Thermochemical investigations of aqueous acetamide solutions with in thetemperature range 25-70°

A C T A

U N I V E R 3 I T A T I S

L O D Z I E N S I S

FOLIA CHIMICA

1 , 1982

Marian Woldan, S t e f a n ia T aniew ska-O sirisk a

thermochemical in v e s t ig a t io n s of aqueous acetamide

SOLUTIONS WITHIN THE TEMPERATURE RANGE 25-70°C

H eat o f s o l u t io n

AHm o f a ce ta m id e

In w a te r a t

2 5 ° ,

40 , 50 , 60

and 70 C

o v e r th e c o n c e n t r a t io n

ran ge

0 - 2

mole AcNH,/kg

H20 was m easured .

U sin g t h e s e v a l u e s th e r e ­

l a t i v e p a r t i a l m o la l e n t h a l p i e s o f b o th

th e com ponents

o f

s o l u t i o n s ,

a c t i v i t y o f w a te r

a 1

and t i p v a l u e s o f th e e x ­

c e s s r e l a t i v e p a r t i a l m o la l e n tr o p y

AS^

f o r w a te r o f

i n ­

v e s t i g a t e d s o l u t i o n s have b een c a l c u l a t e d .

The a n a l y s i s o f th e m en tio n ed

therm odynam ic

f u n c t i o n s

i n r e l a t i o n t o t h e

c o n c e n t r a t io n and

te m p e r a tu r e h a s shown

t h a t th e

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

in tr o d u c e d t o w a te r

s l i g h t l y

d is t u r b

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

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

o f a c e t a m i d e CaCl^»

KNOj,

C s l

a n d N a l

s o l u t i o n s made i t

p o s s i b l e t o o b s e r v e c e r t a i n s i m i l a r i t y

o f p r o p e r t i e s

o f th erm o d y n a m ic s o l u t i o n s

i n m o l t e n a o e t a m i d e an d

i n w a t e r [ 1 3 .

B a s i n g on t h e

a n a l y s i s o f r e s u l t s

o f

th e r m o d y n a ­

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

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

i n d i f f e r e n t

s o l ­

v e n t s [ 2- 5 ] i t may b e assum ed t h a t

t h e s i r ù i l a r i t y o f th e rm o d y n a ­

m ic s a l t

s o l u t i o n s i n m o l te n

a c e t a m i d e

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

c a u s e d

by t h e

r e m a i n i n g s t h r e e - d i m e n t i o n a l

h y d r o g e n bond

n e t w o r k

In

l i q u i d s t a t e o c c u r i n g

b o t h i n s o l i d

a c e t a m i d e [ 6 - 8 ]

and i n

i c e

[ 9 3 .

I t seemed i n t e r e s t i n g

t o e x a m in e t h e

b i n a r y

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

s y s t e m i n o r d e r

t o a t t e m p t t h e

e x p l a n a t i o n

o f m u t u a l

i n t e r a c ­

t i o n s among

t h e m o l e c u l e s o f

t h e s e s u b s t a n c e s .

V

E x p e rim en ta l

R eagen t»

F o r th e h e a t o f s o l u t i o n

m easurem ents t w ic e

d i a t i l l e d w a ter

and p . a . a c e ta m id e produced

by X enon -L 6d i

c r y s t a l l i z e d from 95%

e t h a n o l w ere u se d [1 0 ]«

The m e lt in g

tem p era tu re o f a ce ta m id e was

8 1 -8 2 °C [ 1 1 , 1 2 ] .

A p p ara tu s

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

o f a c e ta m id e i n w a te r was m easured

in

t h e im proved n o n iz o th e r m ic - n o n a d ia b a t ic

c a lo r im e t e r o f V rew skl

t y p e [ 1 3 1 .

Dewar v e s s e l w it h 220 cor*

c a p a c i t y w as u s e d . Tempera*

t u r e

s e n s i t i v i t y was 0 .0 0 2 ° C .

The e r r o r o f m easurem ents was

e s «

tim a te d t o be + 1 ,5 # «

R e s u l t s

The o b ta in e d r e s u l t s o f

i n t e g r a l h e a t o f

s o l u t i o n

AHm

o f

a c e ta m id e i n w a te r

w it h in th e

c o n c e n t r a t io n ra n g e

0 - 2

m ole o f

AcNH2/k g

o f w a te r a t th e tem p. 2 5 ° ,

‘*0°,

5 0 ° ,

6 0 ° and 70°C

a r e

g iv e n i n T a b le 1 .

