Chemistry
Department
CHEM 161
Exam II
-
Using acceptable chemical
nomenclature, provide an unambiguous name for the following compounds:
a.
b.
-
The free energy difference between skew and chair
cyclohexanes is usually so large that the twist conformation is not
detectable. For example, cis-1,3-di-tert-butylcyclohexane overwhelmingly favors this
conformation. However, in trans-1,3-di-tert-butylcyclohexane, the predominant conformation is the
skew boat. Explain this apparent
anomaly.
-
The following table lists the
steric strain due to one hydrogen - substituent 1,3-diaxial interaction in
some monosubstituted cyclohexanes:
|
Substituent |
Strain (kJ/mol) |
|
-Cl |
1.0 |
|
-OH |
2.1 |
|
-CH3 |
3.8 |
|
-CH(CH3)2 |
4.6 |
|
-C(CH3)3 |
11.4 |
a.
Draw the most stable conformation of cis-1-chloro-4-isopropylcyclohexane:
b.
Draw the most stable conformation of trans-1-chloro-4-isopropylcyclohexane:
c.
Using
the principles of conformational analysis (angle, torsional, and steric strain)
evaluate the stability of the structures drawn in (a) and (b) above.
d.
Which
is the most stable structure and by how many kJ?
-
What reagents would you use to
effect the following conversions?
a.
b.
-
Give the major product(s) of the
following reaction:
-
Provide a synthetic pathway for
the following transformation. Begin
your synthesis with the indicated starting material.
-
Iodobenzene dichloride is a
reagent of choice to chlorinate alkanes. Here is the equation for the
overall reaction:
The
initiation step is shown below:
a.
Draw
the transition state for this initiation process.
b.
Explain
the term “chain reaction”.
c.
Propose a chain radical mechanism for the chlorination of
alkane RH by iodobenzene dichloride. The relative reactivity of the hydrogens
(tertiary : secondary : primary) is 5 : 3.8 :1.
-
Explain the following terms:
-
inhibitor
-
activation energy
-
Lewis base
-
electrophile
