89.1 Introduction of Chemical Kinetics Levine p. 528-529 17.1 reaction kinetics rate of reaction rate laws reaction mechanism
§9.1 Introduction of Chemical Kinetics Levine p. 528-529 17.1 reaction kinetics rate of reaction, rate laws, reaction mechanism
89.1 Introduction of Chemical Kinetics (1)What is chemical kinetics? (1)What do we concern about a chemical reaction? N,+3H,C1040m 22NH3 1)Stoichiometric: Reactants, products and their ratios, balance of the equation 2)Thermodynamic: Direction; equilibrium; yields. 3)Kinetic: Rate and mechanism rate; catalyst; mechanism; selectivity
(1) What is chemical kinetics？ 1) Stoichiometric: Reactants, products and their ratios, balance of the equation. 3) Kinetic: Rate and mechanism. rate; catalyst; mechanism; selectivity. 2) Thermodynamic: Direction; equilibrium; yields. (1) What do we concern about a chemical reaction? §9.1 Introduction of Chemical Kinetics
89.1 Introduction of Chemical Kinetics (1)What is chemical kinetics? (2)Definition: a branch of chemistry that concerns reaction rate and reaction mechanism. (3) Brief advancements of chemical kinetics (1)1850s-1910s: Empirical kinetics (2)1910s-1950s: Elementary reactions (3)1950s-present: Microscopic kinetics: molecular dynamics, state-to state dynamics
(3) Brief advancements of chemical kinetics (1) 1850s-1910s: Empirical kinetics (2) 1910s-1950s: Elementary reactions; (3) 1950s-present: Microscopic kinetics: molecular dynamics, state-tostate dynamics (2) Definition: A branch of chemistry that concerns reaction rate and reaction mechanism. (1) What is chemical kinetics？ §9.1 Introduction of Chemical Kinetics
89.1 Introduction of Chemical Kinetics (1)What is chemical kinetics? (4)Main concerns of chemical kinetics 1)Reaction rate: influential factors of reaction rate, such as concentration, temperature catalysts etc. --rate law 2)Reaction mechanism: the series of steps by which a reaction takes place. 3)structure-dependence of reactivity: the correlation between molecular structure and reaction potentiality(structural chemistry)
(4) Main concerns of chemical kinetics: 1) Reaction rate: influential factors of reaction rate, such as concentration, temperature, catalysts, etc. -- rate law. 2) Reaction mechanism: the series of steps by which a reaction takes place. 3) structure-dependence of reactivity: the correlation between molecular structure and reaction potentiality (structural chemistry). (1) What is chemical kinetics？ §9.1 Introduction of Chemical Kinetics
89.1 Introduction of Chemical Kinetics (2)Elementary reaction H2+ Br2=2HBr H+=2HI 1)Br2+M=2Br·+M 1)L2+M=2I+M 2)Br·+H2=HBr+H 2)2I+H2=2H 3)H+ Br2=HBr+ Br. 4)H+ HBr=H,+ Br. multistep reaction 5)2Br+M=Br2+ M Elementary reaction: the reaction that completes in one act Intermediate: the species formed in one step and consumed in a subsequent step and never seen as a product
H2 + I2 = 2HI 1) I2 +M = 2I + M 2) 2I + H2 = 2HI H2 + Br2 = 2HBr 1) Br2 + M = 2Br + M 2) Br + H2 = HBr + H 3) H + Br2 = HBr + Br 4) H + HBr = H2 + Br 5) 2Br + M = Br2 + M multistep reaction Elementary reaction: the reaction that completes in one act Intermediate: the species formed in one step and consumed in a subsequent step and never seen as a product (2) Elementary reaction §9.1 Introduction of Chemical Kinetics
89.1 Introduction of Chemical Kinetics (2) Elementary reaction (2) Category of elementary reactions According to the number of molecules (moiety) involved in the reaction, elementary reactions can be divided into three kinds: unimolecular reaction: 12=21 bimolecular reaction: Br+H,=HBr+H termolecular reaction: 2I+H= 2HI Accurate definition and convention
(2) Category of elementary reactions According to the number of molecules (moiety) involved in the reaction, elementary reactions can be divided into three kinds: unimolecular reaction: I2 = 2I bimolecular reaction: Br + H2 = HBr + H termolecular reaction: 2I + H2 = 2HI (2) Elementary reaction §9.1 Introduction of Chemical Kinetics Accurate definition and convention
89.1 Introduction of Chemical Kinetics (3)Overall reaction (1) Category of chemical reactions According to the number of elementary reactions involved, the overall reaction can be classified into simple reaction Diels-Alder addition Overall reaction ethylene butadiene cyclohexene complex reaction
According to the number of elementary reactions involved, the overall reaction can be classified into: Ethylene butadiene cyclohexene simple reaction Diels-Alder addition: complex reaction Overall reaction (3) Overall reaction (1) Category of chemical reactions §9.1 Introduction of Chemical Kinetics
89.1 Introduction of Chemical Kinetics (4) Reaction Mechanism 1)Br2=2 Br Reaction mechanism/pathway 2)Br+h,=hBr+ h the detailed way by which the reactants 3)H+ Br,= HBr+ br are converted into products, or the series of 4)H+HBr=H,+ Br steps by which a reaction takes place 52 Br= Bi The sum of the elementary reactions and their series
Reaction mechanism/pathway: the detailed way by which the reactants are converted into products, or the series of steps by which a reaction takes place. The sum of the elementary reactions and their series. (4) Reaction Mechanism 1) Br2 = 2 Br 2) Br + H2 = HBr + H 3) H + Br2 = HBr + Br 4) H + HBr = H2 + Br 5) 2 Br = Br2 §9.1 Introduction of Chemical Kinetics
89.1 Introduction of Chemical Kinetics (4) Reaction Mechanism Find differences between mechanisms described in physical chemistry and in organic chemistry Hydrolysis of nitrile NH -H H R H R H2O OH NaOH NNa What is different?
Hydrolysis of nitrile: Find differences between mechanisms described in physical chemistry and in organic chemistry. (4) Reaction Mechanism §9.1 Introduction of Chemical Kinetics What is different?