• YAKHAK HOEJI
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• v.23 no.3_4
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• pp.167-171
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• 1979

It is knwon that in the reaction of .alpha.-diethylaminoacetophenone with potassium cyanide and ammonium carbonate in dilute alcohol solution, 5-phenylhydantoin is formed. In this study the mechanism of the reaction by which diethylaminomethyl group is eliminated, was investigated with applying GC/MS-system. From the fragmentation pattern of mass spectrum of the unknwon compound, which has mol peak 112, it was identified as diethylaminoacetonitrile. According to our GC/MS study of the reaction mixture, it seems likely that diethylaminomethyl group is eliminated neither through the alkali degradation of .alpha.-diethylaminoacetophenone to aldehyde nor after the anticipated hydantoin formation. But it is believed that in the course of ring formation through an unidentified mechanism diethylaminomethyl group is eliminated.

• Journal of the Korean Ceramic Society
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• v.37 no.4
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• pp.332-337
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• 2000

Forming mechanism of fibrous TiC during self-propagating high temperature synthetic reaction was analyzed and suggested. It was revealed that critical temperature for the stable fiber formation was not the melting point of TiC, but the eutectic reaction temperature of TiC and C. Minimum amount of TiC diluent addition required to form fibers was calculated to be 25.6%, which was consistent with the experimental result. Synthesized fibers were found hollow tube-like. The morphology was explained by the diffusion rates of C and Ti in TiC, and by the molar volume chnage of C during the reaction. Expanding shell model was suggested for the hollow fiber formation mechanism.

• Textile Coloration and Finishing
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• v.19 no.4
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• pp.18-25
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• 2007

Kinetics and mechanism for alkaline hydrolysis of C. I. Disperse Green 9(G-9) of dinitrothiophene disperse dye were investigated. As soon as G-9 contacted with alkali, instant and continuous decreases of color strength of G-9 followed with increasing time. The hydrolysis rate of G-9 increased with increasing alkali, and it was found that alkali appeared first order dependence. The observed rate constants obtained from hydrolysis of various amount of dye were similar values, and calculation of initial rates showed that G-9 hydrolyzed by first order reaction for dye. Therefore it was confirmed that the overall reaction was second order, $SN_2$ of nucleophilic substitution reaction. Increasing temperature enhanced the hydrolysis of G-9. From the results of hydrolysis performed at various temperatures, it was obtained that activation energy(Ea) was 12.6 kcal/mole, enthalpy of reaction(${\triangle}H$) was 12.0 kcal/mole, and entropy of reaction(${\triangle}S$) was $29.8J/mol{\cdot}K$.

• Bulletin of the Korean Chemical Society
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• v.33 no.12
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• pp.4079-4083
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• 2012

The mechanism of the cycloaddition reaction between singlet state dichlorosilylene germylidene ($Cl_2Si=Ge:$) and acetone has been investigated with B3LYP/6-$31G^*$ and B3LYP/6-$31G^{**}$ method, from the potential energy profile, we predict that the reaction has one dominant reaction pathway. The presented rule of the reaction is that the two reactants firstly form a Si-heterocyclic four-membered ring germylene through the [2+2] cycloaddition reaction. Because of the 4p unoccupied orbital of Ge atom in the Si-heterocyclic four-membered ring germylene and the ${\pi}$ orbital of acetone forming a ${\pi}{\rightarrow}p$ donor-acceptor bond, the Si-heterocyclic four-membered ring germylene further combines with acetone to form an intermediate. Because the Ge atom in the intermediate hybridizes to an $sp^3$ hybrid orbital after the transition state, then, the intermediate isomerizes to spiro-heterocyclic ring compound involving Si and Ge (P4) via a transition state.

