Nucleophilic Substitution at a Carbooyl Carbon Atom (ⅩI). Solvolysis of Methylchloroformate and Its Thioanalogues in Methanol, Ethanol and Ethanol-Water Mixtures

카르보닐탄소원자의 친핵성 치환반응 (제11보). 메탄올, 에탄올 및 에탄올-물 혼합용매중에서 메틸클로로훠메이트와 그 티오유도체들의 가용매분해반응에 관한 연구

  • Sangmoo La (Department of Chemical Engineering, Ajou Institute of Technology) ;
  • Koh Kyeong Shin (Department of Chemistry, Chung-ang University) ;
  • Ikchoon Lee (Department of Chemistry, Inha University)
  • 나상무 (아주공과대학 화학공학과) ;
  • 고경신 (중앙대학교 문리과대학 화학과) ;
  • 이익춘 (인하대학교 이과대학 화학과)
  • Published : 19800230

Abstract

Solvolysis rate constants for methylchloroformate, methylthionochloroformate, methylthiolchloroformate and methyldithiochloroformate have been determined conductometrically in methanol, ethanol and ethanol-water mixtures and activation parameters have been derived. Results show that methylchloroformate solvolyzes through $S_N2$ process while methyldithiochloroformate solvolyzes by $S_N1$ process in all the solvent systems. The rate of hydrolysis decreased in the order, $CH_3S(CS)Cl>CH_3S(CO)Cl>CH_3O(CS)Cl>CH_3O(CO)Cl$ which corresponds to the order of decreasing $S_N1$ character. In methanol, $CH_3S(CS)Cl$ solvolyzed via the $S_N1$ mechanism while the others solvolyzed via the $S_N2$ process. In ethanol, however, $S_N2$ character was dominant for all the compounds, except methyldithiochloroformate, for which $S_N1$ character was still strong enough to accelerate the rate of ethanolysis. In ethanol-water mixtures, $CH_3S(CS)Cl$ and $CH_3S(CS)Cl$ solvolyzed via $S_N2$ process in ethanol-rich region while the $S_N1$ character increased greatly in water-rich region for the solvolysis of these compounds. The order of $S_N1$ character for solvolysis in water-rich region was the same as the order of hydrolysis rate.

Keywords

References

  1. Can. J. Chem. v.50 D. M. McKinnon;A. Queen
  2. J. Korean Chem. Soc. v.16 I. Lee(et al.)
  3. J. Amer. Chem. Soc. v.83 H. C. Godt, Jr.;R. E. Wann
  4. Ber. Deut. Chem. Ges. v.58 W. Autenieth;H. Hefner
  5. Bull. Soc. Chim. France v.1 H. Rivier
  6. Phil. Mag. v.2 E. A. Guggenheim
  7. Acta. Chem. Scand. v.19 A. Kivinen
  8. J. Amer. Chem. Soc. v.70 E. Grunwald;Winstein
  9. Advances in Phys. Org. Chem. v.14 T. W. Bentley;P. R. R. Schleyer
  10. Tetrahedron v.33 A. Arcoria(et al.)