• The Korean Journal of Pesticide Science
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• v.6 no.4
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• pp.231-243
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• 2002

Starting with linear free energy relationships (LFER), drug design to mimic of the activated complexes at transition state, and hydrolysis mechanisms to control the potency and residual properties of pesticides were introduced and summarized for the necessity. In order to understand the searching or development of new agrochemicals by two dimensional quantitative structure-activity relationship (2D QSAR) methodology, a series of the various descriptors, steric constants, electronic constants including quantum pharmacological parameters and hydrophobic constants were classified and discussed for results of the several studied cases. In addition, the processes of development of new agrochemicals by QSAR techniques were introduced simply.

• The Korean Journal of Pesticide Science
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• v.6 no.3
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• pp.166-174
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• 2002

The fundamental concepts on the basis of linear free energy relationship (LFER), history of development, prediction of pharmacological effects, advantages and disadvantages, etc. according to the 2D and 3D QSAR methodologies were summarized in utilizing the quantitative structure-activity relation ship (QSAR) techniques for searching and development of new agrochemicals. Objectives, role of QSAR techniques in development process of pesticides and limitations in QSARs were discussed and introduced.

• Journal of the Korean Chemical Society
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• v.33 no.5
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• pp.538-544
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• 1989

The increase of B-type hydrogen bonding character between the hydrogen atom($H{\gamma}$) of methylene group in 1-(phenoxymethyl)benzotriazole (1) and 1-(thiophenoxymetyl)benzotriazole (2) derivatives, and solvents was caused by some factors such as;electron withdrawing strength (${\rho} > 0$) of X-substituent; local diamagnetic effect by Y atom (Y = O(1) > S(2)) with adjacent methylene group; and solvent polarity parameter ($E_T$ = Kcal/mol; acetone; 42.2 > chloroform; 39.0). From the basis on the findings, linear free energy relationship (LFER) components on the substituent chemical shift of methylene group ($CH_2-SCS$) in (1) exhibited a tendency that resonance(R)-effect was much larger than field(F) (or inductive(I))-effect in acetone and that the electrical effects were depend upon the solvent.

• Journal of the Korean Chemical Society
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• v.29 no.3
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• pp.277-282
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• 1985

The effects of linear free energy relationship (LFER) on the imidoyl proton (H${\alpha}$)-substituent chemical shift (SCS) in case of varying para-substituted C-phenyl group in N-benzylideneaniline derivatives were studied. The H${\alpha}$-SCS values and LFER parameters such as ${\sigma}$,${\sigma}^+$, ${\sigma}_I$,${\sigma}_R, F and R were applied to the Hammett, Okamoto-Brown, and Taft, Swain-Lupton's dual substituents parameter (DSP) equations. The results were: (1) the blending coefficient values, ${\lambda}$ = 2.8∼3.2, it's means that the resonance effect (R) was larger than inductive effect (I) and field effect (F), and (2) the values of percent resonance and percent field effects were %R = 66.6 and %F = 33.4, respectively, yielding the ratio of resonance effect (R) to field effect (F) of 2 : 1.

• Journal of Korean Society of Environmental Engineers
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• v.31 no.2
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• pp.125-131
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• 2009

Reductive dechlorination of polychlorinated dibenzo-p-dioxins (PCDDs) and its toxicity change were predicted by the linear free energy relationship (LFER) model to assess the zero-valent iron (ZVI) and anaerobic dechlorinating bacteria (ADB) as electron donors in PCDDs dechlorination. Reductive dechlorination of PCDDs involves 256 reactions linking 76 congeners with highly variable toxicities, so is challenging to assess the overall effect of this process on the environmental impact of PCDD contamination. The Gibbs free energies of PCDDs in aqueous solution were updated to density functional theory (DFT) calculation level from thermodynamic results of literatures. All of dechlorination kinetics of PCDDs was evaluated from the linear correlation between the experimental dechlorination kinetics of PCDDs and the calculated thermodynamics of PCDDs. As a result, it was predicted that over 100 years would be taken for the complete dechlorination of octachlorinated dibenzo-p-dioxin (OCDD) to non-chlorinated compound (dibenzo-p-dioxin, DD), and the toxic equivalent quantity (TEQ) of PCDDs could increase to 10 times larger from initial TEQ with the dechlorination process. The results imply that the single reductive dechlorination using ZVI or ADB is not suitable for the treatment strategy of PCDDs contaminated soil, sediment and fly ash. This LFER approach is applicable for the prediction of dechlorination process for organohalogen compounds and for the assessment of electron donating system for treatment strategies.

