• Bulletin of the Korean Chemical Society
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• v.12 no.6
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• pp.625-628
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• 1991

Using uniform flat plate-like samples of ZSM-5 zeolites, diffusion coefficients were measured volumetrically for the diffusion of xylene, ethyltoluene and diethylbenzene by direct measurement of sorption rate. Toluene disproportionation over H(100)-, K(72)-and Cs(82)-ZSM-5 at 773 K and toluene methylation, toluene ethylation and ethylbenzene ethylation over Cs(75)-ZSM-5 at 623 K were carried out. The selective formation of para xylene during the toluene disproportionation, presumably due to the increased tortuosity over Cs-ZSM-5, could be explained by smaller diffusion coefficient in Cs-ZSM-5 than in K-and H-ZSM-5. The para selectivity increased in the order; toluene methylation < toluene ethylation < ethylbenzene ethylation. As the chain length of the alkyl substituent in dialkylbenzenes is increased, the para selectivity of the products was improved. It may be attributed to the differences in the ratios of diffusion coefficient of para products to that of ortho ones. Diffusion coefficient of m-xylene was about 1 order of magnitude smaller than that of o-xylene.

• Analytical Science and Technology
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• v.13 no.5
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• pp.636-645
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• 2000

A method is described for the determination of organotins in water samples by GC/MS. Optimized derivatization methods for ethylation and hydrogenation of organotins were surveyed according to various reaction conditions such as time, pH and concentration of reagents. The organotins were extracted with n-hexane in presence of 0.1% tropolone and hydrogenated with sodium borohydride. Extraction recoveries of organotins with hydrogenation were in the range of 61-112%. After ethylation, organotins in water samples were extracted by liquid-liquid extraction (LLE) and solid-phase extraction (SPE). Using LLE, extraction recoveries were in the range of 74-113%. The recoveries ranged from 61-97% in the case of SPE with styrene-divinylbenzene copolymers. Method detection limits of hydrogenated and ethylated organotins ranged from 0.05 to 0.5 ng/ml and from 0.02 to 0.05 ng/ml, respectively.

• Bulletin of the Korean Chemical Society
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• v.25 no.10
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• pp.1508-1512
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• 2004

A gas chromatography/mass spectrometric (GC/MS) method has been developed for the determination of trace mono-n-butyltin (MBT), di-n-butyltin (DBT), and tri-n-butyltin (TBT) compounds in sediments. Samples were extracted by 10% acetic acid in methanol containing 0.03% tropolone and were then derivatized for GC/MS analysis. Ethylation by sodium tetraethylborate and phenylation by sodium tetraphenylborate were evaluated as a derivatization reaction of the organotins in sample extract. n-Hexane was added into reaction media in the beginning of the reaction for the continuous extraction of derivatized organotins. Ethylation requires less than 2 hours to get proper derivatization yields for MBT, DBT, and TBT altogether and produces relatively low amounts of side reaction products. Compared to ethylation, phenylation requires much longer time but provides relatively lower yield and produces considerable amounts of side reaction products. Therefore, the ethylation reaction was applied for the analysis of organotin compounds in sediment. An isotope dilution mass spectrometric (IDMS) method based on GC/MS has been applied to the accurate determination of DBT compounds in the sediments. The IDMS results from the analyses of sediment samples showed a reasonable repeatability and a good agreement with the values obtained by IDMS based on liquid chromatography/induced coupled plasma/mass spectrometry.

• Applied Chemistry for Engineering
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• v.17 no.3
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• pp.235-242
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• 2006

