Question 1
A set of three nucleophilic displacement reactions is shown below:
Which reaction (A, B, or C) proceeds the fastest?
Which reaction (A, B, or C) proceeds the slowest?
2) A set of three nucleophilic displacement reactions is shown below:
Which reaction (A, B, or C) proceeds the fastest?
Which reaction (A, B, or C) proceeds the slowest?
Question 2
For the Following SN1 reaction.
Unimolecular Substitution Reaction: SN1 stands Unimolecular substitution reaction, it is a type of substitution reaction in which a nucleophile replaces the other nucleophile. It is a two-step reaction. Reaction proceeds via the formation of carbocation(intermediate). Since carbocation is planar so, nucleophiles can attack from both sides of plane. A racemic mixture formed.
Question 3
Question 4
For the following S N 1 reaction, draw the organic product and the ionic byproduct of the reaction, identify the nucleophile, substrate, and leaving group, and determine the rate-limiting step.
Answer to question 1
1) For an SN1 nucleophilic displacement reaction, the order of carbon substrate reactivity follows the order (in decreasing order),
tertiary > secondary > primary
the mechanism of substitution being, generation of a carbocation intermediate. So as the substitution on the carbon having the leaving group increases, the carbocation generated becomes more stable.
So of the given substrates the fastest reaction would be for,
A
The slowest rate of reaction would be seen for
B
2) For an SN2 reaction, the reactivity of carbon goes like (in decreasing order),
primary > secondary > tertiary
So the primary carbon reacts fastest with least steric hindrance in the T.S. with five bonds to the carbon. As the substitution on carbon increases, the T.S. state becomes more crowded, higher energy and less probable the reaction would proceed in forward direction.
Thus of the given substrates the fastest reaction would be with,
A
The slowest reaction would be with,
C.
Answer to question 2
1
The variables are:-
y-axis:- Rate of the reaction
x-Axis:- type of substrate
2
Data follows the trend of stability of carbocation, Since SN1 reaction proceeds through the formation of the carbocation.
The stability order of carbocation is:-
Tertiary carbocation > benzyl carbocation > allyl carbocation > Secondary carbocation > primary carbocation.
Answer to question 3
The solvolysis of 3-iodopentane (substrate) in ethanol initiates with the slow reversible cleavage of the carbon-iodine bond leading to the formation of the carbocation intermediate. This is the rate-determining step of the process.
The iodine atom which gets removed as Iodide ion is the leaving group.
Subsequently, ethanol acts as a nucleophile and attacks the pentyl carbocation at its C-3 position to give the protonated 3-ethoxypentane intermediate.
Finally, loss of a proton from this intermediate results in 3-ethoxypentane as the main product. These processes are illustrated in the figure below:
Answer to question 4
The solvolysis of 3-iodopentane (substrate) in ethanol initiates with the slow reversible cleavage of the carbon-iodine bond leading to the formation of the carbocation intermediate. This is the rate-determining step of the process.
The iodine atom which gets removed as Iodide ion is the leaving group.
Subsequently, ethanol acts as a nucleophile and attacks the pentyl carbocation at its C-3 position to give the protonated 3-ethoxypentane intermediate.
Finally, loss of a proton from this intermediate results in 3-ethoxypentane as the main product. These processes are illustrated in the figure below:
