How do you know your sample does not contain any of the reactants?What temperature did your product come off?

Ethyl ethanoate

Pure ethyl ethanoate boils at 73oC.
This is the same temperature at which you should have seen the product was distilled.
What temperature did your product come off? This is your boiling point.

Infrared spectrum:
Use a pipette to take a drop of your sample. Place it in between two IR discs, and place into the IR machine.
A spectrum will be produced. Label all peaks fully, in particular pay attention to the C=O.
How do you know your sample does not contain any of the reactants?