When to apply vacuum for distillation of binary mixture?

vacuum distillation is when boil point of one of the component is to high or in case of heat sensitive  

for highly boiling point mixture

vacuum distillation is used for mixtures of high boiling points

Vacuum should be applied in mostly two cases.

1. For mixtures that have very high boiling point. 

2. For heat sensitive components. 

the packing of distillation column also has to be changed accordingly.