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Title: A joint experimental and theoretical study on the mechanisms of methyl 2-hydroxypropionate and methyl 2-hydroxyisobutyrate decomposition in the gas phase
Journal: J. Phys. Chem. A
Volume: 108
Page(s): 996 - 1007
Year: 2004
Reference type: Journal article
Squib: 2004SAF/AND996-1007
Reaction:
CH3CH(OH)C(O)OCH3 → CH3OH + CH3CHO + CO
Reaction order:
1
Temperature:
643 - 703
K
Pressure: 9.33E-2 - 0.28 bar
Rate expression:
5.37x1013 [s-1] e-219800 [±2500 J/mole]/RT
Uncertainty:
1.53999996
Category: Experiment
Data type:
Absolute value measured directly
Pressure dependence:
None reported
Experimental procedure:
Static or low flow - Data taken vs time
Excitation technique:
Thermal
Time resolution:
By end product analysis
Analytical technique:
Gas chromatography
Comments:
Combined experimental and computational study. Measured decomposition of hydroxesters in a static reactor seasoned with allyl bromide and using cyclohexene or toluene as a radical inhibitor. Also tested for heterogeneous reactions by packing reactor.
Used ab initio MP2 and B3LYP DFT quantum calculations with 6-31G** and 6-31++G** to elucidate reaction mechanism and energetics. Ab initio calculations gave same barriers within about 10 kJ/mol and A factors within about factor of 3.
Combined experimental and computations point toward a concerted reaction involving 5 membered cyclic transition state for elimination of aldehyde plus CH3OH plus CO. Other elimination channels are energetically unfavorable and few byproducts observed experimentally.
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Rate constant values calculated from the Arrhenius expression:
| T (K) | k(T) [s-1] |
|---|---|
| 643 | 7.57E-5 |
| 650 | 1.17E-4 |
| 675 | 5.26E-4 |
| 700 | 2.13E-3 |
| 703 | 2.52E-3 |