Write a structural formula for each of the following compounds:
a. diethylpropylamine
b. N-methylbenzylamine
c. sec-butylamine
d. 1,5-diaminopentane
e. N,N-dimethylaminocyclopentane
f. N,N-dimethyl-3-hexanamine
g. tetraethylammonium chloride
h. p-nitroaniline
i. 2-aminohexane
j. diphenylamine
k. o-toluidine
l. 3-methyl-2-pentanamine