Viscosimetric investigations of water-acetamide system with in the temperature range 25-85°C

A C T A U N I V E R S I T A T I S L O D Z I E N S I S FOLIA CHIMICA 1 , 1982

S t e f a n i a T a n ie w a k a -O s iris k a , M aria n Woldan

VISCOSIMETRIC INVESTIGATIONS OF WATER-ACETAMIDE SYSTEM

WITHIN THE TEMPERATURE RANGE 2 5 -8 5 ° C *

The v i a c o a l t y o f a q u e o u s

a c e ta m id e s o l u t i o n s

o v e r

t h e

w h o le m l s c i b i l i t y r a n g e

a t t e m p e r a tu r e

2 5 ° ,

4 0 ° , 6 0 ° , 7 5 °

a n d 85 C

h a a b e e n m e a s u re d .

The r e l a t i v e v i s c o s i t y , tem p e­

r a t u r e c o e f f i c i e n t A t p / A T

a n d t h e th erm o d y n a m ic

f u n c t i o n

o f a c t i v a t i o n f o r f l u i d flo w

h a v e b e e n c a l c u l a t e d . The e f ­

f e c t o f d i s s o l v e d

a c e ta m id e on

w a t e r s t r u c t u r e

h a s

b e e n

d i s c u s s e d .

I n r e c e n t y e a r s

many w orka

d e v o te d t o t h e

e x p l a n a t i o n a

o f

i n t e r a c t i o n s

among w a t e r m o le c u le a

a n d v a r i o u s a m id e s h a v e

a p ­

p e a r e d .

T h ia p ro b le m

i s i m p o r t a n t

d u e

t o

t h e

a p p l i c a t i o n

o f

w a te r - a m id e

m i x t u r e s a s p o l a r

a d v e n t s i n

many c h e m ic a l p r o c e s -

a e a .

One o f

p h y s ic o - c h e m i c a l p r o p e r t i e s

o f t h e s e s o l v e n t s i s v i s ­

c o s i t y .

I n a q u e o u a s o l u t i o n s

c o n t a i n i n g v a r i o u s t y p e s

o f

p o l a r

m o le c u le a

( a l c o h o l s ,

a c e t o n e , DMF)

t h e o c c u r e n c e o f

v i s c o s i t y

maximum i s o f t e n

o b s e r v e d ,

w h ic h i s I n t e r p r e t e d

i n many w ays by

v a r i o u s a u t h o r s [ 1 - 7 ] .

The maximum

i s n o t o b s e r v e d i n c a s e

o f

a q u e o u s form am id e

s o l u t i o n s [ 8 ] .

Some a u t h o r s [ 9 , 1 0 ]

s u g g e s t

t h a t t h i s

f a c t p o i n t s t o l a b i l e

s t r u c t u r e

o f w a te r-fo r m a m id e

m i x t u r e . L ack o f d a t a

on v i s c o s i t y o f

w a te r - a c e t a m i d e

s y s te m a t

s e v e r a l t e m p e r a t u r e s

made u s c a r r y

do s u c h m e a s u r e m e n ts . We h a v e

m e a s u re d v i s c o s i t y

o f a q u e o u s a c e ta m id e

s o l u t i o n s o v e r t h e w hole

m l s c i b i l i t y r a n g e

a t t e m p e r a t u r e s :

2 5 ° ,

^ 0 ° ,

60°»

7 5 °

a n d

8 5 * 0 .

* T h e p r e s e n t w ork h a s b e e n

c a r r i e d o u t an d s u p p o r t e d

w i t h i n

t h e fram ew ork o f r e s e a r c h

on I n t e r d e p a r t n i e n t P ro b lem

E x p e r im e n ta l

A l l o f t h e

r e a g e n t s

u s e d i n t h e

i n v e s t i g a t i o n s

was

p u r i ­

f i e d by t h e

m e th o d s d e s c r i b e d e a r l i e r [ 1 1 ] .

The p u r i t y

o f a c e t -

am ld e wa3

c h e c k e d by

m e ltin g p o i n t

d e t e r m i n a t i o n

8 1-82 °C [ 1 2 ] .

V i s c o s i t y m e a s u re m e n ts

w e re made w ith

c a l i b r a t e d

U b b e lo h d e ’ s

v i s c o m e t e r

p l a c e d i n l i q u i d

t h e r m o s t a t

p r e s e r v i n g

t h e r e q u i r e d

te m p e r a t u r e w i t h

t h e p r e c i s i o n

+ p .0 5 ° C .

D e n s ity o f t h e i n v e s t i ­

g a t e d s o l u t i o n s

w as d e te r m in e d by

t h e m a g n e tic

f l o a t d e n s i m e t e r

[ 1 3 ]

w i th t h e p r e c i s i o n

2 .1 0 ” '* g /cm 3 .

The e r r o r

o f

v i s c o s i t y

m e a s u re m e n ts w as

± 0 .8 % .

