What is the relationship between the pressure of water and its boiling point? I am aware that a substance boils as soon as its vapor pressure equals that of the surrounding air. I have researched extensively and the best I could come come up with was rearranging the Goff-Gratch or Arden-Buck equations for temperature. While this does give me accurate approximations, I wonder why no clean formula exists that utilises physical constants, as exist for almost all other relationships in physics. Surely some equation like $F=ma$ or $PV=nRT$ must exist also for this relationship, and not just a function matched to experimental data? I appreciate any help.
$PV=nRT$ is an approximation that is approached by many gases at lower pressures and higher temperatures because the interactions between particles is reduced (and approaches zero).
But liquids exist only because those interactions are significant. The equations for molecular interaction are much messier and aren't as amenable to simplification.