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Journal of the Korean Chemical Society (JKCS)

ISSN 1017-2548(Print)
ISSN 2234-8530(Online)
Volume 31, Number 2
JKCSEZ 31(2)
April 20, 1987 

Theoretical Studies on the Nucleophilic Substitution Reaction of Methyl Thiocyanate

티오시안산 메틸의 친핵성치환 반응에 관한 이론적 연구
Ikchoon Lee, Chang Hyun Song

이익춘, 송창현
반경험적 분자궤도함수법인 MNDO방법을 사용하여 SH-, CN- 그리고 OH-와 메틸티오시아네이트(MTC)의 친핵성치환반응을 연구하였다. 각 친핵체에 대해 MTC세반응중심의 계산된 포텐샬에너지곡면(Intrinsic term)과 전이상태에서의 친핵체의 음전하크기(Solvent term)을 고려하여 가스상과 용액상에 대한 선택성을 논의하였다. 결과로써 SH-에 대해서는 선택성의 두 성분 모두 4-methylbenzylthiocyanate (4-MBTC)에 대해 얻어진 실험결과와 일치한반면 CN-의 경우에는 고유항(Intrinsic term)의 선택성만이 일치하였고 OH-의 경우에는 두 항중 어느것도 실험결과로 얻은 선택성과 일치하지 않았다. 정류점에서 모든 종에 대한 MNDO최적화된 구조들을 밝혔다.

Nucleophilic substitution reactions of methylthiocyanate(MTC) with anion nucleophiles, SH-, CN- and OH-, have been investigated using MNDO method. For the three reaction centers of MTC, gas-phase and solution-phase selectivities are discussed for each nucleophile by considering potential energy profiles calculated(intrinsic term) and magnitudes of negative charge on the nucleophile at the transition state(solvation term). It was found that both components of the selectivity for SH- agreed with the experimental results obtained for 4-methylbenzylthiocyanate (4-MBTC), but the selectivity order for CN- was found to agree only with that of the intrinsic term and that of OH- disagreed with any theoretical selectivity order. The MNDO optimized geometries for all species at the stationary points are reported.

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