Liquid phase alkylation of biphenyl (BP) was studied over large pore zeolites. Selective formation of the least bulky products, 4,4'-diisopropylbiphenyl (4,4'-DIPB) occurred only in the isopropylation of BP over some large pore molecular sieves. H-mordenites (MOR) gave the highest selectivity among them. The dealumination of MOR enhanced catalytic activity and the selectivity of 4,4'-DIPB because of the decrease of coke-deposition. Non-selective catalysis occurs on external acid sites over MOR with the low $SiO_2/Al_2O_3$ ratio because severe coke-deposition deactivates the acid sites inside the pores by blocking pore openings. The selectivity of DIPB isomers was changed with reaction temperature. Selective formation of 4,4'-DIPB was observed at moderate temperatures such as $250^{\circ}C$, whereas the decrease of the selectivity of 4,4'-DIPB occurred at higher temperatures as $300^{\circ}C$. However, 4,4'-DIPB was almost exclusive isomer in the encapsulated DIPB isomers inside the pores even at high temperatures. These decreases of the selectivity of 4,4'-DIPB are due to the isomerization of 4,4'-DIPB on the external acid sites. Some 12-membered molecular sieves, such as SSZ-24, MAPO-5 (M:Mg, Zn, Si), SSZ-31, and ZSM-12, which have straight channels, gave 4,4'-DIPB with moderate to high selectivity; however; SSZ-55, SSZ-42, and MAPO-36 (M: Mg, Zn) gave lower selectivity because of cages in 12-membered one dimensional channels. Three dimensional H-Y and Beta zeolites also yield 4,4'-DIPB in low yield because of their wide circumstances for the isopropylation of BP. The increasing the size of alkylating agent enhanced the shape-selective alkylaiton even for the zeolites, such as UTD-1. The ethylation of BP to ethylbiphenyls (EBPs) and diethylbiphenyls (DEBPs) over MOR was non-selective. The ethylation of BP to EBPs was controlled kinetically. However, there was difference in reactivity of EBPs and DEBPs for their further ethylation. 4-EBP was ethylated preferentially among the isomers, although the formation of 4,4'-DEBP was less selective. The least bulky 4-EBP and 4,4'-DEBP have the highest reactivity among EBPs and DEBPs for the ethylation to polyethylbiphenyls (PEBPs). These results show that the environments of MOR pores are too loose for shape selective formation of the least bulky isomers, 4-EBP and 4,4'-DEBP in the ethylation of BP, and that MOR pores have enough space for the further ethylation of 4,4'-DEBP.

• YAKHAK HOEJI
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• v.19 no.2
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• pp.96-100
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• 1975

2-Ethoxy-4-acetamidobenzoate (III) was synthesized by ethylation of N-formyl compound obtained with formylation of methyl 4-aminosalicylate and 2-ethoxy-4-acetamidobenzamide (VIII) was synthesized by ethylation of 4-acetamidosalicylamide (VII) formed by reacting methyl 4-acetamido-2-acetoxy benzoate with concentrated ammonia water under pressure. 2-Ethoxy-4-acetamido benzamide (VIII) was also synthesized by acetylation of 2-ethoxy-4-aminobenzamide (VI) obtained by pressure eraction of methyl 2-ethoxy-4-formylamido-benzoate (I) with concentrated ammonia water.

• Bulletin of the Korean Chemical Society
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• v.10 no.2
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• pp.214-216
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• 1989

• Proceedings of the KAIS Fall Conference
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• 2011.05a
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• pp.323-326
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• 2011

HZSM-5, synthesized in fluoride medium, showed high selectivity for the formation of 1,4-diethylbenzene (1,4-DEB) in the vapour phase ethylation of ethylbenzene (EB) with ethanol and hence becomes a convenient eco-friendly substitute for hazardous mineral acid catalysts. De-ethylation of EB to benzene was also minimized over this catalyst. As the medium pore size and presence of weak and medium acid sites might be the cause of such benefits, fluoride mediated synthesis of ZSM-5 is proven to be advantageous for para-selective alkylation of alkyl aromatics.

• YAKHAK HOEJI
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• v.35 no.5
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• pp.389-393
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• 1991

A convenient method for the synthesis of indobufen, which is a potent antiinflammatory agent, was described. Ethyl 2-phenylbutyrate(4) was prepared by Friedel-Crafts reaction of benzene with ethyl $\alpha$-chloro-$\alpha$-(methylthio)acetate(l) followed by ethylation and desulfurization of the resultant ethyl 2-(methylthio)phenylacetate(2). Ethyl 2-(p-aminophenyl)butyrate(6) was prepared by nitration of (4) and successive reduction of ethyl 2-(p-nitrophenyl) butyrate(5). Indobufen was obtained by condensation reaction of (6) with phthalic anhydride followed by reduction and hydrolysis of the resultant ethyl 2-[p-(1, 3-dioxo-2-isoindolinyl)phenyl]butyrate(7).

• YAKHAK HOEJI
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• v.36 no.2
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• pp.137-139
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• 1992

A new method for xenbucin, which is a antihypercholesteremic agent, is described. Friedel-Crafts reaction of biphenyl with ethyl ${\alpha}-chloro-{\alpha}-(methylthio)acetate(1)$ afforded ethyl 2-methylthio-2-(4-biphenylyl)acetate(2). Ethyl 2-(4-biphenylyl)butyrate(4) was obtained by ethylation of (2) with NaH and $C_2H_5I$, followed by desulfurization of the resultant ethyl 2-methylthio-2-(4-biphenylyl)butyrate(3) with zinc dust in acetic acid. Xenbucin was synthesized by hydrolysis of (4).

• Bulletin of the Korean Chemical Society
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• v.6 no.4
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• pp.249-251
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• 1985