• Macromolecular Research
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• v.15 no.6
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• pp.541-546
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• 2007

The combination of atom transfer radical polymerization (ATRP) and click chemistry was employed for the efficient preparation of well-defined block copolymers. Bromo terminated poly(methyl acrylate) (pMA-Br) was prepared by an ATRP initiator, ethyl-2-bromoisobutyrate (EBiB). Subsequently, the bromine chain end of pMA-Br was converted to an azide group by simple nucleophilic substitution reaction. ${\alpha}-Alkyn-{\omega}-bromo-functionalized$ polystyrene was also synthesized by ATRP using the alkyn-functionalized initiator, propargyl-2-bromoisobutyrate (PgBiB). In both cases, the conversion was limited to a low level to ensure a high degree of chain end functionality. Then the coupling reaction between the azide end group in $pMA-N_3$ and alkyn-functionalized PgBiB-pSt was performed by Cu(I)catalysis. This coupling reaction was monitored by gel permeation chromatography (GPC). The synthesized block copolymer was characterized by FT-IR, $^1H-NMR$ spectroscopy and $^1H-^1H$ COSY correlation spectroscopy.

• Bulletin of the Korean Chemical Society
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• v.24 no.2
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• pp.205-208
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• 2003

Laser-induced Raman spectroscopy has been utilized to demonstrate its feasibility for studying the kinetics of imine formation in chloroform solvent. The imine formation, by the nucleophilic addition of primary amine to the carbonyl group of ketone, has been monitored at ten minute intervals for eight hours. The intensity of the C=O stretching mode at 1684 $cm^{-1}$ was measured to determine the rate constant of the reaction. In order to correct the sample-to-sample fluctuations in Raman peak area, this peak was normalized to the C-Cl bending peak at 666 $cm^{-1}$. By the peak area change during the course of reaction, the second order rates at three different temperatures have been determined. The substituent effects on the π conjugations of imine product have also been investigated. On the basis of Raman frequency shifts, the delocalization properties of the aromatic system modified by substitution of a hydrogen atom with -Cl and $-CH_3O$ groups could be clearly understood.

• Journal of the Korean Chemical Society
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• v.20 no.5
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• pp.333-339
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• 1976

The rates of solvolysis for 2-thenoyl chloride have been measured in aqueous acetone and aqueous ethanol at various temperatures ranging from 20 to $40^{circ}C$. The activation parameters and the Grundwald-Winstein's slope are determined by the analysis of solvolysis rates. The results indicated that the reaction rates of solvolysis are considerably slower than those of the reaction for benzoyl chloride due to the electron donating effect of thiophene nucleus. The results also showed that the reaction proceeds with the $S_N1$ mechanism in water-rich solvents whereas the $S_N2$ character increases with the decrease of water content, and overall reaction is subject to entropy control.

• Bulletin of the Korean Chemical Society
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• v.21 no.9
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• pp.896-900
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• 2000

A study was done on the synthesis of new poly(arylene ether)s and poly(arylenesulfide) with rigid benzoxazole pendants using nucleophilic aromatic substitution reaction. As a new aromatic monomer, 1,4-bis(2-benzox-azolyl)-2,5-difluorobenzene [I] w as synthesized in three steps starting from 1,4-dibromo-2,5-difluorobenzene. A model reaction of difluoro monomer [I] with two equivalents of m-cresol or thiophenol in a typical ether con-densation reaction conditions gave very high yields ( > 93%) of the desired disubstituted product, suggesting the feasibility of polymer formation in these reaction system. Monomer[I] was polymerized with bisphenols and bisbenzenethiol in NMP using K2CO3 as base. The molecular weight of the resulting polymers, however,seemed relatively low according to their solution viscosity values ( ηinh = 0.15-0.29 dL/g). The poly(arylene ether)s were soluble in several common organic solvents including chloroform, pyridine and N,N'-dimethylfor-mamide. The poly(arylene sulfide) was, however, ony soluble in strong acids like sulfuric acid and trifluoro-acetic acid. The glass transition temperatures were found to be 175-215 $^{\circ}C.$ These polymers were stable up to 380-420 $^{\circ}C$ in both nitrogen and air, as determined by the temperature that a significant weight loss began to appear on TGA.

• Journal of Korea Foresty Energy
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• v.17 no.1
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• pp.30-35
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• 1998

The cellulose modification can be made in steps, giving a range of new products having properties quite different from the parent cellulose. Effective molecular weight control and narrow molecular weight distribution of the polyacrylonitrile can be accomplished by anionic polymerization technique. Preformed polyacrylonitrile was grafted precisely onto cellulose acetate by SN$_2$ reaction mechanism in a simple and effective way under homogeneous reaction condition. The 3.5g of completely dried cellulose acetate(DS=2.4) dissolved in 50ml of dry THF was transferred to the 215m1 polyacrylonitrile solution. The mixture was stirred vigorously under nitrogen atmosphere for 2 hrs. FTIR spectra of cellulose acetate and grafted cellulose acetate were taken, and their characteristic bands were identified.

