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Journal of the Korean Chemical Society (JKCS)

ISSN 1017-2548(Print)
ISSN 2234-8530(Online)
Volume 22, Number 6
JKCSEZ 22(6)
December 20, 1978 

The Kinetics and Activation Energy for the Mutarotation or Optically Active Poly(trans-5-methyl-L-proline

광활성 Poly(trans-5-methyl-L-proline)의 변광회전에 대한 반응속도와 활성화에너지
Man Jung Han

여러 농도와 온도에서 Poly(trans-5-methyl-L-proline)을 trifluoroethanol 용매에서 정방향 변광회전, trifluoroethanol-n-butanol (1 : 4) 용매에서 역방향 변광회전을 시키면서 변광회전속도를 측정하였다. 이 두 방향의 변광회전 현상은 폴리머농도에 대하여 1차 반응이었다. 활성화에너지를 측정하기 위하여 변형된 Arrhenius식을 유도하였는데 이식은 물리적 성질과 농도와의 관계나 반응차수가 불확실한 반응에 이용할 수 있다. 정방향과 역방향 변광회전의 활성화에너지는 잔기몰당 각기 32.5와 33.5kcal이었고 이값은 polyproline 변광회전의 활성화에너지 (아미드결합의 공명에너지)보다 잔기몰당 10kcal가 높다. 이 과량의 활성화에너지는 폴리머아미드 결합이 시스-트란스 이성질화현상이 일어날 때 카르보닐기와 메틸기 사이에 생기는 입체장애에 의한 것이다.

The rates of the forward mutarotation of poly(trans-5-methyl-L-proline) in trifluoro-ethanol and of the reverse mutarotation in trifluoroethanol-n-butanol (1:4 v/v) have been measured at a number of temperatures and polymer concentrations. It was found that both mutarotations are of first-order with respect to the polymer concentration. A modified Arrhenius equation to evalute the activation energy was derived for the reaction kinetics, in which the relation between the measured physical properties and concentration, and the order of tle reaction are uncertain. The activation energies for the forward and reverse mutarotation were found to be 32.5 and 33.5 kcal per residue mole, respectively, which are about 10 kcal per residue mole higher than the Ea for the mutarotation of polyproline (the resonance energy of amide bonds). The excessive quantity of the activation energy was attributed to the steric barrier between carbonyl and methyl groups during the cis-trans isomerization of amide bonds in the polymer.

386 - 395
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