keto-enol tautomerization 

https://doi.org/10.1351/goldbook.08181
Interconversion of ketone and enol tautomers by hydron migration, accelerated by acid or base catalysis.
Example:
Source:
PAC, 2022, 94, 353. 'Glossary of terms used in physical organic chemistry (IUPAC Recommendations 2021)' on page 451 (https://doi.org/10.1515/pac-2018-1010)