. Author manuscript; available in PMC: 2013 Nov 13.

Published in final edited form as: J Chem Theory Comput. 2012 Sep 12;8(11):4405–4412. doi: 10.1021/ct300613v

Table 5.

The effect of shielding the electrostatic interactions with an increasing van-der-Waals radius of the phosphate oxygens. Shown are the solvation free energies (energies 5 and 6 in 2) obtained from TI calculations with variable oxygen radius. For methyl and p-tolyl phosphate charges from Ref.¹² were used and RESP charges for the remaining compounds. The error estimation was conducted for the standard parameter set as described in Ref.²⁸

Molecule Phosphate	r_Original	+0.05Å	+0.1Å	+0.15Å	+0.2Å	+0.3Å	Error Est.
$H_{2} P O_{4}^{-}$	-99.3	-95.7	-92.6	-89.8	-87.1	-82.6	0.30
$H P O_{4}^{2 -}$	-307.8	-301.6	-295.8	-290.1	-285.0	-275.0	0.32
Methyl phosphate
$C H_{4} P O_{4}^{-}$	-94.1	-91.3	-88.7	-86.2	-82.1	-80.3	0.27
$C H_{3} P O_{4}^{2 -}$	-297.5	-292.0	-287.1	-282.1	-277.2	-268.5	0.41
Dimethyl phosphate
$C_{2} H_{6} P O_{4}^{-}$	-92.8	-90.5	-88.1	-86.1	-82.3	-80.9	0.34
Diethyl phosphate
$C_{4} H_{10} P O_{4}^{-}$	-89.1	-86.8	-84.9	-83.0	-81.0	-77.8	0.36
p-Tolyl phosphate
$C_{7} H_{8} P O_{4}^{-}$	-86.6	-83.6	-80.9	-79.3	-77.4	-73.7	0.32
$C_{7} H_{7} P O_{4}^{2 -}$	-262.38	-257.8	-253.7	-249.7	-246.0	-239.0	0.41