Chemistry 232. Kinetics of Complex Reactions. The Pre-Equilibrium Approximation. Examine the following process. Pre-Equilibrium (II). B is obviously an intermediate in the above mechanism. Could use SSA. What if the initial equilibrium is fast? Step 2 is the rds!. Pre-Equilibrium (III).
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Kinetics of Complex Reactions
High Pressure Case
Low Pressure Case
A+B ® C rate constant k
A+B ® C rate constant with catalyst is kcat
2 SO2(g) + O2(g) ® 2 SO3 (g) SLOW
NO (g) + O2 (g) ® NO2 (g)
NO2 (g) + SO2 (g) ® SO3 (g) + NO (g) FAST
H2O (l) + SO3 (g) H2SO4 (aq)
C2H4 (g) + H2(g) C2H6 (g)
E + S ® ES
ES ® P + E
rate = k [ES]
ES – the enzyme-substrate complex.
Initial enzyme concentration
Free enzyme concentration
Note that [E] = [E]o - [ES]
Note – Vmax is the maximum velocity for the reaction. The limiting value of the reaction rate high initial substrate concentrations.
I = Intensity of the absorbed radiation
I 2 R•
M + R• M1 •
M + M1• M2 •
M + M2• M3 •
M + M3• M4 •
M + M3• M4 •
Note – Not all the initiator molecules produce chains
Define = fraction of initiator molecules that produce chains
NH2-(CH2)6-NH2 + HOOC-(CH2)4COOH
NH2-(CH2)6-NHOC-(CH2)4COOH + H2O
Mo = molar mass of monomer
n = number of polymers of mass Mn
MJ = molar mass of polymer of length nJ
Note - xn the number of monomer units in a polymer molecule
Note – monodisperse sample ideally has <M>w=<M>n
Note – as the polymerization proceeds, the ratio of <M>w/<M>n approaches 2!!!
41Mass Distributions in Polymer Samples
Molar mass / (10000 g/mole)