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The hydroxyl radical reaction rate constants and atmospheric reaction products of three siloxanes
Author(s) -
Markgraf Stewart J.,
Wells J. R.
Publication year - 1997
Publication title -
international journal of chemical kinetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.341
H-Index - 68
eISSN - 1097-4601
pISSN - 0538-8066
DOI - 10.1002/(sici)1097-4601(1997)29:6<445::aid-kin6>3.0.co;2-u
Subject(s) - hexamethyldisiloxane , siloxane , chemistry , octamethylcyclotetrasiloxane , reaction rate constant , reaction rate , polymer chemistry , photochemistry , kinetics , organic chemistry , catalysis , polymer , physics , quantum mechanics , plasma
The relative rate technique has been used to measure the hydroxyl radical (OH) reaction rate constant of hexamethyldisiloxane (MM, (CH 3 ) 3 Si‐O‐Si(CH 3 ) 3 ), octamethyltrisiloxane (MDM, (CH 3 ) 3 Si‐O‐Si(CH 3 ) 2 ‐O‐Si(CH 3 ) 3 ), and decamethyltetrasiloxane (MD 2 M, (CH 3 ) 3 Si‐O‐Si(CH 3 ) 2 ‐O‐Si(CH 3 ) 2 ‐O‐Si(Ch 3 ) 3 ). Hexamethyldisiloxane, octamethyltrisiloxane, and decamethyltetrasiloxane react with OH with bimolecular rate constants of 1.32 ± 0.05 × 10 −12 cm 3 molecule −1 s −1 , 1.83 ± 0.09 × 10 −12 cm 3 molecule −1 s −1 , and 2.66 ± 0.13 × 10 −12 cm 3 molecule −1 s −1 , respectively. Investigation of the OH + siloxane reaction products yielded trimethylsilanol, pentamethyldisiloxanol, heptamethyltetrasiloxanol, hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, and other compounds. Several of these products have not been reported before because these siloxanes and the proposed reaction mechanisms yielding these products are complicated. Some unusual cyclic siloxane products were observed and their formation pathways are discussed in light of current understanding of siloxane atmospheric chemistry. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 445–451, 1997.