Theoretical Studies on the Cationic Polymerization Mechanism of Oxetanes(Ⅱ) 


Vol. 40,  No. 1, pp. 11-19, Feb.  1996


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  Abstract

에너지기인 azido기(-CH2N3), nitrato기(-CH2ONO2)로 치환된 옥세탄의 단량체를 BF3촉매하의 공중합에 관해서 반경험적인 MINDO/3, MNDO, AM1 그리고 HF/3-21G 방법 등을 사용하여 이론적으로 고찰하였다. 옥세탄 치환체와 BF3 이분자 착물의 입체적, 정전기적 구조를 이론적으로 설명할 수 있다. 옥세탄의 공중합 성장단계에서 반응성은 옥세탄의 반응중심 탄소의 양전하 크기와 옥세탄 성장단계의 친전자체의 낮은 LUMO에너지에 좌우됨이 예측된다. 옥세탄의 공중합 반응성비는 계산치와 실험값이 일치하는 랜덤 공중합 반응이다. 평형상태의 고리형 oxonium 이온과 열린 carbenium 이온의 농도 크기가 반응 메카니즘의 결정단계이며, 형태와 계산을 기초로하여 빠른 평형을 에상하여 볼 때 선폴리머 성장단계에서 SN1 메카니즘이 SN2 메카니즘보다 빠르게 반응할 것으로 예측된다. The cationic polymerization of energetic substituted oxetanes which have pendant energetic group such as azido and nitrato are investigated theoretically, using semiempirical HF/3-21G, MINDO/3, MNDO and AM1 method. The stereo- and electronic structure of binary molecular complex composed of energetic substituted oxetane and boron trifluoride can be explain by molecular orbital theory. The reactivity of propagation in the copolymerization of oxetanes can be presented by the positive charge on carbon(C2) atom of oxetane and energy level of the lowest unoccupied molecular orbital(LUMO) of propagating species of oxetanes. The reactivity ratios for copolymerization of oxetanes are a random copolymer-zation which is agree with MO calculated and experimental results. The relative equlibrium concentration of cyclic oxonium and open carbenium ions is found to be a major determinant of mechanism, owing to the rapid equilibrium of these cation forms and the expectation based on calculation that in the prepolymer propagation step, SN1 mechanism will be at least as fast as that for SN2 mechanism.

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  Cite this article

[IEEE Style]

J. Park, S. Cho, S. Park, Y. Cheun, "Theoretical Studies on the Cationic Polymerization Mechanism of Oxetanes(Ⅱ)," Journal of the Korean Chemical Society, vol. 40, no. 1, pp. 11-19, 1996. DOI: .

[ACM Style]

Jeong-Hwan Park, Sung-Dong Cho, Seong-Kyu Park, and Young-Gu Cheun. 1996. Theoretical Studies on the Cationic Polymerization Mechanism of Oxetanes(Ⅱ). Journal of the Korean Chemical Society, 40, 1, (1996), 11-19. DOI: .

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