R e s u l t s

The o b t a i n e d r e s u l t s

o f dy n am ic v i s c o s i t y

m e a su re m e n ts

o f

a q u e o u s a c e ta m id e

s o l u t i o n s a r e g iv e n

i n T a b le 1 .

T a b l e

1

The v i s c o s i t y o f a q u e o u s a c e ta m id e s o l u t i o n s

w t

% AcNH2 XAcNH2

m

( m o le /k g )

( c P •

1 0 " 3

P a * a )

25°C

40°C

60°C

75°C

85°C

1

2

•3

4

5

6

7

8

2

0 .0 0 6 2

0 .3 4 5 5

0 .9 2 4

0 .6 7 5

0 .4 8 1

0 .3 8 8

0 .3 4 2

5

0 .0 1 5 8

0 .8 9 1 0

0 .9 7 8

0 .7 1 0

0 .5 0 3

0 .4 0 4

0 .3 5 4

8

0 .0 2 5 8

1.47 21

1 .0 3 5

0 .7 4 3

0 .5 2 7

0 .4 1 9

0 .3 6 6

10

0 .0 3 2 8

1 .8 8 1 0

1 .0 7 6

0 .7 7 3

0 .5 ^ 3

0 .4 3 0

0 .3 7 4

15

0 .0 5 1 0

2 .9 8 7 5

1 .1 3 6

0 .8 4 3

0 .5 8 9

0 .4 6 1

0 .3 9 9

22

0 .0 7 9 1

4 .7 7 4 9

1 .3 6 5

0 .9 5 7

0 .6 6 2

0 .5 1 1

0 .4 4 1

30

0 .1 1 5 5

7 .2 5 5 3

1 .6 1 4

1 .1 2 2

,0 .7 5 7

0 .5 7 9

0 .5 0 0

40

0 .1 6 8 8

1 1 .2 3 6 0

2 .0 2 8

1 .3 8 6

0 .8 9 9

0 .6 8 5

0 .5 8 7

50

0 .2 3 3 6

16 .9 2 9 1

2 .6 0 6

1 .6 9 4

1 .0 9 4

0 .8 3 1

0 .7 0 3

T a b le 1

c o n t d .

1

2

3

4

5

6

7

8

60

0 .3 1 3 7

2 5 .3 9 3 6

2 .2 4 8

1 .3 2 8

0 .9 6 8

0 .8 1 2

70

0 .4 1 5 5

3 9 .5 0 1 2

-

2 .8 8 7

1.71 1

1 .2 4 1

1 .0 0 8

80

0 .5 4 9 3

6 7 .7 1 6 0

_/

-

-

2 .2 2 1

1 .5 1 4

1 .2 4 2

85

0 .6 3 3 3

9 5 .9 3 1 0

•m mm ••

_{1 .6 8 3}

_{1 .3 8 4}

95

0 .8 5 2 7

3 2 1 .6 5 2

m

-

-

-

_{1 .7 4 5}

100

1 .

-

-

-

-

-

2 .0 4 1

T a b le 2

c o n t a i n s th e v a l u e s

o f r e l a t i v e v i s c o s i t y

o f

t h e

i n v e s t i g a t e d s y s t e m s .

A c c o rd in g t o

l i t e r a t u r e [14-16]

r e l a t i v e v i s c o s i t y o f

n o n -

e l e c t r o l y t e s o l u t i o n s

c a n be d e s c r i b e d by t h e e q u a t i o n :

T) /»Jo ■ 1 ♦ Be ♦ Cc2

(1 )

The v a l u e s o f

B

and

C

c o e f f i c i e n t s o f a q u e o u s

a c e ta m id e

s o l u t i o n s e s t i m a t e d g r a p h i c a l l y

a r e shown i n t h e

T a b le 3 .

In o r d e r

t o d e t e r m in e t h e

i n f l u e n c e o f

d i s s o l v e d

a c e ta m id e

on w a te r t h e

v a l u e s o f

th erm o d y n am ic f u n c t i o n s

o f

a c t i v a t i o n

f o r f l u i d flo w w ere c a l c u l a t e d .

A c c o rd in g t o E y r i n g ’ s

t h e o r y [ 1 7 ] c o n c e r n i n g l a m i n a r

flo w

o f l i q u i d t h e

dynam ic v i s c o s i t y o f th e

s o l u t i o n c a n be d e s c r i b e d

by t h e e q u a ti o n

h N . „ AC*

h N

- AS*

AH*

T] »

e x p

~ y ~

ex P

ft

ex P

rT

'

'

w h e re :

AG*, AH* an d AS* - t h e f r e e

e n e rg y o f a c t i v a t i o n

f o r f l u i d

f lo w , e n t h a l p y

and e n t r o p y r e s p e c t i v e l y

h— P l a n c k 's

c o n s t a n t

V - m o la r volum e o f s o l v e n t

N - A vogardo num ber

V a lu e s o f p a r t i c u l a r

th erm o d y n am ic f u n c t i o n s

o f a c t i v a t i o n

f o r f l u i d flo w

w ere c a l c u l a t e d from

t h e fo r m u la e :

