Chemistry Reference
In-Depth Information
Figure 3.5, was studied at 298 K and has preferential solvation parameters qualita-
tively similar to those of pyrrolidine but with somewhat larger values: δ
x
′
WW
(max) =
0.010 near
x
S
= 0.15 and δ
x
′
WW
(max) = 0.030 near
x
S
= 0.80 and δ
x
′
WS
(min) = -0.050
near
x
S
= 0.10. Morpholine, being intermediate between 1,4-dioxane with two -O-
bridges and piperidine with two -NH- bridges between two ethylene chains by hav-
ing one of each kind, was studied at 348 K (Marcus 2002a). Its aqueous mixtures have
positive values for the mutual association δ
x
′
WS
(max) = 0.008 near
x
S
= 0.15 declining
to very near zero values at
x
S
≥ 0.55, but an S-shaped curve for self-association of
the water: it has δ
x
′
WW
(min) = 0.017 near
x
S
= 0.25 rising to δ
x
′
WW
(max) = 0.040 at
x
S
= 0.75. The aqueous pyridine system (Marcus 2001), Figure 3.5, at 298 K resembles
the piperidine system with double-humped (δ
x
′
WW
) and single trough (δ
x
′
WS
) curves
of approximately the same magnitudes as those reported above.
Acetonitrile
(Figure 3.7). As mentioned above, most of the data available for this
system at ambient temperatures for the calculation of the variable
D
of Equation 3.9
0.40
0.40
0.30
0.30
0.20
0.20
0.10
0.10
0.00
0.00
-0.10
-0.10
0.00
0.20
0.40
0.60
0.80
1.00
0.00
0.20
0.40
0.60
0.80
1.00
x
(
i
-PrOH)
x
(HMPT)
0.70
0.40
0.50
0.30
0.30
0.20
0.10
0.10
-0.10
0.00
-0.30
-0.50
-0.10
0.00
0.20
0.40
0.60
0.80
1.00
0.00
0.20
0.40
0.60
0.80
1.00
x
(CH
3
CN)
x
(TMS)
FIGURE 3.7
Volume-corrected preferential solvation parameters
δ
x
′
WW
(
●
) for water-
water interactions and
δ
x
′
WS
(
▲
) for water-solute interactions in the first solvation shell of
aqueous mixtures with solutes identified in the label of the abscissa (HMPT = hexamethyl
phosphoric triamide, TMS = tetramethylene sulfone [sulfolane]). (From Y. Marcus, 2001,
Preferential Solvation in Mixed Solvents, Part 10, Completely Miscible Aqueous Co-Solvent
Binary Mixtures at 298.15 K,
Monatshefte für Chemie
, 132, 1387, by permission of the pub-
lisher, Springer.)