The iz o th e r m s

AHm - f(m )

a r e d e s c r ib e d

by

t h e e q u a tio n

A I^ » a ♦. p Vx*,

and

a , p c o e f f i c i e n t w ere

c a l ­

c u la t e d by th e l e a s t sq u a r e s

method u s in g Odra 1305

co m p u ter.

U sin g th e

v a l u e s o f th e

o b ta in e d

a

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

th e

i n t e g r a l h e a t

o f d i l l u t i o n

AH°m

and th e

d e r i v a t i v e

d ( A H ° ) /

d VST w ere c a l c u l a t e d .

The v a l u e s o f r e l a t i v e

p a r t i a l

m o la l e n th a lp y o f w a te r

a n d a ce ta m id e

w ere d ete rm in ed u s in g

t h e known

d e p e n d e n c ie s

T a b 1 •

1

H eat o f s o l u t i o n

AH^ o í aca ta ffiid e i n w a te r ( k c a l / a o l e )

25e C

40°C

50°C

60°C

70°C

m

m

_AH»

D

AH ,

■

A H .

a

0 .0 2 0 8

2 .3 8

0 .0 2 0 2

2 .6 8

0 .0 2 0 0

2 .8 6

0 .0 2 0 2

3 .0 2

0 .0 2 0 3

3 .1 4

0 .0 4 0 6

2 .3 7

0 .0 4 0 4

2 . 6 7

0 .0 4 0 3

2 . 8 6

0 .0 4 0 5

3 .0 1

0 .0 4 0 5

3 .1 3

0 .0 8 8 3

2 . 3 6

0 .0 9 9 9

2 .6 6

0 .0 8 2 1

2 .8 5

0 .0 5 5 3

3 .0 1

0 .0 7 0 1

3 .1 3

0 .1 2 1 2

2 .3 5

0 .1 0 4 9

2 . 6 6

0 .1 1 1 0

2 .8 4

0 .0 8 8 8

3 .0 0

0 .0 9 9 3

3 .1 3

0 .1 5 0 9

2 .3 5

0 .1 4 7 8

2 .6 5

0 .1 6 7 3

2 .8 4

0 .1 1 8 1

3 .0 0

0 .1 0 8 1

3 .1 3

0 .2 1 0 5

2 .3 4

0 .2 1 8 5

2 .6 4

_{0 .2 4 5 5}

_{2 .8 3}

_{0 .1 4 7 5}

_{2 .9 9}

_{0 .1 2 9 9}

_{3 .1 2}

0 .3 2 2 2

2 .3 3

0 .2 7 1 7

2 . 6 3

0 .3 7 1 4

2 .8 1

0 .2 2 2 3

2 .9 8

0 .2 5 1 7

3 .1 1

0 .4 8 4 9

2 .3 2

0 .3 5 2 7

2 .6 2

0 .5 2 0 3

2 .8 0

0 .3 7 7 0

2 .9 7

O

.3453

3 .1 0

0 .6 3 2 5

2 .3 0

0 .4 9 8 0

2 .6 1

0 .6 9 7 7

2 .7 9

0 .5 0 8 9

2 .9 6

0 .3 9 8 8

3 .1 0

0 .7 8 5 3

2 .2 9

0 .6 3 4 5

2 .6 1

0 .8 5 1 3

2 .7 9

0 .6 5 5 7

2 .9 5

0 .4 7 5 4

3 .1 0

0 .9 4 7 1

2 .2 8

0 .7 8 4 7

2 .6 0

1.01 10

2 .7 8

0 .8 4 0 3

2 .9 5

0 .6 0 6 4

3 .1 0

1 .1 5 4 4

2 .2 7

0 .9 2 0 2

2 .6 0

1 .1 7 3 5

2 .7 8

1.0 0 2 2

2 .9 4

0 .7 8 2 7

3 .0 9

1 .3 5 1 4

2 .2 6

1.01 9 2

2 .5 9

1 .3 6 7 2

2 .7 7

1.2 0 6 6

2 .9 4

0 .9 0 1 2

3 .0 9

1 .5 1 3 2

2 .2 6

1 .2 8 3 5

2 .5 8

1 .5 5 1 4

2 .7 6

1 .4 6 6 7

2 .9 4

1 .1 1 7 3

3 . 0 8

1 .6 9 5 9

2 .2 5

1 .5 3 5 0

2 .5 7

1 .7 3 7 9

2 .7 6

1 .6 2 3 2

2 .9 3

1 .3 0 3 1

* 3 .0 8

1 .8 8 4 1

2 .2 4

1 .7 8 9 4

2 .5 7

1 .9 2 0 3 ’

2 .7 5

1 .8 4 7 2

2 .9 3

1 .6 0 7 2

3 .0 7

2 .0 4 8 9

2 r24

1.9000

2

.

