1. Video Tutorial on Rate Determining Step,Reaction Mechanism and Order of Reaction Prepared by Lawrence Kok http://lawrencekok.blogspot.com

2. Video on Reaction Mechanism and Rate Determining StepsRate determining steps demoOrder of reactionReaction Mechanism for rate determining step Reaction Mechanism for rate determining step 3. Reaction Mechanism Reaction Mechanism Order reaction can only be determined experimentally and cannot be predicted from stoichiometry Mechanism cannot be proven correct, as we can only propose/suggest a most likely mechanism Sequence of reaction steps involving individual/elementary steps from reactants to products Elementary steps involve slow and fast steps, which may contain intermediate species. Mechanism must account for overall stoichiometry of reaction Keywords Molecularity Number of species involve in an elementary step Unimolecular 1 species involve in an elementary step A B+CRate = k[A] Bimolecular 2 species involve in an elementary step A+BC+DRate = k[A][B] Termolecular 3 species involve in an elementary stepA+B+CD+ERate = k[A][B][C] Rate Determining Step (RDS) Slowest step which has the highest activation energy, which limits the rate of overall reaction. Its rate law represent the rate law for overall reactionDifference between Intermediates and Transition statesIntermediatesTransition StateExist for a whileOnly in transient state Occurs at PE minimum Occurs at PE maximumFormed in 1 step andExist through every comsumed instep involving bondsubsequent stepbreaking/making 4. Criteria for proposed mechanisms Mechanism must account for overall stoichiometry of reaction and experimentally determined Rate Law Elementary steps MUST add up to overall balanced equation Elementary steps must be reasonable/likely, which involve unimolecular/bimolecular collision(Termolecular collision, 3 molecules colliding together is unlikely due to probability and orientation factors) Mechanism MUST correlate with Rate Law2NO2 + F2 2NO2F Rate Law = k[NO2]1[F2 ]1Rate is 1st order to NO2 and F2What is the mechanism which correlates with this Rate Law ?Step 1 is rate determining step (slow step)2NO2 + F2 2NO2F Expt Determined Rate Law = k[NO2]1[F2]1Propose mechanism : StepMolecularityRate law for elementary step NO2 + F2 NO2F + F Slow (RDS) 2 Rate = k[NO2]1[F2]1+ NO2 + F NO2FFast 2 Rate = k[NO2]1[F]1 2NO2 + F2 2NO2F (overall balance equation)CHECK if the proposed mechanism correct?1. Each steps adds up to overall balanced equation2. Each step is likely (involve Uni/Bimolecular collision)3. Slow step (RDS) is the same as experimentally Rate Law 5. Criteria for proposed mechanisms Mechanism must account for overall stoichiometry of reaction and experimentally determined Rate Law Elementary steps MUST add up to overall balanced equation Elementary steps must be reasonable/likely, which involve unimolecular/bimolecular collision(Termolecular collision, 3 molecules colliding together is unlikely due to probability and orientation factors) Mechanism MUST correlate with Rate Law2NO2 + F2 2NO2F Rate Law = k[NO2]1[F2 ]1Rate is 1st order to NO2 and F2What is the mechanism which correlates with this Rate Law ?Step 1 is rate determining step (slow step)2NO2 + F2 2NO2F Expt Determined Rate Law = k[NO2]1[F2]1Propose mechanism : StepMolecularityRate law for elementary step NO2 + F2 NO2F + F Slow (RDS) 2 Rate = k[NO2]1[F2]1+ NO2 + F NO2FFast 2 Rate = k[NO2]1[F]1 2NO2 + F2 2NO2F (overall balance equation)CHECK if the proposed mechanism correct?1. Each steps adds up to overall balanced equation2. Each step is likely (involve Uni/Bimolecular collision)3. Slow step (RDS) is the same as experimentally Rate LawRate Law for slow step (RDS) = Expt Rate Law k[NO2]1[F2]1 = k[NO2]1[F2]1Mechanism is correct! 