Reaction of Starch with the Chlorosulfonic Acid-Formamide Reagent

11 Reaction of Starch with the Chlorosulfonic AcidFormamide Reagent F. S C H I E R B A U M and K. K Ö R D E L

Downloaded by MONASH UNIV on May 4, 2015 | http://pubs.acs.org Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0077.ch011

Akademie der Wissenschaften der D D R , Forschungszentrum fur Molekularbiologie und Medizin, Zentralinstitut für Ernährung, Potsdam-Rehbrücke, German Demokratic Republic

Reactions of s t a r c h polysaccharides with s u l f a t i n g agents have been c a r r i e d out (1) f o r making heparinoids with blood a n t i coagulating p r o p e r t i e s (2-4), f o r obtaining products having a n t i u l c e r act i o n by i n h i b i t i n g pepsin (5-7), to produce t h i c k e ning agents f o r foods (8) and a u x i l i a r y substances i n various techniques (9,10) and, g e n e r a l l y to subs t i t u t e for n a t u r a l l y occuring polysaccharide gums (11-13). The methods used f o r introducing s u l f u r i c acid groups i n t o the molecules of s t a r c h vary widely. There are (1) r e a c t i o n s i n homogeneous nonaqeous or aqueous systems, (2) reactions i n heterogeneous liquid systems, and (3) r e a c t i o n in dry s t a t e . A summar i z i n g survey on the most important methods and r e a gents used so far is given i n Table 1. The p r o p e r t i e s of the r e s u l t i n g starch esters depend l a r g e l y on these methods and reagents, and it is shown that r e actions i n homogeneous systems give products with low, medium and high degrees of s u b s t i t i o n (3,6,1417). I t is necessary, however, to p r e - g e l a t i n i z e the starch thus l i m i t i n g the starch concentration by its v i s c o s i t y . Reactions in heterogeneous systems on the other hand which may be performed at higher concent r a t i o n s lead to low degrees of s u b s t i t u t i o n (11,13,18-20). The lowest degrees of s u b s t i t u t i o n are obtained by r e a c t i o n s in a dry state (8,21,22). The system S O 3 - t r i a l k y l a m i n e i s f r e q u e n t l y used and well studied as a reactant i n aqueous a l k a l i n e (6,19, 17,20,23,24) and nonaqeous solvents ( p y r i d i n e , DMF, formamide, dimethylsulfoxide) (6,9,11,15,16,25) using l i q u i d or gaseous s u l f u r t r i o x i d e . Another r e a c t i v e system, c h l o r o s u l f o n i c a c i d (4,6,14,26-28) and formamide (4,14,28,29), seems to be of partial 0-8412-0426-8/78/47-077-173$05.00/0 ©

1978 A m e r i c a n C h e m i c a l Society

In Carbohydrate Sulfates; Schweiger, R.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.


174

CARBOHYDRATE SULFATES

i n t e r e s t with respect to costs and a v a i l a b i l i t y οί' chemicals i n the case of upscaling to an i n d u s t r i a l l e v e l f o r making starch s u l f a t e s as p r o t e i n comp^xing agents (30)· But there i s poor knowledge on the influence of the r e a c t i o n conditions on the proper t i e s of the end products. The purpose of the present a r t i c l e i s to present information on a c o r r e l a t i o n between p r i n c i p a l reac t i o n conditions and the fundamental properties of the r e s u l t i n g esters regarding degree of s u b s t i t u t i o n ( D S ) , degradation and contamination by decomposition reactants. The c h l o r o s u l f o n i c acid-formamide system has been chosen because of i t s several advantages as com pared with other r e a c t i v e systems that have been i n vestigated i n numerous preliminary experiments. Formamide has various functions and acts ciS a swelling and s o l u b i l i z i n g agent f o r s t a r c h granules, a com plexing agent with c h l o r o s u l f o n i c a c i d , a b u f f e r i n g agent during the r e a c t i o n , and as a solvent f o r the r e a c t i o n products. Also, i t may be destroyed i n suf f i c i e n t concentrations of a l k a l i . The main b e n e f i t , however, i s i n the s i m p l i f i c a t i o n of the i n i t i a l r e a c t i o n steps i . e . , the complex may be formed i n the r e a c t i o n v e s s e l by adding c h l o r o s u l f o n i c acid to formamide ( c a l c u l a t e d amounts f o r complex formation and f o r d i s s o l v i n g the starch)immediately followed by the a d d i t i o n of the dry s t a r c h . Under these conditions, the s t a r c h i s suspended at ambient temperature up to concentrations of 30 % of the amount of formamide used f o r d i s s o l v i n g the s t a r c h . There i s no problem with the f l u i d i t y of t h i s system i f i t i s heated slowly up to the r e a c t i o n temperature d e s i r e d . At a s u f f i c i e n t l y high temperature, the s t a r c h granules begin to d i s s o l v e slowly i n the r e a c t i v e system. Con sequently, the r e a c t i o n may be c a r r i e d out a l t e r n a t i v e l y i n heterogenous or homogeneous system (30)· Results C ο e f f i c i ent s of de t erminat i o n . For 16 e f f e c t v a r i a b l e s out of 20 which have been i n v e s t i g a t e d at a r e a c t i o n temperature of bO °C ( l e v e l s ) , c o r r e l a t i o n s by variance between e f f e c t v a r i a b l e s and process v a r i a b l e s have been e s t a b l i s h e d . Only the f o l l o w i n g items are not relevant i n mathematical sense : £*] , c a l c u l a t e d on the basis of anhydroglucose unit ( A G U ) and of pure starch s u l f a t e , R „ c a l c u l a t e d on the basis AGU, and inorganic s u l f a t e ( % S^). At a r e a c t i o n temperature of 70 C ( l e v e l / * ), 12 e f f e c t 9


11.

