Interactions in Aqueous Solutions of Hydrophilic Urea Derivatives and NaI at the Temperatures 293.15 and 303.15 K

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 CHIM ICA a, 1988_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

Ba r t ł o m i e j Pałecz*, S t ef ani a T a n i e w s k a - O s i ń s k a * IN T E R A C T I O N S IN AQ UE O U S SO LU TIO NS OF H Y D R O P H I L I C UREA D E R I V A T I V E S AND Nal AT THE T E M P E R A T U R E S 293. 15 AND 303.15 K

M e a s u r e m e n t s were made of the e n t h a l p i e s of s o l u t i o n of Nal in wa ter and in aq ue ous 0.1, 0.7, 1.0 and 1.5 mol ureas kg H„0 s o l u t i o n s of th iourea (TU) or h y d r o x y u r e a (HU) at the t e m p e r a ­ tures 293.15 and 303.15 K. Taki ng a d v a n t a g e of the s t a n dar d values of s o lu tio n en th alp y of e l e c t r o l y t e s in wa ter and in aq ue ous s o l u tio ns of th iourea and hy d r o x y u r e a , the e n t h a l p i c pair in t e r a c t i o n c o e f f i c i e n t s of uruas m o l e c u l e - a v e r a g e d ion were d e t e r m i n e d [l, 2],

Introduct ion

The pr es ent study is a c o n t i n u a t i o n of the t h e r m o d y n a m i c i n ­ v e s t i g a t i o n s on aq ue ous ureas s o l u t i o n s [3-5], The aim of this r e ­ sear ch was to d e t e r m i n e in te rac ti on s b e t w een h y d r o p h i l i c urea d e r i ­ va ti v e s and el e c t r o l y t in aq ue ous solutions.

Ex p e r i m e n t a 1,

Thiourea (puriss POCh Poland), H y d r o x y u r e a (Polfa Poland) were c r y s t a l l i z e d from et ha nol and dried under re du ced p r e s s u r e at 333 K. Nal (Merck BRD) was c r y s t a l l i z e d from a w a t e r - a c e t o n e m i x t ure and dr ied under reduced p r e s s u r e at 333 K.

D e p a r t m e n t of Ph is ica l Ch em istry, In st i t u t e of Chemistry, Un i v e r s i t y of Ł ódź.

by u s in g an "i s o p e r i b o l " c a l o r i m e t e r [fij a c c u r a t e to 5 x 10 5K. The c a l o r i m e t e r was p l ac ed in w a te r th e r m o s t a t w h os e t e m p e r a t u r e s t a b i ­ lity was 1 x 10_ 5K.

Resu lt and D i s c u s s i o n

The o b ta in e n t h a l p i e s of s o l u t i o n of Nal in w a t e r and in aq ue o u s s o l u t i o n s of t h io ure a (TU) and h y d r o x y u r e a (HU) are c o l l e c t e d in Tabl es 1, 2. As can be seen, i n c r e a s e d e x o t h e r m i c i t y of s o l u t i o n e n t h a lp ie s. A s i m i lar i n c r e a s e of e x o t h e r m i c i t y is b r o u g h t about by t e m p e r a t u r e i n cr eas e e x e m p l i f i e d by the Nal data. On the basis of the s o l u t i o n e n t h a l p y valu es ob ta ine d, s t a n d a r d e n t h a l p i e s of s o l u t i o n of Nal in wa ter and a q u e ous s o l u t i o n s of ur eas (TU or HU) w e re d e t e r m i n e d g r a p h i c a l l y (Tables 1, 2). Such a p r o c e d u r e was n e c e s s i t a t e d by the u n a v a i l a b i l i t y of the t e m p e r a t u r e d e r i v a t i v e s of d i e l e c t r i c c o n s t a n t r e q u i r e d for e x t r a p o l a t i o n by the C r i s s and C o b b l e m e t h o d \l\ . B a si ng on the s t a n d a r d e n t h a l p i e s of e l e c t r o l y t e s o l u t i o n in wa ter and in aq ue o u s u r ea s (TU or HU) s o l u t i o n s s t a n d a r d e n t h a l p i e s of e l e c t r o l y t e t r an sfe r from w a te r to aq ue ous ureas s o l u t i o n s ( c o n c e n t r a t i o n m^) were c a l ­ c u l a t e d :

Ù H E(W-N) = A H s(N) ‘ A H ~(W)

A H E(W-N) = 2v h N E m N + î v hN N E m N + •••

w h er e v is the n u mb er of ions into w h i c h the e l e c t r o l y t e dissociates. F o l l o w i n g that the 2vh^^ v a lu es we re d e t e r m i n e d by p u t t i n g the data on the ab sc iss a and those for - Û H ” (w)] * m N^' Dn *he ordirnate.