T a b l e

2

&

v t

%

25C*C

40(5C

60°C

75°C

85°C

AcNH0_c

C

C

C

C

C

( m o l e / i )

^ r

( m o le /1 ;

^ r

( m o l e / l )

H r

( m o l e / l )

n r

( m o l e / l )

n r

2

0 .3 4 4 9

1 .0 3 8 2

0 .3 4 3 2

1 .0 3 3 7

0 .3 4 0 0

1 .0 3 0 9

0 .3 3 7 1

1 .0 2 5 6

0 .3 3 4 9

1 .0 2 2 4

5

0 .8 9 1 2

1 .0 9 8 8

0 .8 8 6 8

1 .0 8 7 3

0 .8 7 3 2

1 .0 7 8 0

0 .8 7 0 5

1 .0 6 6 5

0 .8 6 4 8

1 .0 5 8 3

8

1 .4 7 5 3

1 .1 6 2 9

1 .4 6 7 3

1 .1 4 0 9

1 .4 5 2 9

1 .1 2 9 4

1 .4 4 0 0

1 .1 0 6 1

1 .4 3 0 4

1 .0 9 4 2

10

• 1 .8 8 7 7

1 .2 0 9 0

1 .8 7 7 1

1 .1 8 3 8

1 .8 5 8 2

1 .1 6 3 7

1 .8 4 1 5

1 .1 3 5 2

1 .8 2 9 2

1 .1 1 8 1

15

3 .0 0 8 1

1 .3 3 2 6

2 .9 8 9 9

1 .2 9 8 6

2 .9 5 8 4

1 .2 6 2 3

2 .9 3 0 8

1 .2 1 7 0

2 .9 1 0 5

1 .1 9 2 8

22

4 .8 3 0 b

1 .5 3 3 7

4 .7 9 8 0

1 .4 6 5 5

4 .7 4 4 0

1 .4 1 8 8

4 .6 9 8 2

1 .3 4 9 0

4 .6 6 3 2

1 .3 1 8 4

50

7 .3 7 9 7

1 .8 1 3 5

7 .3 2 3 1

1 .7 1 8 2

7 .2 3 3 3

1 .6 2 2 4

7 .1 6 2 9

1 .5 2 8 5

7 .1 0 8 2

1 .4 9 4 7

4Q

1 1 .5 5 4 4

2 .2 7 8 6

1 1 .4 5 3 3

2 .1 2 2 5

1 1 .3 0 3 2

1 .9 2 6 7

1 1 .1 8 4 3

1 .8 0 8 3

1 1 .0 9 3 8

1 .7 5 4 8

50

1 7 .4 4 1 0

2 .9 2 8 1

1 7 .2 6 6 8

2 .5 9 4 2

1 7 .0 2 5 6

2 .3 4 4 6

1 6 .8 3 2 8

2 .1 9 3 8

1 6 .6 9 4 8

2 .1 0 1 6

60

-

-

2 6 .0 0 2 5

3 .4 4 2 6

2 5 .6 2 4 7

2 .8 4 6 1

2 5 .3 1 9 4

2 .5 5 5 4

2 5 .1 0 6 9

2 .4 2 7 5

70

■

-

-

4 0 .5 6 9 3

4.A 205

3 9 .9 6 0 6

3 .6 6 6 9

3 9 .4 8 5 4

3 .2 7 6 1

3 9 .1 3 3 8

3 .0 1 3 4

80

-

-

-

-

6 8 .6 2 3 4

4 .7 6 0 0

6 7 .7 5 2 6

3 .9 9 6 8

6 7 .1 6 7 5

3 .7 1 3 0

C D

VJ

>*

_{- .}

_-

_am

_-

_-

_-

_{9 6 .0 0 6 8}

4 .4 4 3 0

9 5 .1 8 6 6

4 .1 3 7 5

95

-

-

-

-

-

-

-

-

3 1 9 .0 4 6 6

5 .2 1 6 7

-

- '

-

-

-

-

-

-

-

6 .1 0 1 6

S

to

fa

n

ia

T

a

n

ie

w

s

k

a

-O

s

ii

s

K

a

,

M

ar

ia

n

W

o

ld

an

AH

« R d I n T ) / d ( f )

AG

- RT I n (

tj

V/UN)

( 3 ) ( 4 )

AS

*

AH* - AG*

( 5 )

The d e r i v a t i v e

d I n t j /d ( ^ - ) w as d e te r m in e d n u m e r i c a l l y u s i n g

t h e e q u a t i o n :

(

6

)

The o b t a i n e d A H *,

AG* an d

AS* v a l u e s o f

aq u e o u a

a c e t -

am id e s o l u t i o n s

a r e g iv e n i n

T a b le 4 .

