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Dynamic Odd-Even Effect in Liquid n-Alkanes Near Their Melting Points

Published

Author(s)

Ke Yang, Zhikun Cai, Abhishek Jaiswal, Madhu Sudan Tyagi, Jeffrey S. Moore, Yang Zhang

Abstract

n-Alkanes are the textbook examples of the odd-even effect. The difference in the packing pattern of odd- and even-numbered n-alkanes results in the odd-even variation of their melting points. In the liquid state, where the packing effects do not hold, it seems natural to assume that the odd-even effect does not exist, which is further supported by the fact that the boiling points of n-alkanes show a monotonic dependence on chain length. Herein, we report a surprising odd-even effect in the translational dynamic properties of n-alkanes in their liquid states. To measure the molecules' dynamics, we performed quasi-elastic neutron scattering measurements on n-alkanes near their melting points. We found that odd-numbered n-alkanes have up to 30 times slower dynamics than even-numbered n-alkanes near their respective melting points. Our results suggest that the dynamic properties of n-alkanes are extremely sensitive to number of carbons despite the fact that n-alkanes are the simplest hydrocarbon molecules.
Citation
Angewandte Chemie-International Edition
Volume
55
Issue
45

Keywords

dynamics, alkanes

Citation

Yang, K. , Cai, Z. , Jaiswal, A. , Tyagi, M. , Moore, J. and Zhang, Y. (2016), Dynamic Odd-Even Effect in Liquid n-Alkanes Near Their Melting Points, Angewandte Chemie-International Edition, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=921819 (Accessed March 3, 2024)
Created October 31, 2016, Updated October 12, 2021