• Membrane Journal
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• v.2 no.1
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• pp.21-32
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• 1992

Hydrogen-permselective silica membranes were synthesized within tim walls of porous Vycor tubes by chemical vapor depostion of $SiO_2$. Film deposition was carried out using $SiCl_4$ hydrolysis either in the oppm shag reactants or in the one-sided geometry. At temperatures above $600^{\circ}C$ the permeation rate of hydrogen thorough the silica films varied between 0.01 and $025cm^3(STP)/cm^2-min-atm$ depending on the reaction geometry and the $H_2 : N_2$ permeation ratio was about 1000. Permeation rates of both $H_2$ and $N_2$ increased with increasing temperature. The silica membranes produced by one-sided deposition have higher hydrogen permmeation rates than those produced by the opposing reactants geometry although the membranes formed in an opposing reactants geometry were relatively stable during the heat treatment or after exposure to ambient air. These membranes can be applied to high temperature gas separations or membrane reactors once the film deposition process is optimized to get high permeability as well as good stability.

• Journal of the Korean Chemical Society
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• v.34 no.1
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• pp.102-107
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• 1990

The reaction of thiazoline-azetidinone (7) with $I_2$ in $CH_2Cl_2-H_2O$ gave directly 3-iodo-3-methylcepham (4). A phase transfer catalyst considerably increased the reaction rate. Similar to the hydrolysis of thiazoline-azetidinone (7) under a weak acidic condition, thiazole (10) was given as major product in the treatment with 0.1 eq. of iodine. The difference between cyclization reaction and hydrolysis could be explained in terms of solvents, the amount of iodine and the nature of thiazoline-azetidinones (7).

• Journal of the Korean Chemical Society
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• v.41 no.10
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• pp.535-540
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• 1997

Potassium carbonate reacts with silicon tetrachloride to form trichlorosilyloxy carbonylchloride which reacts subsequently with another molecule of silicon tetrachloride leading to phosgene eventually in chlorinated solvents. This in situ generated trichlorosilyloxy carbonylchloride or phosgene were found to be very effective for the chlorination of a wide variety of alcohols to the corresponding chlorides. Primary, secondary and benzylic alcohols were converted into corresponding chlorides when treated with silicon tetrachloride in the presence of potassium carbonate at room temperature.

• Journal of the Korean Chemical Society
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• v.38 no.9
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• pp.687-697
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• 1994

• Journal of the Korean Chemical Society
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• v.36 no.3
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• pp.472-474
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• 1992

• Journal of the Korean Chemical Society
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• v.20 no.6
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• pp.453-459
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• 1976

Rate constants for the reaction of methyl chloroformate with substituted anilines, and for the halogen exchanges in phenyl chloroformate have been determined in acetone. Although the rate data can be interpreted equally well with the addition-elimination mechanism($S_AN$) involving an intermediate, results of MO and isotope effect studies strongly favor the synchronous ($S_N2$) mechanism for the reactions studied. It was concluded that for the fast reacting nucleophiles the transition state is of "late" type while for the slow reacting nucleophiles it is of "early" type.

• Journal of the Korean Chemical Society
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• v.19 no.1
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• pp.11-15
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• 1975

Kinetic study of halogen exchange for N,N-dimethylcarbamoyl chloride and N,N-diethylcarbamoyl chloride in acetone by using radioisotopic halide ions has been carried out at two temperatures as a part of studying the reactivity of carbonyl carbon atom. The order of nucleophilicity showed a similar tendency as that for alkyl chloroformate, but reaction rate is much slower than that for solvolysis and alkyl chloroformate. The activation parameters,${\Delta}H^*$and${\Delta}S^*$ were found to decrease in sequence $Cl^{\rightarrow}Br^{\rightarrow}I^-$ for N,N-dialkylcarbamoyl chlorides. The results are interpreted in terms of solvation effect, degree of bond-breaking and bond-formation and electronic requirements.

• 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.

• Journal of the Korean Geosynthetics Society
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• v.20 no.4
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• pp.33-41
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• 2021

Feldspar, along with Quartz, are the most frequently produced minerals in Korea; however, the potential value is estimated to be significantly low because of the scarce research on the development and application of material properties, except for their limited use in manufacturing minerals, glass, and paints. In this study, we analyzed the eco-friendly material and reactivity improvement characteristics of weathered feldspar through activation technique. The joint structural features observed on the surface of the weathered feldspar show that the joint arrangements are irregularly distributed, and the cavities are interconnected. Due to the irregularly connected cavities on the surface of weathered feldspar, the reaction area of the weathered feldspar is increased; hence the weathered feldspar is considered as a highly reactive pozzolan material when combined with cement. As a result of applying the thermal, mechanical, and chemical activation techniques to improve the functionality of the weathered feldspar, the cation exchange capacity, density, and uniaxial compression strength characteristics were improved. It is considered that weathered feldspar by these porous characteristics can be used as an eco-friendly construction material with excellent physical and chemical properties.

• Journal of the Korean Chemical Society
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• v.18 no.4
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• pp.278-288
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• 1974

Starting from p-dichlorobenzene, 2-amino-4-chloroanisole could be prepared via a nitration, a methoxylation, and subsequent reduction. The repeated chlorination of 2-amino-4-chloroanisole resulted 2-amino-3,4,5-trichloroanisole without any isomeric products. The chlorination of 4-chloro-2-nitroanisole could easily give 2,4-dichloro-6-nitroanisole but polychlorination of the product could not be achieved at the atmospherical pressure. The repeated chlorination of 2-amino-4,6-dichloroanisole could give 2-amino-3,4,5,6-tetrachloroanisole, The Schiemann reaction of 2-amino-4-chloroanisole and 2-amino-4,6-dichloroanisole could give 2-fluoro-4-chloroanisole and 2-fluoro-4,6-dichloroanisole, respectively. The repeated chlorination of these fluorochloroanisoles could give 2-fluoro-3,4,5,6-tetrachloroanisole. In each chlorination process, the components of products were examined by means of NMR spectrometry and the chlorination reaction was repeated without isolating each isomeric product. The feasibility of the present routes of preparations was discussed in respects to the conveniency of reaction conditions and respective overall yields of the processes.