【doc】NH2自由基氢转移反应的IRC和速率常数的理论研究

【doc】NH2自由基氢转移反应的IRC和速率常数的理论研究 NH2自由基氢转移反应的IRC和速率常数 的理论研究 I996年6爿 第31卷第2期 北京师范大学(自然科学版) JournalofBeijingNormalUni'~ersityfNaturalScience) JunJ996 ?.31NO2 ABINITIOS1rI)Dl?'5oNTHE?【CANDRATE CONSTANTSF0RTHEHYDROGENABSTRACTION REACTIONOFAMIDOGENRADI(:ALs XuZhenfengFangDecaiFuXiaoyuan (pa^?【ofCl,,emistt~.BeijingNormalUrdversity,100875BeijingPRc) K呻ldTnidO鲫radical;IRC:talecorls'lailt;abinitio:quantumtopology ThehydrogenatomabstractionreactionNH!+NH!一NH+NHjisaveryimportantpro- cessiOthey_jas-ptmsetherma1d~'ornpositionandmmbustionofammonia.1'hereactionmecha. nismofthisradicalreactionhasbeenstudiedbyseveFd1researchersexperimentaUyI21.Unt_] now.toourknowledge.theoreticalstudyhasnotbeenreportedforthisreactionyet.Therefo itisnecessarytostudythedynamicalpropertiesofthereactiontheoreci~lly WeemployspinunrestrictedsecondorderMoller-Plessetperturbationtheory(shortfor UMP21at6_31lGlevelandenergygradientmethodtooptimizethegeometriesofthereactants. transitionstatefrs),andproductsThe"IShasbeencharacterizedbyvibrationalanaasonly oneimaginaryvibrationalfrequency(i2044.7cnl) Figlshowsthestructureandthenunl- beringsystem.ItisofCssymmetry.Theenergypro- 61emlculatedbyusingtheIRCtheoryisgivenin Fig.2.Fromtheenergycurve,weearlseethatthe forwardandreversepotentialbarriersare27.07and H 023 l】O.75kJ?molI.respectively.BycomparingwithFigIThegeomet/~'oflhe(ranstlt?1slate theexperimentalactivationenergyandenthalpy. itisbondlengthinrimandbondangleind锷r foundthatthetheoreti~lforw'drdpotentialbarrier(27.07kJ?mol一1iSlessthantheexper[. mentalone(41.82kJ?mol),andthetheoretimlheatofreactionr83.68kJ?mol)isslightly greaterthanthee~peritrentalone(70.09kJ?1330r.1. InordertorevealtheprocessofbothfonningtheH'一N'bondandbreakingthe N,Hbond,wehavealsomvesfigatedthisreactionbyUStheBader-typetopological pmpenofchargedensitydistribution)ofthegeometriesalongIRCTheLaplacianofchar- gedensityfvP1showsthattherangeofthestructuralWansifionstateofthisreactionloeates atabout:OO3,O_33.Whell>O03,itappearstobethecovalentcombinationbetweenH andN.s>033,theeovalenoepropertybetweenHandNdisappearscompletely. 'SupportedbyiheNationalNaturalSdenceFundationofChina Recev.ed:1996-01—22I' {I l , 斯际抓LliNH,f基氯转移反应的]RC嗣I建率常数时;仑研究 Thereactionlco0nstarlls,?】?calcu一 1atedbvusingcano11[ca【variat[ona1transition' slatetheor'viC?,andsma{I--,cutwaItwe tunnelingapproximalion(sc~AG)TheIoca tioi1oftheCVTtransitionstateisabout S=0.05,O.06Thethoacetica1r'3.teconstants aretabulatedinFable】.Wherethesvmbol? standsfortheconventionaItpansitionstatethe一 0t'yItjSdearthatthetheomticalratecon— Stafttsagreewel1withtheexperimentalresults OVCFthetempemturerange!)0,1900K 一 2l0 )eI础pmnkol "111ee【 12 hereactionalongIRC TlRe~'dmratem嘞kl0',cin,一tool'?S IMdkrJAB0nxjnCTMochanismandmodelingOt"nitrogenchemistryincombustionPK~g ressEnergy' Combt~lSci,I989,I5287 Da\.q,dsonj)FKohse-HoLnghaLLSK.ChangAYetalApyrolysismechanismIbrammonial nlJ ChemKinel1990.22513 3JsN山K,Momktln~tKKon~omickJ NCfltt0dHTCHCH一 +H 4tderRWFAIL)『njfIIIXIO[O,~LZIL'M 5Trul1brDGIsaaeson CRCPce.t5砸 AneLntrinsicreactionCoordinate:Anab】nitioealculat[onrHCN JChemPh3s1977662153 4UntheoD~Oxford:(~'eealon1990 BCTheoryofc]~ml-'calrffdctiOlldynatrficsVol4-呦RalonFL: 6D一/, NH!自由基氢转移反应的IRC和速率常数的理论研究 /1,至羔蔓,壁殳尊孝怨06/.t 厂7,I化上化学岳101)875IL,帮作打39,男iip0r~) 摘要采ill-g"七学从弹时NH自fjI基氧转{善'i成NH+NH-NH+NH讨l士甲屹研究 得到L逆眨Ii抖垒别址170,}10.75kJ?ITIO]'利J日[RC伦l耍分过渡忐婵i亡汁"Cf,Ss?J与史黄相 比较的门'论I空牛牧.ii;l1:蔓僻.1笫十旬廿毪苦l域.jr进rJi,J芑. 关键词 分类号 H.Ii聪— 皇翌皇竺:c_),堡童堂墼:兰兰:.量f拓扑学 一二鼍