• Journal of the Korean Chemical Society
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• v.22 no.3
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• pp.150-157
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• 1978

The rate constants for the hydrolysis of the derivatives of N-(p-nitrophenyl)-benzohydrazonyl azide (p-$CH_3,\;p-CH_3O,\;p-NO_2$, p-Cl, p-Br) have been determined by UV spectrophotometry in 50% dioxane-water at $25^{\cicr}C$ and a rate equation which can be applied over wide pH range was obtained. Below pH 5, the rate of hydrolysis of hydrazonyl azides is accelerated by electron-donating group ($\rho$ = -0.47), whereas at the pH values greater than 7, the $\rho$-value is 0.68. The effect of salt, solvent, substituent and azide ion on the rate of hydrolysis are rationalized in terms of $S_N1$ and $S_N2$ mechanism; below pH 5, the hydrolysis proceed through $S_N1$, however, above pH 7, the hydrolysis is started by the attack of hydroxide ion and in the range of pH 5∼7, these two reactions occur competitively.

• Journal of the Korean Chemical Society
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• v.36 no.4
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• pp.584-588
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• 1992

The rate constants of hydrolysis of ${\alpha}$-(n-butyl)-N-phenylnitrone and its derivatives have been determined by UV spectrophotometry at 25$^{\circ}C$ and a rate equation which can be applied over a wide pH range was obtained. On the basis of rate equations derived and judging from the hydrolysis products obtained and from general base and substituent effects, plausible mechanisms of hydrolysis in various pH range have been proposed. Below pH 4.5, the hydrolysis was initiated by the protonation and followed by the addition of water to ${\alpha}$-carbon. Above pH 10.0, the hydrolysis was proceeded by the addition of hydroxide ion to ${\alpha}$-carbon. In the range of pH4.5∼10.0, the addition of water to nitrone is rate controlling step.

• Journal of Applied Biological Chemistry
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• v.43 no.1
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• pp.25-30
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• 2000

The main form of nitrogen fertilizer applied to lowland rice is urea, but little is known about its transport in waterlogged soil. This study was conducted to investigate the transport of urea in waterlogged soil column using WAVE (simulation of the substances Water and Agrochemicals in the soil, crop and Vadose Environment) model which includes the parameters for urea adsorption and hydrolysis, The adsorption distribution coefficient and hydrolysis rate of urea were measured by batch experiments. A transport experiment was carried out with the soil column which was pre-incubated for 45 days under flooded condition. The urea hydrolysis rate (k) was $0.073h^{-1}$. Only 5% of the applied urea remained in soil column at 4 days after urea application. The distribution coefficient ($K_d$) of urea calculated from adsorption isotherm was $0.21Lkg^{-1}$, so it was assumed that urea that urea was a weak-adsorbing material. The maximum concentration of urea was appeared at the convective water front because transport of mobile and weak-adsorbing chemicals, such as urea, is dependent on water convective flow. The urea moved down to 11 cm depth only for 2 days after application, so there is a possibility that unhydrolyzed urea could move out of the root zone and not be available for crops. A simulated urea concentration distribution in waterlogged soil column using WAVE model was slightly different from the measured concentration distribution. This difference resulted from the same hydrolysis rate applied to all soil depths and overestimated hydrodynamic dispersion coefficient. In spite of these limitations, the transport of urea in waterlogged soil column could be predict with WAVE model using urea hydrolysis rate (k) and distribution coefficient ($K_d$) which could be measured easily from a batch experiment.

• Polymer(Korea)
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• v.35 no.4
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• pp.302-307
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• 2011

The parameters of silanol formation reaction of organosilane including solvent type, solution concentration, pH and hydrolysis time influence the adhesion property of 2 layer flexible copper clad laminate (FCCL). Especially, the hydrolysis reaction time of silane coupling agent affects the formation of the silanol groups and their self-condensation to generate oilgomeric structure to enhance the surface treatment as an adhesive promoter. In our study, we prepared the binary silane coupling agents to control hydrolysis reaction rate and surface energy after treatment of silane coupling agents for increasing the adhesive property between a copper layer and a polyimide layer. The surface morphology of rolled copper foil, as a function of the contents of the coated binary silane coupling agent, was fully characterized. As fabricated 2-layer FCCL, we observed that adhesive properties were changed by hydrolysis rate and surface energy.

