Experimental Plan

Kinetic Analysis of Spectroscopic DataKoushik PonnuruApril 16 2015

Research Plan

1OutlineComparison of classical Kinetic methodology vs. kinetic analysis of in-situ Spectroscopic dataDriving Force Analysis - Different Excess ProtocolProcess Robustness Analysis - Same Excess Potocol

ReactIR 45M fitted with a dicomp ATR probe

Spectroscopic datatimeChanges in absorption correlated to the concentration of the speciesConcentrationJ. Am. Chem. Soc. 2012, 134, 4600Reaction progress Kinetic Analysis

Typical trace of reactant consumption over time:One initial rate point per experimental runRPKA teaches us how to extract information from hereExtract Kinetic InformationConcentration DependenceCatalyst Stability Analysis

Classical Methodology measures a small change in concentration at the beginning of the reaction over a short period of timeClassical Kinetic methodology : Drawbacks

Diels Alder Reaction Large number of separate experiments requiredConcentrations are distorted from synthetically relevant conditionsDrawbacksElementary Reactions : Different Excess

Excess [e] = [2]0 [1]0 = [2] [1] [2] = [1]+ [e]

Difference between concentrationsIf we know the concentration of one we know the concentration of the otherDiels Alder Reaction [e] has units of concentration[e] does not change as the reaction progressesKinetic Analysis of Elementary reactions[1]0 [2]0 [e] = [2]0 [1]0 = [2] [1]Exp. A0.2M0.6 M0.4 MExp. B0.2M0.4M

0.2M

We See curvature because both [1] and [2] are changing over the course of the reactionJACS, 2007,129,15100.Kinetic Analysis of Elementary reactions

Rearranged rate equationRate equationRate Law for Catalytic Cycle

Power law formSteady state rate lawApproximates

This formJACS, 2007,129,15100.

Rate Law for Catalytic CyclePlot the normalized form of the power law rate equation for two different excess experiments

When Y is chosen correctly, we obtain straight linesWhen X is chosen correctly, the two curves overlayAmino acid catalyzed aldol condensation

1.5M0.75M

11Same Excess Protocol Explained

The working system after 50 turnovers

The fresh system at the same concentrationIf the catalyst is robust the rates should be identical at this point of the snapshotWhat happens if we start a new experiment in a new rxn vial at the conditions of 25 % conv

12Same Excess Protocol Design Conditions

Same Excess I @ 25% conversion = Same Excess II @ 0% conversion If the simple catalytic cycle truly describes the process, then at a given set of concentrations, the fresh and the working systems should give the same rate (Overlay)

Proline Catalysed Aldol reaction : Role of water

[e] = 0 MSecond Experiment startsRed Data : 0.5M 0.5MBlue Data: 1.0M 1.0MNo overlay : process is not robust overlay : process is robustRole of water in the catalytic cycle

Rate = Kobs [H20]0.7True mechanistic dependence of rate on H20

Under the conditions where the catalyst concentration is stable within the cycle addition of water suppresses the rate within the cycleJACS, 2007,129,15100.

Role of water in the catalytic cycleWater suppresses the side reaction that consumes the reactant E and removes the catalyst from the cycleTherefore addition of water increases the yieldWater suppresses the rate of main catalytic cycleWater decreases the rate

Safety momentDMSO Slightly hazardous in case of inhalation, ingestion, and skin contact Flammable in presence of open flames and sparks2-ChlorobenzaldehydeVery very hazardous in case of skin contact, eye contact, ingestion, and inhalationCombustible liquid with a flash point between 37.8C (100F) and 93.3C (200F)AcetoneFlammable liquid flash point below 100 FProduce CO upon combustionHazardous in case of skin contact (irritant), of eye contact (irritant), of ingestion, of inhalation. Slightly hazardous in case of skin contact (permeator)SummarySame Excess protocolCatalyst Stability / process robustnessComparison between on cycle vs. off cycle processesDifferent Excess ProtocolReaction orders in substrate concentrationsRate constantsProvide full kinetic analysis from a minimum number of experimentsTHANKS FOR YOUR ATTENTION