6. Criteria for proposed mechanisms Mechanism must account for overall stoichiometry of reaction and experimentally determined Rate Law Elementary steps MUST add up to overall balanced equation Elementary steps must be reasonable/likely, which involve unimolecular/bimolecular collision(Termolecular collision, 3 molecules colliding together is unlikely due to probability and orientation factors) Mechanism MUST correlate with Rate Law2ICI + H2 2HCI + I2 Rate Law = k[ICI]1[H2]1Rate is 1st order to ICI and H2What is the mechanism which correlates with this Rate Law ?Step 1 is rate determining step (slow step)2ICI + H2 2HCI + I2 Expt Determined Rate Law = k[ICI]1[H2]1Propose mechanism : StepMolecularityRate law for elementary step ICI + H2 HCI + HI Slow (RDS) 2 Rate = k[ICI]1[H2]1+ ICI + HI HCI + I2 Fast 2 Rate = k[ICI] [HI]1 2ICI + H2 2HCI + I2(overall balance equation)CHECK if the proposed mechanism correct?1. Each steps adds up to overall balanced equation2. Each step is likely (involve Uni/Bimolecular collision)3. Slow step (RDS) is the same as experimentally Rate Law 7. Criteria for proposed mechanisms Mechanism must account for overall stoichiometry of reaction and experimentally determined Rate Law Elementary steps MUST add up to overall balanced equation Elementary steps must be reasonable/likely, which involve unimolecular/bimolecular collision(Termolecular collision, 3 molecules colliding together is unlikely due to probability and orientation factors) Mechanism MUST correlate with Rate Law2ICI + H2 2HCI + I2 Rate Law = k[ICI]1[H2]1Rate is 1st order to ICI and H2What is the mechanism which correlates with this Rate Law ?Step 1 is rate determining step (slow step)2ICI + H2 2HCI + I2 Expt Determined Rate Law = k[ICI]1[H2]1Propose mechanism : StepMolecularityRate law for elementary step ICI + H2 HCI + HI Slow (RDS) 2 Rate = k[ICI]1[H2]1+ ICI + HI HCI + I2 Fast 2 Rate = k[ICI] [HI]1 2ICI + H2 2HCI + I2(overall balance equation)CHECK if the proposed mechanism correct?1. Each steps adds up to overall balanced equation2. Each step is likely (involve Uni/Bimolecular collision)3. Slow step (RDS) is the same as experimentally Rate LawRate Law for slow step (RDS) = Expt Rate Law k[ICI]1[H2]1 = k[ICI]1[H2]1Mechanism is correct! 8. Mechanism whereby Step 2 is the rate determining step2NO + O2 2NO2Rate Law = k[NO]2[O2]1Rate is 2nd order to NO and 1st order to O2What is the mechanism which correlates with this Rate Law ? Step 1 is rate determining step (slow step) 2NO + O2 2NO2 Expt Determined Rate Law = k[NO]2[O2]1Propose mechanism : Step Molecularity Rate law for elementary step NO + NO + O2 2NO2 Slow (RDS)3 Rate = k[NO]2[O2]1 2NO + O2 2NO2(overall balance equation)CHECK if the proposed mechanism correct?1. Each steps adds up to overall balanced equation2. Each step is likely (involve Uni/Bimolecular collision)3. Slow step (RDS) is the same as experimentally Rate Law 9. Mechanism whereby Step 2 is the rate determining step2NO + O2 2NO2Rate Law = k[NO]2[O2]1Rate is 2nd order to NO and 1st order to O2What is the mechanism which correlates with this Rate Law ? Step 1 is rate determining step (slow step) 2NO + O2 2NO2Expt Determined Rate Law = k[NO]2[O2]1Propose mechanism : Step Molecularity Rate law for elementary step NO + NO + O2 2NO2 Slow (RDS)3 Rate = k[NO]2[O2]1 X 2NO + O2 2NO2 (overall balance equation)CHECK if the proposed mechanism correct?1. Each steps adds up to overall balanced equation2. Each step is likely (involve