T a b l e 3

The v a l u e s o f B an d C c o e f f i c i e n t s

( e q u a t i o n [ 1 ] ) o f a q u e o u a a c e ta m id e s o l u t i o n s

T

( ° C )

B

( 1 / m o le )

C

( l 2/m o le 2 )

AB/AT • 1 0 5

25

0 .1 1 1

- 0 .0 0 0 3

- 0 . 7

40

0 .1 0 0

- 0 .0 0 0 4

- 0 . 7

60

0 .0 8 7

- 0 .0 0 0 4

- 0 . 7

75

0 .0 7 7

- 0 .0 0 0 4

- 0 . 9

85

0 .0 6 8

- 0 .0 0 0 4

The e n t h a l p y , f r e e e n e r g y a n d

f l u i d flo w o f a q u e o u s

M ole

f r a c t i o n

XA

c

NH2

25°C

■

N

_40°C

AH*

AG*

>

CO

-M

-AH*

AG*

>

w

■H

-AH*

k J

k J

J

k J

m ole

kJ

m ole

J

k J

m ole

mole

m ole * K

m ole-K

m ole

0 . 0

1 6 .4 8

9 .1 6

2 4 .6

_{1 5 .3 1}

_{8 .8 3}

_{2 0 .7}

_{1 3 .9 2}

0 .0 0 6 2

1 6 .6 5

9 .2 5

2 4 .8

1 5 .5 2

8 .9 1

2 1 .1

1 4 .1 7

0 .0 1 5 8

1 6 .8 8

9 .3 9

2 5 .1

1 5 .7 9

9 .0 4

2 1 .6

1 4 .5 0

0 .0 2 5 8

1 7 .0 9

9 .5 3

2 5 .4

_{1 6 .0 7}

_{9 .1 7}

_{2 2 .0}

_{1 4 .8 5}

0 .0 3 2 8

1 7 .1 9

9 .6 3

2 5 .4

1 6 .2 6

9 .2 6

_{2 2 .3}

_{1 5 .1 5}

0 .0 5 1 0

1 7 .6 0

9 .8 7

2 5 .9

1 6 .6 3

9 .5 0

2 2 .8

_{1 5 .5 9}

0 .0 7 9 1

1 8 .1 3

1 0 .2 2

2 6 .6

1 7 .2 7

9 .8 2

2 3 .8

1 6 .1 8

0-. 1155

1 9 .0 2

1 0 .6 3

2 8 .1

1 8 .0 5

1 0 .2 3

2 5 .0

1 6 .9 0

0 .1 6 8 8

2 0 .5 2

1 1 .2 0

3 1 .3

1 9 .3 0

.1 0 .7 8

2 7 .2

1 7 .8 4

0 .2 3 3 6

2 2 .6 0

1 1 .8 2

3 6 .2

2 0 .3 5

1 1 .3 1

2 8 .9

1 8 .9 0

0 .3 1 3 7

-

-

m

_{2 1 .7 2}

_{. 1 2 .0 4}

3 0 .9

2 0 .1 0

0 .4 1 5 5

-

m

_-

_{2 3 .2 5}

_{1 2 .6 9}

3 3 .7

2 1 .4 0

0 .5 4 9 3

-

-

•m

_-

--

2 3 .0 0

T a b l e

4

*

e n t r o p y o f a c t i v a t i o n s f o r

a c e ta m id e s o l u t i o n s

60°C

75°C

85°C

AG* AS* AH* AG*

<

!

