Chical chemistr Reaction Kinetico 温度对反应速率影响的类型 通常有五种类型 7 5 (1)反应速率随温度的升高而逐渐加快,它们之 间呈指数关系,这类反应最为常见。 (2)开始时温度影响不大,到达一定极限时,反 应以爆炸的形式极快的进行
6 温度对反应速率影响的类型 r T r T r T r T r T (1) (2) (3) (4) (5) 通常有五种类型： （1）反应速率随温度的升高而逐渐加快，它们之 间呈指数关系，这类反应最为常见。 （2）开始时温度影响不大，到达一定极限时，反 应以爆炸的形式极快的进行。 Physical Chemistry Reaction Kinetics
Chical chemistr 温度对反应速率影响的类型 7 (3) (5) (3)在温度不太高时,速率随温度的升高而加 快,到达一定的温度,速率反而下降。如多相催 化反应和酶催化反应。 (4)速率在随温度升到某一高度时下降,再升 高温度,速率又迅速增加,可能发生了副反应。 (5)温度升高,速率反而下降。这种类型很少, 如一氧化氮氧化成二氧化氮
7 温度对反应速率影响的类型 （3）在温度不太高时，速率随温度的升高而加 快，到达一定的温度，速率反而下降。如多相催 化反应和酶催化反应。 （4）速率在随温度升到某一高度时下降，再升 高温度，速率又迅速增加，可能发生了副反应。 （5） 温度升高，速率反而下降。这种类型很少， 如一氧化氮氧化成二氧化氮。 r T r T r T r T r T (1) (2) (3) (4) (5) Physical Chemistry
Ch ical chemistr Reaction Kinetic Chain reactions Free- Radical polymerizations Chain reaction A series of steps: a reactive intermediate is consumed Reactants are converted to products Cycle is repeated The intermediate is regenerated The structure of chain reactions Chain carriers: the intermediates responsible for the propagation of a chain reaction Radical chain carriers the chain carriers are radicals Radicals: Species with unpaired electrons Ions, neutrons(in nuclear fission
8 Chain Reactions & Free-Radical Polymerizations Physical Chemistry A series of steps: a reactive intermediate is consumed Chain reaction Reactants are converted to products The intermediate is regenerated Cycle is repeated The structure of chain reactions Chain carriers: the intermediates responsible for the propagation of a chain reaction Radical chain carriers: the chain carriers are radicals Radicals: Species with unpaired electrons Ions, neutrons (in nuclear fission) Reaction Kinetics
Ch ical chemistr Reaction Kinetic Chain reactions Free- Radical polymerizations a chain reaction leads to a complicated rate law H+b→2HB d[Hbr] kh2[Br2]3/ dt [Br2]+k'LHBr] d[HBr]k[H2I[Br21/2 dt 1+j[HBr]/[ Br Derive the rate law for the formation of hBr according to the mechanism given below
9 Physical Chemistry Chain Reactions & Free-Radical Polymerizations A chain reaction leads to a complicated rate law. H Br 2HBr 2 + 2 → [ ] '[ ] [ ] [ ][ ] 2 3/ 2 2 2 Br k HBr k H Br dt d HBr + = 1 [ ]/[ ] [ ] [ ][ ] 2 1/ 2 2 2 j HBr Br k H Br dt d HBr + = Derive the rate law for the formation of HBr according to the mechanism given below. Reaction Kinetics
Ch ical chemistr Reaction Kinetic Chain reactions Free- Radical polymerizations The following radical chain mechanism has been proposed a initiation B→2b· r=kalBr2l (b) Propagation:Br·+H2→>BB+H =kb[B°[H2] H+B→HB+b· r=kblH-LBr2l (C) Retardation:H·+B→H2+B· kchollHBrI (d) Termination:B·+·B+M→B2+Mr=kJ|Br2 The third body m removes the energy of recombination; the constant concentration of m has been absorbed into the rate constant
10 Physical Chemistry Chain Reactions & Free-Radical Polymerizations The following radical chain mechanism has been proposed: (a) Initiation: Br →2Br • 2 [ ] Br2 r k = a (b) Propagation: Br •+H → HBr + H • 2 [ ][ ] Br H2 r kb = • H •+Br → HBr + Br • 2 [ ][ ] 2 ' r k H Br b = • (c) Retardation: H •+HBr → H + Br • 2 r k [H ][HBr] c = • (d) Termination: Br •+•Br + M → Br2 + M 2 r = k [Br•] d The third body M removes the energy of recombination; the constant concentration of M has been absorbed into the rate constant. Reaction Kinetics