Reaction of 2-propanol with ozone in aqueous media

Erika Reisz,Clemens Von Sonntag,Agnes Tekle-Röttering,Sergej Naumov,Winfried Schmidt,Torsten C Schmidt

doi:10.1016/j.watres.2017.10.035

Abstract

This paper deals with reactions occurring in the aqueous system of 2-propanol/ozone. The considered reactions are discussed from thermodynamic and kinetic points of view. The major finding refers to the fact that 2-propanol reacts with O3 mainly via hydride transfer:(HO)(H3C)2CH + O3 → [(HO)(H3C)2C+ + HO3−]cage → (HO)(H3C)2C+ + HO3− → (H3C)2CO + H2O + O2Arguments supporting this proposed mechanism are: high exergonicity of reaction (ΔG = −234 kJ mol−1 for the first two steps), low HO yield - (2.4 ± 0.5)% and high acetone yield - (87.2 ± 1.5)%. Other oxidation products detected within the system are acetaldehyde - (1.4 ± 0.1)%, formaldehyde - (4.0 ± 0.1)%, acetic acid - (2.8 ± 0.2)%, formic acid - (0.6 ± 0.2)% and hydrogen peroxide - (1.5 ± 0.1)%. The temperature dependence of the second order rate constant for the reaction 2-propanol + O3 → products is ln kII = 29.64–8500 × T−1. The activation energy and pre-exponential factor derived from this relationship are (71 ± 3) kJ mol−1 and (7.5 ± 6.4) × 1012 M−1 s−1, respectively. At 23 °C, the second order rate constant is kII = (2.7 ± 0.1) M−1 s−1. The low reaction rate can be explained by the transfer of one hydride ion from 2-propanol to electrophilic ozone.

Highlights

This paper is one of a series that tries to shed some light on ozone reactions with compounds characterised by C–H active sites only, compounds known as less reactive
This study confirms the supposition that ozone reacts with 1-propanol in aqueous media mainly by hydride transfer as expected based on the results for 2-propanol/ozone aqueous system
In contrast to 2-propanol/ozone system, where insertion and H-abstraction have a share of a small percentage, ozone reacts with 1-propanol with yields of one order of magnitude higher as part of the afore-mentioned mechanisms

Summary

Introduction

This paper is one of a series that tries to shed some light on ozone reactions with compounds characterised by C–H active sites only, compounds known as less reactive. Working Conditions pH = 2 t = (20 ± 0.5) ◦C pH = 7 t = 23 ◦C pH = 7 pH = 10.7 pH = 7 pH = 14

Objectives

Discussion

Conclusion