Chemistry 212
Spring 2013
Kinetically Controlled Rxns
Elimination Reactions-2
1. Additional Reactions
Reactions
CH 3
(1)
CH3
C
OH
+
C
HCl
CH3
(2)
Relative
Rates
CH3
CH2
+ H3 O ++ Cl -
(1)
CH3
CH3
CH
CH OH
+ HCl
CH3
CH 3
C
CH 2
+
+
H3 O + Cl -
C
H 3O
1
CH3
C
OH
C
+ HCl
+
CH2
+
H3 O + Cl
108
-
(3)
Br + H2 O
∆
C
H
CH3
H
H
H
+
H3O
H
∆
H
OH H
H
CH3
OH
H
(2)
CH3
CH3
+
H2O
25%
H3O+
H
H
H
75%
CH3
CH3
+
H
H
∆
H
H H2O
H
25%
H
75%
H
C
CH2
+ H3 O+ + I -
C
CH2
+ H3 O+
+ Br
C
CH 2
+ H3 O+
+ Cl -
10
5
H 3O
+
CH3
∆
-
102
CH 3
CH3
CH3
Relative
Rates
CH3
CH 3
CH3
(2)
CH 3
H
+ H2 O
CH3
CH3
(1)
I
+
CH3
CH 3
(3)
105
Reactions
CH3
Cl +
H2 O
H 3O +
CH3
∆
1
CH3
2. Questions:
a. What similarities are there between the overall reactions and
reaction conditions in this activity and those in Elimination
Reactions-1?
Elimination Reactions
2
b. What structure and reaction condition differences exist between reactions in Elimination-1 & -2?
c. Can the E2 mechanism devised in our class discussion from the data Elimination Reactions-1 account for the rate data given for the
reactions in this activity? If so, explain how. If not, could either the Proton-First or Leaving Group-First mechanism better accommodate
the new data? Be sure to identify the data set you found to be most import in determining your claim? Provide a warrant explaining why
that data set was the key to your analysis.
3. a. Circle the product(s) that would be expected in the following reactions?
b. Given the outcomes shown below, consider the reaction conditions and the reactions you have seen previously and propose a mechanism
that can account for any unexpected products formed in these reactions.
From Experiment 3
O
H
H3PO4
+
+
Major Product
+
Additional Example
+ H2O
Elimination Reactions
H
H O
H
3
H
H
H
H
H2SO4
+
+
H
Major Product
+
+ H 2O
Elimination Reactions
4
4. Using your conclusions from this activity and from Eliminations-1, reconsider your predictions for the 4 reactions that are being analyzed in
Experiment 4. Do you see additional possible products that might form? Are their products you previously proposed that now seem
unlikely? Indicate structure added or eliminated and provide your warrant for the changes.
5. Now show how your mechanisms for dehydration (Acidic conditions) and dehydrohalogenation (Basic conditions) account for the formation
the 3 alkene products found in Experiment 3.