What is H3C-CH2-CH2-CH2-CH3?

Answer 1

No such compound because the 2nd C from the left has only 2 bonds, and it needs to have 4 bonds. If you mean H3C --CH2--CH2--CH3, then this compound is n-butane.

Answer 2

This is the chemical formula for n-butylamine, which is a primary aliphatic amine. It is a clear, colorless liquid with a fish-like odor, commonly used in organic synthesis and as a corrosion inhibitor.