• Title/Summary/Keyword: reaction pathway

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Theoretical Study on the Mechanism of the Addition Reaction between Cyclopropenylidene and Formaldehyde

  • Tan, Xiaojun;Li, Zhen;Sun, Qiao;Li, Ping;Wang, Weihua
    • Bulletin of the Korean Chemical Society
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    • v.33 no.6
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    • pp.1934-1938
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    • 2012
  • The reaction mechanism between cyclopropenylidene and formaldehyde has been systematically investigated employing the MP2/6-311+$G^*$ level of theory to better understand the cyclopropenylidene reactivity with carbonyl compound. Geometry optimization, vibrational analysis, and energy property for the involved stationary points on the potential energy surface have been calculated. Energies of all the species are further corrected by the CCSD(T)/6-311+$G^*$ single-point calculations. It was found that one important reaction intermediate (INTa) has been located firstly $via$ a transition state (TSa). After that, the common intermediate (INTb) for the two pathways (1) and (2) has been formed $via$ TSb. At last, two different products possessing three- and four-membered ring characters have been obtained through two possible reaction pathways. In the reaction pathway (1), a three-membered ring alkyne compound has been obtained. As for the reaction pathway (2), it is the formation of the four-membered ring conjugated diene compound. The energy barrier of the ratedetermining step of pathway (1) is lower than that of the pathway (2), and the ultima product of pathway (2) is more stable than that of the pathway (1).

Single Electron Transfer (SET) Pathway: Nucleophilic Substitution Reaction of 4-Chloro-7-nitrobenzofurazan with Anilines in MeOH-MeCN Mixtures

  • Choi, Ho-June;Yang, Ki-Yull;Lee, Sang-Gyeong;Lee, Jong-Pal;Koo, In-Sun
    • Bulletin of the Korean Chemical Society
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    • v.31 no.10
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    • pp.2801-2805
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    • 2010
  • A nucleophilic substitution reaction of 4-chloro-7-nitrobenzofurazan (NBF-Cl) with anilines in MeOH-MeCN mixtures was conducted at 25, 35, and $45^{\circ}C$. Based on the higher $\beta_{nuc}$ values (1.0 - 1.6) of the reaction and a good correlation of the rate constants with the reduction potentials of the aniline nucleophiles, the present reaction was initiated by a single electron transfer (SET). After this step, the reaction proceeds through a transition state similar to the normal $S_NAr$-Ad.E pathway.

Mapping Between Models for Pathway Dynamics and Structural Representations of Biological Pathways

  • Yavas, Gokhan;Ozsoyoglu, Z. Meral
    • Proceedings of the Korean Society for Bioinformatics Conference
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    • 2005.09a
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    • pp.415-420
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    • 2005
  • Mathematical modeling and simulation of biochemical reaction networks gained a lot of attention recently since it can provide valuable insights into the interrelationships and interactions of genes, proteins and metabolites in a reaction network. A number of attempts have been made for modeling and storing biochemical reaction networks without their dynamical properties but unfortunately storing and efficiently querying of the dynamic (mathematical) models are not yet studied extensively. In this paper, we present a novel nested relational data schema to store a pathway with its dynamic properties. We then show how to make the mapping between this dynamic pathway schema with the corresponding static pathway representation.

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A Density-Functional Theory Study on Mechanisms of the Electrochemical Nitrogen Reduction Reaction on the Nickel(100) Surface (범밀도함수이론에 기초한 니켈(100) 표면에서의 전기화학적 질소환원반응 메커니즘에 관한 연구)

  • Minji Kim;Sangheon Lee
    • Korean Chemical Engineering Research
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    • v.61 no.4
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    • pp.604-610
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    • 2023
  • The nitrogen reduction reaction (NRR), which produces NH3 by reducing N2 under ambient conditions, is attracting attention as a promising technology that can reduce energy consumption in industrial processes. We investigated the adsorption behaviors at various active sites on the Ni (100) surface, which is widely used among catalytic metal surfaces capable of adsorbing and activating N2, based on density-functional theory calculations. We also investigated two N2 adsorption structures, so-called end-on and side-on structures. We find that for the end-on case, N2 is adsorbed on a top site, and the reaction proceeded in a distal pathway, while for the side-on case, N2 is adsorbed on a bridge site, and the reaction proceeded with enzymatic pathway. Finally, this study provides insight into the adsorption of metal catalyst surfaces for the NRR reactions based on the calculated Gibbs free energy profiles of the thermodynamically most favorable pathways.

