Temperature Dependence of the Relative Rates of Chlorination and Hydrolysis of N2O5 in NaCl-Water Solutions.

19 September 2022, Version 2
This content is a preprint and has not undergone peer review at the time of posting.


We have measured the temperature dependence of the ClNO2 product yield in competition with hydrolysis following N2O5 uptake to aqueous NaCl solutions. For NaCl-D2O solutions spanning 0.0054 to 0.21 M, the ClNO2 product yield decreases on average by only 5% from 5 to 25 ˚C. Less reproducible measurements at 0.54 and 2.4 M NaCl also fall within this range. The ratio of the rate constants for chlorination and hydrolysis of N2O5 in D2O is determined to be 1147 ± 65 at 25 °C, favoring chlorination. An Arrhenius analysis reveals that the activation energy for hydrolysis is just 3.0 ± 1.8 kJ/mol larger than for chlorination. In combination with the measured pre-exponential ratio favoring chlorination of 419 (-215) (+542), we conclude that the strong preference of N2O5 to undergo chlorination over hydrolysis is driven by dynamic and entropic, rather than enthalpic, factors. Molecular dynamics simulations elucidate the distinct solvation between strongly hydrated Cl- and the hydrophobically solvated N2O5. Combining this molecular picture with the Arrhenius analysis implicates the role of water in mediating interactions between such distinctly solvated species and suggests a role for diffusion limitations on the chlorination reaction.


Competative Reactions
Gas-Liquid Interactions

Supplementary materials

Supporting Information for Temperature Dependence of the Relative Rates of Chlorination and Hydrolysis of N2O5 in NaCl-Water Solutions
This supporting information contains all of the experimental measurements of the ClNO2 product yield, an expanded set of Arrhenius analysis plots similar to Fig.5 in the manuscript, and schematics of the PTFE solution holders. It also contains a description of the theoretical methods utilized to generate and analyze Fig. 6.


Comments are not moderated before they are posted, but they can be removed by the site moderators if they are found to be in contravention of our Commenting Policy [opens in a new tab] - please read this policy before you post. Comments should be used for scholarly discussion of the content in question. You can find more information about how to use the commenting feature here [opens in a new tab] .
This site is protected by reCAPTCHA and the Google Privacy Policy [opens in a new tab] and Terms of Service [opens in a new tab] apply.