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Reaction of 2-propanol with ozone in aqueous media.

Authors :: Reisz E
von Sonntag C
Tekle-Röttering A
Naumov S
Schmidt W
Schmidt TC
Source :: Water research [Water Res] 2018 Jan 01; Vol. 128, pp. 171-182. Date of Electronic Publication: 2017 Oct 20.
Publication Year :: 2018
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 O <subscript>3</subscript> mainly via hydride transfer: (HO)(H <subscript>3</subscript> C) <subscript>2</subscript> CH + O <subscript>3</subscript>  → [(HO)(H <subscript>3</subscript> C) <subscript>2</subscript> C <superscript>+</superscript>  + HO <subscript>3</subscript> <superscript>-</superscript> ] <subscript>cage</subscript>  → (HO)(H <subscript>3</subscript> C) <subscript>2</subscript> C <superscript>+</superscript>  + HO <subscript>3</subscript> <superscript>-</superscript>  → (H <subscript>3</subscript> C) <subscript>2</subscript> CO + H <subscript>2</subscript> O + O <subscript>2</subscript> Arguments supporting this proposed mechanism are: high exergonicity of reaction (ΔG = -234 kJ mol <superscript>-1</superscript> 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 + O <subscript>3</subscript>  → products is ln k <subscript>II</subscript>  = 29.64-8500 × T <superscript>-1</superscript> . The activation energy and pre-exponential factor derived from this relationship are (71 ± 3) kJ mol <superscript>-1</superscript> and (7.5 ± 6.4) × 10 <superscript>12</superscript>  M <superscript>-1</superscript>  s <superscript>-1</superscript> , respectively. At 23 °C, the second order rate constant is k <subscript>II</subscript>  = (2.7 ± 0.1) M <superscript>-1</superscript>  s <superscript>-1</superscript> . The low reaction rate can be explained by the transfer of one hydride ion from 2-propanol to electrophilic ozone.<br /> (Copyright © 2017 Elsevier Ltd. All rights reserved.)