Uni/Bimolecular collision) X3. Slow step (RDS) is the same as experimentally Rate LawProposed Mechanism is possible but UNLIKELY due to 3 molecules colliding together 10. Mechanism whereby Step 2 is the rate determining step2NO + O2 2NO2Rate Law = k[NO]2[O2]1Rate is 2nd order to NO and 1st order to O2What is the mechanism which correlates with this Rate Law ? Step 1 is rate determining step (slow step) 2NO + O2 2NO2Expt Determined Rate Law = k[NO]2[O2]1Propose mechanism : Step MolecularityRate law for elementary step NO + NO + O2 2NO2 Slow (RDS)3Rate = k[NO]2[O2]1 X 2NO + O2 2NO2 (overall balance equation)CHECK if the proposed mechanism correct?1. Each steps adds up to overall balanced equation2. Each step is likely (involve Uni/Bimolecular collision) X3. Slow step (RDS) is the same as experimentally Rate LawProposed Mechanism is possible but UNLIKELY due to 3 molecules colliding together Step 2 is rate determining step (slow step)Propose mechanism : Step MolecularityRate law for elementary step NO + O2 NO3 Fast 2 Rate = k[NO]1[O2]1+ NO3 + NO 2NO2 Slow (RDS) 2 Rate = k[NO3]1[NO]1 2NO + O2 2NO2 (overall balance equation)Rate Law do not contain intermediates - NO3 is an intermediate which depend on NO and O2Conc of [NO3] = [NO][O2] from step 1Rate = k[NO3]1[NO]1 = k [NO][O2][NO] = k[NO]2[O2]1CHECK if the proposed mechanism correct?1. Each steps adds up to overall balanced equation2. Each step is likely (involve Uni/Bimolecular collision)3. Slow step (RDS) is the same as experimentally Rate Law 11. Mechanism whereby Step 2 is the rate determining step2NO + O2 2NO2Rate Law = k[NO]2[O2]1Rate is 2nd order to NO and 1st order to O2What is the mechanism which correlates with this Rate Law ? Step 1 is rate determining step (slow step) 2NO + O2 2NO2Expt Determined Rate Law = k[NO]2[O2]1Propose mechanism : Step MolecularityRate law for elementary step NO + NO + O2 2NO2 Slow (RDS)3Rate = k[NO]2[O2]1 X 2NO + O2 2NO2 (overall balance equation)CHECK if the proposed mechanism correct?1. Each steps adds up to overall balanced equation2. Each step is likely (involve Uni/Bimolecular collision) X3. Slow step (RDS) is the same as experimentally Rate LawProposed Mechanism is possible but UNLIKELY due to 3 molecules colliding together Step 2 is rate determining step (slow step)Propose mechanism : Step MolecularityRate law for elementary step NO + O2 NO3 Fast 2 Rate = k[NO]1[O2]1+ NO3 + NO 2NO2 Slow (RDS) 2 Rate = k[NO3]1[NO]1 2NO + O2 2NO2 (overall balance equation)Rate Law do not contain intermediates - NO3 is an intermediate which depend on NO and O2Conc of [NO3] = [NO][O2] from step 1Rate = k[NO3]1[NO]1 = k [NO][O2][NO] = k[NO]2[O2]1CHECK if the proposed mechanism correct?Rate slow step (RDS) = Expt Rate Law1. Each steps adds up to overall balanced equationk[NO]2[O2]1 = k[NO]2[O2]12. Each step is likely (involve Uni/Bimolecular collision)3. Slow step (RDS) is the same as experimentally Rate Law Mechanism is correct! 12. Mechanism whereby Step 2 is the rate determining stepA+B+C DRate Law = k[A]1[B]1 [C]1Rate is 1st order to A, B and CWhat is the mechanism which correlates with this Rate Law ? Step 1 is rate determining step (slow step) A+B+CD Expt Determined Rate Law = k[A]1[B]1[C]1Propose mechanism : Step Molecularity Rate law for elementary stepA + B + C DSlow (RDS)3 Rate = k[A]1[B]1[C]1A + B + C D(overall balance equation)CHECK if the proposed mechanism correct?1. Each steps adds up to overall balanced equation2. Each step is likely (involve Uni/Bimolecular collision)3. Slow step (RDS) is the same as experimentally Rate Law 13. Mechanism whereby Step 2 is the rate determining stepA+B+C