• Bulletin of the Korean Chemical Society
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• v.32 no.12
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• pp.4361-4365
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• 2011

The nucleophilic substitution reactions of bis(N,N-dimethylamino) phosphinic chloride (3) with substituted anilines ($XC_6H_4NH_2$) and deuterated anilines ($XC_6H_4ND_2$) are investigated kinetically in acetonitrile at $65.0^{\circ}C$. The anilinolysis rate of 3 is rather slow to be rationalized by the conventional stereoelectronic effects. The magnitudes of ${\rho}_X$ (= -6.42) and ${\beta}_X$ (= 2.27) values are exceptionally great. The deuterium kinetic isotope effects (DKIEs; $k_H/k_D$) are secondary inverse ($k_H/k_D$ = 0.69-0.96). A concerted $S_N2$ mechanism involving a backside attack is proposed on the basis of secondary inverse DKIEs and the variation trend of the $k_H/k_D$ values with X. The anilinolyses of six phosphinic chlorides in MeCN are briefly reviewed by means of DKIEs, steric effects of the two ligands, positive charge of the reaction center phosphorus atom, and selectivity parameters to obtain systematic information on phosphoryl transfer reaction mechanism.

• Bulletin of the Korean Chemical Society
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• v.31 no.11
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• pp.3279-3282
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• 2010

The reaction rates of 4-X-2,6-dinitrochlorobenzenes (X = $NO_2$, CN, $CF_3$) with Y-substituted benzylamines (Y = p-$OCH_3$, p-$CH_3$, H, p-Cl) in MeOH-MeCN mixtures were measured by conductometry at $25^{\circ}C$. It was observed that the rate constant increased in the order of X = $NO_2$ > CN > $CF_3$ and in the order of Y = p-$OCH_3$ > p-$CH_3$ > H > p-Cl. When the solvent composition was varied, the rate constant increased in the order of 100% MeOH < 50% (v/v) MeOH-MeCN < 100% MeCN. These results may be ascribed to the formation of hydrogen bonds between the alcoholic hydrogen and nitrogen of benzylamines in groud state (GS). We conclude that the reaction takes place via $S_NAr$ base on the transition state parameters ${\rho}x$, ${\rho}Y$, $\beta_{nuc}$, and solvent effects.

• Journal of the Korean Chemical Society
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• v.37 no.1
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• pp.136-140
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• 1993

New synthetic method for diethyl N-[4-{[(2,4-diamino-6-yl)methyl]-amino}benzoyl]-L-glutamate(10) which is an intermediate of methotrexate is described. p-Nitrobenzoyl-L-glutamate was obtained via a two-step sequence which involves condensation of p-nitrobenzoyl chloride with diethyl-L-glutamate and Fischer esterification reaction with ethanol. Reductive methylation of diethyl-p-nitrobenzoyl-L-glutamate were carried out by reaction with formic acid and paraformaldehyde in the presence of $PtO_2$ catalyst and yielded diethyl N-(4-methylaminobenzoyl)-L-glutamate(7). It was followed by allylation and iodoazidozation to give the diethyl-p-[N-(2-azido-3-iodopropyl)-N-methyl]aminobenzoyl-L-glutamate(9). The cyclization reaction of compound(9) with 2,4,5,6-tetraaminopyrimidine was carried out by intermolecular nucleophilic substitution to give the desired methotrexate diethylester.

• Bulletin of the Korean Chemical Society
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• v.32 no.7
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• pp.2423-2427
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• 2011

Pseudo-first-order rate constants ($k_{obsd}$) have been measured spectrophotometrically for nucleophilic substitution reactions of 3,4-dinitrophenyl diphenylphosphinothioate 9 with alkali metal ethoxides (EtOM, M = Li, Na, K) in anhydrous ethanol at $25.0{\pm}0.1^{\circ}C$. The plot of $k_{obsd}$ vs. [EtOM] is linear for the reaction of 9 with EtOK. However, the plot curves downwardly for those with EtOLi and EtONa while it curves upwardly for the one with EtOK in the presence of 18-crown-6-ether (18C6). Dissection of $k_{obsd}$ into $k_{EtO^-}$ and $k_{EtOM}$ (i.e., the second-order rate constant for the reaction with dissociated $EtO^-$ and ion-paired EtOM, respectively) has revealed that the reactivity increases in the order $k_{EtOLi}$ < $k_{EtONa}$ < $k_{EtO^-}$ ${\approx}$ $k_{EtOK}$ < $k_{EtOK/18C6}$, indicating that the reaction is inhibited by $Li^+$ and $Na^+$ ions but is catalyzed by 18C6-crowned $K^+$ ion. The reactivity order found for the reactions of 9 contrasts to that reported previously for the corresponding reactions of 1, i.e., $k_{EtOLi}$ > $k_{EtONa}$ > $E_{EtOK}$ > $k_{EtO^-}$ ${\approx}$ $k_{EtOK/18C6}$, indicating that the effect of changing the electrophilic center from P=O to P=S on the role of $M^+$ ions is significant. A four-membered cyclic transition-state has been proposed to account for the $M^+$ ion effects found in this study, e.g., the polarizable sulfur atom of the P=S bond in 9 interacts strongly with the soft 18C6-crowned $K^+$ ion while it interacts weakly with the hard $Li^+$ and $Na^+$ ions.

• Archives of Pharmacal Research
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• v.25 no.6
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• pp.790-794
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• 2002

A series of novel exomethylene cyclopropyl nucleosides have been synthesized starting from Feist's acid. Classical nucleophilic substitution conditions ($K_2CO_3$, 18-crown-6) of the tosylate 2 as well as Mitsunobu reaction (DEAD, $PPh_3$) of alcohol 1 with pyrimidine bases afforded a series of novel cyclopropyl nucleosides. Compound 4b displayed moderate anti-HBV activity without any cytotoxicity up to $100{\;}{\mu}M$.