Abstract
The potential ability of the phosphoryl group to undergo enolisation is demonstrated. The conditions for enolisation of phosphoryl and thiophosphoryl groups are examined. In order to determine the acidifying capacity of groups attached to the α-carbon atom, constants that depend on the number of substituents on this atom have been used. The limiting values of the totals of the constants that are responsible for enolisation of the phosphoryl group have been calculated. It is shown that enolisation of the phosphoryl group obeys the laws comprising the theory of prototropic tautomeric acid–base equilibrium. The bibliography includes 71 references.