5 6

!

2 .0 9 4 5

2 .7 5

2 .0 2 0 0

2 .9 2

1 .8 9 1 8

3 .0 7

2 .1 0 0 2

2 .2 3

2 .0 7 2 0

2 .5 6

2 .1 0 0

2 .9 2

2 .0001

3 .0 6

2 .1 0 0

2 .5 5

2 .1 0 6 5

3 .0 6

Th

er»

o

ch

o

m

le

a

l

in

v

e

s

ti

g

a

ti

o

n

s

of

aq

u

eo

u

s

V a lu e s o f thermodynamic f u n c t i o n s f o r AcNH,-H90

sy stem a t 2 5 *C

m

(m o le /k g )

( c a l / m o l e )

L2

( c a l/ m o l e )

a 1

AS®

( I 0 3c a l / m o l e • d a g )

0

0

0

0

0 .0 2 0 8

0 .0 0 3

2 3 .5

0 .9 9 9 7

0

0 .0 4 0 6

0 .0 0 8

3 3 .2

0 .9 9 9 4

0

0 .0 8 8 3

0 .0 2 6

4 9 .4

0 .9 9 8 4

0

0 .1 2 1 2

• ’ 0 .0 4 2

5 7 .9

0 .9 9 7 8

0 .1

0 .1 5 0 9

0 .0 5 8

6 4 .6

0 .9 9 7 3

0 . 2

0 .2 1 0 3

0 .0 9 6

7 6 .2

0 .9 9 6 2

0 . 4

0 .3 2 2 2

0 .1 8 2

9 4 .3

0 .9 9 4 2

0 . 6

0 .4 8 4 9

0 .3 3 7

1 1 5 .7

0 .9 9 1 4

1.1

0 .6 3 2 5

0 .5 0 1

1 3 2 .2

0 .9 8 9 0

1 .2

0 .7 8 5 3

0 .6 9 4

1 4 7 .3

0 .9 8 6 4

1 .5

0 .9 4 7 1

0 .9 1 9

1 6 1 .7

0 .9 8 3 8

2 . 0

1 .1 5 4 4

1 .2 3 7

1 7 8 .5

0 .9 8 0 5

2 .5

1 .3 5 1 4

1 .5 6 6

.

1 9 3 .2

0 .9 7 7 4

3 .0

1 .5 1 3 2

1 .8 5 6

2 0 4 .4

0 .9 7 4 8

3 .4

1 .6 9 5 9

2 .2 0 2

2 1 6 .4

0 .9 7 2 0

4 .0

1 .8 8 4 1

2 .5 7 9

2 2 8 .1

0 .9 6 9 1

4 . 7

2 .0 4 8 9

2 .9 2 4

2 3 7 .9

0 .9 6 6 7

5 .2

2 .1 0 0

3 .0 3 4

2 4 0 .8

0 .9 6 5 9

5 .4

I « U «

3

V a lu e s o f thermodynamic f u n c t i o n s f o r AcNH--H,0

s y s t e m a t **0 #C

¿

¿

m

( ■ o l e / k g )

( c a l / B o le )

L2

( c a l /m o le )

*1

AS®

(lO ^ o a l/m o le • d e g )

