Enols, or more formally,
alkenols, are a type of reactive structure or
intermediate in
organic chemistry that is represented as an
alkene (
olefin) with a
hydroxyl group attached to one end of the alkene
double bond. The terms enol and alkenol are
portmanteaus deriving from "-ene"/"alkene" and the "-ol" suffix indicating the
hydroxyl group of
alcohols, dropping the terminal "-e" of the first term. Generation of enols often involves removal of a hydrogen adjacent (
a-) to the carbonyl group—i.e.,
deprotonation, its removal as a
proton, H
+. When this proton is not returned at the end of the stepwise process, the result is an
anion termed an
enolate (see images at right). The enolate structures shown are schematic; a more modern representation considers the
molecular orbitals that are formed and occupied by electrons in the enolate. Similarly, generation of the enol often is accompanied by "trapping" or
masking of the hydroxy group as an ether, such as a
silyl enol ether.