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Vibrational overtone initiated unimolecular dissociation of HOCH_2OOH and HOCD_2OOH: Evidence for mode selective behavior

Matthews, Jamie and Fry, Julie L. and Roehl, Coleen M. and Wennberg, Paul O. and Sinha, Amitabha (2008) Vibrational overtone initiated unimolecular dissociation of HOCH_2OOH and HOCD_2OOH: Evidence for mode selective behavior. Journal of Chemical Physics, 128 (18). Art. No. 184306. ISSN 0021-9606.

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The vibrational overtone induced unimolecular dissociation of HMHP (HOCH2OOH) and HMHP-d2 (HOCD2OOH) into OH and HOCH2O (HOCD2O) fragments is investigated in the region of the 4nuOH and 5nuOH bands. The unimolecular dissociation rates in the threshold region, corresponding to the 4nuOH band, exhibit measurable differences associated with excitation of the OH stretch of the alcohol versus the peroxide functional group, with the higher energy alcohol OH stretching state exhibiting a slower dissociation rate compared to the lower energy peroxide OH stretch in both HMHP and HMHP-d2. Predictions using the Rice–Ramsperger–Kassel–Marcus theory give rates that are in reasonably good agreement with the measured dissociation rate for the alcohol OH stretch but considerably differ from the measured rates for the peroxide OH stretch in both isotopomers. The present results are interpreted as suggesting that the extent of intramolecular vibrational energy redistribution (IVR) is different for the two OH stretching states associated with the two functional groups in HMHP, with IVR being substantially less complete for the peroxide OH stretch. Analysis of the OH fragment product state distributions in conjunction with phase-space theory simulation gives a D0 value of 38±0.7 kcal/mole for breaking the peroxide bond in HMHP.

Item Type:Article
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URLURL TypeDescription
Roehl, Coleen M.0000-0001-5383-8462
Wennberg, Paul O.0000-0002-6126-3854
Sinha, Amitabha0000-0002-7122-3549
Additional Information:© 2008 American Institute of Physics. Received 1 February 2008; accepted 27 March 2008; published 9 May 2008. Funding for this work was provided by grants to A.S. from the National Science Foundation Division of Chemistry (CHE-0642640) and to P.O.W. from the National Science Foundation Division of Atmospheric Sciences (ATM-0432377). We also thank Dr. Shuping Li for assistance with certain portions of the measurements.
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Subject Keywords:bonds (chemical), dissociation, organic compounds, spectrochemical analysis, vibrational modes
Issue or Number:18
Record Number:CaltechAUTHORS:MATjcp08
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:10557
Deposited By: Archive Administrator
Deposited On:17 May 2008
Last Modified:09 Mar 2020 13:19

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