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Original Experimental Approach for Assessing Transport Fuel Stability
Published on: October 21, 2016
Correlation effects on the relative stabilities of alkanes
William C McKee1, Paul von Ragué Schleyer
1Center for Computational Chemistry and Department of Chemistry, University of Georgia, Athens, Georgia 30602, United States.
Journal of the American Chemical Society
|August 6, 2013
Summary
Highly branched alkanes and those with "protobranches" are more stable due to electron correlation effects. These effects, particularly between 1,3-alkyl groups, enhance alkane stability and correlation energies.
Area of Science:
- Computational Chemistry
- Organic Chemistry
- Physical Chemistry
Background:
- The alkane branching effect describes increased stability in branched alkanes (e.g., isobutane) compared to their linear isomers (e.g., n-butane).
- Linear alkanes exhibit
- protobranches
- which are 1,3-alkyl-alkyl interactions contributing to lower energies.
Purpose of the Study:
- To investigate the origins of stabilization energies in branched and protobranched alkanes.
- To elucidate the role of electron correlation in alkane stability.
Main Methods:
- Isodesmic comparisons of protobranched alkanes with ethane.
- Accurate ab initio calculations utilizing post-self-consistent field (SCF) treatments.
- Localized molecular orbital second-order Møller-Plesset (LMO-MP2) partitioning of correlation energies.
Main Results:
- Branching and protobranching lead to significant stabilization energies in alkanes.
- Medium-range electron correlation (1.5-3.0 Å) is crucial for accurately characterizing stability.
- LMO-MP2 analysis revealed that electron correlation between 1,3-alkyl groups is the primary driver of enhanced stability.
Conclusions:
- Electron correlation effects, especially within 1,3-alkyl interactions, are responsible for the enhanced stability of branched and protobranched alkanes.
- Accurate quantum chemical methods are necessary to capture these subtle stabilization effects.
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