/i

-4*C

AH*

>

a

■H

-A S *

k J

J

k J

k J

j

k J

k J

J

m ole

mole*K

mole

m ole

m ole-K

m ole

m ole

m o le •£ *

8 .4 8

1 6 .3

1 2 .9 8

8 .2 9

1 3 .5

1 2 .4 0

8 .1 7

1 1 .8

8 .5 7

1 6 .8

1 3 .2 5

8 .3 6

1 4 .1

1 2 .6 9

8 .2 4

1 2 .4

8 .6 9

1 7 .4

1 3 .6 2

8 .4 7

1 4 .8

1 3 .0 8

8 .3 4

1 3 .2

8 . 8 2

1 8 .1

1 4 .0 3

8 .5 8

1 5 .7

1 3 .5 3

8 .4 4

1 4 .2

8 .9 0

1 8 .8

1 4 .4 0

8 .6 5

1 6 .5

1 3 .9 4

8 .5 1

1 5 .2

9 . 1 3

1 9 .4

1 4 .8 0

8 .8 5

1 7 .1

1 4 .2 8

8 .7 0

(

1 5 .6

9 .4 5

2 0 .2

1 5 .4 1

9 .1 5

1 8 .0

1 4 .9 1

9 .0 0

1 6 .5 ,

9 .8 2

2 1 .2

1 6 .1 2

9 .5 1

1 9 .0

1 5 .6 4

9 .3 7

1 7 .5

1 0 .3 0

2 2 .6

1 7 .2 0

1 0 .0 0

2 0 .7

1 6 .6 5

9 .8 5

1 9 .0

1 0 .8 4

2 4 .2

1 8 .3 0

1 0 .5 6

2 2 .2

1 7 .7 5

1 0 .3 8

2 0 .6

1 1 .3 8

2 6 .2

1 9 .4 0

1 1 .0 0

2 4 .1

1 8 .9 0

10 .8 1

2 2 .6

1 2 .0 8

2 8 .2

2 0 .8 3

1 1 .7 2

2 6 .2

2 0 .2 5

1 1 .4 6

2 4 .5

1 2 .8 0

3 0 .6

2 2 .0 7

1 2 .3 0

2 8 .1

2 1 .7 0

1 2 .0 8

2 6 .9

D is c u s s io n

On F i g . 1 an d 2

t h e d e p e n d e n c e s

o f dynam ic

v i s c o s i t y

o f

a q u e o u s a c e ta m id e

s o l u t i o n s on

c o n c e n t r a t i o n a n d te m p e r a t u r e a r e

p r e s e n t e d .

As i t i s se e n

fro m F i g . 1

v i s c o s i t y o f

w a t e r - a c e t -

am ide m i x tu r e s

i n c r e a s e s m o n o to n o u sly w i t h

t h e

g ro w th o f n o n ­

e l e c t r o l y t e c o n t e n t s

i n w a te r o v e r

t h e w h o le

I n v e s t i g a t e d

tem ­

p e r a t u r e r a n g e ( 2 5 - 8 5 ° C ) .

A t t h e te m p . 85°C

t h e

d e p e n d e n c e

o f

v i s c o s i t y o f

AcNH2-H 20

m ix tu r e on t h e

c o m p o s itio n

i s

a lm o s t

l i n e a r .

The

g ro w th

o f

te m p e r a t u r e

c a u s e s

t h e

d e c r e a s e

o f

v i s c o s i t y

o f

t h e

s o l u t i o n ,

b u t

th e

c h a r a c t e r

o f

t] «■ "f

(m o le # )

f u n c t i o n r e m a in s

u n c h a n g e d .

From F i g . 2

i t

c a n

b e

F i g . 1 . D ependence o f v i s c o s i t y

o f a q u e o u s a c e ta m id e

s o l u t i o n s

v s . c o m p o s itio n o f m ix tu r e

s e e n t h a t t h e

e f f e c t o f te m p e r a t u r e

on t h e v i s c o s i t y

o f

i n ­

v e s t i g a t e d s o l u t i o n s

i n c r e a s e s

w it h t h e g ro w th o f a c e ta m id e co n ­

t e n t s i n w a t e r .

I t I s c o n n e c te d w ith

t h e f a c t t h a t t h e v i s c o s i t y

o f p u r e a c e ta m id e

d e c r e a s e s w ith

t h e g ro w th o f t e m p e r a t u r e

much

q u i c k e r th a n

v i s c o s i t y o f w a t e r .

The o c c u r a n c e o f h y d ro g e n b o n d s

i n m ixed a s s o c i a t e s w e a k e r

th a n h y d ro g e n

b o n d s I n p u r e

w a te r i s

an a d d i t i o n a l f a c t o r .

F i g . 2 . D ependence

o f v i s c o s i t y o f

a q u e o u s

a c e ta m id e

s o l u t i o n s

v s . te m p e r a t u r e

I n o r d e r t o co m pare

a c e ta m id e w ith

o t h e r a m id e s

t h e

c o u r s e

o f r e l a t i o n b e tw e e n

v i s c o s i t i e s o f

w a te r-a m id e m i x tu r e s an d

th e

m ixed s o l v e n t s

c o m p o s itio n i s p r e s e n t e d on

F i g . 3 .

As i t i s s e e n

from t h e F i g . 3

i n c a s e o f s im p le

a m id e s

(F

a n d A

c

NH2 )

m onotonous i n c r e a s e

o f v i s c o s i t y o f t h e m ix tu r e w ith

t h e g ro w th o f am ide

c o n t e n t s c a n be o b s e r v e d .

F i g . 3 . D ependence o f v i s c o s i t y

o f a q u e o u s a m id e s

s o l u t i o n s

v s .

c o m p o s i t io n o f m ix tu r e

a t 2?°C :

A - a c e ta m id e ,

F -

fo rm a m id e ,

N K F-,N -m ethylf orm am ide, DMF- N ,N - d im e th y lf orm am ide,

D E F -N ,N -d ie -

th y lf o r m a m id e ,

D X A -N ,N -d im e th y la c e ta m id e ,

D E A - N ,N - d ie th y la c e ta -

m id e,

N M A -N -m ethy lacetam ide,

N £ A -N -e th y la c e ta m ld e

V i s c o s i t y o f

w a te r-fo rm a m id e

m ixed s o l v e n t

i s

s m a l l e r th a n

v i s c o s i t y o f a q u e o u s a c e ta m id e

s o l u t i o n a t t h e

t e m p e r a t u r e 25°C .

