O

n-Propyl urea CH3CH2CH2NHCNH2 0.89

k

a-Amino acids These compounds have the lowest Ko/w values of all q

R CHCOOH organic molecules and are essentially impermeable 11 0.66 1 due to large dipole-dipole interactions with water Proprionamide CH3CH2CNH2 0.89 NH2 l-Amino-2- CH3CHOHCH2NH2

propanol n g j CH2OHCH2CH2OH

Alanine CH3CHC—OH 006

k

Sulfur functional groups

Sulfur replacement of oxygen

(a) Sulfur compounds have greater Ko/w values and permeate membranes more readily than the corresponding oxygen compound; this is a result of poor H-bond formation between sulfur and water compared with the oxygen analog

(b) Sulfoxides (R2S=0) are less permeable than the corresponding ketone (R2C=0) due to stronger H-bond formation with water

1-Thioglycerol Glycerol Thiodiglycol Diethylene glycol (ohch2ch2)20 O

Acetone

CH2OHCHOHCH2SH 0.69 CH2OHCHOHCH2OH (OHCH2CH2)2S 0-95

0 0

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