**EA:**

The data adds up to 100% so there are no "hidden elements" but we don't
know the molecular weight. That doesn't matter because the data can
still
provide the empirical formula (*simplest ratio*) by considering
using
a 100g and remembering NEVER TO ROUND DATA during EA calculations (it
will
invariably mean you get the wrong answer).

%C = 85.63 divide by atomic weight
: 85.63/12.011 = 7.129
moles

%H = 14.37 divide by atomic weight : 14.37/1.008 = 14.256
moles

So we have 7.129 moles of C for every
14.256 moles of H, by dividing
by the smallest, that tells us for each C there are 2.0 H atoms.... or
C_{1}H_{2}

Hence empirical formula, the simplest integer ratio is **CH _{2}**.

So if we have 6 C atoms, then the
molecular formula = **C _{6}H_{12}**.

Remember isomerism is a pair relationship and the compounds

Enantiomers are non-superimposable
mirror images, for that they need
a chirality center, which is this case needs to be an sp^{3} C
with 4 different substituents attached. There are three possible pairs
for C_{6}H_{12}:

Constitutional isomers contain different
"pieces" having either different
functional groups (e.g. alkene and cycloalkane here) or different
connectivity
orders. There are lots of possibilities here, a *small*
selection
of compounds are shown below, any pair from this list would be
constitutional
isomers:

Geometric isomers are *cis*- or *trans*-
alkenes. In order
for this to be possible, the two substiutents at each end of the double
bond must be different.