Hydrotropic Solubilization by Urea Derivatives: A Molecular Dynamics Simulation Study

Table 1

Hydrogen bonds in the four hydrotropic solutions (with NF) and the four hydrotropic agent solutions (without NF).

	Time^a	HA–HA^b	HA–H2O	NF–HA	NF–H2O	H2O–H2O	Total number of; H-bonds ± SD	Average length of; H-bonds ± SD, Å
NF + UR + Water	Starting	14 ± 5	348 ± 8	1 ± 1	4 ± 2	1660 ± 14	2027 ± 15	2.0013 ± 0.0182
	Ending	23 ± 4	341 ± 8	1 ± 1	4 ± 1	1754 ± 14	2123 ± 20	1.9740 ± 0.0051
UR + Water	Starting	20 ± 3	327 ± 14			1683 ± 31	2030 ± 35	2.0040 ± 0.0173
	Ending	20 ± 3	343 ± 14			1769 ± 15	2133 ± 17	1.9776 ± 0.0052
NF + MU + Water	Starting	21 ± 4	295 ± 16	0	4 ± 1	1682 ± 32	2002 ± 27	2.0125 ± 0.0228
	Ending	93 ± 4	167 ± 11	4 ± 2	2 ± 1	1833 ± 21	2099 ± 27	1.9830 ± 0.0065
MU + Water	Starting	17 ± 4	298 ± 17			1687 ± 37	2002 ± 25	2.0152 ± 0.0240
	Ending	106 ± 8	155 ± 11			1845 ± 23	2105 ± 23	1.9867 ± 0.0055
NF + EU + Water	Starting	21 ± 3	281 ± 13	0	5 ± 1	1648 ± 28	1955 ± 31	2.0119 ± 0.0126
	Ending	94 ± 9	120 ± 10	1 ± 1	5 ± 1	1836 ± 20	2080 ± 21	1.9850 ± 0.0054
EU + Water	Starting	22 ± 5	287 ± 14			1652 ± 22	1961 ± 17	2.0111 ± 0.0148
	Ending	83 ± 5	178 ± 12			1834 ± 16	2094 ± 16	1.9829 ± 0.0063
NF + BU + Water	Starting	5 ± 1	155 ± 23	0	5 ± 1	1698 ± 40	1863 ± 49	2.0083 ± 0.0173
	Ending	41 ± 4	92 ± 8	3 ± 1	2 ± 1	1871 ± 18	2009 ± 16	1.9811 ± 0.0042
BU + Water	Starting	9 ± 2	150 ± 27			1728 ± 34	1887 ± 40	2.0143 ± 0.0175
	Ending	38 ± 5	95 ± 5			1861 ± 24	1994 ± 25	1.9788 ± 0.0053
Water	Ending					1964 ± 19		1.9712 ± 0.0065

aThe HBs were averaged over the first 5 and the last 20 ps of each simulations.
^bHAs: hydrotropic agents, that is, UR, MU, EU, and BU, respectively.