I t i s p r o b a b ly

c o n n e c te d

w ith g r e a t e r volum e o f

a c e ta m id e m o le­

c u l e i n

c o m p a riso n w ith fo rm am ide

m o le c iile .

A g r e a t e r num ber o f

s p a c i a l

h y d ro g e n b o n d s

i n p u r e

a c e ta m id e ca n

a l s o b e

t h e

a d ­

d i t i o n a l f a c t o r .

V i s c o s i t y o f

p u r e a m id e s

N , N - d i s u b s t i t u t e d i s

a u c h lo w e r th a n

t h a t o f m o n o s u b s ti tu t e d

( F i g . 3 ) .

I t

p ro b a b ly

f o l l o w s fr o m

t h e f a c t t h a t

i n m o n o s u b s ti t u t e d

a m i d e s ' i n t e r m o l e -

b o n d i n g

o c c u r s ( c h a i n

a s s o c i a t e s ) w h ile

i n N,N-

!t«"i a m id e s i t d o e s n o t .

I n c a s e o f sy s te m

o f N - m o n o s u b s titu te d a m id e s

w ith w a t e r t h e

o c c u r a n c e o f s m a ll

maximum on t h e c u r v e

i) * f ( x ) o f t h e v i s c o ­

s i t y o f s o l u t i o n

n e a r a m ole r a t i o 1 ! 1

c a n b e o b s e r v e d , w h ile i n

a q u e o u s s o l u t i o n s

o f N , N - d i s u b s t i t u t e d

a m id e s a p ro n o u n c e d m ax i­

mum o f v i s c o s i t y

o f t h e m ix tu r e

i n m ole r e l a t i o n

o f

c o m p o n e n ts

3 :1 o c c u r s .

The p r e s e n c e

o f v i s c o s i t y maximum

o f a q u e o u s

s o l u ­

t i o n s o f N-mono- an d

N , N - d i s u b s t i t u t e d

a m id e s c a n b e

e x p l a i n e d

b y f o r m a tio n

o f m ixed a s s o c i a t e s

w i th p r e c i s e l y d e te r m in e d

com­

p o s i t i o n [ 3 , 4 ]

o r by g r e a t e r d e n s i t y

o f h y d ro g e n b o n d s [1 9 3.

The l a c k o f extrem um

on c u r v e

t

) » f ( x )

o f

w a te r-fo r m a m id e

s y s te m s a u b s t a n c i a t e s

p r o b a b ly t h e l a b i l e

s t r u c t u r e o f t h e abov'e

m e n tio n e d

m i x t u r e s [ 9 , 1 0 ] .

A c c o rd in g t o Nomoto a n d

Endo

[ 2 0 ]

i n

F-HgO

s y s te m h y d r a t e s

o f c l a t h r a t e

ty p e o c c u r ,

i n

w hich

am id e m o le c u le s

a r e b u i l t i n w a te r

s t r u c t u r e . I t c a n

be

su p ­

p o s e d , t h a t a s i m i l a r

phenom enon

o c c u r s i n c a s e

o f

w a t e r - a c e t -

am ide m i x t u r e s .

The ab o v e s t a t e m e n t

i s i n a g r e e m e n t w i t h

t h e

r e s u l t s o f

m e a su re m e n ts o f

d i e l e c t r i c p e r m i t t i v i t y

o f

a q u e o u s

a c e ta m id e m i x tu r e s [ 2 1 - 2 3 ] .

G o ncharov e t a l . [ 2 3 ]

s u g g e s t

t h a t

a c e ta m id e m o le c u le c a n b u i l t

i n w a te r s t r u c t u r e

fo r m in g h y d ro g e n

b o n d s w ith

w a te r m o l e c u l e s .

T h e se b o n d s a r e

s l i g h t l y w eaker th a n

h y d ro g e n b o n d s

i n p u r e w a t e r .

U sin g t h e d a t a

from T a b le 2

t h e te m p e r a t u r e

c o e f f i c i e n t *

A rj /A T o f a q u e o u s a c e ta m id e

s o l u t i o n s w ere

c a l c u l a t e d

( T a b le

5 ) . r

T a b l e

5

The v a l u e s o f t e m p e r a t u r e c o e f f i c i e n t

Ar}r /A T o f a q u e o u s a c e ta m id e s o l u t i o n s

X

25-40°C

4 0-60°C

6 0 - 7 5°C

7 5 -8 5 °C

0 .0 5

- 0 . 0 0 2

- 0 . 0 0 2

- 0 .0 0 2

- 0 . 0 0 2

0 .1 0

- 0 .0 0 6

- 0 . 0 0 5

- 0 .0 0 4

- 0 .0 0 3

0 ;1 5

- 0 . 0 1 0

- 0 .0 0 9

- 0 . 0 0 7

- 0 .0 0 5

0 .2 0

- 0 .0 1 7

- 0 .0 1 2

- 0 . 0 1 0

- 0 .0 0 9

0 .3 0

•»

- 0 .0 2 9

- 0 .0 1 9

- 0 .0 1 2

0 .4 0

«

- 0 .0 3 2

- 0 . 0 2 5

- 0 .0 2 2

0 .5 0 .

