CAJ | 학술논문

一般情况下双取代乙烯衍生物的反式构象要比顺式构象稳定.但是例外也存在,例如1,2-二氟乙烯和1,2-二氯乙烯.这种双取代乙烯衍生物顺式构象的超常稳定性被称之为顺式效应.该效应的起源和本质目前仍没有定论.本文以12个体系(XHC=CHY (X, Y=F, Cl, Br, CN, CH3, C2H6, OCH3))为例,对顺式效应的有效性、起源和本质进行系统的密度泛函理论研究,其中9个体系存在顺式效应,另外3个为正常体系没有该效应.采用一系列泛函和基组研究其有效性,并运用四种分析手段,如自然键轨道(NBO)、能量分量分析(EDA)、密度泛函活性理论(DFRT)和非共价相互作用(NCI)分析,剖析该效应的起源和本质.发现在顺式构象的两个取代基之间存在一种微弱的非共价相互吸引作用.能量分析表明,静电效应、立体效应等对顺式效应的存在都起着重要作用,但是它们均不能单独用来解释顺式效应的起源.也就是说顺式效应没有一个简单的起源,它是多种作用合力的结果.本文采用双变量解释得到比较合理的相关回归系数R2=0.86-0.87,较好地解释了顺式效应的本质和起源.
일반정황하쌍취대을희연생물적반식구상요비순식구상은정.단시예외야존재,례여1,2-이불을희화1,2-이록을희.저충쌍취대을희연생물순식구상적초상은정성피칭지위순식효응.해효응적기원화본질목전잉몰유정론.본문이12개체계(XHC=CHY (X, Y=F, Cl, Br, CN, CH3, C2H6, OCH3))위례,대순식효응적유효성、기원화본질진행계통적밀도범함이론연구,기중9개체계존재순식효응,령외3개위정상체계몰유해효응.채용일계렬범함화기조연구기유효성,병운용사충분석수단,여자연건궤도(NBO)、능량분량분석(EDA)、밀도범함활성이론(DFRT)화비공개상호작용(NCI)분석,부석해효응적기원화본질.발현재순식구상적량개취대기지간존재일충미약적비공개상호흡인작용.능량분석표명,정전효응、입체효응등대순식효응적존재도기착중요작용,단시타문균불능단독용래해석순식효응적기원.야취시설순식효응몰유일개간단적기원,타시다충작용합력적결과.본문채용쌍변량해석득도비교합리적상관회귀계수R2=0.86-0.87,교호지해석료순식효응적본질화기원.
It is wel known that the trans isomer of a doubly substituted ethylene is more stable than its cis counterpart because of the more favorable electrostatic and steric interactions in the trans conformer. Exceptions do exist nevertheless. 1,2-Difluoroethylene is such an example, so is 1,2-dichloroethylene. The unusual stability of the cis isomer of these doubly substituted ethylene compounds is referred to as the cis-effect, whose nature and origin are stil not wel understood. In this work, using 12 simple molecules, XHC=CHY (X, Y=F, Cl, Br, CN, CH3, OCH3, C2H6), as examples, we perform systematic studies to investigate the validity, nature, and origin of this effect. Among the systems studied, 9 of them exhibit the @@@@existence of the cis-effect and the remaining 3 systems are conventional systems used for the comparison purpose. We employ a large number of density functionals and basis sets to confirm its validity. We also use a few wel-established analysis tools, such as natural bond orbital (NBO), energy decomposition analysis (EDA), density functional reactivity theory (DFRT), and non-covalent interaction (NCI) analysis, to pinpoint its nature and origin. We found that there exists a weak but attractive non-covalent interaction between the two substituting groups in the cis conformer. We also found that electrostatic, steric, and kinetic energies al play important roles for the validity of the cis-effect. Nevertheless, none of these quantities can be solely used as the single reason governing the general validity of the cis-effect, suggesting that the origin of the effect is complicated and its validity results from compound interactions from a number of interactions. In this work, we employ two-variable explanations to justify its validity through the electrostatic interaction plus steric effect or kinetic energy, with which reasonable fits with R2=0.86-0.87 were obtained.