dioxetane compounds reactable with an enzyme to release optically detectable eneregy are disclosed . these compounds have the formula : ## str1 ## wherein t is a cycloalkyl group or a fused polycyclo - alkylidene group bonded to the dioxetane ring through a spiro linkage ; y is a fluorescent chromophore capable of absorbing energy to form an excited energy state from which it emits optically detectable energy to return to its original energy state ; x is hydrogen or an alkyl , aryl , aralkyl , alkaryl , heteroalkyl , heteroaryl , cycloalkyl or cycloheteroalkyl group , or an enzyme - cleavable group containing a bond cleavable by an enzyme to yield an electron - rich moiety bonded to the dioxetane ring , z is hydrogen , hydroxyl or an enzyme - cleavable group containing a bond cleavable by an enzyme to yield an electron - rich moiety bonded to the dioxetane ring , at least one of x and z being an enzyme - cleavable group , and t also includes a substituent which enhances the solubility of the dioxetane in aqueous solution , or a substituent which facilitates bonding of the dioxetane to a membrane , film , bead , polymer or polymerizable group , or a substituent which enhances the kinetics of the dioxetane enzyme degradation .