• Archives of Pharmacal Research
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• 제20권3호
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• pp.269-274
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• 1997

Solubilities of oleanolic acid and ursolic acid in aqueous surfactant solutions, liquid polyethylene glycols (PEG), and solvents of various polarity were measured. The results showed that the solutes were slightly or moderately solubilized in the surfactant solutions and the liquid PEGS. It was also revealed that the solutes were slightly soluble in the solvent of either extreme polarity or nonpolarity, but moderately soluble in solvents of intermediate polarity of which solubility parameters are around 10. The solubility parameters of these solutes were calculated from the group contribution to be 10.2 for both of them. Of the solvents tested, tetramethylurea was exceptionally effective in solubilizing the solutes. The solutes were also moderately soluble in the aqueous cosolvents containing tetramethylurea. This suggests that the mixed systems of tetramethylurea could be employed for the solubilization in the formulation of these compounds as an aqueous system.

• 대한화학회지
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• 제20권5호
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• pp.374-379
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• 1976

요소, 1,3-디메틸요소(DMU)및 1,1,3,3-테트라메틸요소(TMU)의 $25^{\circ}C$에서의 겉보기 몰랄부피를 dimethylsulfoxide와 메탄올용액에서 밀도측정으로 얻었다. Dimethylsulfoxide에서 요소는 특히 묽은 용액에서 자체회합성을 보이고, DMU와 TMU는 용질-용매상호작용을 함을 알았다. 한편, 양성자성 용매인 메탄올에서 위의 3가지 용질분자는 모두 용질-용매상호작용을 우세하게 일으키고 있음을 알았다.

• Bulletin of the Korean Chemical Society
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• 제19권1호
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• pp.110-114
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• 1998

The hydrogen-bonding interactions between thioacetamide (TA) and urea derivatives such as tetramethylurea (TMU) and dimethyldiphenylurea (DMDPU) have been studied using near-infrared absorption spectroscopy. Thermodynamic parameters for the interactions between TA and urea derivatives were determined by analyzing the $v^{as}_{N-H}$+Amide Ⅱ combination band of TA at 1970 nm. The ΔH° values, indicating the intrinsic strength of hydrogen bonding, are - 23.0 kJ/mole and - 19.8 kJ/mol for TMU and DMDPU, respectively. This is well explained by the inductive effects of substituents. Ab initio molecular orbital calculations for the proton affinity of TMU, N,N-dimethylformamide (DMF), and N,N-dimethylacetamide (DMA) in gas phase have been carried out at HF/3-21G ad HF/6-31G(d) levels, showing that the proton affinity of TMU is larger than that of DMA, which agrees well the experimental results.