Why can vacuum distillation prevent some substances from decomposing?

Vacuum distillation prevents substances from decomposing by allowing them to boil at significantly lower temperatures than they would under standard atmospheric pressure.12

In a standard distillation process, a substance must be heated until its vapor pressure equals the surrounding atmospheric pressure to reach its boiling point. For many compounds, this required temperature is high enough to cause thermal decomposition, effectively destroying the material before it can be purified.32

By using a vacuum pump to reduce the pressure within the distillation apparatus, the boiling point of the liquid is lowered. Because the substance can transition into a vapor phase at a much cooler temperature, it avoids the heat-induced chemical breakdown that would otherwise occur at higher temperatures. This method is particularly useful for processing substances that have inconveniently high boiling points or are sensitive to heat.12