solubility and distribution. molecular interactions ionic interactions dipole-dipole interactions...
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SOLUBILITY ANDDISTRIBUTION
SOLUBILITY ANDDISTRIBUTION
Molecular InteractionsMolecular Interactions
Ionic interactions Dipole-dipole interactions Induced dipoles Hydrogen bond
+ --+
+-
+ - + - + -
Water MiscibilityWater Miscibility
Solvents with relatively high polarity are miscible in water (e.g. acetic acid, ethanol, dioxane, DMSO).
Solvent with low polarity or non-polar are water-immiscible (hexane, petroleum ether) Ask your advisor for the Solvent Miscibility Table
Solvent - Solute InteractionsSolvent - Solute Interactions Polar solvents (e.g., water): (1) owing to
high dielectric constant reduce ionic attraction between oppositely charged ions in crystals; (2) break covalent bonds of strong electrolytes resulting in dissociation; (3) solvate molecules through dipole interaction
forces (particularly, hydrogen bond). Nonpolar solvents (e.g. hydrocarbons):
dissolve nonpolar compounds through
induced dipole interactions. Semipolar solvents (ketones, alcohols):
can induce polarity in nonpolar solvent molecules (co-solvents).
Solvent PolaritySolvent Polarity
Dielectricconstant,
Solvent Solute
80 water Inorganic and organic salts
50 glycols Sugars, tannins
30 methyl and ethyl alcohols Caster oil, waxes
20 Aldehydes, ketones, andhigher alcohols, ethers,
esters
Resins, volatile oils, weak electrolytesincluding barbiturates, alkaloids and
phenols5 Hexane, benzene, carbon
tetrachloride, ethyl ether,petroleum ether
Fixed oils, fats, petrolatum, paraffin,other hydrocarbons
0 Mineral oil and fixedvegetable oils
-
Liquid-Liquid SystemsLiquid-Liquid Systems
Miscibility: polar and semipolar solvents (e.g. water and alcohol, glycerin and alcohol, alcohol and acetone) are completely miscible in all proportions.
Partial miscibility: With certain proportions two liquid layers are formed (e.g., water-ether, phenol-water)
Miscibility is characterized by the phase diagram.
A
100% A
100% B100% C
B
C
Miscible
LPS
Effects on SolubilityEffects on Solubility
Pressure: increases solubility of gases (Henry’s law: PB = PB
o. A xB)
Temperature: solubilty of most gases decreases, solubility of liquids and solids may be affected both ways
Co-solvents: increase solubility by changing the solvent polarity.
Salting out: elaboration of gases from solutions by electrolytes (NaCl) and highly polar nonelectrolytes (glucose)
Doxorubicin and TaxolDoxorubicin and Taxol
O
OH
O
O
OOH
HO
O
O
O
O
OO
O
N
DoxorubicinTaxol
OO
HO
OH
HO
H
HHH
H
O
HO
HO
OH
H
O
O
OH
OH
HO
H HH
H
H
H
H
H
H
H
O
O
OH
OHHO
H
H
H
HHH
H
H H
OO
O OH
HO
OHH
H
H
H
H
O
HO
HO
OH
O
CyclodextrinCyclodextrin
More DrugsMore Drugs
Aspirin
Erythromycin
Bactrim (sulfamethoxazole)
AZT (Zudovudine)
Acyclovir (Zovirax)
Even More DrugsEven More Drugs
Ibuprofen (Advil)
Lavimudine (3TC)
Acetaminophen (Paracetamol)
Retinol (Vitamin A)Vitamin B12
Solubility of Acids/BasesSolubility of Acids/Bases
HAsold = HAsolution HAsolution + H2O = H3O+ + A-
[HAsolution] = so ; Solubility: s = so + [A-]
]OH[]OH[
]HA[]A[
33
ao
solutea
KsK
]OH[
13
ao
Kss
s
so
pKa
2so
pH