Journal of the Korean Chemical Society (대한화학회지)

Korean Chemical Society (대한화학회)
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Base Catalysed Hydrolysis of Aryl Phenylacetates

Aryl Phenylacetate류의 염기촉매 가수분해 반응

  • Duk-Young Cheong (Department of Chemistry Education, Kyungpook National University) ;
  • Soo-Dong Yoh (Department of Chemistry Education, Kyungpook National University) ;
  • Jae-Hwan Choi (Department of Science Education, Taegu Teacher's College) ;
  • Kwang-Taik Shim (Department of Industrial Chemistry, Ulsan Junior College)
  • 정덕영 (경북대학교 화학교육과) ;
  • 여수동 (경북대학교 화학교육과) ;
  • 최재환 (경북대학교 대구교육대학 과학교육과) ;
  • 심광택 (울산전문대학 공업화학과)
  • Published : 1992.06.20
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Abstract

The rates of hydrolysis of aryl phenylacetates have been measured in the presence of piperidine in 80% acetonitrile-20% water(v/v). For the electron withdrawing substituents of leaving group, the hydrolysis is catalyzed by a general base and the Hammett $\rho_{LG}$ and Bronsted value $\beta$ are 5.28 and -2.72 at $30^{\circ}C$, respectively. These high senstivities of Hammett and Bronsted values are $E1_{C}B$ mechanism. But in the electron donating ones, the hydrolysis is catalyzed by a specific base and $B_{AC}2 mechanism is predominated. $pK_{SH}'s of phenylacetic acid ester and rate constants of hydrolysis $k_1$, $k_{-1)$, $k_2$ were calculated.

80% acetonitrile-20% water(v/v) 용액에서 piperidine에 의한 aryl phenylacetate류의 가수분해 반응 속도를 측정하였다. 이탈되는 phnol의 치환기가 전자받개인 경우, 가수분해는 일반 염기촉매로 진행되며 $30^{\circ}C$에서 Hammett $\rho_{LG}$값은 5.28, Bronsted $\beta$값은 -2.72이었다. 이와 같이 매우 큰 Hammett 및 Bronsted 값은 이 반응이 $E1_{C}B$ 메카니즘으로 가수분해됨을 나타낸다. 한편, 전자주개 치환기의 경우는 특수 염기촉매에 의해 가수분해되며 $B_{AC}2 메카니즘이 우세하게 나타났다. Phenylacetic acid ester의 $pK_{SH}를 구하였으며, piperidine에 의한 ester 반응의 가수분해 속도 상수 $k_1$, $k_{-1)$, $k_2$도 계산하였다.

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