Theoretical Study on the Reaction Mechanism of Azacyclopropenylidene with Epoxypropane: An Insertion Process

  • Tan, Xiaojun;Wang, Weihua;Li, Ping
    • Bulletin of the Korean Chemical Society
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    • v.35 no.9
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    • pp.2717-2722
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    • 2014
  • The reaction mechanism between azacyclopropenylidene and epoxypropane has been systematically investigated employing the second-order M${\o}$ller-Plesset perturbation theory (MP2) method to better understand the reactivity of azacyclopropenylidene with four-membered ring compound epoxypropane. Geometry optimization, vibrational analysis, and energy property for the involved stationary points on the potential energy surface have been calculated. It was found that for the first step of this reaction, azacyclopropenylidene can insert into epoxypropane at its C-O or C-C bond to form spiro intermediate IM. It is easier for the azacyclopropenylidene to insert into the C-O bond than the C-C bond. Through the ring-opened step at the C-C bond of azacyclopropenylidene fragment, IM can transfer to product P1, which is named as pathway (1). On the other hand, through the H-transferred step and subsequent ring-opened step at the C-N bond of azacyclopropenylidene fragment, IM can convert to product P2, which is named as pathway (2). From the thermodynamics viewpoint, the P2 characterized by an allene is the dominating product. From the kinetic viewpoint, the pathway (1) of formation to P1 is primary.

Time-resolved polarization and depolarization tracking on reaction pathway of calcium carbonates in a view of non-classical nucleation theory (비전통핵생성 이론 관점에서 탄산칼슘의 반응경로에 대한 시간분해 분극 및 탈분극 추적)

  • Kim, Gwangmok
    • Journal of Urban Science
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    • v.9 no.2
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    • pp.45-50
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    • 2020
  • The formation characteristics of calcium carbonates are closely related to the durability and mechanical properties of cement-based materials. In this regard, a deep understanding of the reaction pathway of calcium carbonates is critical. Recently, non-classical nucleation theory was summarized and it was presumed that prenucleation clusters are present. The formation of the prenucleation cluster at undersaturated condition (≈ 0.1 ml) in the present study was investigated via electrical characteristics of an electrolytic solution. Calcium chloride dihydrate (CaCl2·2H2O) and sodium carbonate (Na2CO3) were used as starting materials to supply calcium and carbonate sources, respectively. Furthermore, the reaction pathway of calcium carbonates was investigated by time-resolved polarization and depolarization characteristics of the electrolytic solution. The time-resolved polarization and depolarization tests were conducted by switching polarity with an interval of 20 seconds for 1 hr and by measuring the variation of electrical resistance. It can be inferred from the results obtained in the present study that the reactive constituent for the formation of calcium carbonates was mostly consumed in the period possibly associated with the prenucleation and the reaction pathways may be governed by the monomer-addition mechanism.

Degradation of Polyvinyl Alcohol by Brevibacillus laterosporus: metabolic Pathway of Polyvinyl Alcohol to Acetate

  • Lim, Joong-Gyu;Park, Doo-Hyun
    • Journal of Microbiology and Biotechnology
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    • v.11 no.6
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    • pp.928-933
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    • 2001
  • Approximately 0.1 mg/ml of polyvinyl alcohol (PVA) was degraded by the growing cell, Brevibacillus laterospours, for 30 h, and 0.2 mg/ml of PVA was degraded by the cell-free extract that was isolated from Brevibacillus laterosporus. Approximately $0.29{\mu}g$/ml of acetic acid was produced from PVA by using the cell-free extract as a catalyst for 40 min. $V_{max}\;and\;K_m$ value of purified PAV-degradation enzyme was 3.75g/l and 2.75 g/l/min in reaction with EDTA and 3.99 g/l and 2.98 g/l/min in reaction without EDTA, respectively. Molecular weight of the purified enzyme determined by SDS-PAGE was 63,000 Da. Alcohol dehydrogenase and aldehyde dehydrogenase activities were qualitatively detected on a native acrylamide gel by an active staining method, indicating the existence of the metabolic pathway to use PVA as a substrate.

