The 1,3-intramolecular hydrogen transfer in the HSCH(O) ⇌ (S)CHOH and HSNO ⇌ SNOH reactions isstudied through density functional theory calculations. The reaction force together with structural and electronicproperties is monitored along the reaction path to characterize the mechanism of hydrogen transfer. It isfound that in both reactions the hydrogen transfer is activated by the structural rearrangement of the backboneatoms that allow the electrostatic interactions to promote the hydrogen transfer in a stepwise mechanism.