Table 2.

Deuterium Oxide Kinetic Isotope Effects on Decarbamoylation Rate Constants k₂₁ at 25 °C ^a

Carbamoyl Group Substituents	Leaving Group b	nc	k21 H2O / k21D2O c
N-monomethyl	HTMA	1	2.8 ± 0.2
N,N-dimethyl	HTMA	4	2.4 ± 0.2
N-ethyl-N-methyl	HTMA	3	1.8 ± 0.2
N,N-diethyl	HTMA	3	1.1 ± 0.2

^aValues of k₂₁ obtained as outlined in the Experimental Procedures and Table 2.

^bLeaving group structures are shown in Figure 1.

^cPairs of duplicate or triplicate measurements of k₂₁ in H₂O or D₂O were collected, and the ratio of the means of k₂₁ in H2O to k₂₁ in D2O (k₂₁ ^H2O / k₂₁^D2O) in each pair comprised one independent measurement. The means and standard errors of n independent measurements are tabulated.