Table 8.

Comparison of Second-Order Rate Constants for Reactions of H_peroxo and Q with Substrates

Substratea	Species	kobs (M-1 s-1)b	kperoxo/kQ	D(R+H-) (kcal/mol)c	-ΔGhydride (R+)s (kcal/mol)d	D(RH) (kcal/mol)
(CH3CH2)2Oe	Hperoxo	17 ± 1
	Q	2.2 ± 1	7.7	214	94.8	89.0f
CH3CH2CHO	Hperoxo	85.5 ± 0.1
	Q	14.10 ± 0.02	6.06	224	103.8	87.5g
CH3CHO	Hperoxo	110.08 ± 0.03
	Q	81.7 ± 0.1	1.35	231.4	110.5	94.3f
CH3CH2OH	Hperoxo	12.13 ± 0.01
	Q	35.7 ± 0.1	0.34	231.9	110.9	94.6f
CH3OH	Hperoxo	2.4 ± 0.6
	Q	218 ± 8	0.011	255	131.8	96.1f

^aD(R⁺H^-) and D(RH) are given for the bolded C–H bond.

^bSecond-order rate constants for Class III substrates are given by the measured k_init values. Only Class III substrates for which k_init values were discretely measured by collecting >5 data points at low substrate concentration in the linear region of the curve are shown.

^cData from (64).

^dCalculated using -ΔG_hydride (R⁺)s = 0.904D(R⁺H^-) – 98.7 kcal/mol from (65). This relationship was originally derived for aromatic molecules in acetonitrile and DMSO, but should provide a good approximation for non-aromatic systems in aqueous solution.

^eData from (26).

^fData from (47).

^gData from (66).