0

0

0

1

0

0 .0 2 0 2

0 .0 0 2

20*0

0 .9 9 9 7

0

0 .0 4 0 4

0 .0 0 7

2 8 .3

0 .9 9 9 4

0

0 .0 9 9 9

0 .0 2 7

4 4 .7

0 .9 9 8 2

0

0 .1 0 4 9

0 .0 2 9

4 5 .8

0 .9 9 8 1

0 .1

0 .1 4 7 8

0 .0 4 8

_{5 4 .3}

_{0 .9 9 7 3}

0 . 2

0 .2 1 8 5

0 .0 8 7

6 6 .1

0 .9 9 6 1

0 . 3

0 .2 7 1 7

0 .1 2 0

7 3 .7

0 .9 9 5 1

0 . 5

0 .3 5 2 7

0 .1 7 8

8 4 .0

0 .9 9 3 7

0 . 6

0 .4 9 8 0

0 .2 9 8

9 9 .8

0 .9 9 1 1

0 . 9

0 .6 3 4 5

0 .4 2 9

1 1 2 .6

0 .9 8 8 9

1 .0

0 .7 8 4 7

0 .5 9 0

1 2 5 .2

0 .9 8 6 4

1 .2

0 .9 2 0 2

0 .7 4 9

1 3 5 .6

0 .9 8 4 1

1 .5

1 .0 1 9 2

0 .8 7 3

1 4 2 .7

0 .9 3 2 6

1 .5

*

1 .2 8 3 5

1 .2 3 3

1 6 0 .2

0 .9 7 8 3

2 .1

1 .5 3 5 0

1 .6 1 3

1 7 5 .1

0 .9 7 4 4

2 . 6

1 .7 8 9 4

2 .0 3 0

1 8 9 .1

0 .9 7 0 4

3 .2

1 .9 0 0 0

2 .2 2 1

1 9 4 .9

0 .9 6 8 7

3 .4

2 .0 7 2 0

2 .5 3 0

2 0 3 .5

0 .9 6 6 1

3 .8

2 .1 0 0

2 .5 8 1

2 0 4 .9

0 .9 6 5 7

3 .9

T a b 1 •

4

V a lu e s o f thermodynamio f u n c t i o n s f o r AcNU

9

>H90

s y s t e a s t

50

*C

a

( a o l e / k g )

£ 1

( c a l / a o l e )

h

( c a l / a o l e )

•1

t ą

d O ^ c a l/m o le * d e g )

0

0

0

1

0

0 .0 2 0 0

0 .0 0 2

1 9 .5

0 .9 9 9 7

0

0 .0 4 0 3

0 .0 0 7

2 7 .6

0 .9 9 9 4

0

0 .0 9 2 1

0 .0 2 0

3 9 .6

0 .9 9 8 6

₀

0 .1 1 1 0

0 .0 3 1

4 6 .0

0 .9 9 8 0

0 .1

0 .1 6 7 3

0 .0 5 7

5 6 .5

0 .9 9 7 0

0 .2

0 .2 4 5 5

0 .1 0 1

6 8 .5

0 .9 9 5 6

0 . 4

0 .3 7 1 4

0 .1 8 8

8 4 . 2

0 .9 9 3 4

0 .6

0 .5 2 0 3

0 .3 1 1

9 9 . 7

0 .9 9 0 7

0 . 9

0 .6 9 7 7

0 . 4 8 3

1 1 5 .4

0 .9 8 7 9

0 . 9

0 .8 5 1 3

0 .6 5 1

1 2 7 .5

0 .9 8 5 2

1 .3

1 .0 1 1 0

0 .8 4 3

1 3 8 .9

0 .9 8 2 7

1 . 4

1 .1 7 3 5

1 .0 5 4

1 4 9 .7

0 .9 8 0 0

1 . 9

1 .3 6 7 2

1 .3 2 5

1 6 1 .6

0 .9 7 6 9

2 .2

1 .5 5 1 4

1 .6 0 2

1 7 2 .1

0 .9 7 4 0

_{2 . 5}

1 .7 3 7 9

1 .9 0 0

1 8 2 .2

0 .9 7 1 1

_{2 . 9}

1 .9 2 0 3

2 .2 0 6

1 9 1 .5

0 .9 6 8 3

3 . 3

2 .0 9 4 5

2 .5 1 3

2 0 0 .0

0 .9 6 5 6

_{3 . 7}

T h e r m o c h o n l c a l i n v e s t i g a t i o n s o f a j u e o u s

₉

V a lu e s o f thermodynamic f u n c t i o n s f o r AcNH^-H-O

sy3tem a t 70°C

m

(m o le /k g )

L1

( c a l/m o le )

L2

( c a l/m o le )

a 1

AS®

(lO ^ c a l/m o le ♦ d eg )

