Table 2. Comparison of SCRF-PCM and LD Activation Free Energies for BPL Alkylation of Methylated Nucleobases.

	guanined (kcal/mol)			adenine(kcal/mol)			cytosine(kcal/mol)			thymine(kcal/mol)
method/basis set	ΔGgas⧧a	ΔGSCRF⧧b	ΔGLD⧧c	ΔGgas⧧a	ΔGSCRF⧧b	ΔGLD⧧c	ΔGgas⧧a	ΔGSCRF⧧b	ΔGLD⧧c	ΔGgas⧧a	ΔGSCRF⧧b	ΔGLD⧧c
AM1	51.86			51.68			52.98			66.96
PM3	52.17			54.29			56.03			94.60
HF/6-31 G(d)	45.10	25.30	15.56	47.14	29.62	22.71	49.18	27.74	19.29	71.71	47.52	41.51
HF/6-31+ G(d,p)	42.72	22.06	11.83	44.72	26.42	19.16	46.84	24.53	13.14	66.91	41.82	34.01
HF/6-311++ G(d,p)	43.31	22.45	12.06	45.12	26.98	19.54	47.11	25.15	13.87	67.16	42.61	34.25
MP2/6-31 G(d)	44.12	19.81	16.78	46.75	25.68	21.97	49.74	24.47	17.09	72.23	42.32	40.25
MP2/6-31+ G(d,p)	42.08	15.49	11.69	44.10	21.53	17.58	47.29	20.08	12.36	66.98	34.91	33.09
MP2/6-311++ G(d,p)	42.81	21.96	10.69	44.23	23.16	18.29	47.88	21.76	13.73	67.61	35.84	34.69
M06-2X/6-31 G(d)	42.63	25.65	14.05	42.26	26.98	19.26	45.74	26.76	17.46	64.34	43.51	37.05
M06-2X/6-31+ G(d,p)	39.98	20.36	8.26	39.28	23.54	15.24	42.94	23.18	12.37	59.54	37.96	29.66
M06-2X/6-311++ G(d,p)	40.14	20.75	8.34	39.08	23.33	15.01	42.58	23.08	12.53	59.58	38.35	28.62
mPWPW91/6-31 G(d)	40.53	22.01	12.03	41.10	25.60	18.07	44.15	24.69	15.25	64.52	44.77	36.33
mPWPW91/6-31+ G(d,p)	38.06	18.99	6.75	38.43	22.53	13.71	41.65	21.44	10.49	59.89	39.33	29.05
mPWPW91/6-311++ G(d,p)	38.20	19.22	7.20	38.27	22.53	14.00	41.37	21.43	10.31	59.76	39.61	27.97

^aThe gas-phase activation energy of the alkylation reaction of a specific methylated nucleobase with β-propiolactone.

^bActivation free energies of the alkylation reaction between a specific methylated nucleobase and β-propiolactone obtained by the SCRF-PCM method.

^cActivation free energies of the alkylation reaction between a specific methylated nucleobase and β-propiolactone obtained by the LD method.

^dExperimental value: ΔG^⧧ = 20.8 ± 0.5 kcal/mol.