectroscopy, and the relevant intramolecular 1,5-CH⋯O interaction was examined by density functional calculations. The conformer with trans– trans– gauche ± around the CH 3O–CH 2–CH 2–SCH 3 bonds is the most stable in an argon matrix and the conformer with trans– gauche ±– gauche ∓ is the second most stable. The energy difference between the two conformers was determined to be 0.7±0.4 kJ mol −1 using thermal effusive sources. The 1,5-CH⋯O interaction is responsible for the high stability of the trans– gauche ±– gauche ∓ conformer, since the nonbonded (C)H⋯O distance associated with this interaction is shorter than the corresponding van der Waals separation by 0.15 Å. The energy of the 1,5-CH⋯O interaction was evaluated to be 4.0 kJ mol −1 .