• 대한화학회지
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• 제13권1호
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• pp.75-82
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• 1969

4-Ethyltropolone has been prepared in three steps from cyclopentadiene by a dichloroketene process, and at the same time, a comparison has also been made with the case of tropolone synthesis. In the addition reaction of dichloroketene to cyclopentadiene as well as to ethylcyclopentadiene, and also in the separation of cycloadducts from reaction mixture, the best results were given by prevention of the reactants from dimerization. Under these condition, the yields of cycloadducts were around 70% for both. Tropolone and 4-ethyltropolone were obtained in the yield of 51% and 32%, respectively, by hydrolysis of cycloadducts with potassium acetate in aqueous acetic acid. These results revealed that the steric effect of ethylgroup was more sensitive to the hydrolysis than to the cycloaddition reaction. A comparison of UV, IR and NMR spectroscopic results of 4-ethyltropolone with those of tropolone was also made together with a brief discussion of the tropolone ring system and ethylgroup effect.

• Bulletin of the Korean Chemical Society
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• 제33권1호
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• pp.39-42
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• 2012

The use of Smiles rearrangement in Ugi-type couplings with tropolone allows very straightforward multicomponent formation of 2-(N,N-dialkylamino)-2,4,6-cycloheptatrien-1-one derivatives. The Ugi four-component reaction of isocyanides with tropolone (2-hydroxy-2,4,6-cycloheptatrien-1-one), primary amines and aldehydes proceeds smoothly and cleanly under mild conditions to afford 2-(N,N-dialkylamino)-2,4,6-cycloheptatrien-1-one derivatives in fairly good yields.

• 대한화학회지
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• 제13권1호
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• pp.83-88
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• 1969

By the three-step synthesis of alkyltropolone from five-membered cyclopentadiene, as described in Part Ⅰ, methyltropolone has been prepared. From the hydrolysis product of dichloroketene-methylcyclopentadiene cycloadduct, ${\beta}$-(Ⅰ) and ${\gamma}$-methyltropolone (Ⅱ) were separated, with the first predominating, by means of repeated fractional recrystallization and fractional vacuum sublimation. The total yield of these methyltropolones in the hydrolysis step was about 40%. Comparison of this result with those obtained in part Ⅰ revealed the following order as the relative readiness of their preparation: tropolone > methyltropolone > ethyltropolone. The reason for formation of the isomeric (Ⅱ) was discussed by an interpretation of NMR spectrum of cycloadduct in the unsaturation and methylgroup region.

• Bulletin of the Korean Chemical Society
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• 제24권6호
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• pp.695-702
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• 2003

Recent experimental and theoretical advances on the aromatic alcohol-water clusters are reviewed, focusing on the structure of the hydrogen bonding between the alcoholic OH group and the binding water molecules. The interplay of experimental observations and theoretical calculations for the elucidation of the structure is demonstrated for phenol-water, benzyl alcohol-water, substituted phenol-water, naphthol-water and tropolone -water clusters. Discussion is made on assigning the role (either proton-donating or -accepting) of the hydroxyl group by measuring the shifts of infrared frequency of the OH stretching mode in the cluster from that of bare aromatic alcohol for the experimental determination of the cluster structure.

• 대한화학회지
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• 제13권1호
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• pp.89-95
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• 1969

The structural investigations on the adducts, formed from dichloroketene with cyclopentadiene, methyl and ethylcyclopentadiene, have been carried out by means of infrared and nuclear magnetic resonance spectroscopy and also by their chemical behaviors. It was confirmed by this study that the adducts were formed by 1, 2-cycloaddition reaction and had the fundamental structure of bicyclo [3. 2. 0]-7,7-dichloro-2-heptene-6-one. These results were well agreed with the hypothesis that a diradical intermediate was formed as the first step in 1, 2-cycloaddition. The reaction mechanism for the process in which tropolones were formed from these adducts was also discussed.

• KSBB Journal
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• 제27권4호
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• pp.257-262
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• 2012

The gene encoding Thermus thermophilus HJ6 laccase (Tt-laccase) was cloned, sequenced, and comprised of 1,389 nucleotides encoding a protein (462 amino acids) with a predicted molecular mass of 51,049 Da. The deduced amino acid sequence of Tt-laccase showed 99.7% and 44.3% identities to the Thermus thermophilus HB27 laccase and Synechococcus sp. RS9917 laccase, respectively. Tt-laccase gene was expressed as a fusion protein with six histidine residues in E. coli Rosetta-gami (DE3) cells, and the recombinant protein was purified to homogeneity. UV-Vis spectrum analysis revealed that the enzyme has copper atoms, a type I Cu(II) and a type III binuclear Cu(II). The optimum pH for the oxidation of guaiacol was 5.0 and the optimum temperature was $90^{\circ}C$ The half-life of heat inactivation was about 120 min at $90^{\circ}C$ The enzyme reaction was inhibited by sodium azide, L-cystein, EDTA, dithiothreitol, tropolone, and kojic acid. The enzyme oxidized various known laccase substrates, its lowest $K_m$ value being for 4-hydroxyindole, highest $k_{cat}$ value for syringaldazine, and highest $k_{cat}/K_m$ for guaiacol.