DRate Law = k[A]1[B]1 [C]1Rate is 1st order to A, B and CWhat is the mechanism which correlates with this Rate Law ? Step 1 is rate determining step (slow step) A+B+CDExpt Determined Rate Law = k[A]1[B]1[C]1 Propose mechanism :Step Molecularity Rate law for elementary step A + B + C D Slow (RDS)3 Rate = k[A]1[B]1[C]1 X A + B + C D(overall balance equation)CHECK if the proposed mechanism correct?1. Each steps adds up to overall balanced equation2. Each step is likely (involve Uni/Bimolecular collision) X3. Slow step (RDS) is the same as experimentally Rate LawProposed Mechanism is possible but UNLIKELY due to 3 molecules colliding together 14. Mechanism whereby Step 2 is the rate determining stepA+B+C DRate Law = k[A]1[B]1 [C]1Rate is 1st order to A, B and CWhat is the mechanism which correlates with this Rate Law ? Step 1 is rate determining step (slow step) A+B+CDExpt Determined Rate Law = k[A]1[B]1[C]1 Propose mechanism :Step MolecularityRate law for elementary step A + B + C D Slow (RDS)3Rate = k[A]1[B]1[C]1 X A + B + C D(overall balance equation)CHECK if the proposed mechanism correct?1. Each steps adds up to overall balanced equation2. Each step is likely (involve Uni/Bimolecular collision) X3. Slow step (RDS) is the same as experimentally Rate LawProposed Mechanism is possible but UNLIKELY due to 3 molecules colliding together Step 2 is rate determining step (slow step) Propose mechanism :Step MolecularityRate law for elementary step A+B X Fast 2Rate = k[A]1[B]1+X+C D Slow (RDS) 2Rate = k[X]1[C]1 A+B+CD(overall balance equation)Rate Law do not contain intermediates - X is an intermediate which depend on A and BConc of [X] = [A][B] from step 1Rate = k[X]1[C]1 = k [A][B][C]CHECK if the proposed mechanism correct?1. Each steps adds up to overall balanced equation2. Each step is likely (involve Uni/Bimolecular collision)3. Slow step (RDS) is the same as experimentally Rate Law 15. Mechanism whereby Step 2 is the rate determining stepA+B+C DRate Law = k[A]1[B]1 [C]1Rate is 1st order to A, B and CWhat is the mechanism which correlates with this Rate Law ? Step 1 is rate determining step (slow step) A+B+CDExpt Determined Rate Law = k[A]1[B]1[C]1 Propose mechanism :Step MolecularityRate law for elementary step A + B + C D Slow (RDS)3Rate = k[A]1[B]1[C]1 X A + B + C D(overall balance equation)CHECK if the proposed mechanism correct?1. Each steps adds up to overall balanced equation2. Each step is likely (involve Uni/Bimolecular collision) X3. Slow step (RDS) is the same as experimentally Rate LawProposed Mechanism is possible but UNLIKELY due to 3 molecules colliding together Step 2 is rate determining step (slow step) Propose mechanism :Step MolecularityRate law for elementary step A+B X Fast 2Rate = k[A]1[B]1+X+C D Slow (RDS) 2Rate = k[X]1[C]1 A+B+CD(overall balance equation)Rate Law do not contain intermediates - X is an intermediate which depend on A and BConc of [X] = [A][B] from step 1Rate = k[X]1[C]1 = k [A][B][C]Rate slow step (RDS) = Expt Rate LawCHECK if the proposed mechanism correct?k[A]1[B]1[C]1 = k[A]1[B]1[C]11. Each steps adds up to overall balanced equation2. Each step is likely (involve Uni/Bimolecular collision)3. Slow step (RDS) is the same as experimentally Rate Law Mechanism is correct! 