TY - JOUR

T1 - Theoretical study of hydroxyl radical (OH˙) induced decomposition of tert-butyl methyl ether (MTBE)

AU - Tawabini, Bassam S.

AU - Nielsen, Ole John

AU - Sølling, Theis I.

PY - 2020/4/29

Y1 - 2020/4/29

N2 - We have characterized the various pathways for OH radical (OH˙) induced decomposition of tert-butyl methyl ether (MTBE) and found an oxidative pathway that leads to complete degradation under the prerequisite that OH radicals are present in excess. A simple polarizable continuum model is used to predict the behavior in an aqueous medium and the behavior is unchanged compared to that in the gas phase. The computational study has also revealed some of the fundamental aspects of hydrogen transfer from asymmetric ethers; the ˙OH assisted hydrogen abstraction has a barrier when the reaction takes place at a distance from the heteroatom, that is, at the tert-butyl group, whereas hydrogen abstraction from the methyl group proceeds without a barrier. The addition of ˙OH to (CH3)3COCH2˙ also proceeds without a barrier, and so does hydrogen abstraction from the resulting adduct ((CH3)3COCH2OH) to form (CH3)3COCH(OH)˙. However, a barrier is yet again found in the hydrogen abstraction from the latter to form (CH3)3COCH[double bond, length as m-dash]O and yet again in the formation of the formyl radical (CH3)3COC[double bond, length as m-dash]O˙ by hydrogen abstraction. The latter is the last step before the final stage of complete oxidation of MTBE to form CO2.

AB - We have characterized the various pathways for OH radical (OH˙) induced decomposition of tert-butyl methyl ether (MTBE) and found an oxidative pathway that leads to complete degradation under the prerequisite that OH radicals are present in excess. A simple polarizable continuum model is used to predict the behavior in an aqueous medium and the behavior is unchanged compared to that in the gas phase. The computational study has also revealed some of the fundamental aspects of hydrogen transfer from asymmetric ethers; the ˙OH assisted hydrogen abstraction has a barrier when the reaction takes place at a distance from the heteroatom, that is, at the tert-butyl group, whereas hydrogen abstraction from the methyl group proceeds without a barrier. The addition of ˙OH to (CH3)3COCH2˙ also proceeds without a barrier, and so does hydrogen abstraction from the resulting adduct ((CH3)3COCH2OH) to form (CH3)3COCH(OH)˙. However, a barrier is yet again found in the hydrogen abstraction from the latter to form (CH3)3COCH[double bond, length as m-dash]O and yet again in the formation of the formyl radical (CH3)3COC[double bond, length as m-dash]O˙ by hydrogen abstraction. The latter is the last step before the final stage of complete oxidation of MTBE to form CO2.

U2 - 10.1039/c9em00588a

DO - 10.1039/c9em00588a

M3 - Journal article

C2 - 32119021

AN - SCOPUS:85084177660

VL - 22

SP - 1037

EP - 1044

JO - Environmental Science. Processes & Impacts

JF - Environmental Science. Processes & Impacts

SN - 2050-7887

IS - 4

ER -