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1、四川大学硕士学位论文TheoreticalStu勿ontheBimolecularNucleophilicSubstitutionReactionsatNitrogenMajorPhysicalChemistryStudentJingYangTutorYiRenNucleophilicsubstitutionreactionisoneofthemostfundamentalchemicalreactions.Mostworkpublishedsofarwerethenucleophilicdisplacementreactionsatal
2、iphaticcarbon.Inthelastdecade,SN2reactionsatneutralnitrogenbecamethefocusofatentionbecauseoftheirsynthetic,biochemicalandtheoreticalimportance.SN2reactionatnitrogenwasstudiedtheoreticallyandsystematicallyusingtheDFTmethods.Thispaperistoexplorethereactionrule,revealsomesim
3、ilaritiesanddiferencesbetweenSN2reactionsatnitrogenandcarbon,researchthereactionmechanismsandinvestigateeachofthereactionpaths.Atthesametime,energybarriercurveswereestimatedsothatdynamicandthermodynamicparametersofchemicalreactionsandtherelationshipsbetweenenergyparameter
4、andstructurecouldbeobtained.Wehopetheresultscanprovidesometheoreticalbasesforexperimenters.Accordingtothediferenceofthenucleophilesandthesubstratesinvolvedinthereactions,wedivideourresearchprojectintothreeparts(Inthefollowingcontext,NuandLgareusedtodenotenucleophileandsub
5、strateinordertobeconvenientfordepiction):FirstpartisthereactionsofhalogenanionNuactedasnucleophileandneutralsubstrateNH2Lg.Thenucleophileandleaving-groupareallF-,Cl",Br',orF.Theequationcanbedescribedas:Nu"+NH2Lg”NH2Nu+Lg(Nu,Lg=F,Cl,Br,I)Thesecondpart,thereactionsofhalogen
6、ionNuactedasnucleophileandN(CH3)2Lg.Thenucleophileandleaving-grouparealsoF',Cl",Br,orT.The四川大学硕卜学位论文equationis:Nu+N(CH3)2Lg一N(CH3)2Nu+Lg一(Nu,Lg=F,Cl,Br,I)Thelast,neutralnucleophileNureactstoneutralsubstrateNHZLg.Inthispart,thenucleophileision-pairandtheLgconcludes:F-,Cl",
7、Br,andF.Theexpressionisasthefollow-ing:NIlX+NH,Lg一NH2X+MLg(X,Lg=F,Cl,Br,I;M=Li)AllcalculationswereperformedusingGAUSSIAN-98package.Allelectron(AE)calculationswerecarriedoutforthefirst-andsecond-periodelements,whileeffectivecorepotentials(ECP)wereusedforthird-andfour-perio
8、delements.ThemolecularstructureswereoptimizedusingtheDFTmethodsInspecific,westudiedthebimolecula