The e n t h a l p i c c o e f f i c i e n t s of urea s (TU or HU) m o l e c u l e - a v e r a g e d ion h ^ in t e r a c t i o n s o b t a i n e d in this way are list ed in Table 3.

A view held by many a u t h ors [ l , 2, 8 , 9] and shar ed by us is that the qu ite large n e g a t i v e valu es of e n t h a l p i c i n t e r a c t i o n c o e f ­ f i c i e n t s for pa irs of m o l e c u l e s or ions of the same or d i f f e r e n t ki nds are an i n d i cat io n of s t ro ng i n t e r a c t i o n s ampng the d i s s o l v e d mo le cul es . The ur eas m o l e c u l e - a v e r a g e d ion in t e r a c t i o n c o e f f i c i e n t s

T a b l e 1 E n t h a l p i e s of s o l u t i o n s (AHS ) of Mai in w a te r and w a t e r - t h i o u r e a (TU) m i x t u r e s

at the te m p e r a t u r e s 293. 15 K and 303.15 K (1 cal = 4.184 3)

j__ H20 0.1 mol TU/kg H 2 0 0.7 mol T U /k g H 20 | 1.0 mol TU/k g H 2 0 1.5 mol T U /k g HjO

m(Nal) -AH

s m(Nal) -Û H s m(Nal) - A H s m(Na l) - A H s m(Na l) - A H s

m o l / k g ca l/ mol m o l / k g cal/mol mo l/ kg ca l/ mol m o l / k g ca l/ m o l mol/ kg c a l / m o l

...

293. 15 K 0.00 00 1680 0 .0000 1722 0.0000 1950 0.0000 2050 0.00 00 2220 0.0042 1663 0.0051 1700 0.0035 1925 0 . 0 0 4 9 2020 0.0051 2200 0.0089 1650 0.00 72 1694 0.0081 1904 0 . 00 79 2004 0.0099 2184 0.0125 1640 0 . 01 58 1669 0.0110 1896 0 . 01 05 1996 0.0145 2173 0.0320 1603 0.02 90 1644 0.0325 1850 0 . 01 99 1974 0.0321 2149 0.04 52 1588 0.0542 1612 0 .0521 1820 0.03 11 1954 0.0542 2121 0 . 07 48 1560 0.0698 1597 0.0685 1805 0.0528 1928 0.0701 2105 303.15 K 0.00 00 2005 0.0000 2045 0.0000 2260 0.00 00 2360 0.0000 2510 0.00 40 1978 0.0059 2015 0.0041 2238 0.00 39 2336 0.0049 2486 0.0091 1957 0.0079 2004 0.00 92 2220 0 .0079 2320 0.0089 2476 0.0185 1931 0.0124 1991 0.0180 2195 0 . 01 09 2315 0.0158 2460 0.0341 1910 0.0295 1955 0.0279 2177 0 .0199 2297 0.0301 2436 0.0502 1892 0.0389 1944 0.0411 2160 0.0311 2275 0.0448 2416 0.0692 1875 0.0521 1928 0.05 99 2140 0.0551 2244 0.0647 2391 I n t e r a c t i o n s in A q u e o u s S o l u t i o n s

En t h a l p i e s of s o l u t i o n s ( A H S ) of Nal in w a t e r - h y d r o x y u r e a (HU) m i x t u r e s at the t e m p e r a t u r e s 293. 15 K and 303.15 K (1 cal = 4 . 18 4 3)

j 0.1 mol H U / k g H 20 0.7 mol H U / k g H 20 1.0 mol H U / k g H 2 0 1.5 mol H U /k g H 2 0

m(Na l) - A H s m(Nal) -AH

s m( NaI ) -AHs m ( N a I ) - A H s

m o l/ kg ca l/ mol m o l/ kg ca l/ mol m o l / k g c a l / m o l m o l / k g ca l/ mol