• Korean Journal of Agricultural Science
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• v.11 no.1
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• pp.176-181
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• 1984

Linear free energy relation ship(LFER) on the insecticidal activity of O,O-diethylphenylphosphate (A) and 3,5-dimethylphenyl-O,O-diethylphosphate (B) derivatives were studied by EHT MO calculation method and regression analysis method. LFER between varying substituent constants and $pI_{50}$ constants of phosphates, (A) & (B) were calculated with applying Hammett, Okamoto-Brown, Taft and Swain-Lupton's DSP equations;percent resonance effect(R) and field effect(F) of (A) were %R=33.5 & %F=66.5 and also that of (B) were %R=2 & %F=98, respectively. On the basis of above findings, the insecticidal activities were similar for both (A) and (B), but (B) have larger field and inductive contribution than (A), due to the 3,5-dimethyl group of (B).

• Applied Biological Chemistry
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• v.32 no.2
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• pp.170-177
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• 1989

In order to seek the molecular basis of higher insecticidal activity of the carbamates with two methyl groups, m-xylyl-N-methylcarbamate(MXNMC) than the corresponding unsubstituted phenyl N-methylcarbamate(PNMC), these two derivatives have been studied by molecular orbital(MO) theoretically using extended $H\ddot{u}ckel$ theory(EHT), and analysis of regression and linear free energy relationship(LFER). The most stable stereo structure(Z, Z) shows that the phenyl group occupies vertical(${\theta}=90^{\circ}$) position on the plane of the N-methylcarbamyl group. Regression analysis shows that especially good correlation exists between the $pI_{50}$ values and the calculated MO quantities when the hydrogen atomic charge of metaposition and of m-methyl groups, and LUMO energy are taken as variables. The LFER analysis on the carbamylation indicates that field(F) effect(60%) is slightly larger than resonance(R) effect(40%) in PNMC(E>R), whereas, in case of MXNMC, R effect(98.6%) is much larger than F effect(1.4%)($R{\gg}F$). From the basis on the findings, the enhancement of insecticidal activity of MXNMC may be the result of hyperconjugation by m-methyl groups.

• Bulletin of the Korean Chemical Society
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• v.35 no.8
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• pp.2263-2270
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• 2014

Solvolysis rate constants of 2-phenylethyl-(2-$PhCH_2CH_2OCOCl$, 1) and 2,2-diphenylethyl chloroformate (2,2-$Ph_2CHCH_2OCOCl$, 2), together with the previously studied solvolyses of ${\alpha}$- and ${\beta}$-substituted chloroformate ester derivatives, are reported in pure and binary solvents at $40.0^{\circ}C$. The linear free energy relationship (LFER) and sensitivities (l and m) to changes in solvent nucleophilicity ($N_T$) and solvent ionizing power ($Y_{Cl}$) of the solvolytic reactions are analyzed using the Grunwald-Winstein equation. The kinetic solvent isotope effects (KSIEs) in methanol and activation parameter values in various solvents are investigated for 1 and 2. These results support well the bimolecular pathway with same aspects. Furthermore, the small negative values of the entropies of activation of solvolysis of 1 and 2 in the highly ionizing aqueous fluoroalcohols are consistent with the ionization character of the rate-determining step, and the KSIE values of 1.78 and 2.10 in methanol-d indicate that one molecule of solvent acts as a nucleophile and the other acts as a general-base catalyst. It is found that the ${\beta}$-substituents in alkyl chloroformate are not the important factor to decide the solvolysis reaction pathway.