• 분석과학
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• 제13권5호
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• pp.636-645
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• 2000

본 연구에서는 GC/MS를 이용하여 수질시료로부터 7종의 유기주석화합물을 분석하는 방법을 연구하였다. Hydrogenation과 ethylation의 반응시의 pH, 반응시간, 반응시약의 농도 등을 변화시켜 최적 반응조건을 조사하였다. n-Hexane을 용매로 사용한 액체-액체 추출 후 hydrogenation에 의한 유기주석염화물의 추출 회수율은 61-112% 범위로 나타났다. 물시료에서 ethylation한 후 n-hexane으로 추출한 경우의 추출 회수율이 74-113% 범위로 나타나 hydrogenation의 경우보다 높은 추출율을 보였다. 또한 ethylation후 styrene-divinylbenzene (SDB) 재질의 disk형의 고체상을 사용하고 추출 용매로 methylene chloride를 사용한 경우 61-97% 범위의 회수율을 나타냈다. Hydrogenation과 ethylation에 의한 검출한계는 각각 0.05-0.5 ng/ml와 0.02-0.05 ng/ml로 나타났다.

• Bulletin of the Korean Chemical Society
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• 제25권10호
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• pp.1508-1512
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• 2004

A gas chromatography/mass spectrometric (GC/MS) method has been developed for the determination of trace mono-n-butyltin (MBT), di-n-butyltin (DBT), and tri-n-butyltin (TBT) compounds in sediments. Samples were extracted by 10% acetic acid in methanol containing 0.03% tropolone and were then derivatized for GC/MS analysis. Ethylation by sodium tetraethylborate and phenylation by sodium tetraphenylborate were evaluated as a derivatization reaction of the organotins in sample extract. n-Hexane was added into reaction media in the beginning of the reaction for the continuous extraction of derivatized organotins. Ethylation requires less than 2 hours to get proper derivatization yields for MBT, DBT, and TBT altogether and produces relatively low amounts of side reaction products. Compared to ethylation, phenylation requires much longer time but provides relatively lower yield and produces considerable amounts of side reaction products. Therefore, the ethylation reaction was applied for the analysis of organotin compounds in sediment. An isotope dilution mass spectrometric (IDMS) method based on GC/MS has been applied to the accurate determination of DBT compounds in the sediments. The IDMS results from the analyses of sediment samples showed a reasonable repeatability and a good agreement with the values obtained by IDMS based on liquid chromatography/induced coupled plasma/mass spectrometry.

• Bulletin of the Korean Chemical Society
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• 제30권1호
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• pp.205-213
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• 2009

This study reports on the geometry optimizations and electronic structure calculations for methyl pyropheophorbide (MPPa), tropolonyl methyl pyropheophorbides (TMPPa, ITMPPa), and cationic tropolonyl methyl pyropheophorbides ($TMPPa^+{{\cdot}BF_4}^-,\;ITMPPa^+{{\cdot}BF_4}^-,\;TMPPa^+,\;and\;ITMPPa^+$) using Local Spin Density Approximation (LSDA/ 6-31G*) and the Restricted Hatree-Fock (RHF/6-31G*) level theory. From the calculated results, we found that substituted cationic tropolonyl groups have larger structural effects than those of substituted neutral tropolonyl groups. The order of structural change effects is $ITMPPa^+ > ITMPPa^+{{\cdot}BF_4}^-$ > ITMPPa, as a result of the isopropyl group. Because it is an electron-releasing group, the substituted isopropyl group electronic effect on a 3-position tropolone increases the Highest Occupied Molecular Orbital and Lowest Unoccupied Molecular Orbital (HOMO-LUMO) energy gap. It was constituted that the larger the cationic characters of these photosensitizers, the smaller the HOMOLUMO band gaps are. The orbital energies of the cationic systems and the ions are stronger than those of a neutral system because of a strong electrostatic interaction. However, this stabilization of orbital energies are counteracted by the distortion of chlorin macrocycle, which results in a large destabilization of chlorin-based compound HOMOs and smaller destabilization of LUMOs as shown in TMPPa (ITMPPa), $TMPPa^+{{\cdot}BF_4}^- (ITMPPa^+{{\cdot}BF_4}^-),\;and\;TMPPa^+\;(ITMPPa^+)$ of Figure 6 and Table 6-7. These results are in reasonable agreement with normal-coordinate structural decomposition (NSD) results. The HOMO-LUMO gap is an important factor to consider in the development of photodynamic therapy (PDT).