CAJ | 학술논문

采用密度泛函理论对以偶氮二异丁腈为引发剂形成的丙烯腈单体自由基（CH3）2（CN）C-CH2-（CN）CH的终止方式反应机理进行研究。先用B3LYP/6-31G（d）基组对反应物、偶合中间体、过渡态、歧化产物的几何构型进行优化，并计算了各物种经过零点能校正后的总能量，红外频率和电子结构，同时对过渡态结构进行了验证。研究结果表明，反应物先通过自由基的偶合终止方式形成偶合中间体a，再由此经过氢迁移、裂解等机理得到歧化终止产物 P [p1（CH3）2（CN ） C CH CHCN ＋ p2（CH3）2（CN ）C-CH2-CH2CN]。双自由基发生偶合和歧化终止反应分别形成偶合中间体a和歧化终止产物P均为放热反应，且偶合产物有着更低的能量。反应过程的速控步骤a→T S→P在常温下的速率常数表示为 k（298.15 K ）＝2.71×10-59。歧化终止反应随着反应温度的升高易于进行，歧化产物所占的比例也增加。通过对反应过程各物种红外谱图的分析，说明自由基在整个终止反应的化学变化，同时分析了 HOMO-LUMO电子密度分布的信息，验证丙烯腈双自由基偶合终止方式和各物种结构的准确性。
채용밀도범함이론대이우담이이정정위인발제형성적병희정단체자유기（CH3）2（CN）C-CH2-（CN）CH적종지방식반응궤리진행연구。선용B3LYP/6-31G（d）기조대반응물、우합중간체、과도태、기화산물적궤하구형진행우화，병계산료각물충경과영점능교정후적총능량，홍외빈솔화전자결구，동시대과도태결구진행료험증。연구결과표명，반응물선통과자유기적우합종지방식형성우합중간체a，재유차경과경천이、렬해등궤리득도기화종지산물 P [p1（CH3）2（CN ） C CH CHCN ＋ p2（CH3）2（CN ）C-CH2-CH2CN]。쌍자유기발생우합화기화종지반응분별형성우합중간체a화기화종지산물P균위방열반응，차우합산물유착경저적능량。반응과정적속공보취a→T S→P재상온하적속솔상수표시위 k（298.15 K ）＝2.71×10-59。기화종지반응수착반응온도적승고역우진행，기화산물소점적비례야증가。통과대반응과정각물충홍외보도적분석，설명자유기재정개종지반응적화학변화，동시분석료 HOMO-LUMO전자밀도분포적신식，험증병희정쌍자유기우합종지방식화각물충결구적준학성。
By using the density functional theory ,the study of reaction termination mechanism of two (CH3 )2 (CN)C-CH2 -(CN)CH was carried out at the B3LYP/6-31G(d) level .The initiator AIBN was used .Reactants ,coupled intermediates ,transi-tion states and disproportionation products were optimized at the B 3LYP/6-31G(d) level .Then the total energies corrected by zero-point energy ,vibrational frequencies and electronic structures were calculated ,the transition states structure was also veri-fied .The results show that it forms the energy-rich adducts a through the coupling termination .Then ,the disproportionation product P[p1(CH3)2(CN) C CH CHCN + p2(CH3)2(CN)C-CH2 -CH2CN]formed via hydrogen shift and dissociation . The reactions of coupling termination and disproportionation termination are all exothermic reactions ,and the coupled product has lower energy .The rate constant of step a→ TS→ P is k(298.15 K)=2.71 × 10-59 at the normal atmospheric temperature . Disproportionation termination occurs more easily with the reaction temperature rising ,so the proportion of disproportionation products is increasing .Also ,the analysis of infrared spectrogram of each species in reaction process shows chemical change of free radicals in the whole termination reaction .The authors give the HOMO-LUMO in this paper to verify the accuracy of biradi-cal coupling termination and structures .It has important guiding significance to controlling the free radicals termination methods of acrylonitrile monomer .