• Journal of the Korean Chemical Society
• /
• v.32 no.5
• /
• pp.416-421
• /
• 1988

Kinetic studies for the nucleophilic substitution reactions of benzyl halides(para-substituted benzyl bromides and benzyliodide) with substituted pyridines in MeOH-MeCN mixtures have been carried out in order to elucidate the reaction mechanism. Cross interaction coefficient, ${\rho}_{XY}$ values suggested that the reactions between benzylhalides and substituted pyridines exhibit an dissocitive $S_N$2 mechanism. Hammett (${\rho}_X$, ${\rho}_Y$), Br${\o}$nsted ${\beta}_N$ and solvatochromic correlation coefficient a, s, a/s values were illustrated. Kinetic results were compared between potential energy surface model and quantum mechanical model. The quantum mechanical approach showed to be consistent with kinetic results.

• Corrosion Science and Technology
• /
• v.4 no.1
• /
• pp.8-14
• /
• 2005

The corrosion behaviour of mild steel in phosphoric acid solution in the presence and absence of pollutants viz. Chloride, Fluoride and Sulfate ions at 302K-333K was studied using mass loss and potentiostatic polarization methods. The addition of chloride and sulfate ions inhibits the mild steel corrosion in phosphoric acid while fluoride ions stimulate it. The effect of temperature on the corrosion behaviour of mild steel indicated that inhibition of chloride and sulfate ions decreased with increasing temperature. The adsorption of these ions (Chloride and sulfate) on the mild steel surface in acid has been found to obey Langmuir adsorption isotherm. The values of activation energy (Ea) and free energy of adsorption ($\Delta$) indicated physical adsorption of these ions (chloride and sulfate) on the mild steel surface. The plot of $logW_{f}$ against time (days) at 302K gives a straight line, which suggested that it obeys first order kinetics and also calculate the rate constant k and half-life time $t_{1/2}$.

• Bulletin of the Korean Chemical Society
• /
• v.11 no.2
• /
• pp.109-114
• /
• 1990

The anionic transition metal hydrides $(HW(CO)_4P(OMe)_3\;^-,\;HW(CO)_5\;^-,\;HCr(CO)_5\;^-,\;HFe(CO)_4\;^-)$ react with transition metal alkyl $(CpMo(CO)_3(CH_3)$ to yield $CH_4\;and\;CH_3CHO$ in addition to the inorganic products $(CpMo(Co)_3\;^-$, etc.). The reaction of these anionic metal hydrides with CpMo(CO)3{CH2CH(CH2)2} may lead to an elucidation of the reaction mechanisms involved; the organic product distributions are among $CH_4,\;CH_2\;=\;CHCH_2CH_3$, and $CH_3CH(CH_2)_2$, depending upon the anionic metal hydride used. These anionic metal hydrides also are reported to undergo a hydride-halide exchange reaction with organic halides; therefore, these similar reactions have been compared in terms of leaving group ability $(CpMo(CO)_3\;^-\;vs.\;Br^-)$ and the mechanistic pathways.

• Bulletin of the Korean Chemical Society
• /
• v.15 no.6
• /
• pp.465-468
• /
• 1994

The charge transfer compounds $(TTF)_4FeCl_3{\cdot}CH_3OH,\;(TTF)_4SbCl_4\;and\;(TTF)_5(SbBr_4)_2{\cdot}CH_3COCH_3$ were prepared from reactions of the TTF (tetrathiafulvalene) and metal halides. The compounds were characterized by spectroscopic (UV,IR, EPR and XPS) methods, magnetic susceptibility and electrical conductivity measurements. The d.c electrical conductivities of the pressed pellets are in the order of $10^{-1}-10^{-3} Scm^{-1}$, which lies in the range of semiconductor region at room temperature. It means that the partially ionized TTF has stacked in low-dimensional chain in each compound. Spectroscopic properties also indicate that TTF molecules are partially ionized and charge transfer has occurred from (TTF)n to Fe(III) center in $(TTF)_4FeCl_3{\cdot}CH_3OH$ whereas to the $-SbX_4^-$ entity in $(TTF)_4SbCl_4\;and\;(TTF)_5(SbBr_4)_2{\cdot}CH_3COCH_3$. The EPR g values are consistent with TTF radical formation and EPR linewidths suggest the delocalization of unpaired electrons along TTF stacks. A signal arised from metal (Fe and Sb) ions were not detected in EPR spectra, indicating that metal ion is in the diamagnetic state in each compound. The diamagnetic state was also examined by the magnetic susceptibility measurement. The magnetic properties reveal the significant interaction between the $TTF^+$ radical cations in the stacks. The oxidation state of metal ions was also investigated by XPS spectra.

