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GATE 2022 CY – Question 18

Inorganic Chemistry · Bioinorganic Chemistry: Ion (Na+ and K+) transport, oxygen binding, transport and utilization, electron transfer reactions, nitrogen fixation, metalloenzymes containing magnesium, molybdenum, iron, cobalt, copper and zinc. · 1 mark · Multiple choice

The O–O resonance Raman stretching frequencies (cm$^{-1}$) of coordinated dioxygen in oxyhemoglobin and oxyhemocyanin appear, respectively, nearly at ______.

  1. 1136 and 744
  2. 1550 and 744
  3. 744 and 1136
  4. 744 and 1550

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Correct answer: (A) 1136 and 744

Explanation

Oxygen in oxyHb has substantial superoxide character, giving an O–O stretch around 1136 cm⁻¹. In oxyhaemocyanin, the dicopper site binds a peroxide unit, whose lower bond order lowers the frequency to about 744 cm⁻¹.

Thus **1136,744, A**; free O2 instead lies near 1550 cm⁻¹.