Where's the bend? Locating the first folded structure in straight chain alkylbenzenes in a supersonic jet expansion

Hewett, Daniel M.

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https://hdl.handle.net/2142/91232 Copy

Description

Title

Where's the bend? Locating the first folded structure in straight chain alkylbenzenes in a supersonic jet expansion

Author(s)

Hewett, Daniel M.

Contributor(s)

• Zwier, Timothy S.
• Suhm, Martin A.
• Bocklitz, Sebastian

Issue Date

2016-06-20

Keyword(s)

Conformers, isomers, chirality, stereochemistry

Abstract

Alkylbenzenes make up 20-30\% of petroleum fuels and are important intermediates in combustion. In gasoline, these alkyl chains are relatively short, but extend to 20 or more carbons in length in diesel fuels. While one tends to think of these chains as extending out away from the phenyl ring in an all-trans configuration, dispersive interactions between segments of the alkyl chain and between the alkyl chain and the ring will stabilize more compact geometries in which the alkyl chain folds back on itself and extends over the aromatic $\pi$ cloud. This talk seeks to answer the following question: How long must the alkyl chain be before it starts to fold back over itself? Studies of the pure n-alkanes by the Suhm group have shown the turn to favorably occur for a chain about 17 carbon atoms in length. The studies presented here focus on the affect the aromatic ring has on when this turn becomes favorable. Jet-cooled laser-induced fluorescence excitation and single-conformation IR spectra have been recorded in the alkyl CH stretch region for a series of alkylbenzenes with chain lengths ranging from two to ten carbon atoms. We show, through a combination of experiment, high level calculation, and theoretical modeling, that conformations begin to form that fold back over the aromatic ring at about n=8.

Publisher

International Symposium on Molecular Spectroscopy

Type of Resource

text

Language

En

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http://hdl.handle.net/2142/91232

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Copyright 2016 by the authors

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