• Bulletin of the Korean Chemical Society
• /
• v.16 no.12
• /
• pp.1218-1222
• /
• 1995

The pKa values of benzyltetrahydrothiophenium halides 1a-f in water have been estimated by measuring the absorbances of the solution in aqueous hydroxide ion solution. Assuming that the ratios of the activity coefficients remains close to unity, the absorbance of the solution can be expressed as A/[SH]o=(εSH+εS-K[OH-])/(1+K[OH-]), where A, [SH]o, K, εSH, and εS- are the absorbance of solution, the initial concentration of 1a-f, the equilibrium constant, and the extinction coefficients for SH and S-, respectively. The εS- and K values that best fit with this equation were calculated by a nonlinear regression analysis with a large number of absorbance data determined at different [OH-] and [SH]o. The pKa values of the SH were then calculated with the relationship Ka=-log K+14. The validity of this method has been demonstrated by the excellent agreements between the experimental and literature pKa values of three organic acids. The pKa values of 1a-f estimated by this method are in the range of 12.5-15.3 and correlate well with the Hammett equation. The large negative deviation for the pKa values of 1e and 1f from the Hammett plot has been attributed to the extra hydrogen bonding between the phenyl group and water molecules attracted by the hydrophilic substituents.

• Bulletin of the Korean Chemical Society
• /
• v.15 no.3
• /
• pp.221-227
• /
• 1994

The barrier heights of the internal rotations for ethyl halides calculated by ab initio methods differ from those of experiments by more than 0.2 kcal/mol. The use of basis sets larger than the $6-31G^{\ast}$ set and the inclusion of correlation do not improve the agreement between the calculated and experimental values. The zero-point vibration corrections are substantial in the HF calculations with $6-31G^{\ast}$ basis sets, but become negligible in the MP2 calculations with $6-311G^{{\ast}{\ast}}$ basis sets for $C_2H_5F\;and\;C_2H_5Cl$. It is shown that the rigid rotor approximation and the assumed shape of the potential curve as a cos2${\theta}$ curve could also be the sources of discrepancies between calculated and experimental values. Higher order perturbation corrections narrow the gap between experimental and theoretical values, but there still remains about 10% overestimate of 0.3 kcal/mol. Optimized geometries from the HF and MP2 calculations are in good agreement with those from experiments. Dipole moments calculated from the MP2 densities show slightly better agreement with experiments than those from the HF densities.

• Proceedings of the Korean Society of Applied Pharmacology
• /
• 1994.04a
• /
• pp.221-221
• /
• 1994

The cross-coupling reaction of organo tin reagents with a variety of organic halides, catalyzed by palladium, provides a novel method for generating a carbon-carbon bond. We use this method for antibacterial agents, and synthesis of new quinolone derivatives which have carbon-carbon bond at C-7 position of general quinolone moieties. Aryl tin, quinolone moieties, and palladium catalyst were refluxed in DMF to afford new quinolone derivatives. This palladium catalyzed coupling reactions have capacity for further synthetic elaboration.

• Archives of Pharmacal Research
• /
• v.29 no.1
• /
• pp.46-49
• /
• 2006

In this study, 2-N-arylimino-2,3-dihydro-1,3,4-thiadiazoles derivatives (6a-h) were synthetized. The mechanism of the studied reactions was discussed. The chemical structures of the compounds were elucidated by their IR, $^1H-NMR,\;^{13}C-NMR$, and Mass spectral data and elemental analyses. The compounds were tested for antimicrobial activity using diffusion agar technique.

• Journal of the Korean Chemical Society
• /
• v.14 no.1
• /
• pp.13-18
• /
• 1970

非水溶液 Ethylenediamine 中에서 水銀電極의 標準電位 및 水銀鹽化物, $HgCl_2,\;HgBr_2,\;HgI_2$의 Ion-Pair 形成恒數를, Hg電極/$HgX_2$ 또는 $HgX_2$+NaX//亞鉛아마르감 參照電極과 같은 Cell의 構成으로서 電位差法에 依하여 測定하였다.

• Bulletin of the Korean Chemical Society
• /
• v.31 no.6
• /
• pp.1735-1738
• /
• 2010