. Author manuscript; available in PMC: 2010 Oct 7.

Published in final edited form as: J Am Chem Soc. 2009 Oct 7;131(39):13963–13971. doi: 10.1021/ja905081x

Table 1.

Optimized donor (O-H) and acceptor (C-H) bond lengths (Ǻ) at the transition states along with the calculated and experimental free energies of activation (kcal/mol) for the proton transfer reactions between substituted α-methoxystyrenes (X-1) and acetic acids (Y-CH₂CO₂H) at 25°C.^a

Reaction		TS structure		ΔG^≠		ΔG^o
X-1	Y-CH₂CO₂H	R(O—H)	R(C—H)	Calc.	Expt.	Calc.	Expt.
4-MeO-	Cl-	1.3190	1.3224	14.6	15.2	1.8	3.2
H-	Cl-	1.3557	1.2966	16.4	16.6	5.8	5.6
4-NO₂-	Cl-	1.4247	1.2552	20.4	19.3	13.0	9.2
3,5-di-NO₂-	Cl-	1.4758	1.2318	22.6	21.1	16.3	12.2
H-	di-Cl-	1.3201	1.3225	14.5	15.0	1.4	3.4
H-	NC-	1.3421	1.3070	15.7	16.5	5.1	5.1
H-	Cl-	1.3557	1.2966	16.4	16.6	5.8	5.6
H-	MeO-	1.3928	1.2741	18.4	17.5	9.1	6.6
H-	H-	1.4188	1.2600	19.6	18.7	10.3	8.3
4-NO₂-	di-Cl-	1.3753	1.2837	18.4	17.6	8.6	7
4-NO₂-	NC-	1.4030	1.2676	19.7	19.1	12.3	8.6
4-NO₂-	Cl-	1.4247	1.2552	20.4	19.3	13.0	9.2
4-NO₂-	MeO-	1.4754	1.2317	22.4	20.2	16.3	10.1
4-NO₂-	H-	1.5181	1.2145	23.7	21.4	17.5	11.9

See Supporting Information for details on the calculations of the potential energy surface and transition state optimization at the PCM-B3LYP/6-31+G(d,p) level.