0

0

0

1

0

0 .0 2 0 2

0 .0 0 2

1 6.6

0 .9 9 9 7

0

0 .0 4 0 5

0 .0 0 6

2 3 .5

0 .9 9 9 4

0

0 .0 5 5 3

0 .0 0 9

2 7 .6

0 .9 9 9 1

0

0 .0 8 8 8

0 .0 1 9

3 5 .0

0 .9 9 8 4

0

0 .1 1 8 1

0 .0 2 9

4 0 .3

0 .9 9 7 9

0 .1

0 .1 4 7 5

0 .0 4 0

4 5 .1

0 .9 9 7 3

0 . 2

0 .2 2 2 3

0 .0 7 4

5 5 .3

0 .9 9 6 0

0 . 3

0 .3 7 7 0

0 .1 6 3

7 2 .1

0 .9 9 3 3

0 . 5

0 .5 0 8 9

0 .2 5 6

8 3 .7

0 .9 9 0 9

0 . 8

0 .6 5 5 7

0 .3 7 4

9 5 .1

0.98Q 5

0 . 7

0 .8 4 0 3

0 .5 4 3

1 0 7 .6

0 .9 8 5 4

1 .0

1 .0 0 2 2

0 .7 0 7

1 1 7 .5

0 .9 8 2 8

1 .0

1 .2 0 6 6

0 .9 3 4

1 2 8 .9

0 .9 7 9 4

1 .5

1 .4 6 6 7

1 .2 5 1

1 4 2 .2

0 .9 7 5 3

1 .7

1 .6 2 3 2

1 .4 5 7

1 4 9 .6

0 .9 7 2 8

1 .9

1 .8 4 7 2

1 .7 6 8

1 5 9 .5

0 .9 6 9 3

2 .2

2 .0 2 0 0

2 .0 2 2

1 66.8

0 .9 6 6 7

2 .4

2 .1 0 0 0

2 .1 4 3

1 7 0 .1

0 .9 6 5 5

2 .6

T a b l e

6

V a lu e s o f thermodynamic f u n c t io n s f o r AcNH?-»HLO

sy stem a t 70°C

A *

m

(m o le /k g )

L1

( c a l/m o le )

L2

( c a l/m o le )

a 1

AS®

(1 0 ^ c a l/m o le • d eg)

0

0

0

1

0

0 .0 2 0 3

0 .0 0 2

1 3 .3

0 .9 9 9 7

0

0 .0 4 0 5

0 .0 0 5

1 8 .8

0 .9 9 9 4

0

0 .0 7 0 1

0 .0 1 0

2 4 .9

0 .9 9 8 8

0

0 .0 9 9 3

0 .0 1 8

2 9 .7

0 .9 9 8 2

0

0 .1 0 8 1

0 .0 2 0

3 0 .9

0 .9 9 8 0

0

0 .1 2 9 9

0 .0 2 6

3 3 .9

0 .9 9 7 7

0 .1

r

0 .2 5 1 7

0 .0 7 1

4 7 .2

0 .9 9 5 4

0 . 3

0 .3 4 5 3

0 .1 1 5

5 5 .3

0 .9 9 3 8

0 . 4

0 .3 9 8 8

0 .1 4 2 .

5 9 .4

0 .9 9 2 9

0 . 4

0 .4 7 5 4

0 .1 8 5

6 4 .9

0 .9 9 1 5

0 . 6

0 .6 0 6 4

0 .2 6 7

7 3 .3

0 .9 8 9 3

0 . 6

' 0 .7 3 2 7

0 .3 9 1

8 3 .3

0 .9 8 6 4

0 . 6

0 .9 0 1 2

0 .4 3 3

8 9 .3

0 .9 8 4 3

0 . 8 - .

1 .1 1 7 3

0 .6 6 7

9 9 .5

0 .9 8 0 8

0 . 8

I

1 .3031

0 .8 4 0

1 0 7 .4

0 .9 7 7 8

0 . 9

I

1 .6 0 7 2

1 .1 5 1

1 1 9 .3

0 .9 7 3 0

1 .0

!

1 .3 9 1 8

1 .4 6 9

1 2 9 .5

0 .9 6 3 6

1 .2

2 .0 0 0 1

1 .5 9 7

13 3.1

0 .9 6 6 9

1 .2

2 .1 0 6 5

1 .7 2 6

1 3 6 .6

0.96f>3

* 1 .3

(2)

The v a l u e s o f

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

p a r t i a l m o l a l e n t r o p y

o f

w a t e r 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 e re c a l c u l a t e d

from

t h e

e q u a t i o n

-

mole f r a c t i o n o f s o l v e n t

a^ - a c t i v i t y o f s o l v e n t

W a te r a c t i v i t y ( a ^

o c c u r l n g i n e q u a t i o n ( 3 )

was

c a l c u l a t e d

f r o m t h e e q u a t i o n :

The f u n c t i o n

L..CT)

was e x p r e s s e d by t h e

e q u a t i o n

L 1(T)

•

■ a ♦ bT ♦ cT

an d t h e v a l u e s

a 1

c o r r e s p o n d i n g

t o t h e t e m p e r a ­

t u r e 25°C

(293°K )

was c a l c u l a t e d u s i n g

t h e d a t a on v a p o u r p r e s ­

s u r e

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

o b t a i n e d by Kangro

a n d

G r o e n e v e l d

[ 1 ^ ] .

