Journal of the Korean Chemical Society (대한화학회지)

Korean Chemical Society (대한화학회)
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Partial molal volumes of n-alkylamine hydrochlorides in methanol-water mixtures

메탄올-물 혼합액에서의 n-Alkylamine 염산염의 분 몰랄 부피

  • Uhm, Tae-Sup (Dept. of Chemistry, Dong-A University) ;
  • Yoon, Sang-Ki (Dept. of Chemistry, Dong-A University) ;
  • Lee, Ik-Choon (Dept. of Applied Chemistry, College of Engineering, Seoul National University)
  • 엄태섭 (동아대학교 문리대 화학과) ;
  • 윤상기 (동아대학교 문리대 화학과) ;
  • 이익춘 (서울대학교 공대 응용화학과)
  • Published : 19700300
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Abstract

The apparent molal volumes(${\phi}_v$) of the homologous salts $RNH_3Cl$, where R varies from methyl-($CH_{3^-}$) to n-butyl-(n-$C_4H_{9^-}$) in a series of methanol-water mixtures have been determined at 30$^{\circ}C$ by means of a float method to fifth decimal places down to 0.01 m. The values of ${\phi}_r$ extrapolated to infinite dilution give partial molal volumes $\bar{V}^{\circ}$which varies considerably in accordance with the solvent composition. that is, mole fraction of methanol. The experimental results are discussed in terms of the varying size and charge effect, hydrophobic nature of the solute species, and also the additivity relationship between successive homologous and the structure of the binary solvent. The results indicate that at 0.1 mole fraction methanol the enhanced structuredness of water cause a minimum in the partial molal volumes of cations $\bar{V}^{\circ}_+$, while at 0.4 mole fraction the solvent structure is such that the free volume is a minimum but the effect of electrostriction is a maximum.

Methyl에서 n-butyl까지의 n-alkylamine 염산염동족체($RNH_3Cl$)의 "겉보기몰랄부피"(apparent molal volume)${\phi}_v$를 30$^{\circ}C$에서 여러가지 조성의 methanol-물 혼합액을 써서 측정하였다. 아민염의 농도는 0.01M까지, 밀도는 부력법을 적용하여 소수점이하 5위까지 택하였다. 관측된 ${\phi}_v$값을 무한대의 농도 쪽으로 extapolation하여 "분몰랄부피"(partial molal volume)$\bar{V}^{\circ}$V를 구하였다. 실험결과는 용질입자의 크기, charge 및 hydrophobic effect등에 관하여 논의되었고 또한 동족체간에일정한 몰랄부피차(${\Delta}\bar{V}^{\circ}$)를 갖는다는 사실과 아울러 혼합용매의 구조에 대하여도 검토하였다. 메탄올-물 0.1몰분율(m.f.)에서는 물의 구조증대로 cation의 "분몰랄부피($\bar{V}^{\circ}_+$)가 최소이고, 한편 0.4m.f. 에서는 charge 효과에 의한 electrostriction effect의 최대화 free volume이 최소라는 사실들이 관찰되었다.

Keywords

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