• Bulletin of the Korean Chemical Society
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• 제16권1호
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• pp.12-16
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• 1995

The diastereoselectivity of addition reaction of crotylmetal reagents to cobalt-complexed acetylenic aldehydes and metal-free aldehydes was examined. The anti-diastereomer was the predominant product when the crotyl metallics were Cr, Sn, and Zr. In THF, the uncomplexed aldehydes normally gave higher anti-diastereoselectivity. However, the cobalt-complex of silicon-substituted propynals with three bulky substituents produced increased proportions of syn-diastereomer. In DMF, the selectivity shifted towards syn-isomer except in the case of dimethylphenylsilyl substituent. When tributylstannane was used in the presence of BF3 etherate, moderate syn- selectivity was observed with uncomplexed aldehydes, but only decomposed products from complexed aldehydes.

• Bulletin of the Korean Chemical Society
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• 제16권1호
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• pp.21-26
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• 1995

Electrochemical reduction of oxygen has been carried out at glassy carbon electrode and carbon ultramicroelectrode, the surface of which is modified with a new Co(Ⅱ)-Schiff base complex, Co(Ⅱ)-3,4-bis(salicylidene diimine)toluene in 1 M KOH solution. The results obtained from cyclic voltammetric and chronoamperometric experiments are consistent with the formation of the reasonably stable superoxide ions as a primary electron transfer reaction product. The exchange rate constant obtained for oxygen reduction is about 0.02 cm/s.

• Bulletin of the Korean Chemical Society
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• 제19권1호
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• pp.103-106
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• 1998

The oxidation product bis(2-oxo-3H-1,3,4-thiadiazolidinyl)-5,5-disulfide (5b) was obtained from an attempted synthesis of 5-thioxo-3H,4H-1,3,4-thiadiazolidin-2-one (1). Spectroscopic results indicate that the most stable tautomeric form of 1 is the lactam-thiol form (1b). The computed total energies and relative energies at the MP4 level also showed that the most stable tautomer is 1b.

• Bulletin of the Korean Chemical Society
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• 제1권4호
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• pp.123-126
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• 1980

Benzene solution of trans-1,2-bispyrazylethylene and electron deficient olefin, tetracyanoethylene, as a ${\pi}$-acceptor gave 1,2-bispyrazyl-3,3,4,4-tetracyanocyclobutane, a 2${\pi}$ + 2${\pi}$ cycloaddition product, on irradiation with 350 nm UV light. Fluorescence studies revealed the reaction to proceed through a singlet exciplex. The fluorescence of trans-1,2-bispyrazylethylene was quenched very efficiently by tetracyanoethylene with the quenching constant of 1.6 ${\times}$ 10$^{10}$M$^{-1}$s$^{-1}$ while electron rich olefin, tetramethylethylene, did not quench the fluorescence of bispyrazylethylene.

• Bulletin of the Korean Chemical Society
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• 제17권8호
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• pp.686-688
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• 1996

We have produced nanophase iron clusters inside a gas cell by decomposing iron pentacarbonyls from the mixture of ~20 Torr Fe(CO)5/~3 Torr SF6 with a pulsed CO2 laser. The product displayed a black tint. Its composition was identified to be mostly iron from an inductively coupled plasma (ICP) atomic emission spectrum. The X-ray diffraction (XRD) pattern indicates a body-centered cubic structure for the cluster. A transmission electron micrograph proves that their diameter ranges between 50 and 70 Å and their average diameter is 60 Å.

• Bulletin of the Korean Chemical Society
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• 제10권4호
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• pp.372-374
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• 1989

The new viscosity theory is applied to the abnormal behavior of the viscosity near the critical point. This theory suggests that the viscosity is equal to the product of the absolute pressure(kinetic pressure + internal pressure) and the collision time. We can find this abnormal behavior to be due to the large collision time near the critical point. The agreements between theoriticals and experimentals of the critical enhancement are satisfactory.

• Bulletin of the Korean Chemical Society
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• 제12권4호
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• pp.380-382
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• 1991

Pictet-Spengler reaction of the N-hydroxytryptophan ethyl ester (4) with N-protected thiazolidine aldehyde (8) has been carried out. The product, compound (9b), might be a possible precursor for the eudistomins C, E, K, and L.

• Bulletin of the Korean Chemical Society
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• 제12권4호
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• pp.423-429
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• 1991

Global and local memory functions, defined by Quack and Troe, were calculated for the rotationally inelastic collision of O + SO(v, j)→ [O--S--O]→O + SO(v, j'). It is seen to decrease steadily as total energy increases. Distribution of scattering cross section over product rotational states also shows the decreasing memory of initial state as total energy is increased. These results are interpreted in terms of energy scrambling at high energy due to the availability of more phase space and also the influence of strong dynamical constraints.

• Bulletin of the Korean Chemical Society
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• 제20권12호
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• pp.1433-1436
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• 1999

The 2-(2,4-dimethoxyphenyl)-4-MDO (2) underwent polymerization with ring opening as well as cyclization reaction in the presence of various cationic catalysts such as boron trifluoride, trifluoromethanesulfonic acid, p-toluenesulfonic acid, hydrochloric acid and trifluoroacetic acid. They afforded a mixture of the ring-opened poly(keto ether) and 3(2H)-dihydrofuranone derivative. Both the methylene group and oxygen atom of 1,3-dioxolane ring were participated in the reaction with cationic catalyst. The contents of the polymer and cyclization product were variable according to the acid strength of the cationic catalysts.

• Bulletin of the Korean Chemical Society
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• 제13권5호
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• pp.538-541
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• 1992

An approximate scheme for evaluating total reaction probability is proposed. Semiclassical boundary conditions are imposed well before the asymptotic region in the reactant and product channels to calculate the Green's function and its derivatives. Propagations are confined to a limited regime near the activated complex. Calculations are made for one dimensional Eckart barrier model of H + $H_2$ reaction. Implications of the procedure in multi-dimensional systems are discussed.