Counterintuitive mp/bp Comparisons
Every pair here shares one molecular formula, and the two properties refuse to move together — one ranking follows attraction, the other follows crystal packing. Rank the pair by both and see where your intuition holds.
Pick the higher boiling point and the higher melting point, then check both at once. All values are measured.
Compound A
Compound B
Which boils higher?
Which melts higher?
Common Questions
How can two compounds boil at the same temperature but melt 100 degrees apart?
Boiling only asks how strongly molecules attract; melting also asks how neatly they pack into a crystal. Isomers with identical forces boil together, but if one packs well and the other doesn't, their melting points separate dramatically. Anthracene and phenanthrene boil one degree apart yet melt 117 degrees apart.
What is an mp/bp order flip?
A pair where one compound boils higher but the other melts higher. The boiling order follows attraction strength; the melting order follows crystal packing, and the two rankings can genuinely disagree — cis-1,2-dichloroethylene boils higher than trans (bigger dipole), while trans melts higher (straighter molecule, better stacking).
Are these boiling points really tied?
Pairs marked as ties differ by 6 °C or less — within the scatter of experimental boiling-point measurements, so no exam would ask you to rank them. The melting gaps in the same pairs are 60 °C or more: two orders of magnitude past measurement noise.