16. Mechanism whereby Step 2 is the rate determining stepA + 3B AB3Rate Law = k[A]1[B]2Rate is 1st order to A and 2nd order to BWhat is the mechanism which correlates with this Rate Law ? Step 1 is rate determining step (slow step) A + 3B AB3Expt Determined Rate Law = k[A]1[B]2Propose mechanism : Step Molecularity Rate law for elementary stepA + B + B AB2 Slow (RDS) 3 Rate = k[A]1[B]2+ AB2 + B AB3 Fast 2 Rate = k[AB2]1[B]1A + 3B AB3(overall balance equation)CHECK if the proposed mechanism correct?1. Each steps adds up to overall balanced equation2. Each step is likely (involve Uni/Bimolecular collision)3. Slow step (RDS) is the same as experimentally Rate Law 17. Mechanism whereby Step 2 is the rate determining stepA + 3B AB3Rate Law = k[A]1[B]2Rate is 1st order to A and 2nd order to BWhat is the mechanism which correlates with this Rate Law ? Step 1 is rate determining step (slow step) A + 3B AB3 Expt Determined Rate Law = k[A]1[B]2 Propose mechanism :Step Molecularity Rate law for elementary step A + B + B AB2 Slow (RDS) 3Rate = k[A]1[B]2 X+AB2 + B AB3 Fast 2Rate = k[AB2]1[B]1 A + 3B AB3(overall balance equation)CHECK if the proposed mechanism correct?1. Each steps adds up to overall balanced equation2. Each step is likely (involve Uni/Bimolecular collision) X3. Slow step (RDS) is the same as experimentally Rate LawProposed Mechanism is possible but UNLIKELY due to 3 molecules colliding together 18. Mechanism whereby Step 2 is the rate determining stepA + 3B AB3Rate Law = k[A]1[B]2Rate is 1st order to A and 2nd order to BWhat is the mechanism which correlates with this Rate Law ? Step 1 is rate determining step (slow step) A + 3B AB3 Expt Determined Rate Law = k[A]1[B]2 Propose mechanism :Step Molecularity Rate law for elementary step A + B + B AB2 Slow (RDS) 3Rate = k[A]1[B]2 X+AB2 + B AB3 Fast 2Rate = k[AB2]1[B]1 A + 3B AB3(overall balance equation)CHECK if the proposed mechanism correct?1. Each steps adds up to overall balanced equation2. Each step is likely (involve Uni/Bimolecular collision) X3. Slow step (RDS) is the same as experimentally Rate LawProposed Mechanism is possible but UNLIKELY due to 3 molecules colliding together Step 2 is rate determining step (slow step) Propose mechanism :StepMolecularityRate law for elementary step A + B ABFast 2Rate = k[A]1[B]1 AB + B AB2Slow (RDS) 2Rate = k[AB]1[B]1+AB2 + B AB3 Fast 2Rate = k[AB2]1[B]1 A + 3B AB3(overall balance equation)Rate Law do not contain intermediates - AB is an intermediate which depend on A and BConc of [AB] = [A][B] from step 1Rate = k[AB]1[B]1 = k [A][B][B] = k[A]1[B]2CHECK if the proposed mechanism correct?1. Each steps adds up to overall balanced equation2. Each step is likely (involve Uni/Bimolecular collision)3. Slow step (RDS) is the same as experimentally Rate Law 19. Mechanism whereby Step 2 is the rate determining stepA + 3B AB3Rate Law = k[A]1[B]2Rate is 1st order to A and 2nd order to BWhat is the mechanism which correlates with this Rate Law ? Step 1 is rate determining step (slow step) A + 3B AB3 Expt Determined Rate Law = k[A]1[B]2 Propose mechanism :Step Molecularity Rate law for elementary step A + B + B AB2 Slow (RDS) 3Rate = k[A]1[B]2 X+AB2 + B AB3 Fast 2Rate = k[AB2]1[B]1 A + 3B AB3(overall balance equation)CHECK if the proposed mechanism correct?1. Each steps adds up to overall balanced equation2. Each step is likely (involve Uni/Bimolecular collision) X3. Slow step (RDS) is the same as experimentally Rate LawProposed Mechanism is possible but UNLIKELY due to 3 molecules colliding together Step 2 is rate determining step (slow step) Propose mechanism :StepMolecularityRate law for elementary step A + B ABFast 2Rate = k[A]1[B]1 AB + B AB2Slow (RDS) 2Rate = k[AB]1[B]1+AB2 + B AB3 Fast 2Rate = k[AB2]1[B]1 A + 3B AB3(overall balance equation)Rate Law do not contain intermediates - AB is an intermediate which depend on A and BConc of [AB] = [A][B] from step 1Rate = k[AB]1[B]1 = k [A][B][B] = k[A]1[B]2CHECK if the proposed mechanism correct? Rate slow step (RDS) = Expt Rate Law1. Each steps adds up to overall balanced equation k[A]1[B]2 = k[A]1[B]22. Each step is likely (involve Uni/Bimolecular collision)3. Slow step (RDS) is the same as experimentally Rate Law Mechanism is correct! 