• Journal of the Korean Chemical Society
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• v.38 no.5
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• pp.366-371
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• 1994

The kinetics of the hydrolysis of 5,6-dihydro-1,4-thiazine derivatives was investigated by ultraviolet spectrophotometry in $H_2O$ at 25$^{\circ}C$. A rate equation which can be applied over a wide pH range was obtained. The substituent effects on the hydrolysis of 5,6-dihydro-1,4-thiazine derivatives were studied and the rate of hydrolysis was shown to be accelerated by electron donating groups. Final product of the hydrolysis was 2-(N-acetylaminoethylthio)-acetoacetanilide enol from Judging from the results of the rate equation, general base effect, activation parameters and final products, the hydrolysis of 5,6-dihydro-1,4-thiazine derivatives seemed to be initiated by the neutral $H_2O$ molecule which does not dissociate at pH below 10.0, but proceeded by the hydroxide ion at pH above 11.0, and those two reactions occurred competively at pH 10.0∼11.0 range. On the basis of these findings a plausible mechanism for the hydrolysis of 5,6-dihydro-1,4-thiazine derivative was proposed.

• Journal of the Korean Wood Science and Technology
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• v.40 no.6
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• pp.389-396
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• 2012

In this study, we investigated the kinetics of acid-catalyzed hydrolysis of xylan over a 60 min at $120^{\circ}C$. Sulfuric, oxalic and maleic acids were used as acid catalyst for hydrolysis. The calculated degradation rate constants ($k_1$) showed a correlation with the acid concentration, meaning that the stronger the acid, the higher the xylan degradation rate. Among sulfuric, oxalic and maleic acid catalyzed hydrolysis, the xylan degradation rate to xylose was highest with sulfuric acid. At equivalent solution pH, acid catalyzed hydrolysis was proportional to $H^+$ concentration. The $k_1$ of dicarboxylic acid such as oxalic and maleic acid was higher than that of sulfuric acid at same pH values during hydrolysis.

• Korean Chemical Engineering Research
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• v.49 no.4
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• pp.470-474
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• 2011

Rice straw is the main grain straw and is produced in large quantities every year in Korea. Pretreatment of lignocellulosic biomass using soaking process was carried out mild conditions at atmospheric pressure and temperature of $60^{\circ}C$. We found enzymatic hydrolysis condition of pretreated biomass. In case of a rice straw, compared with previous lignocellulosic biomass, we found that hydrolysis time was a shorter than others. Hydrolysis of SAA-treated rice straw has shown conversion rate was higher at $50^{\circ}C$. Hydrolysis was ended between 40~48 hour. Glucose conversion rate was higher when enzyme loading is 65 FPU/ml and 32 CbU/ml. When substrate concentration was 5%(w/v), it was that conversion rate was 83.8% after hydrolysis for 72 hr. In simultaneous saccharification and fermentation(SSF) experiment about SAA-treated rice straw, ethanol productive yield was highest from $40^{\circ}C$. The yield of that time was 33.05% from 48 hour.

• Journal of the Korean Chemical Society
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• v.18 no.6
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• pp.430-436
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• 1974

The rate constants of hydrolysis of 1,1-dicyano-2-p-dimethylaminophenyl-2-chloroethylene(DPC) were determined at various pH and the rate equation which can be applied over wide pH range is obtained. From the rate equation the mechanism of the hydrolysis of a DPC over wide pH range is fully explained; below pH 3 and above pH 7.5, the rate constant is proportional to the concentration of hydronium ion and hydroxide ion, respectively. However, in the range of pH 3 to 7.5, water, hydronium ion and hydroxide ion catalyze the hydrolysis of DPC.

• Journal of the Korean Ceramic Society
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• v.28 no.12
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• pp.975-980
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• 1991

Chelated titanium alkoxides are hydrolysed showly and stable enough to prepare multicomponent gels of titania without its precipitation due to the fast hydrolysis of Ti alkoxide. The alkoxy groups of chelated titanium alkoxide are hydrolysed as fast as that of titanium alkoxide but the chelating groups are stable even in aqueous solution. The chelating groups showed different rates of hydrolysis in aqueous ammonia solution and water added one. Those rates were monitored with UV-VIS spectrophotometer by using their unique absorption bands before and after hydrolysis.

• Journal of the Korean Chemical Society
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• v.40 no.2
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• pp.128-134
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• 1996

The kinetics of the hydrolysis of dihydro-1, 4-oxathiin derivatives were investigated by ultraviolet spectrophotometry in H2O at $25^{\circ}C.$ A rate equation which can be applied over a wide pH range was obtained. The substituent effects on the hydrolysis of dihydro-1, 4-oxathiin derivatives were studied and the rate of hydrolysis was shown to be accelerated by electron accepting groups. Final product of the hydrolysis was 2-(2-hydroxyethylthio)acetoacet-anilide enol form. On the basis of rate equations derived and judging from hydrolysis products obtained and from general base effect and substituent effects, plausible mechanism of the hydrolysis in various pH range have been proposed. Below pH 3.5, the hydrolysis was initiated by the protonation and followed by the addition of water to 2-carbon. Above pH 10.0, the hydrolysis was proceeded by the addition of hydroxide to 2-carbon. In the range of pH 4.0∼10.0, the addition of water to dihydro-1,4-oxathiin is rate controlling step.