Chemistry Reference
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QUESTIONS AND PROGRAMS
PROGRAM 7 Isomers
A The molecular formula of an organic compound can give lots of information about
possible structural features. There are often many possible isomeric ways that the
atoms can be joined together.
For example, because of tetravalency requirements, alkanes have molecular formulae
that fit the general expression C
n
H
2
n
+2
. Alkenes fit the general formula C
n
H
2
n
. Alkynes
fit the general formula C
n
H
2
n
-2
.
Draw a C
5
example of each to show that they fit the above formulae.
B Some simple examples that you might have drawn are:
Other examples are branched structural isomers. With more practice, you will see that
the general formulae for alkanes, alkenes, and alkynes are equal to the loss of H
2
to
increase the bond order from C-C < C
]
C < C
^
C.
What additional structures might also equal C
n
H
2
n
and C
n
H
2
n
-2
?
C These general formulae equal the loss of H
2
and the formation of extra C-C bonds.
Many different structures are possible. Instead of forming a C
]
C, the loss of H
2
can
also give a cyclic structure. Both of these options give an additional C-C bond. For
example, a formula of C
n
H
2
n
can be for an alkyne, a diene, a cyclic alkene, or a bicyclic.
Is there an easy way to explain these observations?
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