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Elementary reaction

About: Elementary reaction is a research topic. Over the lifetime, 2972 publications have been published within this topic receiving 76110 citations.


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TL;DR: A detailed model of the PO reaction is presented which is capable of simulating the recent period doubling experiments of Geest et al., using the proper rate constants and the same conditions as in the experiments.
Abstract: published in Advance ACS Abstmcrs, June 1, 1995. into the reaction scheme.7-" Although both types of models are capable of exhibiting complex dynamics, including chaos, the simple models have, up to now, outperformed the detailed models in reproducing the reaction's individual features, such as the waveform of the oscillations and their nonuniformity.I2 Furthermore, in the detailed models most of the rate constants used to obtain complex dynamics are not in accordance with the experimentally determined rate constants. Here we present a detailed model of the PO reaction which is capable of simulating the recent period doubling experiments of Geest et al.,I3 using the proper rate constants and the same conditions (enzyme concentration, 02 and NADH supply rates) as in the experiments. The model is a slight extension of a model recently proposed by Olson et al.'' under the name Urbanalator. The Model The model is built using the same elementary reaction steps as in previous detailed models such as the Yokota-Yamazaki (YY) ~cheme,~ the Fedkina-

66 citations

Journal ArticleDOI
TL;DR: In this paper, the growth of diamond from acetylene is explained by the addition of an acetylene molecule that forms a bridge between adjacent (100)-(2x1) dimer rows, where the admolecule can undergo a series of H-additions, H-abstractions, and [beta]-scissions.
Abstract: Kinetically and thermodynamically plausible reactions that can explain the growth of diamond from acetylene are introduced. This class of reactions includes the addition of acetylene to a biradical with at least one of its sites being either a (100)-(2x1) dimer carbon or a secondary carbon, so that the admolecule can undergo a series of H-additions, H-abstractions, and [beta]-scissions leading to incorporation of its carbon atoms into a diamond lattice. Several examples are presented and supported with the results of semiempirical quantum-chemical and transition-state-theory calculations. Among those considered, the most favorable reaction pathway is initiated by the addition of an acetylene molecule that forms a bridge between adjacent dimer rows. 34 refs., 2 figs., 1 tab.

66 citations

Journal ArticleDOI
TL;DR: The dynamics of some elementary reactions of N(2D), C(3P,1D) and CN(X2 sigma +) of importance in combustion have been investigated by using the crossed molecular beam scattering method with mass spectrometric detection and the occurrence of the spin-forbidden molecular pathway in this reaction has been rationalized.
Abstract: The dynamics of some elementary reactions of N(2D), C(3P,1D) and CN(X2Σ+) of importance in combustion have been investigated by using the crossed molecular beam scattering method with mass spectrometric detection. The novel capability of producing intense, continuous beams of the radical reagents by a radio-frequency discharge beam source was exploited. From angular and velocity distribution measurements obtained in the laboratory frame, primary reaction products have been identified and their angular and translational energy distributions in the center-of-mass system, as well as branching ratios, have been derived. The dominant N/H exchange channel has been examined in the reaction N(2D) + CH4, which is found to lead to H + CH2NH (methylenimine) and H + CH3N (methylnitrene); no H2 elimination is observed. In the reaction N(2D) + H2O the N/H exchange channel has been found to occur ia two competing pathways leading to HNO + H and HON + H, while formation of NO + H2 is negligible. Formation of H + H2CCCH (propargyl) is the dominant pathway, at low collision energy (Ec), of the C(3P) + C2H4 reaction, while at high Ec formation of the less stable C3H3 isomers (cyclopropenyl and/or propyn-1-yl) also occurs; the H2 elimination channel is negligible. The H elimination channel has also been found to be the dominant pathway in the C(3P,1D) + CH3CCH reaction leading to C4H3 isomers and, again, no H2 elimination has been observed to occur. In contrast, both H and H2 elimination, leading in comparable ratio to C3H + H and C3(X1Σg+) + H2(X1Σg+), respectively, have been observed in the reaction C(3P) + C2H2(X1Σg+). The occurrence of the spin-forbidden molecular pathway in this reaction, never detected before, has been rationalized by invoking the occurrence of intersystem crossing between triplet and singlet manifolds of the C3H2 potential energy surfaces. The reaction CN(X2Σ+) + C2H2 has been found to lead to internally excited HCCCN (cyanoacetylene) + H. For all the reactions the dynamics have been discussed in the light of recent theoretical calculations on the relevant potential energy surfaces. Previous, lower resolution studies on C and CN reactions carried out using pulsed beams are noted. Finally, throughout the paper the relevance of these results to combustion chemistry is considered.

65 citations

Journal ArticleDOI
TL;DR: In this paper, the rate constant for the N + NO2 reaction was determined with pseudo first-order kinetic analysis ([NO]0/[N]0 1] 1] ).
Abstract: Kinetic studies of the reactions of NO, (1) and of NO2, (2), with N 4S atoms have been made using direct mass spectrometric detection of N atoms in a discharge flow system. The rate constant k1(cm3 molecule–1 s–1) for the rapid reaction (1), N + NO [graphic omitted] N2+ O (1), has been determined with pseudo first-order kinetic analysis ([NO]0/[N]0 1). The mean value for k1 was (2.2 ± 0.2)× 10–11 at 298 K, and between 298 and 670 K, k1 was given by the expression (8.2 ± 1.4)× 10–11 exp[–(410 ± 120) K/T].Similar kinetic studies of the N + NO2 reaction, using pseudo first-order analysis with very large excesses of NO2([NO2]0/[N]0 > 80), showed the rate constant for this reaction to be an order of magnitude less than the literature value. However, at lower values of [NO2]0/[N]0, much greater apparent rate constants for the N + NO2 reaction were obtained, similar to those found previously. These high values are attributed to a rapid catalytic cycle capable of removing both N atoms and NO2, i.e., N + NO2 [graphic omitted] N2O + O (2A), O + NO2 [graphic omitted] NO + O2(3), N + NO [graphic omitted] N2+ O (1). Reactions (1)+(3) have the stoichiometry, N + NO2→ N2+ O2: No evidence was found from N2O yields in the N + NO2 reaction for any reactive channel involving N + NO2 other than reaction (2A). The results give a mean value for k2A equal to (1.4 ± 0.2)× 10–12 cm3 molecule–1 s–1 at 298 K.

65 citations

Journal ArticleDOI
TL;DR: In this paper, the results of a combined experimental and theoretical investigation of the reaction of molecular oxygen with a partially hydroxylated TiO2(110) surface were reported.
Abstract: We report the results of a combined experimental and theoretical investigation of the reaction of molecular oxygen with a partially hydroxylated TiO2(110) surface. The consecutive steps of both primary and secondary site-specific reactions have been tracked with high-resolution scanning tunneling microscopy (STM). We have directly imaged stable, adsorbed hydroperoxyl (HO2) species, which is believed to be a key intermediate in many heterogeneous photochemical processes but generally metastable and “elusive” until now. We also found terminal hydroxyl groups, which are another critical but never previously directly observed intermediates. Conclusive evidence that O2 reacts spontaneously with a single bridging OH group as an initial reaction step is provided. The experimental results are supported by density functional theory (DFT) calculations that have determined the energies and configurations of these species. Reported observations provide a base for a consistent description of the elementary reaction st...

65 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202321
202229
202185
202088
201971
201871