• Title/Summary/Keyword: chemical reactivity

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Selective Reduction of Organic Compounds with Al-Methanesulfonyldiisobutylalane

  • Cha, Jin-Soon;Noh, Min-Yeong
    • Bulletin of the Korean Chemical Society
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    • v.31 no.4
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    • pp.840-844
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    • 2010
  • The new MPV type reagent, Al-methanesulfonyldiisobutylalane ($DIBAO_3SCH_3$), has been prepared and its reducing characteristics in the reduction of selected organic compounds containing representative functional groups have been examined in order to find out a new reducing system with high selectivity in organic synthesis. In general, the reagent is extremely mild, showing only reactivity toward aldehydes, ketones and epoxides. The reagent exhibits a unique reducing applicability in organic synthesis. Thus, the reagent can achieve a clean 1,2-reduction of $\alpha,\beta$-unsaturated aldehydes and ketones to produce the corresponding allylic alcohols in 100% purity. In addition, the reagent shows an excellent regioselectivity in the ring-opening reaction of epoxides. Finally, $DIBAO_3SCH_3$ shows a high stereoselectivity in the reduction of cyclic ketones to produce the thermodynamically more stable epimers exclusively.

Cobalt(III) Complexes of Various Salen-Type Ligand Bearing Four Quaternary Ammonium Salts and Their Reactivity for CO2/Epoxide Copolymerization

  • Kim, Bo-Eun;Varghese, Jobi Kodiyan;Han, Yong-Gyu;Lee, Bun-Yeoul
    • Bulletin of the Korean Chemical Society
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    • v.31 no.4
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    • pp.829-834
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    • 2010
  • Ligand variation was carried out on a cobalt(III) complex of Salen-type ligand comprised of 1,2-cyclohexenediamine and salicylaldehyde bearing a methyl substituent on 3-position and -[$CMe(CH_2CH_2CH_2N^+Bu_3)_2$] on 5-position, which is a highly active catalyst for $CO_2$/propylene oxide copolymerization. Replacement of the methyl substituent with bulky isopropyl group resulted in alteration of the binding mode, consequently lowering turnover frequency significantly. Replacement with an ethyl group preserved binding mode and activity. Replacement of the tributylammonium unit with trihexylammonium or trioctylammonium, or replacement of 1,2-cyclohexenediamino unit with -$NC(Me)_2CH_2N$- decreased activity, even though the binding mode was unaltered.

Reaction of Lithium Cyanoaluminum Hydride with Selected Organic Compounds Containing Representative Functional Groups. Comparison of Reducing Characteristics between Lithium and Sodium Cyanoaluminum Hydrides

  • Cha, Jin-Soon;Yu, Se-Jin
    • Bulletin of the Korean Chemical Society
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    • v.30 no.7
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    • pp.1588-1592
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    • 2009
  • Lithium cyanoaluminum hydride (LCAH) was prepared by the metal cation exchange reaction of sodium cyanoaluminum hydride with lithium chloride in tetrahydrofuran. The reducing characteristics of LCAH were explored systematically by the reaction with selected organic compounds containing representative functional groups under the standardized conditions (tetrahydrofuran, 0 ${^{\circ}C}$). The reducing ability of LCAH was also compared with of the sodium derivative, sodium cyanoaluminum hydride (SCAH). Generally, the reducing behavior of LCAH resembles that of SCAH closely, but the reactivity of LCAH toward representative organic functional groups appeared to be stronger than that of SCAH. Thus, the regent reduces carbonyl compounds, epoxides, amides, nitriles, disulfides, carboxylic acids and their acyl derivatives to the corresponding alcohols or amines, at a relatively faster rate than that of SCAH. The cyano substitution, a strong election-withdrawing group, diminishes the reducing power of the parent metal aluminum hydrides and hence effects the alteration of their reducing characteristics.

A Kinetic Study on the Oxidation of Indole by Peroxomonosulphate in Acetonitrile Solvent

  • Kavery, Muniyappan;Govindasamy, Chandramohan;Johnson, Stephen
    • Journal of the Korean Chemical Society
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    • v.57 no.2
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    • pp.210-215
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    • 2013
  • Kinetics of oxidation of indole by peroxomonosulphate (PMS) in aqueous acetonitrile medium has been investigated. The reaction follows a total second order, first order each with respect to [Indole] and [PMS]. The rate of the reaction was not affected by added [$H^+$]. Variation of ionic strength (${\mu}$) had no influence on the rate. Increase of percentage of acetonitrile decreased the rate. Absen ce of any polymerization indicated a nonradical pathway. Activation and thermodynamic parameters have bee n computed. A suitable kinetic scheme based on these observations is proposed. The reactivity of PMS towards Indole was found to be higher than that with peroxodisulphate.

The Reaction Rate Constants of ${\alpha}-Methylstyrene-co-Methylmethacrylate\;{\alpha}Methylstyrene-co-Acrylonitrile$ (알파메틸스티렌-메틸메타이크릴레이트 및 알파메틸스티렌-아크릴로니트릴의 라디칼 공중합의 반응속도상수)

  • Kim, Nam-Seok;Seul, Soo-Duk
    • Elastomers and Composites
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    • v.28 no.3
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    • pp.183-190
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    • 1993
  • The radical copolymerization with propagation and depropagation is presented in order to estimate reactivity rate of monomers and $K_{11}$(the equilibrium constant for propagation and depropagation) in the copolymerization of ${\alpha}-methylstyrene-co-methylmethacrylate$ and ${\alpha}-methylstyrene-acrylonitrile$. The value of ${\alpha}-methylstyrene$ and methylmethacrylate and $K_{11}$ are found to be 0.48, 0.47 and 5.0 respectively. The value of ${\alpha}-methylstyrene$ and acrylonitrile and the $K_{11}$ are found to be 0.1251, 0.0577 and 23.8 respectively. The treatment rate constant of ${\alpha}-methylstyrene-co-methylmethacrylate$ and ${\alpha}-methylstyrene-co-acrylonitrile$ in the copolymerization is estimated to be 2.5, 80.72 regardless of monomer feed composition.