20. Mechanism for Iodination of Propanone with IntermediatesCH3COCH3 + I2 CH3 COCH2I + H+ + I- Rate Law = k[CH3COCH3 ][H+]Rate is 1st order to CH3COCH3 and H+What is the mechanism which correlates with this Rate Law ?CH3COCH3 + I2 CH3COCH2I + H+ + I- Expt Determined Rate Law = k[CH3COCH3]1[H+]1Propose mechanism : StepMolecularityCH3COCH3 + H+ CH3C(OH+)CH3Slow (RDS) 2CH3C(OH+)CH3 CH2=C(OH)CH3 + H+ Fast 2+ CH2=C(OH)CH3 + I2 CH3 COCH2I + H+ + I- Fast 2 CH3COCH3 + I2 CH3 COCH2I + H+ + I- (overall balance equation)CHECK if the proposed mechanism correct?1. Each steps adds up to overall balanced equation2. Each step is likely (involve Uni/Bimolecular collision)3. Slow step (RDS) is the same as experimentally Rate Law 21. Mechanism for Iodination of Propanone with IntermediatesCH3COCH3 + I2 CH3 COCH2I + H+ + I- Rate Law = k[CH3COCH3 ][H+]Rate is 1st order to CH3COCH3 and H+What is the mechanism which correlates with this Rate Law ?CH3COCH3 + I2 CH3COCH2I + H+ + I- Expt Determined Rate Law = k[CH3COCH3]1[H+]1Propose mechanism : StepMolecularityCH3COCH3 + H+ CH3C(OH+)CH3Slow (RDS) 2CH3C(OH+)CH3 CH2=C(OH)CH3 + H+ Fast 2+ CH2=C(OH)CH3 + I2 CH3 COCH2I + H+ + I- Fast 2 CH3COCH3 + I2 CH3 COCH2I + H+ + I- (overall balance equation)CHECK if the proposed mechanism correct?1. Each steps adds up to overall balanced equation2. Each step is likely (involve Uni/Bimolecular collision)3. Slow step (RDS) is the same as experimentally Rate LawRate Law for slow step (RDS) = Expt Rate Law Mechanism is correct! k[CH3COCH3]1[H+]1 = k[CH3COCH3]1[H+]1 22. Mechanism for Iodination of Propanone with IntermediatesCH3COCH3 + I2 CH3 COCH2I + H+ + I- Rate Law = k[CH3COCH3 ][H+]Rate is 1st order to CH3COCH3 and H+What is the mechanism which correlates with this Rate Law ?CH3COCH3 + I2 CH3COCH2I + H+ + I- Expt Determined Rate Law = k[CH3COCH3]1[H+]1Propose mechanism : Step MolecularityCH3COCH3 + H+ CH3C(OH+)CH3Slow (RDS)2CH3C(OH+)CH3 CH2=C(OH)CH3 + H+ Fast2+ CH2=C(OH)CH3 + I2 CH3 COCH2I + H+ + I- Fast2 CH3COCH3 + I2 CH3 COCH2I + H+ + I- (overall balance equation)CHECK if the proposed mechanism correct?1. Each steps adds up to overall balanced equation2. Each step is likely (involve Uni/Bimolecular collision)3. Slow step (RDS) is the same as experimentally Rate LawRate Law for slow step (RDS) = Expt Rate Law Mechanism is correct! k[CH3COCH3]1[H+]1 = k[CH3COCH3]1[H+]1Intermediates Transition StateExist for a while Only in transient state Occurs at PE minimum Occurs at PE maximumFormed in 1 step and Exist through every comsumed in step involving bondsubsequent step breaking/making 23. Mechanism for Iodine Clock reaction with IntermediatesH2O2 + 2H+ + 2I- 2H2O + I2 Rate Law = k[H2O2 ][I-]Rate is 1st order to H2O2 and I-What is the mechanism which correlates with this Rate Law ?H2O2 + 2H+ + 2I- 2H2O + I2Expt Determined Rate Law = k[H2O2 ]1[I-]1Propose mechanism : Step MolecularityH2O2 + I- H2O + IO- Slow (RDS)2IO- + H+ HIO Fast2+ HIO + H + I+- H2O + I2Fast2H2O2 + 2H+ + 2I- 2H2O + I2 (overall balance equation)CHECK if the proposed mechanism correct?1. Each steps adds up to overall balanced equation2. Each step is likely (involve Uni/Bimolecular collision)3. Slow step (RDS) is the same as experimentally Rate Law 24. Mechanism for Iodine Clock reaction with IntermediatesH2O2 + 2H+ + 2I- 2H2O + I2 Rate Law = k[H2O2 ][I-]Rate is 1st order to H2O2 and