*Article* **Perturbing the O–H ... O Hydrogen Bond in 1-oxo-3-hydroxy-2-propene**

**Ibon Alkorta 1,\*, José Elguero 1 and Janet E. Del Bene 2,\***

**\*** Correspondence: ibon@iqm.csic.es (I.A.); jedelbene@ysu.edu (J.E.D.B.)

**Abstract:** Ab initio MP2/aug'-cc-pVTZ calculations have been carried out to identify and characterize equilibrium structures and transition structures on the 1-oxo-3-hydroxy-2-propene: Lewis acid potential energy surfaces, with the acids LiH, LiF, BeH2, and BeF2. Two equilibrium structures, one with the acid interacting with the C=O group and the other with the interaction occurring at the O–H group, exist on all surfaces. These structures are separated by transition structures that present the barriers to the interconversion of the two equilibrium structures. The structures with the acid interacting at the C=O group have the greater binding energies. Since the barriers to convert the structures with interaction occurring at the O–H group are small, only the isomers with interaction occurring at the C=O group could be experimentally observed, even at low temperatures. Chargetransfer energies were computed for equilibrium structures, and EOM-CCSD spin–spin coupling constants 2hJ(O–O), 1hJ(H–O), and 1J(O–H) were computed for equilibrium and transition structures. These coupling constants exhibit a second-order dependence on the corresponding distances, with very high correlation coefficients.

**Keywords:** intramolecular hydrogen bonds; structures and binding energies; charge-transfer interactions; spin–spin coupling constants
