Time-resolved molecular dynamics of single and double hydrogen migration in ethanol

Being the lightest, most mobile atom that exists, hydrogen plays an important role in the chemistry of hydrocarbons, proteins and peptides and most biomolecules. Hydrogen can undergo transfer, exchange and migration processes, having considerable impact on the chemical behavior of these molecules. Although much has been learned about reaction dynamics involving one hydrogen atom, less is known about those processes where two or more hydrogen atoms participate. Here we show that single and double hydrogen migrations occurring in ethanol cations and dications take place within a few hundred fs to ps, using a 3D imaging and laser pump-probe technique. For double hydrogen migration, the hydrogens are not correlated, with the second hydrogen migration promoting the breakup of the C–O bond. The probability of double hydrogen migration is quite significant, suggesting that double hydrogen migration plays a more important role than generally assumed. The conclusions are supported by state-of-the-art molecular dynamics calculationsThis work was funded by the National Science Foundation under award No. 1700551, the MINECO projects FIS2016-77889-R and CTQ2016- 76061-P, ‘Severo Ochoa’ Programme for Centres of Excellence in R&D (SEV-2016-0686) and ‘María de Maeztu’ Programme for Units of Excellence in R&D (MDM-2014-0377). We acknowledge the generous allocation of computer time at the Centro de Computación Científica at the Universidad Autónoma de Madrid (CCC-UAM). S.D.-T. gratefully acknowledges the “Ramón y Cajal” program (RYC-2010-07019) of the Spanish Ministerio de Educación y Cienci