2 9 3. 15 K 0.00 00 1720 0. 00 00 1925 0.00 00 2015 0.00 00 2170 0.00 52 1697 0.00 49 1896 0.00 62 1986 0.00 59 2146 0 .0085 1685 0.00 99 1878 0. 00 83 1978 0 . 00 78 2137 0. 01 45 1671 0 . 01 98 1853 0.01 98 1950 0.01 10 2128 0.02 59 1648 0 . 02 45 1844 0.0221 1946 0.0291 2090 0.04 21 1624 0 . 03 88 1823 0 . 0 4 3 2 1916 0.0421 2070 0 . 06 25 1600 0 . 05 92 1798 0 . 06 51 1894 0.05 99 2050 303.15 K 0 . 00 00 2040 0 . 00 00 2235 0 . 0 0 0 0 2325 0.00 00 2465 0 . 00 49 2016 0 . 00 69 2208 0 . 0 0 4 9 2303 0.0059 2448 0.00 78 2000 0 . 0 0 8 9 2196 0 . 0 0 7 9 2292 0.0098 2437 0.0151 1980 0. 01 49 2180 0 . 0 1 5 1 2270 0.0148 2425 0.0329 1950 . 0.0251 2160 0. 03 21 2241 0.0241 2412 0.0501 1930 0.04 01 2142 0. 05 02 2217 0.0301 2400 0. 06 89 1908 0 . 05 52 2125 0. 06 49 2204 0. 05 49 2375 B a r t ł o m i e j P a ł e c z , S t e f a n i a T a n i e w s k a -O s i ń s k a

T a b l e En t h a l p i c pair i n t e rac ti on c o e f f i c i e n t s of Nal

- urea d e r i v a t i v e s in w a te r s o l u t i o n s

ob t a i n e d have n e ga tiv e values (Table 3), w h ic h may be due to stro ng i n t e r a c t i o n s b e t w een the m o l e c u l e s of h y d r o p h i l i c urea d e r i v a t i v e s (TU, HU) and the e l e c t r o l y t e pr es e n t in the solution. As the t e m p e ­ ratu re increases, the a b s o lut e h ^ valu es d e c r e a s e (Table 3) which may be r e l a ted to w e a k e n e d i n t e r ac ti on s b e t w e e n ur eas m o l e c u l e s (TU, HU) and ions (Na+ I~), br ou ght about by i n c r eas ed i n t e nsi ty of thermal m o t i ons in the solution.

Re f e r e n c e s [1] C a s s e 1 R. B., W o o d R. H., 3. Phys. Chem., 28. 2465 (1974). [2] P e r r o n G., 3 o 1 y 0 . , D e s n o y e r s 3. E . , A v e - d i k i a n L., M o r e l 3. P . , Can. 3. Chem. , 56, 552 (1978). [3] T a n i e w s k a-0 s i r i s k a S., P a 1 e c z B., 3. Chem. T h er mod yn am ics , V i , 775 (1980). [4] T a n i e w s k a-0 s i h s k a S . , P a l e c z 8., 3. Chem. T h e r m o d yn am ics , 1^, 11 (1982). [ 5 ] P a l e c z B . , T a n i e w s k a-0 s i ri s k a S . , Thermo- ch im ica Acta 1 1 6 , 349 (1987). [6] P a l e c z B., T a n i e w s k a-0 s i rt s k a S . , Thermo- ch im i c a Acta, J9_, 299 (1984).

[7] C r i s s C. M., C o b b l e 3. W., J. Am. Chem. Soc., £3, 3223 (1961).

[8] F u c h s R., H a g e n C. P., 3. Phys. Chem., 21, 179(1973). [9] P i e k a r s k i H., Can. 3. Chem., 62, 2203 (1983).

O D D Z I A Ł Y W A N I A P O M I Ę D Z Y H Y D R O F I Ł O W Y M I P O C H O D N Y M I M O C Z N I K A I Nal W W O D N YCH R O Z T W O R A C H W T E M P E R A T U R A C H 293. 15 i 303.15 K

Z m i e r z o n o e n t a l p i ę r o z p u s z c z a n i a Nal (w z a k r e s i e s t ę ż e ń 0.00 4- -0.1 mol N a l/ kg r o z p u s z c z a l n i k a ) w w o dz ie i w o d n y c h r o z t w o r a c h hy- d r o f i l o w y c h p o c h o d n y c h m o c z n i k a ( t i o m o c z n i k a i h y d r o k s y m o c z n i k a ) z a w i e r a j ą c y c h 0.1, 0.7, 1.0 i 1.5 mol (TU, H U ) / k g H2 0. P o m i a r y były w y k o n a n e w t e m p e r a t u r a c h 293.15 i 303.15 K. W y k o r z y s t u j ą c wart ośc i e n t a lpi i r o z p u s z c z a n i a o b l i c z o n o s t a n d a r d o w e e n t a l p i e r o z p u s z c z a n i a i e n t a l p o w e w s p ó ł c z y n n i k i o d d z i a ł y w a n i a par c z ą s t e c z k a p o c h o d n e j m o c z n i k a - u ś r e d n i o n y jon (Na+ J").