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Photocatalytic Degradation Mechanism of Methyl Mercaptan using $TiO_2$ (TiO$_2$를 이용한 메틸메르캅탄의 광촉매 분해메커니즘)

  • Lee, Byung-Dae;Lee, Jin-Shik;Kim, Yeoung-Chan
    • Journal of the Korean Applied Science and Technology
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    • v.24 no.3
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    • pp.296-300
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    • 2007
  • This paper presents applicability of photocatalytic decomposition of methyl mercaptan using $TiO_2$. A quartz reactor was used in order to elucidate reaction pathway in photocatalytic decomposition of methyl mercaptan. Experimental results showed that more than 99.9% of methyl mercaptan was decomposed within 30 minutes. It was found that the photocatalytic decomposition of methyl mercaptan followed pseudo first order and its reaction coefficient was $0.05min^{-1}$ During 30 minutes in the photocatalytic reaction, the concentration of methyl mercaptan, dimethyl disulfide, $SO_2$, $H_2SO_4$, COS, $H_2S$ were determined. These results showed that 64% of methyl mercaptan were compensated for the increase in sulfur after 30 minutes through the mineralization. The proposed main photocatalytic decomposition pathway of methyl mercaptan was methyl $mercaptan{\rightarrow}dimethyl$ $disulfide{\rightarrow}SO_2{\rightarrow}H_2SO_4$.

A DFT Study for the Reaction Pathway(s) of Polycyclic Aromatic Hydrocarbons I: Phenanthrene Degradation with two OH Radicals (다고리 방향족 탄화수소의 반응 경로에 대한 DFT 연구 I: 2개의 OH 라디칼에 의한 페난트렌의 분해 반응)

  • Lee, Min-Joo;Lee, Byung-Dae
    • Journal of the Korean Chemical Society
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    • v.65 no.1
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    • pp.9-14
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    • 2021
  • In this study, the DFT calculation was performed using the B3LYP/6-31G(d,p) basis sets for the reaction process in which phenanthrene decomposes due to the chain reaction of two OH radicals on phenanthrene in the gaseous state of 298 K at 1 atm. As a result of the calculation, even when two OH radicals act on phenanthrene in a chain, the reaction for producing phenanthren-9-ol is predicted to be more advantageous than the reaction for producing phenanthren-1-ol. On the other hand, it was predicted that the OH addition process at room temperature would be advantageous for the priority of the OH addition and H abstraction process.

Polyhydroxyamic Acid from 3,3′ - Dihydroxybenzidine and Pyromellitic Dianhydride as a Fire-safe Polymer

  • Park, Seung Koo;Farris, Richard J.;Kantor, Simon W.
    • Fibers and Polymers
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    • v.5 no.2
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    • pp.83-88
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    • 2004
  • In order to assess the potential of the hydroxy-containing polyamic acid (PHAA) synthesized from 3,3'-dihydroxy benzidine and pyromellitic dianhydride for a fire-safe polymer, the cyclization pathway of PHAA has been investigated using a model compound prepared from 2-aminophenol and phthalic anhydride. The reaction was monitored. by $^1{H-nuclear}$ magnetic resonance. N-(2-hydroxyphenyl) phthalamic acid is converted to N-(2-hydroxyphenyl) phthalimide at ca. 175$^{\circ}C$, showing endothermic reaction. The imide structure is rearranged to the benzoxazole structure over ca. $400^{\circ}C$. These results are similar with that of PHAA. According to pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) data, water and carbon dioxide are released during the cyclization and rearrangement reaction. One DMAc molecule is complexed with one carboxyl acid group in PHAA, which accelerates the imidization process to release more easily the flame retardant, water.