- 0 .0 4 4

- 0 .0 2 5

0 .6 0

-

-

- 0 .0 2 9

c

o

e

ff

ic

i«

it

A

i)

r/

A

T

of

so

m

e

no

n

e

le

c

tr

o

ly

te

s

o

lu

ti

o

n

s

in

w

a

te

r

vO

«a

H

>.«

■C

TJ

♦* H*"-1

S I ?

^ Hi—i a u i o SS<H (Or-y

£

n

S»1—•

I

H air—i

>.®<r

■C

UCM **

3 i—i

«

<9

O)

t.'~<

3<r

O <M

•H i

—l a fr> ttr—i t

* ;

=>*-»

TJ

«H

6

a

o

< 9> n

-H '—»

s ?

S‘—1

c

-O

b.

£t

L

cr C

F o r t h e s a k e o f

c o m p a ris o n

t h e

s i g n o f c o e f f i c i e n t

A t)r /A T o f

some

n o n e l e c t r o l y t e

s o l u t i o n s i n w a te r was

g iv e n i n T a b le 6 .

From t h e d a t a

i n T a b le 6 i t

f o l ­

lo w s

t h a t

te m p e r a t u r e

c o e f f i c i e n t

A r]r /A T i s p o s i t i v e i n c a s e o f a q u e o ­

u s s o l u t i o n s

o f fo rm a m id e ,

u r e a

a n d

t h i o u r e a an d n e g a t i v e

f o r

a c e ta m id e ,

DMF a n d

e t h y l - u r e a d e r i v a t i v e

s o l u ­

t i o n s . I f we c o n c lu d e

i n t h e same way

a s i n c a s e

o f e l e c t r o l y t e

s o l u t i o n s ,

we c a n s u p p o s e

t h a t DMF,

e t h y l - and

d i e t h y l u r e a o r d e r

w a t e r

s t r u c t u r e ,

w h il e fo rm a m id e ,

u r e a a n d

t h i o u r e a

h a v e b r e a k i n g e f f e c t .

The v a l u e s o f B

c o e f f i c i e n t

o f

e q u a ti o n (1 ) ( T a b le 3 )

o f

a c e ta m id e

i n w a te r a r e

p o s i t i v e a n d t h e y d e c r e ­

a s e w ith th e te m p e r a t u r e

g r o w th . Thus,

A B /A T

c o e f f i c i e n t i s n e g a t i v e , a l i k e

A»}r /A T . As i t i s

s e e n fro m

T a b le 7

t h e v a l u e s o f

B

c o e f f i c i e n t o f

am i­

d e s i n c r e a s e w i t h

t h e g ro w th

o f am-

m ount o f h y d ro p h o b ic

m e th y l

g r o u p s ,

w h ic h i s

c o n n e c te d w i t h

th e

g ro w th

o f volum e

o f t h e i r m o le c u le s an d p r o ­

b a b ly w i t h

t h e g ro w th o f i n t e r a c t i o n s

b e tw e e n am ide

an d w a t e r

( h y d r o p h o b ic

h y d r a t i o n ) .

S i m i l a r c h a n g e s

c a n

b e

o b s e r v e d

i n c a s e o f C c o e f f i c i e n t o f

e q u a ti o n ( 1 ) ( T a b le 7 )

r e l a t i n g

t o

i n t e r a c t i o n s among

d i s s o l v e d

am ide

m o l e c u l e s .

The d e c r e a s e

o f v a l u e

o f

B

c o e f f i c i e n t o f

a c e ta m id e i n

w a te r

w it h te m p e r a t u r e

g ro w th

i s

p r o b a b ly

c a u s e d by

s m a l l e r c o n t r i b u t i o n o f hy­

d ro p h o b ic h y d r a t i o n .

From t h e w ork« o f Good [ 2 5 ]

an d N i g h t i n g a l e [ 2 6 ]

i t

f o l l o w s

t h a t i n c a s e

o f w a te r s t r u c t u r e

o r d e r i n g s u b s t a n c e s b o th

e n t ­

h a l p y an d e n tr o p y

o f a c t i v a t i o n f o r

f l u i d flo w grow

w ith

t h e

i n c r e a s e o f

s o l u t i o n c o n c e n t r a t i o n .

The g ro w th o f t e m p e r a t u r e o f

t h e s o l u t i o n c a u s e s

t h e d e c r e a s e

o f v a l u e s o f t h e s e

f u n c t i o n s ,

b e c a u s e t h e

s t r u c t u r e o f s o l u t i o n

i s more an d m ore

d i s t u r b e d by

th e r m a l m o tio n s o f m o l e c u le s .

