Synthesis and structure determination of amines

Exercise 1

$27.0\;g$ of a saturated monocyclic monoamine contains $5.18\;g\;N$. Find its molecular formula!

$\%_N$ $=$ $\frac{5.18\cdot 100}{27.0}$ $=$ $19.18$ General formula: $C_nH_{2n+3}N$ $\%_N$ $=$ $\frac{14\cdot 100}{12n+2n+3+14}$ $\frac{1400}{14n+17}$ $=$ $19.18$ $n$ $=$ $4 $ Molecular formula: $C_4H_{11}N$