CHEMISTRY 1b, SPRING, 2007
DISCUSSION PROBLEM
ISOMERS AND CONFORMERS
The structure of the compound trans 1,2-dibromocyclohexane is given below. A few
comments on its name are instructive. Hexane indicates that the compound contains 6
carbon atoms and only carbon-carbon single bonds. The cyclo indicates that the 6 carbon
atoms form a hexagonally shaped ring. The dibromo indicates that two of the hydrogen
atoms in the parent molecule, cyclohexane, have been replaced by bromines. The prefix
1,2 indicates that the bromine atoms are located on consecutive carbons.
Molecular-model kits will be provided for this problem.
1) The hydrogen atoms are not shown in the structure below. How many hydrogen atoms
are located on each carbon atom?
2) How many isomers are possible with the molecular formula C6H10Br2? What types of
isomers? In answering this question, do not change the carbon framework. That is, keep
the 6 carbons linked in the 6-membered cyclic structure shown below. Otherwise, the
number of isomers becomes very large.
3) Play with a model for the trans 1,2-dibromocyclohexane isomer shown below. Are
conformers possible? Do they have the same energy? Hint: bromine atoms are large.
Br
Br
trans 1,2-dibromocyclohexane