HOME
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33
34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64
65

<<< PREVIOUS_______ NEXT >>>

6

 

Monolayers at the air-water interface

 

 

         Stearic acid molecule

 

Chemical formula:               H3C-(CH2)16-COOH

Model (grey - carbon, white - hydrogen, red - oxygen):

         Interaction of amphiphilic moleciles with water and with each other

 

Surface tension of water:                                72-73 mN/m

Surface tension of octadecane:                      28-29 mN/m

__________________

Energy of hydrogen bond:                             4-7 kCal/mol

Energy of Van der Waals interaction per CH2-group inside the monolayer:                                                       2.0-2.2 kCal/mol

Energy of Van der Waals interaction between adjacent monolayers (per one molecule):                                                         1.9-2.1 kCal/mol

(For comparison, kT SYMBOL 187 \f "Symbol" 0.5 kCal/mol, energy of covalent bond is of about 50 kCal/mol.)

__________________

Solubility of fatty acids in water (g/l, at 20C):

         Valeric acid                (C4H9-COOH)          -        32.0

         Caproic acid               (C5H11-COOH)        -        9.7

         Enanthic acid             (C6H13-COOH)        -        2.4

         Caprylic acid              (C7H15-COOH)        -        0.68

         Pelargonic acid          (C8H17-COOH)        -        0.26

         Stearic acid                 (C17H35-COOH)      -        0.0029

___________________

<<< PREVIOUS_______ NEXT >>>
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33
34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64
65