(2): A selenenylsulfide's exchange intermediate should have the attacking nucleophile bound to Se, not to S: The initial kinetic products of exchange with symmetrical cyclic dichalcogenides can rearrange intramolecularly within milliseconds to form the thermodynamic products. However, the thermodynamic preference for exchange intermediates to be Se-bound rather than S-bound is strong, regardless of the attacking nucleophile. For selenolate attack, a proximally N-acylated linear diselenide intermediate has E° ca. 270 mV lower than the alternative linear selenenylsulfide (ca. -550 mV vs -280 mV): so the diselenide should be the favoured intermediate (e.g. B rather than E in Fig. ). For thiolate attack, linear selenenylsulfides have E° ca. 70 mV lower than the alternative disulfide (ca. -280 mV vs -210 mV), also favouring the Se-bound intermediate (e.g. D rather than F in Fig. ). Thus, the kinetically-favoured attack at Se (see (1)) also gives the thermodynamic intermediates, and these are the only intermediates relevant to probe evolution (B and D for probes of type A; H and K for probes of type G; Fig. ): which simplifies the pathways to cargo release (c.f. Fig. ).