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Acetate-Promoted Aldol-Type Reaction: Scope and Reactivity of Acetates and Aldehydes

  • Kim, Dong-Hyeon;Rahman, A. F. M. Motiur;Jeong, Byeong-Seon;Lee, Eung-Seok;Jahng, Yurng-dong
    • Bulletin of the Korean Chemical Society
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    • v.30 no.4
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    • pp.797-802
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    • 2009
  • Potential of acetates and related compounds in glacial acetic acid as a catalyst for aldol-type condensation reactions was examined. Reactions of cycloalkanones or selected heteroaromatics with aldehydes in presence of 10 mol% of various acetates in acetic acid afforded ${\alpha},{\alpha}$'-bis(substituted-benzylidene)cycloalkanones and substituted-benzylidene-mackinazolinones, respectively, in good yields. Among the compounds tested, ammonium acetate is the best and effective especially towards the reactions of mackinazolinone and aliphatic aldehydes to afford 6-alkylidenemackinazolinones.

Photoreactivity and Thermogravimetry of Copper(II) Complexes of N-Salicylideneaniline and Its Derivatives

  • Osman, Ahmed H.;Aly, Aref A.M.;El-Mottaleb, Mohamed Abd;Gouda, Gamal A.H.
    • Bulletin of the Korean Chemical Society
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    • v.25 no.1
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    • pp.45-50
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    • 2004
  • $Cu^{II}$-complexes of N-salicylideneaniline and its derivatives were not light sensitive in most solvents such as acetonitrile. A photo-decomposition occurred upon irradiation in halocarbon solvents such as $CHCl_3$. It has been suggested that such photoreactivity is attributed to the reactivity of charge-transfer to solvent (CTTS) excited state attained upon irradiation. A mechanism has been proposed to account for the results obtained. The complexes have been thermally analysed in nitrogen and static air using thermogravimetry (TG) and derivative thermogravimetry (DTG). The thermal degradation of the complexes proceeds in two or three stages. The kinetic parameters obtained from the Coats-Redfern and Horowitz-Metzger equations show the kinetic compensation effect.

A Study of Cutting Factor Analysis and Reliability Evaluation of ASTM(F136-96) Material by Taguchi Method (다구치 방법에 의한 ASTM(F136-96)의 절삭인자 분석과 신뢰성 평가)

  • Jang, Sung-Minl;Yun, Yeo-Kwon
    • Journal of the Korean Society of Safety
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    • v.23 no.6
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    • pp.1-6
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    • 2008
  • Machine operator and quality are affected by chip during cutting process to product machine parts. This paper presents a study of the influence of cutting conditions on the surface roughness obtained by turning using Taguchi method for safety of turning operator. In the machining of titanium alloy, high cutting temperature and strong chemical affinity between the tool and the work material are generated because of its low thermal conductivity and chemical reactivity. Therefore titanium alloys are known as difficult-to materials. An orthogonal array, the signal-to-noise ratio, the analysis of variance are employed to investigate the cutting characteristics of implant material bars using tungsten carbide cutting tools of throwaway type. Also Experimental results by orthogonal array are compared with optimal condition to evaluate advanced reliability. Required simulations and experiments are performed, and the results are investigated.

A Study on Fire and Explosion Index in the Petro-chemical Plant (위험성 평가중 화재.폭발 지수 산정방법에 관한 고찰)

  • 김진곤;김광일
    • Fire Science and Engineering
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    • v.7 no.1
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    • pp.17-29
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    • 1993
  • The method has been proposed for the risk assessment of petro-chemical plant, specially which can evaluate relative risk levels on the materials and process-es. The each potential risk of materials and processes are derived numerically and combined these values, finally Fire and Explosion Index was found. Material factor was evaluated with the flammability and the reactivity and process factor with emprical factor called penalty. This F&EI can be performed for relative risk assesment at the whole plant and directely applicable at the line.

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Effects of Added Anions on the Reaction of Nitrous Acid with Hydrogen Peroxide

  • Park, Jong-Yoon;Choi, Eun-Jin;Park, Joon-Woo
    • Bulletin of the Korean Chemical Society
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    • v.13 no.1
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    • pp.37-41
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    • 1992
  • The reactions of nitrous acid with hydrogen peroxide in acidic aqueous solution in the presence of several added anions have been studied at $0^{\circ}C$ and pH 2-4 to investigate the nucleophilic catalysis of these anions. From the dependence of reaction rates on the anion concentrations, significant catalytic effects were found for $Cl^-,\;Br^-,\;SCN^-$, in order of effect $SCN^-\;{\approx}\;Br^->Cl^-$, while no observable effect was found for ${ClO_4}^-$ and ${NO_3}^-$. These results support O-nitrosation reaction is the rate-determining step and NOX formed in the presence of an anion ($X^-$) also acts as a nitrosating agent and accelerates the overall reaction rate. The order of reactivity was found to be NOCl>NOBr>NOSCN, which is consistent with the results of N-nitrosation and S-nitrosation reactions.