Hydrogen Bond
A strong dipole interaction between a hydrogen atom bonded to N, O or F and a lone pair on another such atom.
Formula / equation
X–H···Y (X, Y = N, O, F)
Unit
kJ/mol
In depth
At 10–40 kJ/mol it is far stronger than an ordinary dipole interaction because hydrogen is tiny and effectively bare when bonded to a very electronegative atom. Hydrogen bonding gives water its anomalously high boiling point, its expansion on freezing, and holds together the DNA double helix and protein secondary structure.
Examples in the real world
Water boiling at 100 °C rather than the −80 °C its size predicts; the base pairing of adenine with thymine.