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Why tert-butyl alcohol associates in aqueous solution but trimethylamine-N-oxide does not

TitleWhy tert-butyl alcohol associates in aqueous solution but trimethylamine-N-oxide does not
Publication TypeJournal Article
Year of Publication2006
AuthorsPaul, S, Patey, GN
JournalJournal of Physical Chemistry B
Volume110
Pagination10514-10518
Date PublishedJun
Type of ArticleArticle
ISBN Number1520-6106
KeywordsBINARY-MIXTURES, CLATHRATE HYDRATE FORMATION, ELECTROLYTE SOLUTIONS, HYDROGEN-BOND DYNAMICS, HYDROPHOBIC INTERACTIONS, LIGHT-SCATTERING, LIQUID, MOLECULAR-DYNAMICS, SIMULATION, WATER MIXTURES
Abstract

In dilute aqueous solution, tert-butyl alcohol (TBA) tends to aggregate but trimethylamine-N-oxide ( TMAO) does not. Given that both molecules have very similar geometry with hydrophobic and hydrophilic groups, it is interesting to ask why they behave so differently in aqueous solution. To explore this question, we use molecular dynamics simulations to study two models representing TBA and TMAO that differ essentially only in their electrostatic properties. It is shown that this difference is sufficient to give the different solution behavior. Furthermore, the principal difference identified is that the hydrophilic group of TMAO ( the oxygen) interacts on average much more strongly with water than the corresponding group ( the hydroxyl) of TBA. A hydrogen-bond analysis shows that water-TBA and water-TMAO hydrogen bonds are similar in number, but that the hydrogen-bond energy is much more negative for water-TMAO. In all likelihood, this accounts for the different behavior in dilute aqueous solution.

URL<Go to ISI>://000237844900046