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남기평,차진순 대한화학회 2013 Bulletin of the Korean Chemical Society Vol.34 No.8
Relative reactivity of various Al-substituted dialkylalans (AlR2(X)) in reduction of acetone has been studied with density functional theory and MP2 method. Formation of the alan dimers and the alan-acetone adduct, and the transition state for the Meerwein-Ponndorf-Verley (MPV) type reduction of the adduct were calculated to figure out the energy profile. Formation of dimeric alans is highly exothermic. Both the relative free energies for acetone-alan adduct formation and the TS barriers for the MPV type reduction with respect to alan dimers and acetone were calculated and they show the same trend. Based on these energetic data, relative reactivity of alans is expected to be; AlR2(Cl) > AlR2(OTf) > AlR2(O2CCF3) > AlR2(F) > AlR2(OMs) > AlR2(OAc) > AlR2(OMe) > AlR2(NMe2). The energy profile is relatively well correlated with the experimental order of the reactivity of Al-substituted dialkylalans. It is noted that the substituents of alans have initial effects on the relative free energies for the carbonyl-adduct formation. Therefore, an AlR2(X) which forms a more stable carbonyl-adduct is more reactive in carbonyl reduction.
A Theoretical Study on the Alkylation of the Ambident Enolate from a Methyl Glycinate Schiff Base
남기평,Seungmin Lee 대한화학회 2012 Bulletin of the Korean Chemical Society Vol.33 No.8
The alkylation of the ambident enolates of a methyl glycinate Schiff base with ethyl chloride was studied at B3LYP and MP2 levels with 6-31+G* basis set. The free (E)-enolates and (Z)-enolate are similar in energy and geometry. The transition states for the alkylation of the free (E)/(Z)-enolate with ethyl chloride have similar energy barriers of ~13 kcal/mol. However, with a lithium ion, the (E)-enolate behaves as an ambident enolate and makes a cyclic lithium-complex in bidentate pattern which is more stable by 11-23 kcal/mol than the (Z)- enolate-lithium complexes. And the TS for the alkylation of (E)-enolate-lithium complex coordinated with one methyl ether is lower in energy than those from (Z)-enolate-lithium complexes by 4.3-7.3 kcal/mol. Further solvation model (SCRF-CPCM) and reaction coordinate (IRC) were studied. This theoretical study suggests that the alkylation of ambident enolates proceeds with stable cyclic bidentate complexes in the presence of metal ion and solvent.
남기평 대한화학회 2014 Bulletin of the Korean Chemical Society Vol.35 No.2
Relative reactivity of various carbonyl and acid derivatives in MPV-type (Meerwein–Ponndorf–Verley) reduction with an DIBAL(F) model has been studied via DFT and MP2 methods. Free energies of initial adduct formation (△G add ) of DIBAL(F) model and carbonyls are in the order of amide < ester < aldehyde < ketone < acid chloride; in the alan-amide adduct, the developed positive charge at carbonyl carbon is expected to be stabilized by amide resonance, but in the acid chloride adduct it is destabilized by inductive effect of chloride. However the TS barrier energies (△G TS ) for the MPV-type hydride reduction of the carbonyl adducts are in the order of aldehyde < ketone < acid chloride << ester < amide; presumably decreasing order of electrophilicity of carbonyl carbon at adducts, which is well correlated with experimental data. It is noted that the relative reactivity of carbonyl derivatives in MPV-type reduction with DIBAL(X) is not governed by the alan-adduct formation energies, but follows the order of electrophilicity of carbonyl carbon of transition states.
김준영,도정연,남기평,박노국,지준화,강미숙 한국공업화학회 2019 한국공업화학회 연구논문 초록집 Vol.2019 No.0
The power generation process used for gasification of coal to drive the fuel cell has a better emission reduction effect of the greenhouse gas as compared with the existing power generation, and shows excellent efficiency. However, in the process of gasification, a sulfur compound is generated, and this by-product causes poisoning of the fuel cell and deteriorates its performance. The aim of this research is to develop an adsorbent for the removal of toxic COS gas among the sulfur compounds released during the process of coal power generation. We have tried to make adsorbent which is in the form of a crosslinked carbonate form by adding KOH to activated carbon which is inexpensive and porous and shows good adsorption power. The content of activated carbon was fixed at 80% to optimize adsorption at low temperature. The synthesized adsorbents were characterized by XRD, SEM and BET. In addition, the adsorption/desorption mechanism was analyzed by FT-IR, XPS and MASS analysis.