. Author manuscript; available in PMC: 2009 Nov 12.

Published in final edited form as: J Am Chem Soc. 2008 Oct 17;130(45):15002–15021. doi: 10.1021/ja803112w

Table 3.

Reaction free energies of small molecules in kcal/mol at four levels of theory with comparison to experiment


Reaction	PW91	OPBE	B3LYP	B3LYP*	Exp'tl

[5] O₂)_gas + H₂)_gas --> H₂O₂)_gas
	−21.67	−12.3	−22.84	−22.86	−25.25
[6] H₂O₂)_gas + H₂)_gas --> 2 H₂O)_gas
	−76.63	−80.64	−73.75	−72.58	−84.01
[7] O₂)_gas + 2 H₂)_gas --> 2 H₂O)_gas
	−98.3	−93.01	−96.59	−95.45	−109.3
[8] H₂O₂)_gas + 2 e⁻(SHE) + 2 H⁺)_aq --> 2 H₂O)_liq
	−80.69	−84.84	−77.87	−74.04	−88.11
[9] O₂)_aq + 4 e-(SHE) + 4 H⁺)_aq --> 2 H₂O)_liq
	−106.28	−101.16	−104.68	−103.54	−117.4
[4] O₂ )_aq + 4 e- (from cyt c²⁺) + 8 H⁺)_aq(pH7) --> 2 H₂O)_liq + 4 H⁺)_aq(pH3)
	−27.97	−22.85	−26.37	−25.23	−38.7

In Eq. 8 and 9, pH = 0 and [O₂]_aq = 1 M. The free energy difference between Eq. 6 and Eq. 8 is due solely to the different standard states of H₂O)_gas (1 atm) vs. H₂O)_liq (55 M). Similarly, the free energy difference between Eq. 7 and Eq. 9 is due to the different standard states of O₂)_gas (1 atm) vs. O₂)_aq (1 M) and H₂O)_gas vs. H₂O)_liq.