| Title: | Isotope Effects on the Vaporization of Organic Compounds from an Aqueous Solution-Insight from Experiment and Computations |
| Author(s): | Rostkowski M; Schurner HKV; Sowinska A; Vasquez L; Przydacz M; Elsner M; Dybala-Defratyka A; |
| Address: | "Institute of Applied Radiation Chemistry, Faculty of Chemistry, Lodz University of Technology, Zeromskiego 116, 90-924 Lodz, Poland. Chair of Analytical Chemistry and Water Chemistry, Technical University of Munich, Elisabeth-Winterhalter-Weg 6, 81377 Munich, Germany" |
| ISSN/ISBN: | 1520-5207 (Electronic) 1520-6106 (Print) 1520-5207 (Linking) |
| Abstract: | "An isotope fractionation analysis of organic groundwater pollutants can assess the remediation at contaminated sites yet needs to consider physical processes as potentially confounding factors. This study explores the predictability of water-air partitioning isotope effects from experiments and computational predictions for benzene and trimethylamine (both H-bond acceptors) as well as chloroform (H-bond donor). A small, but significant, isotope fractionation of different direction and magnitude was measured with epsilon = -0.12 per thousand +/- 0.07 per thousand (benzene), epsilon(C) = 0.49 per thousand +/- 0.23 per thousand (triethylamine), and epsilon(H) = 1.79 per thousand +/- 0.54 per thousand (chloroform) demonstrating that effects do not correlate with expected hydrogen-bond functionalities. Computations revealed that the overall isotope effect arises from contributions of different nature and extent: a weakening of intramolecular vibrations in the condensed phase plus additional vibrational modes from a complexation with surrounding water molecules. Subtle changes in benzene contrast with a stronger coupling between intra- and intermolecular modes in the chloroform-water system and a very local vibrational response with few atoms involved in a specific mode of triethylamine. An energy decomposition analysis revealed that each system was affected differently by electrostatics and dispersion, where dispersion was dominant for benzene and electrostatics dominated for chloroform and triethylamine. Interestingly, overall stabilization patterns in all studied systems originated from contributions of dispersion rather than other energy terms" |
| Keywords: | Carbon Isotopes Chemical Fractionation *Groundwater Volatilization Water; |
| Notes: | "MedlineRostkowski, Michal Schurner, Heide K V Sowinska, Agata Vasquez, Luis Przydacz, Martyna Elsner, Martin Dybala-Defratyka, Agnieszka eng Research Support, Non-U.S. Gov't 2021/12/16 J Phys Chem B. 2021 Dec 30; 125(51):13868-13885. doi: 10.1021/acs.jpcb.1c05574. Epub 2021 Dec 15" |