• Bulletin of the Korean Chemical Society
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• v.24 no.5
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• pp.671-673
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• 2003

• Bulletin of the Korean Chemical Society
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• v.33 no.8
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• pp.2719-2723
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• 2012

A kinetic study is reported for nucleophilic substitution reactions of benzyl 4-pyridyl carbonate 6 with a series of alicyclic secondary amines in MeCN. The plot of pseudo-first-order rate constant ($k_{obsd}$) vs. [amine] curves upward, which is typical for reactions reported previously to proceed through a stepwise mechanism with two intermediates (i.e., a zwitterionic tetrahedral intermediate $T^{\pm}$ and its deprotonated form $T^-$). Dissection of $k_{obsd}$ into the second- and third-order rate constants (i.e., $Kk_2$ and $Kk_3$, respectively) reveals that $Kk_3$ is significantly larger than $Kk_2$, indicating that the reactions proceed mainly through the deprotonation pathway (i.e., the $k_3$ process) in a high [amine] region. This contrasts to the recent report that the corresponding aminolysis of benzyl 2-pyridyl carbonate 5 proceeds through a forced concerted mechanism. An intramolecular H-bonding interaction was suggested to force the reactions of 5 to proceed through a concerted mechanism, since it could accelerate the rate of leaving-group expulsion (i.e., an increase in $k_2$). However, such H-bonding interaction, which could increase $k_2$, is structurally impossible for the reactions of 6. Thus, presence or absence of an intramolecular H-bonding interaction has been suggested to be responsible for the contrasting reaction mechanisms (i.e., a forced concerted mechanism for the reaction of 5 vs. a stepwise mechanism with $T^{\pm}$ and $T^-$ as intermediates for that of 6).

• Microbiology and Biotechnology Letters
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• v.14 no.5
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• pp.407-413
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• 1986

In an agitated bead reaction system, the enzymatic saccharification of uncooked starch was substantially enhanced. The enhancement mechanism was investigated front the view of the structural aspect of starch. The mechanical impact caused by the movement of the attrition-milling media resulted neither the destruction of microcrystalline structure nor the fragmentation of starch granule. instead, the most distinct phenomenon was the swelling of starch granule up to about 2.5 times, and the swelling mechanism was not similar with that caused by cooking. However, in the case of the enzyme addition in the attrition coupled reaction system, the swollen starch was easily fragmented into the large number of small particles by the synergistic action of the enzyme and milling-media. The exposed surface area of the fragmented particles plays the major role in enhancing the saccharification. The saccharification rate was quite different depending on the source of starch, the reason was discussed in terms of the granular structure of uncooked starches.

• Bulletin of the Korean Chemical Society
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• v.21 no.9
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• pp.901-904
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• 2000

The mechanism for the photo-Fries rearrangement of phenyl acetate andbiphenylyl acetates were reinvestigat-ed in phenol (or phenol derivatives) containing media. The results showed that the phenol (or phenol deriva-tives) which is the most common by-product of Fries reaction reacts with acyl radical togive Fries-product. These phenol (or phenol derivatives) contributions to the Fries-products were suggested as the Trivial mecha-nism for the photo-Fries reaction.

• Journal of Photoscience
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• v.9 no.2
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• pp.1-4
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• 2002

Hula-twist is a volume-conserving photoisomerization reaction mechanism postulated in 1985 to account for the rapid photoisomerization of the retinyl chromophore in rhodopsin. The requisite stereochemical consequence of simultaneous isomerization of a double bond and an adjacent single bond has recently been demonstrated in isomerization of pre-vitamin D in an organic glass and by many other examples of organic systems already reported in the literature This paper reports the consequence in applying the mechanism to the primary photochemical process of several photosensitive biopigments: bilirubin, photoactive yellow protein, bacteriorhodopsin and rhodopsin. It is shown that the anchored nature of the chromophores must first be taken into consideration.

• Journal of the Korean institute of surface engineering
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• v.21 no.3
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• pp.95-102
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• 1988

The anodic oxidation of aniline in aqueous sulfuric acid solution on a platinum was studied. To examine of mechanism of this reaction, the date were obtained during controlled potential electrolysis, aided by computer system. The reaction mechanism was assumed the electrochemical-chemical-electrochemical(ECE) mechanism. We obtained the result that the intial charge transfer step proceeds through a radical cation, and this radical cation were bound cation led to may type of dimer in which p-aminodiphenylamine was de-electronated again to give the polymer.