A large number of Michael adducts have been prepared from β-morpholinoethanethiol and α,β-unsaturated compounds bearing a variety of functional groups. The extent of cleavage of 23 of these under reversal conditions has been determined quantitatively. The relation between structure and amount of cleavage has been discussed. A few heterocyclic thiols were also employed, to extend the generality of the reactions. With the latter, the thiol-cleaved product was separated and identified, to show that the cleavage was normal.