Catalysis and Enzymatic Reactions
Catalysis is the kind of chemical reaction in which the rate (speed) of a reaction is enhanced by the catalyst which is not consumed during the process of reaction and afterward it is removed when the catalyst is not used to make up the impurity in the product. The enzymatic reaction is the reaction that is catalyzed via enzymes.
Lock And Key Model
The lock-and-key model is used to describe the catalytic enzyme activity, based on the interaction between enzyme and substrate. This model considers the lock as an enzyme and the key as a substrate to explain this model. The concept of how a unique distinct key only can have the access to open a particular lock resembles how the specific substrate can only fit into the particular active site of the enzyme. This is significant in understanding the intermolecular interaction between proteins and plays a vital role in drug interaction.
![2) Finally, the polymerization conditions were optimized to get a polymer which the
structure is shown below. The termination occurs 100% by coupling
(combination). Write the chemical structure of the initiator used and its
decomposition reaction. Give the definition of the initiator efficiency (f)
H₂C
CH3
CH₂
H₂C
CH-CH₂-
2-C-(CH₂=CH-C
H₂C
NC
CN
CH₂
3) What is the other possible mode of termination in conventional radical
polymerization?
4) Finally, poly(styrene) (PS) is prepared using [styrene] = 1 mol/L in toluene and
[initiator] = 5 x 10 mol/L.
Propagation rate: Rp = 6.62 x 10-6 mol/L/s
f=0.60
Demonstrate that the half-life of a radical initiator is t1/2 = 0.693/kd
5) Knowing that the ten hours half-life of the initiator (used for the synthesis of PS) is
achieved at 51 °C in toluene, calculate the constant ka
6) Calculate the initiation rate (R₂)
7) Give the definition of the kinetics chain length >
8)
Calculate the number average degree of polymerization (DP) assuming that the
termination occurs by combination only.
9) What is the value of Mn?
10) The DP, is determined experimentally by elemental analysis which gives the wt%
of nitrogen (N = 14) in the polymer. Which %N value is expected of which
experimental(s) method(s) could be used to confirm the value of DP?
11) After analyzing PS by size exclusion chromatography, the polydispersity (Đ) of the
polymer sample calculated is 2.1. Give the definition of polydispersity. Is this value
consistent with the polymerization method used ?
12) The polymer chemist was not satisfied by the value of Đ. He (she) decided to
change the polymerization method to obtain a PS sample with a polydispersity near
1. To this end, the following reaction is performed:
AIBN
60°C
What is the name of the polymerization method ? Write the chemical structure of
PS obtained in such conditions. What is the role of the dithioester (CPADB)?
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