A l l c a l c u l a t e d by u s

v a l u e s o f th erm o d y n a m ic f u n c t i o n s

o f

a q u e o u s

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

a r e p r e s e n t e d i n t a b l e s 2- 6 .

The c o u r s e o f d e p e n d e n c e

o f i n t e g r a l h e a t

o f s o l u t i o n

AHm

o f a c e t a m i d e i n w a t e r

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

i s

p r e ­

s e n t e d on

F i g . 1 .

As i t c a n b e s e e n t h e

• f ( m )

i s o t h e r m s

sh ow -m onotonous c o u r s e .

The e x o t e r m i c i t y o f t h e

a c e t a m i d e i n wa­

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

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

w i t h t h e g r o w t h o f t h e c o n c e n ­

t r a t i o n o f t h e

s o l u t i o n and

d e c r e a s e s

w i t h

t h e

t e m p e r a t u r e

g r o w t h .

The s l o p e o f

A l ^ - f ( m )

c u r v e s d e c r e a s e s

w i t h t h e s o ­

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

t e m p e r a t u r e g r o w t h .

293

( 4 )

D i s c u s s i o n

3,2

-- J ---1---1--- >---1--- J --- J___________ I___________ I___________ I .

0.2

0.4

0,6

0,8

1,0

1,2 '

1,4

1,6

1,8

2.0

[m ole/k g]

F i g . 1 . D ependence o f h e a t o f s o l u t i o n

AHm o f a c e t a m i d e

i n wa­

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

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

i n f l u e n c e o f s o l u t e on s o l v e n t

ca n

be drawn fr o m

t h e a n a l y s i s - o f t h e

c o u r s e o f

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

and

t e m p e r a t u r e d e p e n d e n c e

o f r e l a t i v e

p a r t i a l m o l a l

e n t h a l p i e s

o f

t h e s o l u t i o n

c o m p o n e n ts

an d e s s p e c i a l l y

fr o m t h e c o u r s e o f

t h e

f u n c t i o n

AS.j * f ( m , T ) .

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

d i s c u s s e d

th e rm o d y ­

nam ic f u n c t i o n s

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

i n w a t e r

( T a b l e s

2- 6 )

c a l c u l a t e d by u s

a r e p r e s e n t e d on

F i g . 2 - 4

a s c u r v e s

L„

«

—

—E

*

» f ( m ) ,

L2 « f ( m )

a n d

A S 1 ■ f ( m )

c o r r e s p o n d i n g

t o t h e

te m p .

2 5 ° ,

**0°,

5 0 ° ,

6 0 °

an d

70°C

( F i g . 2 - 4 ) .

As i t i s

s e e n fr o m

F i g . 2

t h e d e p e n d e n c e o f

r e l a t i v e p a r t i a l

m o l a l e n t h a l p y o f wa­

t e r

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

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

and

tem pe­

r a t u r e

i s s i m i l a r

t o t h a t i n

c a s e o f a q u e o u s

u r e a

s o l u t i o n s

[ 1 5 3 and w a t e r

s t r u c t u r e . b r e a k i n g

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

Thus t h e c o n ­

c l u s i o n on b r e a k i n g

p r i m a r y w a t e r

s t r u c t u r e by a c e t a m i d e m o le c u ­

l e s c a n be d r a w n .

F i g . 2 . D ependence o f

o f a c e t a m i d e - w a t e r s y s t e m v s

c o n c e n ­

t r a t i o n a t v a r i o u s t e m p e r a t u r e s

I t i s a l s o

known, t h a t p o s i t i v e

L1

v a l u e s p o i n t t o t h e f a c t

t h a t m o l a l

e n t h a l p y o f

e v a p o r a t i o n o f

s o l v e n t from

s o l u t i o n i s

s m a l l e r

t h a n m o l a l

e n t h a l p y

o f e v a p o r a t i o n

o f p u r e

s o l v e n t . I t

f o l l o w s t h a t

i n a q u e o u s a c e t a m i d e

s o l u t i o n s

w a t e r m o l e c u l e s a r e

b o n d ed w e a k e r

t h a n i n p u r e

w a t e r . Thus

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

b e

drawn a b o u t

t h e d i s t u r b a n c e o f

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

b y

i n t r o d u c i n g

a c e t a m i d e m o l e c u l e s

t o I t .

