Chemical Kinetics

Question 1

What does chemical kinetics study?

Answer 1

Collisions, energetics of rxn, rxn rate

Question 2

What are the uses of chemical kinetics in PS?

Answer 2

Measure & predict shelf life
Formulate optimal stability
Understand degradation during processing

Question 3

What is reaction rate defined by?
What is it measured by?

Answer 3

Balanced chemical reaction
Decline in reactant concentration or appearance in production concentration

Question 4

What are reactions governed by?

Answer 4

Collisions between reactant that gain sufficiency to become products

Question 5

What stresses are responsible for accelerating drug instability?

Answer 5

Temp, moisture, pH, oxidation

Question 6

Reaction rates obey a rate law with a specific order in respect to?

Answer 6

Reactants and sometimes products

Question 7

How must rate laws be determined?

Answer 7

Experimentally unless reaction is elementary

Question 8

What reaction order to aqueous suspensions exhibit?

Answer 8

Zero order

Question 9

What is Arrhenius theory used for?

Answer 9

To perform accelerated stablility
Predict shelf life

Question 10

What does transition state theory allow for?

Answer 10

Estimation of medium effects on reaction rate

Question 11

Because ph has a complex and criticial medium effects on reaction rate, what exists?

Answer 11

optimal pH for maximal stability of drugs

Question 12

What is a balanced reaction?

Answer 12

Aa + bB=cC +dD

Question 13

What are units of reaction rate?

Answer 13

Mol/ L-s

Or 1/s

Or g/s or g/ml-s

Question 14

With what methods do we monitor the decline reactants or appearance of products?

Answer 14

UV/vis spectroscopy—absorbance

HPLC with UV/vis—-peak area

Use of MS—most common to identify products

Question 15

What group is deformylated of vincristine sulfate?

Answer 15

N formyl group

Question 16

How must rate laws be determined and how can it not be determined?
What does rate law commonly resemble?

Answer 16

Experimentally

Based on balanced chemical reaction

Balanced reaction because it is elementary

Question 17

What is zero order?
1st?
2nd?

Answer 17

A=A0-kot

A=A0e^-k1t

A=A0/ 1+ k2(Ao)t

Question 18

What is the half life of zero order?
1st?
2nd?

Answer 18

Ao/2ko—> depends on Ao

0.693/k1–> does not depend on Ao

1/k2(Ao)—> depends on A0

Question 19

What does linear plots of 1 and 2nd order kinetics allows for?

Answer 19

For determination of the rate constant of the reaction

Question 20

What is reaction order with respect to drug & other components important for?

Answer 20

What is product shelf life from accelerated stability data
How we can stabilize the drug & improve formulation

Question 21

How do we determine reaction rate based on half life?

Answer 21

Find slope—> M=(1-n)—> find N

Question 22

For aspirin, the decomposition follows zero order for a ? And follows first order for a?

Answer 22

Suspension, solution

Question 23

For suspension & solution, what is the same?
What is different?
What happens when aspirin reacts in solution?

Answer 23

Both are first order hydrolysis—> solution rate law

Suspension the aqueous conc is saturated —> solution conc & rxn rate is constant

More solid aspirin rapidly dissolves to offset the diss appearance in solution —> keeps solution conc & rxn rate Constant

Question 24

What is different between elementary & complex reactions?

Answer 24

Elementary—- single transition state

Complex—multiple transitory state

Question 25

What is the numer of reactants that form the TS called? What is most common, middle, least?

Answer 25

Molecularity Bimolecular—2 Unimolecular—1 Termolecular—3

Question 26

If it is elementary, how can we get The order and the rate law?

Answer 26

Via stoichiometry

Question 27

When describing an overall complex rxn by 2 or more elements, what is the group called?

Answer 27

Reaction scheme

Question 28

When describing an overall complex rxn by 2 or more elements, what is the group called?

Answer 28

Reaction scheme

Question 29

What must reactants pass thru to become products? What is TS energy like? What is required to react to achieve TS? What happens at TS?

Answer 29

Transitions state Higher energy than reactants or products Threshold energy Probability of the TS will become products

Question 30

What does Arrhenius explain?

Answer 30

Reactants need to attain a threshold energy in order to react The fraction of molecules possessing this threshold energy , freq factor A—> is related to frequency molecules attaining threshold energy

Question 31

What is transition state theory? What does it show?

Answer 31

Fast equilibrium between reactant and TS species Rxn rate is proportional to concentration of TS species Uses thermodynamics to describe how hard it is to get on top of the hill