I-What is the mechanism which correlates with this Rate Law ?H2O2 + 2H+ + 2I- 2H2O + I2 Expt Determined Rate Law = k[H2O2 ]1[I-]1Propose mechanism :StepMolecularityH2O2 + I- H2O + IO- Slow (RDS)2IO- + H+ HIO Fast2+ HIO + H + I+- H2O + I2Fast2H2O2 + 2H+ + 2I- 2H2O + I2(overall balance equation)CHECK if the proposed mechanism correct?1. Each steps adds up to overall balanced equation2. Each step is likely (involve Uni/Bimolecular collision)3. Slow step (RDS) is the same as experimentally Rate LawRate Law for slow step (RDS) = Expt Rate Law Mechanism is correct! k[H2O2 ]1[I-]1 = k[H2O2 ]1[I-]1 25. Mechanism for Iodine Clock reaction with IntermediatesH2O2 + 2H+ + 2I- 2H2O + I2 Rate Law = k[H2O2 ][I-]Rate is 1st order to H2O2 and I-What is the mechanism which correlates with this Rate Law ?H2O2 + 2H+ + 2I- 2H2O + I2 Expt Determined Rate Law = k[H2O2 ]1[I-]1Propose mechanism :Step MolecularityH2O2 + I- H2O + IO- Slow (RDS) 2IO- + H+ HIO Fast 2+ HIO + H + I+- H2O + I2Fast 2H2O2 + 2H+ + 2I- 2H2O + I2(overall balance equation)CHECK if the proposed mechanism correct?1. Each steps adds up to overall balanced equation2. Each step is likely (involve Uni/Bimolecular collision)3. Slow step (RDS) is the same as experimentally Rate LawRate Law for slow step (RDS) = Expt Rate Law Mechanism is correct! k[H2O2 ]1[I-]1 = k[H2O2 ]1[I-]1 IntermediatesTransition State Exist for a whileOnly in transient stateOccurs at PE minimum Occurs at PEmaximum Formed in 1 step andExist through everycomsumed instep involving bond subsequent stepbreaking/making 26. Hydrolysis of 2-bromo -2methylpropane by OH - is by SN1 mechanism with Intermediates(CH3)3CBr + OH - (CH3)3COH + Br-Rate Law = k[(CH3)3CBr]1 (Substitution Nucleophilic Unimolecular)Rate is 1st order to (CH3)3CBrWhat is the mechanism which correlates with this Rate Law ?(CH3)3CBr + OH - (CH3)3COH + Br-Expt Determined Rate Law = k[(CH3)3CBr]1Propose mechanism : StepMolecularity Rate law for elementary step(CH3)3CBr (CH3)3C++ Br -Slow (RDS)1 Rate = k[(CH3)3CBr]1+ (CH3)3C+ + OH- (CH3)3COH Fast2 Rate = k[(CH3)3C+]1[OH-]1 (CH3)3CBr + OH- (CH3)3COH + Br - (overall balance equation)CHECK if the proposed mechanism correct?1. Each steps adds up to overall balanced equation2. Each step is likely (involve Uni/Bimolecular collision)3. Slow step (RDS) is the same as experimentally Rate Law 27. Hydrolysis of 2-bromo -2methylpropane by OH - is by SN1 mechanism with Intermediates(CH3)3CBr + OH - (CH3)3COH + Br-Rate Law = k[(CH3)3CBr]1 (Substitution Nucleophilic Unimolecular)Rate is 1st order to (CH3)3CBrWhat is the mechanism which correlates with this Rate Law ?(CH3)3CBr + OH - (CH3)3COH + Br-Expt Determined Rate Law = k[(CH3)3CBr]1Propose mechanism : StepMolecularity Rate law for elementary step(CH3)3CBr (CH3)3C++ Br -Slow (RDS)1 Rate = k[(CH3)3CBr]1+ (CH3)3C+ + OH- (CH3)3COH Fast2 Rate = k[(CH3)3C+]1[OH-]1 (CH3)3CBr + OH- (CH3)3COH + Br - (overall balance equation)CHECK if the proposed mechanism correct?1. Each steps adds up to overall balanced equation2. Each step is likely (involve Uni/Bimolecular collision)3. Slow step (RDS) is the same as experimentally Rate Law Rate Law for slow step (RDS) = Expt Rate LawMechanism is correct! k[(CH3)3CBr]1= k[(CH3)3CBr]1 28. Hydrolysis of 2-bromo -2methylpropane by OH - is by SN1 mechanism with Intermediates(CH3)3CBr + OH - (CH3)3COH + Br-Rate Law = k[(CH3)3CBr]1 (Substitution Nucleophilic Unimolecular)Rate is 1st order to (CH3)3CBrWhat is the mechanism which correlates with this Rate Law ?