The changes (from A-D given below) which occur when $\mathrm{O_2}$ binds to hemerythrin are
(A) One iron atoms is oxidized
(B) Both the iron atoms are oxidized
(C) $\mathrm{O_2}$ binds to one iron atom and is also hydrogen bonded.
(D) $\mathrm{O_2}$ binds to both the iron atoms and is also hydrogen bonded.
(a)B and C
(b)B and D
(c)A and D
(d)A and C
Answer
Answer: A ✓ checked by 4AB · confidence high
Answer: (b) and (c).
Explanation
Deoxyhemerythrin contains two Fe(II) centres bridged by a hydroxo group and two carboxylates (Glu, Asp). When O₂ binds, both irons are oxidised to Fe(III) and O₂ is reduced by two electrons to peroxide, which takes up the bridge proton as hydroperoxide (OOH⁻). The hydroperoxide is bound terminally to only one iron (the five-coordinate one) and is hydrogen-bonded to the now μ-oxo bridge. So statements B and C are correct and A and D are wrong — option (a).