The a b o v e

c o n c l u s i o n i s

a l s o

s u p ­

p o r t e d by

t h e c o u r s e o f

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

an d t e m p e r a t u r e d e p e n d e n ­

c e o f

r e l a t i v e p a r t i a l

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

a c e t a m i d e

i n

t h e

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

s o l u t i o n s

( F i g . 3 ) .

The d e c r e a s e o f t h e

a b s o l u t e

v a l u e s

L1

and

Lg

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

g r o w t h c a n be

e x p l a i n e d by

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

o f p r i m a r y

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

by t h e r m a l

mo­

t i o n s o f i t s

m o l e c u l e s ,

t h e i n t e n s i t y

o f w h ic h grow s

w i t h

t h e

t e m p e r a t u r e g r o w t h .

F i g . 3 . Dependence o f L2

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

c o n c e n ­

t r a t i o n a t v a r i o u s t e m p e r a t u r e s

A c c o r d i n g t o many a u t h o r s [ 1 6 - 2 0 ]

t h e b e s t m e a s u r e

o f e i t h e r

d e s t r u c t i v e o r o r d e r i n g i n f l u e n c e

o f t h e s o l u t e

on s o l v e n t

a r e

t h e v a l u e s

AS“‘

o f t h e e x c e s s

o f r e l a t i v e p a r t i a l

m o l a l e n t r o *

py

g i

t h e s o l v e n t .

T h i s v a l u e i s

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

s u b s t a n c e s

o r d e r i n g t h e s t r u c t u r e

o f s o l v e n t

a n d p o s i t i v e f o r t h o s e d i s t u r ­

b i n g i t .

•

The c o u r s e o f

d e p e n d e n c e o f t h e

v a l u e s o f t h e

e x c e s s

r e l a

-~E

t i v e p a r t i a l

m o l a l e n t r o p y o f w a t e r

AS1

f o r a q u e o u s

a c e t a m i d e

s o l u t i o n s on

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

an d t h e

t e m p e r a t u r e

a r e p r e s e n ­

t e d on F i g . A,

F o r t h e

s a k e

o f

c o m p a ris o n

t h e

d i s c u s s e d

r e l a t i o n

f o r

a q u e o u s u r e a

s o l u t i o n s a t

t h e t e m p . 25°C

h a s a l s o b e e n

showed

[ 2 6 ] .

As i t 4 s

s e e n from F i g . 4

t h e v a l u e s

AS^

o f

a q u e o u s

a c e t a m i d e

s o l u t i o n s a r e p o s i t i v e

and t h e y d e c r e a s e w i t h

t h e

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

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

So i t i s

p o s s i b l e

t o

d ra w

a c o n c l u s i o n

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

t h e w a t e r

s t r u c t u r e by a c e ­

t a m i d e .

--E

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

g ro w th t h e v a l u e s

AS..'

d e c r e a s e

an d

a p p r o a c h to z e r o .

T h is i m p l i e s

t h a t t h e d i s o r d e r i n g i n f l u e n c e o f

a c e ta m id e on w a te r d e c r e a s e s w ith t h e

te m p e r a t u r e

g ro w th

w h ich

seem s o b v io u s i f

c o n s i d e r t h e

g ro w in g d i s t u r b a n c e o f w a te r s t r u ­

c t u r e by

more i n t e n s i v e th e r m a l

m o tio n s o f m o le c u le s

i n

h i g h e r

t e m p e r a t u r e .

HE

F i g . A. The e x c e s s o f r e l a t i v e p a r t i a l m o l a l e n t r o p y

AStr

o f

wa-t e r - a c e wa-t a m i d e sy s wa-te m

—

£

V e ry s m a l l

AS^

v a l u e s o f a q u e o u s a c e t a m i d e

s o l u t i o n s a l l o w

t o s u p p o s e t h a t

a c e t a m i d e m o l e c u l e s

i n t r o d u c e d

t o

w a t e r w h i l e

b u i l d i n g i n t h e i c e - l i k e

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

s l i g h t l y

d i s t u r b

i t

a n d p r o b a b l y fo rm mixed

a g r e g a t e s

o f m o l e c u l e s

bound w i t h

hy­

d r o g e n b o n d s .

