Dioxetanes half-life

However, formation of the dioxetane intermediate might be preceded by the formation of a peroxide intermediate, which could be trapped as an addition product with an alcohol or an amine (half-life of the peroxide (R = Me) is ca 20 min at 30 °C in CDC13)19. As neither dioxetanes nor peroxiranes are known to react with nucleophiles, an initially formed peroxide zwitterion is probably the species intercepted by a nucleophile or competitively rearranges to a dioxetane (Scheme 5). 

Matsumoto, Watanabe N, Kobayashi H, Matsubara J, Kitano Y, Suganuma H, Matsubara J, Kitano Y, Ikawa H. Synthesis of 3-alkoxymethyl-4-aryl-3-tret-butyl-4-methoxy-1,2-dioxetanes as a chemiluminescent substrate with short half-life emission. JCS Chem Commun 1995 431-2. 

Fig. 38. Chemiluminescence properties of the phenolic anions of two substituted adamantyl naphthyl dioxetanes. The emission wavelength and half-life of compound (a) are 550 nm and 23 min, respectively, while the corresponding values for compound (b) are 459 nm and 9 sec. These data are taken from Edwards et at. (El).

Fig. 41. Alkaline-phosphatase-triggered cleavage of the highly stable adamantyl meta-phenyl phosphate dioxetane, to give the unstable, light-emitting phenoxide ion. The half-life values were measured in an aqueous medium at 30°C (B18,E1).

Dioxetanones are too unstable ever to be isolable when directly attached to the fluorescent donor, but the related dioxetans can usually be characterised. Some have already been discussed (p. 63) but direct relation to the acridan esters would provide the best connection with the luciferins. Even dioxetans present stability problems. For example, treatment of (25) with singlet oxygen gave a dioxetan [39] with a half life of 8 min. at 25 C, decomposing with a quantum yield of 0.25. This decomposition could be followed by N.M.R. 

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