CONFORMATIONAL TRANSFORMATION OF FIVE-MEMBERED RINGS: THE GAS PHASE STRUCTURE OF 2-METHYLTETRAHYDROFURAN

Van, Vinh

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https://hdl.handle.net/2142/79071 Copy

Description

Title

CONFORMATIONAL TRANSFORMATION OF FIVE-MEMBERED RINGS: THE GAS PHASE STRUCTURE OF 2-METHYLTETRAHYDROFURAN

Author(s)

Van, Vinh

Contributor(s)

• Stahl, Wolfgang
• Nguyen, Ha Vinh Lam

Issue Date

22-Jun-15

Keyword(s)

Structure determination

Abstract

2-Methyltetrahydrofuran (2-MeTHF) is a promising environmentally friendly solvent and biofuel component which is derived from renewable resourcesfootnote{V. Pace, P. Hoyos, L. Castoldi, P. Dom'{i}nguez de Mar'{i}a, A. R. Alc'{a}ntara, textit{ChemSusChem} textbf{5} (2012), 1369$-$1379.}. Following the principles of Green Chemistry, 2-MeTHF has been evaluated in various fields like organometallics, metathesis, and biosynthesis on the way to more eco-friendly synthesesfootnote{a) D. F. Aycock, textit{Org. Process Res. Dev.} textbf{11} (2007),156$-$159. b) M. Smole'{n}, M. Kc{e}dziorek, K. Grela, textit{Catal. Commun.} textbf{44} (2014), 80$-$84.}. Cyclopentane as the prototype of five-membered rings is well-known to exist as twist or envelope structures. However, the conformational analysis of its heterocyclic derivative 2-methyl-tetrahydrothiophene (MTTP) yielded two stable twist conformers and two envelope transition statesfootnote{V. Van, C. Dindic, H.V.L. Nguyen, W. Stahl, textit{ChemPhysChem} textbf{16} (2015), 291$-$294.}. Here, we report on the heavy atom $r_s$ structure of the oxygen-analog of MTTP, 2-MeTHF, studied by a combination of molecular beam Fourier transform microwave spectroscopy and quantum chemistry. One conformer of 2-MeTHF was observed and highly accurate molecular parameters were determined using the XIAM programfootnote{H. Hartwig, H. Dreizler, textit{Z. Naturforsch. A} textbf{51} (1996), 923$-$932.}. In addition, all chem{^{13}C}-isotopologues were assigned in natural abundance of 1%. A structural determination based on the $r_s$ positions of all carbon atoms was achieved via Kraitchman�s equationsfootnote{J. Kraitchman, textit{Am. J. Phys.} textbf{21} (1953), 17$-$24.}. The methyl group in 2-MeTHF undergoes internal rotation and causes A�E splittings of the rotational lines. The barrier was calculated to be 1142 wn at the MP2/6-311++G(d,p) level of theory, which is rather high. Accordingly, narrow A�E splittings could be observed for only a few transitions. However, the barrier height could be fitted while the angles between the internal rotor axis and the principal axes of inertia were taken from the experimental geometry.

Publisher

International Symposium on Molecular Spectroscopy

Type of Resource

text

Language

English

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http://hdl.handle.net/2142/79071

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