The c o n c l u s i o n drawn fro m

t h e c o u r s e o f d e p e n d e n c e

o f AS^

o f t h e s o l u t i o n s i n v e s t i g a t e d by u s i s c o n f i r m e d by d e n -

s i m e t r i c [ 2 1 ] ,

v i s c o s i m e t r i c [ 2 2 ]

an d d i e l e c t r i c [ 2 3 - 2 5 ]

i n v e ­

s t i g a t i o n s

o f a q u e o u s a c e t a m i d e s o l u t i o n s .

As i t i s s e e n

from p l o t

U

t h e

v a l u e s AS^

o f a q u e o u s

u r e a

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

a l s o p o s i t i v e [ 2 6 ]

b u t t h e y a r e

b i g g e r i n

compa-

r i s o n t o t h o s e o b t a i n e d

f o r

a q u e o u s

a c e t a m i d e

s o l u t i o n s .

I t

p o i n t s t o a s t r o n g e r d i s t u r b a n c e o f p r i m a r y w a t e r s t r u c t u r e

by

u r e a t h a n by a c e t a m i d e .

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D e p a rtm e n t o f P h y s i c a l C h e m i s t r y

1

I n s t i t u t e o f

C h e m i s t r y

U n i v e r s i t y o f Łódź

M a ria n Woldan, S t e f a n i a T a n i e w s k a - O s i ń s k a

TERMOCHEMICZNE BADANIA WODNYCH ROZTWORÓW ACETAMIDU

W ZAKRESIE TEMP. 2 5 - 7 0 °C

P rz e p ro w a d z o n o p o m ia ry c i e p ł a

r o z p u s z c z a n i a

AHm

a c e t a m i d u

w w o d z ie w t e m p e r a t u r z e

2 5 ° ,

4 0 ° , 5 0 ° ,

60° i 70°C

w

z a k r e s i e

s t ę ż e ń 0 - 2 m o ll

AcNH2/ k g wody.

K o r z y s t a j ą c z o t r z y m a n y c h

w a r t g -

ś c i

AHm o b l i c z o n o w z g lę d n ą c z ą s t k o w ą molową

e n t a l p i ę wody

Lj

i a c e t a m i d u Lo

o r a z a k ty w n o ść wody

a 1

i w a r t o ś c i

n a d m i a r u

w z g l ę d n e j c z ą s t k o w e j m olow ej

e n t r o p i i wody

A S ł

b a d a n y c h

r o z ­

tw o ró w .

Na p o d s t a w i e a n a l i z y z a l e ż n o ś c i

w y m ie n io n y c h f u n k c j i t e ­

rm odynam icznych

od s t ę ż e n i a i t e m p e r a t u r y r o z t w o r u

w ysnuto w n io ­

s e k , ż e

a c e t a m i d wprowadzony do wody

pow oduje n i e z n a c z n e

z a k ł ó ­

c e n i e j e j s t r u k t u r y .

Map/tH Bo^ł a u k, CteiaHHH TaHeBCKa-OcnHbCKa

T E ? MO XHMHMECiGiE tf CCJIEHOBAHHH BOHHHX PACTBOPOB AUETAIMUA IIPH 2 5 - 7 0 °C

ripoBe^eHO H3MepeHHH

xenuioru

p a c T B o p e m i *

AHm aueTaM iua

b

bohb

npH 2 5 ° , 4 0 ° , 5 0 ° , 6 0 ° h 70®C b HH TepBane K O H u en ip a u H u 0 - 2 m

Ac-.<H2/ K r ^ 9 . H

0

.Kb

3

y.scb

aHaHeHHHMH AHm

paoćHHTano:

O T H O c s i T e j i b - nyio n a p a n a j! b a y x ) MOJiHJibHyw DHTajitrmio o f i o n x k o m h o h c h t o b p a c T B o p a , a K T U B H O O T Ł BOĄal K£ H 3 6 U T OHHyiO O T H O C H T e JIb H y iO l i a p u H a j I b H y » MCWIfUIbHyiO aHTponuK) BOĄa

As,

H canenoB aH M x p a o T B o p o B .

Ha

ocH OBe aHajiH3a 3 a - BHCHMOCTH y n O M H H y T N X T e p M O j;H K a M M > łe C K H X ł y H K I l H H OT K O H q e H T p a U H H H T e M n e p a y y p t j p a o T B o p a c ą e j i a H b h b o a, s t o a « e T a M H . n c j i a 6 o p a a p y s o a e T

c rp y x ry p y bojju.