Chem 3325 Problems
58. In each of the following reactions the reactant alkyl halide has two sites where the specified
reaction can occur. For each reaction specify which site is favored, give the product formed
and briefly explain your reasoning :
59. Explain using mechanism why 3-bromo-1-butene and 1-bromo-2-butene react with I-
via the SN1 mechanism and form the same products
60. For reactions involving alkyl halides, give the reaction conditions which
(i) favor the SN2 reaction over the E2 reaction
(ii) favor the SN1 reaction over the SN2 reaction
(iii) favor the E2 reaction over the SN2 reaction
61. Draw all possible resonance forms of the anion A below :
62. (i) Draw all possible resonance structures for the cation A below :
(ii) Decide, showing your reasoning,whether cation B below is more or
less stable than A above
63. For the reaction :
-CN + (R)3C-Br -> (R)3C-CN + Br-
(i) predict the preferred mechanism when R=H
(ii) predict the preferred mechanism ehen R=Et
(iii) for the case where R=H predict the effect on the rate of reaction of changing the solvent from acetone to 50% acetone and 50% alcohol (EtOH)
(iv) for the case where R=Et predict the effect on the rate of reaction of changing the solvent from acetone to 50% acetone and 50% alcohol (EtOH)
64. For the reaction below explain the following observations :
(i) even though the carbon at which substitution occurs is 1o the mechanism observed is SN1
(ii) the product given above is only the minor product. Give the structure of the major product
and explain its formation in terms of mechanism
65. The bromoalkane I below does not undergo nucleophilic substitution by either the SN1 or the
SN2 mechanism. Explain why :
68. For molecule I below a) how many chiral centers, i.e. assymetric carbon atoms, are there
and b) how many stereoisomers are possible for I
69. A below is the molecule norepinephrine. Draw its Fischer projection and assign
a configuration to the assymetric carbon atom
70. For glyceraldehyde below give its configuration :
71. For molecules A and B below decide whether they are :
(i) enantiomers (ii) diastereomers (iii) identical
72. A below is the molecule norepinephrine. Draw its Fischer projection and assign
a configuration to the assymetric carbon atom
74. (i) By first assigning a configuration to each (show method) decide whether the following are :
a) enantiomers b) diastereomers c) identical :
75. Explain why the following molecule cannot be chiral (i.e. optically active) :
10. (i) Suggest a mechanism for the following reaction :
(ii) Explain why none of the isomer B below is formed :
11. (i) Propose a mechanism for the following :
(ii) Explain why for reaction II belowthe opposite regiochemistry is observed :
12. Using ethanol as your only organic material and any reagents propose a multistep
synthesis of 2-butanol
13. Give the two deuterated products generated by the reduction of aldehyde A below under
the two sets of conditions given : [ D = 2H]
17. (i) Give the mechanism for the following reaction :
(ii) Predict the major for the reaction :
2