Chemiluminescent compositions, methods, assays and kits for oxidative enzymes are described. Further disclosed are dioxetane compounds of the form: 0-0 ΛR R R T (i) where R can independently be any branched alkyl or cycloalkyl group which provides stabilization for the dioxetane or where both R groups together form a cycloalkyl or polycycloalkyl moiety spiro bound to the dioxetane ring, wherein each R group or the spiro bound moiety can be unsubstituted or substituted with one or more electron-withdrawing groups or electron donating groups, or groups providing preferential oxidative isozyme substrate recognition, and wherein Ri is an aryl group, or an alkyl group of 1-20 carbon atoms, which can be optionally substituted with 1 or more halogen atoms, and wherein T is an aryl or heteroaryl ring capable of emitting light upon enzyme activated decomposition of the dioxetane I. Kits, methods and assays are also disclosed that comprise the dioxetane compounds.