T a b l e

7

The v a l u e s o f B an d C c o e f f i c i e n t s

( e q u a t i o n 1) o f a m id e s i n w a te r a t 25°C

Amides

B

C

Form am ide

0 .0 1 9

- 0 .0 0 1

A c etam id e

0 .1 1 1

- 0 .0 0 0 3

P ro p io n a m id e

0 . 1cJ3

0 .0 0 4

n -B u ty ra m id e

0 .2 6 4

0 .0 1 3

N ,N -D im eth y lfo rm a m id e

0 .1 7 1

0 .0 0 1

N, N-Di m e th y la c e ta m i de

0 .2 6 7

0 .0 0 7

As i t i s s e e n

from T a b le 4

i n c a s e o f

a q u e o u s

a c e ta m id e

s o l u t i o n s b o th

e n t h a l p y and e n t r o p y o f

a c t i v a t i o n f o r f l u i d flo w

grow w ith t h e I n c r e a s e

o f a c e ta m id e c o n c e n t r a t i o n

i n w a t e r . From

t h i s f a c t i t

f o l l o w s t h a t

v i s c o u s flo w

o f a q u e o u s a c e ta m id e s o ­

l u t i o n d e s e r v e s

m ore e n e rg y i n

c o m p a riso n t o w a t e r .

I t

seem s

p r o b a b l e t h a t i t i s

c o n n e c te d w i t h g r e a t e r

p a c k in g o f

m o le c u le s

i n w ater-A cN H ^

sy s te m th a n i n p u r e w a t e r .

I n t e r m o l e c u l a r d i s t a n ­

c e s grow w ith t h e

i n c r e a s e o f

t e m p e r a t u r e ,

w h ic h

f a s c i l i t a t e s

■the v i s c o u s flo w o f t h e

s o l u t i o n .

E n th a lp y an d

e n t r o p y o f a c t i ­

v a t i o n f o r

f l u i d flo w o f

th e d i s c u s s e d

sy s te m d e c r e a s e

an d th e

e f f e c t o f t h e

s o l u t i o n c o n c e n t r a t i o n

on t h e i r v a l u e s a l s o

d e c ­

r e a s e s .

A lik e i n

w a te r - a c e ta m i d e

s y s te m e n t h a l p y o f

a c t i v a t i o n

f o r

f l u i d flo w

o f water-DM F sy ste m

grow s w i t h i n t h e

r a n g e

0 ~ 20

m ole 96 o f DMF,

w h i le i n

c a s e o f a q u e o u s form am ide

s o l u t i o n s t h e

d i s c u s s e d f u n c t i o n

d e c r e a s e s w i t h i n

t h e r a n g e

0 ~ 30 m ole >>

o f

form am id e

( F i g . 4 ) .

From th e c o m p a ris o n

o f t h e d i s c u s s e d a m id e s

i t c a n b e

s u p p o s e d t h a t fo rraam id e

b r e a k s w a te r

s t r u c t u r e ,

DMF

o r d e r s i t fo r m in g

m ixed a s s o c i a t e s

o f p r e c i s e l y

d e te r m in e d com­

p o s i t i o n w h ile

a c e ta m id e fo rm s n e tw o rk

o f h y d ro g e n

b o n d s

w i t h

w a t s r m o le c u le s , s l i g h t l y d i s t u r b i n g

p r im a r y

w a te r

s t r u c t u r e .

mole % amide

F i g . 4 . The e n t h a l p y o f a c t i v a t i o n f o r

f l u i d flo w o f

H ,0-A cN H ,,

H20 -F

an d H20-DMF s y s te m s

a t 25°C

I t c a n b e ,

t h u s s u p p o s e d , t h a t i n

c a s e o f n o n e l e c t r o l y t e

s o l u ­

t i o n s i t i s i m p o s s i b l e

t o draw a n y

c o n c l u s i o n s a b o u t

t h e e f f e c t

o f d i s s o l v e d

n o n e l e c t r o l y t e

on w a te r s t r u c t u r e

on t h e

b a s e

o f

t h e s i g n o f t e m p e r a t u r e

c o e f f i c i e n t s

A B /A T o r

Ar)r / A T .

D if ­

f e r e n t s i g n s o f t h e s e

c o e f f i c i e n t s o f t h e

d i s c u s s e d

w a te r f o r m

-a m id e ,

w a te r - a c e t a m id e

an d water-DM P

s y s te m s s u b s t a n t i a t e

o n ly

t h e d i f f e r e n t s t r u c t u r e

o f a q u e o u s am ide s o l u t i o n s .

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[ 1 7 ] G l a s s t o n e

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J . P h y s . C hem .,

7 7 , 373 ( 1 9 7 3 ) .

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Z a v e d . Khim. Khim.

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12 , 1031 ( 1 9 6 7 ) .

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