A 1,2-dioxetane derivative of the formula (I):
##STR1##
wherein Ar is an aryl group which may have an alkyl group, an aryl group, a
halogen atom, an alkoxyl group, a carboxyl group, a formyl group, an alkyl
ester, an aryl ester, an alkylketone, an arylketone or a hetero ring
bonded thereto, X is a substituent capable of labeling an organic compound
or a biological molecule, or an ester, Y is a hydrogen atom, an acyl group
or a group of the formula --Si(R.sub.4 R.sub.5 R.sub.6) (wherein each of
R.sub.4, R.sub.5 and R.sub.6 which are independent of one another, is an
alkyl group or an aryl group), Z is an alkyl group, an aryl group, an
oxygen atom, a sulfur atom, a carbonyl group, --(CO)--O--, --O--(CO)--,
--NH--, --NH--CO--, --CO--NH--, --OSi(R.sub.7 R.sub.8)-- (wherein each of
R.sub.7 and R.sub.8 which are independent of each other, is an alkyl group
or aryl group) or a group of the formula --(R.sub.9 R.sub.10)SiO--
(wherein each of R.sub.9 and R.sub.10 which are independent of each other,
is an alkyl group or an aryl group), each of R.sub.1 and R.sub.2 is an
alkyl group or an aryl group, and R.sub.3 is a spacer.