(CH3)3CBr + OH - (CH3)3COH + Br-Expt Determined Rate Law = k[(CH3)3CBr]1Propose mechanism : StepMolecularity Rate law for elementary step(CH3)3CBr (CH3)3C++ Br -Slow (RDS)1Rate = k[(CH3)3CBr]1+ (CH3)3C+ + OH- (CH3)3COH Fast2Rate = k[(CH3)3C+]1[OH-]1 (CH3)3CBr + OH- (CH3)3COH + Br - (overall balance equation)CHECK if the proposed mechanism correct?1. Each steps adds up to overall balanced equation2. Each step is likely (involve Uni/Bimolecular collision)3. Slow step (RDS) is the same as experimentally Rate Law Rate Law for slow step (RDS) = Expt Rate LawMechanism is correct! k[(CH3)3CBr]1= k[(CH3)3CBr]1 IntermediatesTransition State Exist for a whileOnly in transient stateOccurs at PE minimum Occurs at PEmaximum Formed in 1 step andExist through everycomsumed instep involving bond subsequent stepbreaking/making 29. Hydrolysis of bromomethane by OH - is by SN2 mechanism with Transition StateCH3Br + OH - CH3OH + Br- Rate Law = k[CH3Br]1[OH -]1Substitution Nucleophilic BimolecularRate is 1st order to CH3Br and OH -What is the mechanism which correlates with this Rate Law ?CH3Br + OH - CH3OH + Br-Expt Determined Rate Law = k[CH3Br]1[OH-]1 Propose mechanism :Step Molecularity Rate law for elementary step CH3Br + OH - HO---CH3--- Br CH3OH + Br -Slow (RDS) 2Rate = k[CH3Br]1[OH-]1+ CH3Br + OH - CH3OH + Br -(overall balance equation)CHECK if the proposed mechanism correct?1. Each steps adds up to overall balanced equation2. Each step is likely (involve Uni/Bimolecular collision)3. Slow step (RDS) is the same as experimentally Rate Law 30. Hydrolysis of bromomethane by OH - is by SN2 mechanism with Transition StateCH3Br + OH - CH3OH + Br- Rate Law = k[CH3Br]1[OH -]1Substitution Nucleophilic BimolecularRate is 1st order to CH3Br and OH -What is the mechanism which correlates with this Rate Law ?CH3Br + OH - CH3OH + Br-Expt Determined Rate Law = k[CH3Br]1[OH-]1 Propose mechanism : Step Molecularity Rate law for elementary step CH3Br + OH - HO---CH3--- Br CH3OH + Br - Slow (RDS)2 Rate = k[CH3Br]1[OH-]1+ CH3Br + OH - CH3OH + Br -(overall balance equation)CHECK if the proposed mechanism correct?1. Each steps adds up to overall balanced equation2. Each step is likely (involve Uni/Bimolecular collision)3. Slow step (RDS) is the same as experimentally Rate Law Rate Law for slow step (RDS) = Expt Rate Law Mechanism is correct! k[CH3Br]1[OH-]1 = k[CH3Br]1[OH-]1 31. Hydrolysis of bromomethane by OH - is by SN2 mechanism with Transition StateCH3Br + OH - CH3OH + Br- Rate Law = k[CH3Br]1[OH -]1 Substitution Nucleophilic BimolecularRate is 1st order to CH3Br and OH -What is the mechanism which correlates with this Rate Law ?CH3Br + OH - CH3OH + Br-Expt Determined Rate Law = k[CH3Br]1[OH-]1 Propose mechanism : StepMolecularityRate law for elementary step CH3Br + OH - HO---CH3--- Br CH3OH + Br - Slow (RDS)2 Rate = k[CH3Br]1[OH-]1+ CH3Br + OH - CH3OH + Br -(overall balance equation)CHECK if the proposed mechanism correct?1. Each steps adds up to overall balanced equation2. Each step is likely (involve Uni/Bimolecular collision)3. Slow step (RDS) is the same as experimentally Rate Law Rate Law for slow step (RDS) = Expt Rate LawMechanism is correct! k[CH3Br]1[OH-]1 = k[CH3Br]1[OH-]1HO---CH3--- BrIntermediatesTransition StateExist for a whileOnly in transient stateOccurs at PE minimumOccurs at PE maximumFormed in 1 step andExist through every comsumed instep involving bondsubsequent stepbreaking/making 32. AcknowledgementsThanks to source of pictures and video used in this presentationThanks to Creative Commons for excellent contribution on licenseshttp://creativecommons.org/licenses/Prepared by Lawrence KokCheck out more video tutorials from my site and hope you enjoy this tutorialhttp://lawrencekok.blogspot.com