Article

Direct evidence for base-mediated decomposition of alkyl hydroperoxides (ROOH) in the gas phase.

Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO 80309, USA.
Journal of the American Chemical Society (Impact Factor: 11.44). 05/2002; 124(13):3196-7. DOI: 10.1021/ja017658c
Source: PubMed

ABSTRACT The reaction of F(-) with CH(3)OOH has been studied in the gas phase using a tandem flowing afterglow-selected ion flow tube apparatus. The reaction is rapid (k = 1.23 x 10(-9) cm(3) s(-1), 49% efficiency), and formation of HO(-) + CH(2)O + HF is the major reaction channel observed (85%). Isotopic labeling, reactions of F(-) with larger alkyl hydroperoxides, and computational studies demonstrate that the major product ion, HO(-), is formed via a concerted elimination mechanism that appears to be general to all alkyl hydroperoxides possessing an alpha-hydrogen. This mechanism represents a base-mediated decomposition of alkyl hydroperoxides in the gas phase that may have important implications for solution and biochemical reactions. The reverse reaction, CH(3)OO(-) + HF is also efficient (k = 2.43 x 10(-9) cm(3) s(-1)). The major product ensemble HO(-) + CH(2)O + HF (81%) is identical to that of the forward reaction, and represents a novel neutral-catalyzed decomposition of the anion.

0 Bookmarks
 · 
70 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: The B3LYP theory and scaled hypersphere search method are utilized to explore pathways of (HO)2PS2Cu-mediated CH3OOH decomposition, a model reaction of alkyl hydroperoxide with cuprous dialkyldithiophosphate [(RO)2PS2Cu]. It is found that the decomposition of CH3OOH mediated by the copper(I) complex may lead to formaldehyde and water molecules via O–O bond heterolysis and subsequent intramolecular hydrogen transfer, with retainment of the copper(I) complex. The subsequent hydrogen transfer event and formation of water may add new understanding to the (RO)2PS2Cu-mediated decomposition process of alkyl hydroperoxide. The oxygen transfer from CH3OOH to (HO)2PS2Cu moiety, as an O–O bond cleavage manner of CH3OOH, is also found to occur.
    Tetrahedron Letters 11/2008; 49(48):6841-6845. · 2.39 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Classical chemical dynamics simulations of post-transition state dynamics are reviewed. Most of the simulations involve direct dynamics for which the potential energy and gradient are obtained directly from an electronic structure theory. The chemical reaction attributes and chemical systems presented are product energy partitioning for Cl- ··· CH3Br --> ClCH3 + Br- and C2H5F --> C2H4 + HF dissociation, non-RRKM dynamics for cyclopropane stereomutation and the Cl- ··· CH3Cl complexes mediating the Cl- + CH3Cl SN2 nucleophilic substitution reaction, and non-IRC dynamics for the OH- + CH3F and F- + CH3OOH chemical reactions. These studies illustrate the important role of chemical dynamics simulations in understanding atomic-level reaction dynamics and interpreting experiments. They also show that widely used paradigms and model theories for interpreting reaction kinetics and dynamics are often inaccurate and are not applicable.
    International Reviews in Physical Chemistry 07/2008; 27(3):361-403. · 4.92 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: In classical and quasiclassical trajectory chemical dynamics simulations, the atomistic dynamics of collisions, chemical reactions, and energy transfer are studied by solving the classical equations of motion. These equations require the potential energy and its gradient for the chemical system under study, and they may be obtained directly from an electronic structure theory. This article reviews such direct dynamics simulations. The accuracy of classical chemical dynamics is considered, with simulations highlighted for the F− + CH3OOH reaction and of energy transfer in collisions of CO2 with a perfluorinated self-assembled monolayer (F-SAM) surface. Procedures for interfacing chemical dynamics and electronic structure theory computer codes are discussed. A Hessian-based predictor–corrector algorithm and high-accuracy Hessian updating algorithm, for enhancing the efficiency of direct dynamics simulations, are described. In these simulations, an ensemble of trajectories is calculated which represents the experimental and chemical system under study. Algorithms are described for selecting the appropriate initial conditions for bimolecular and unimolecular reactions, gas-surface collisions, and initializing trajectories at transition states and conical intersections. Illustrative direct dynamics simulations are presented for the Cl− + CH3I SN2 reaction, unimolecular decomposition of the epoxy resin constituent CH3NHCHCHCH3 versus temperature, collisions and reactions of N-protonated diglycine with a F-SAM surface that has a reactive head group, and the product energy partitioning for the post-transition state dynamics of C2H5F → HF + C2H4 dissociation. © 2012 John Wiley & Sons, Ltd.
    Wiley Interdisciplinary Reviews: Computational Molecular Science. 05/2013; 3(3).

Preview

Download
0 Downloads
Available from