Concept:

When organic compounds have very high boiling points, they often chemically decompose before they can reach the temperature required to boil at normal atmospheric pressure.

Formula:

$$ P_{\text{external}} \downarrow \implies \text{Boiling Point} \downarrow $$

Solution:

• To safely distill these sensitive compounds, a vacuum pump is attached to the distillation apparatus to forcefully remove air and drastically lower the internal pressure.



• Because boiling occurs when vapor pressure equals external pressure, lowering the external pressure means the liquid will boil at a much cooler, safer temperature.



• This specific technique is formally classified as Vacuum distillation.

Why other options are incorrect:

Fractional distillation separates mixtures based on close boiling points at normal pressure. Steam distillation uses steam to lower the partial pressure of immiscible oils. Destructive distillation is a high-heat decomposition process in the absence of air.