SCHIERBAUM AND KÔRDEL

Starch and Chlorosulfonic

Acid-Formamide

175


v a r i a b l e s out oi' 2 0 are c o r r e l a t e d with process v a r i ables. S i m i l a r l y ^ p r o p e r t i e s without s a t i s f a c t o r y corr e l a t i o n are |V} , inorganic s u l f u r , R g , c a l c u l a t e d on the basis of pure and crude starch s u l f a t e , the o p t i c a l density of s o l u t i o n s , and the y i e l d of pure s t a r c h s u l f a t e , the l a t t e r being e v i d e n t l y more dependent on p u r i f i c a t i o n than r e a c t i o n c o n d i t i o n s . F i s h e r Tggt. The combination of four independent process v a r i a b l e s by assuming a s i n g l e e f f e c t and double and t r i p l e i n t e r a c t i o n s r e s u l t s i n 1 6 explanatory v a r i a b l e s . Twelve of these v a r i a b l e s show a s i g n i f i c a n t influence on e f f e c t v a r i a b l e s . They are summarized i n Table 2 and are v a l i d f o r the two r e a c t i o n temperatures used. Independent from the general a c t i o n of the temperature, which i s of predominant influence on the q u a l i t y of e f f e c t v a r i ables, Table 2 gives a sequence of v a l i d i t y f o r the explanatory v a r i a b l e s involved i n the process. The concentration of water (w), which i s shown 6 7 times to be s i g n i f i c a n t i n s i n g l e and m u l t i p l e a c t i o n and the concentration of S O 3 ( r ) , s i g n i f i c a n t i n 6 4 cases of action are most e s s e n t i a l from t h i s point of view. The concentration of s t a r c h i n formamide ( s ) with 1 9 s i g n i f i c a n t actions and f i n a l l y the time of r e a c t i o n ( t ) with only 7 cases of s i g n i f i c a n c e are l e s s important. The r e a c t i o n time, however, may be of greater importance i f the r e a c t i o n i s c a r r i e d out at a temperature of below 5 0 ° C . analysis and i n t e r p r e t a t i o n of eqations of r e gression. In the f o l l o w i n g only a few c o r r e l a t i o n s between process v a r i a b l e s and e f f e c t v a r i a b l e s may be regarded, s e l e c t i n g those with the greatest importance f o r the process to be studied: S u l f u r , bound i n ester groups, S·.,.; Highly e s t e r i f i e d products containing more than 1 6 % S J J , ( D S > 1 , 4 ) may be obtained only at a temperature of 7 0 ° C and a SO3/AGU r a t i o of 4 : 1 . The water content of s t a r c h , when i n creased from b % to 2 0 % acts i n favor of higher degrees of e s t e r i f i c a t i o n ( f i g . 1 ) . At a SO3/AGU r a t i o of 2 : 1 , however, the degree of e s t e r i f i c a t i o n i s low and appears to decrease with i n c r e a s i n g water content. Very low degrees of e s t e r i f i c a t i o n ( < 1 0 % D S < 0 , 7 ) are also obtained at bO ° C . At both SO3/AGU r a t i o s , the degree of e s t e r i f i c a t i o n increases with i n c r e a s i n g water content, the increase being more pronounced at the 4 : 1 than the 2 : 1 r a t i o ( f i g . 1 ) . F i g . 2 shows that, at 7 0 ° C , the degree of este9

9



Non flu id,

dry,

Aqueous, alkaline, homogene ous, heterogeneous inhibitors)

(^swelling

soin.

dit. alkali

bases

organ. N'contatning

homogeneous

heterogeneous

Solvent

Non aqueous,

System

organ.

[amides)

[urea

\

SO 3

salts

sulfite

or

sulfate

acidic

LioM

α min es

3

S0

oleum,

tri alky Ι

bases

acid,

-

-

chlorosulfonic

3

SO Donor

-300

65

- 65

20

-100

hours

-several

1h

0,22

max.

0,01 -1J

1h -2*th

days

0,1 - 2,6

15min

Degree of Esterificatior, DS

-several

Time

0

Temp. °C

and reagents, used for preparing starch sulfates literature)

Complexing Agent *

from

methods

N'contatning

(taken

survey on preferred

of

Summarizing

Characteristics

Tab. 1


-4


SINGLE EFFECT w Γ

· · * · · ·

Γ r W w r 8

t

(w

F

-

-

TIME OF ACTION)

3

5

MOL. RATIO AGU/S0 , β

5

2

-

3 1 1

4

4

-

7

10

-

7 3

>

-

F

4

10

17 12 6

>

WATER CONTENT OF THE STARCH, r

8 · W · Γ t · 8 · Γ

TRIPLE INTERACTION

w s 8 t t t

DOUBLE INTERACTION

t

8

EFFECT

5 1

3 1 1 1

1

4

2 1

4

1

^ 3

£

12 1

21 9 6 2 2 1

25 19 12 1

ACTIONS

STARCH CONCENTRATION IN FORMAMIDE

F

F I S H E R - T E S T FOR PROVING SIGNIFICANCE BETWEEN EXPLANATORY VARIABLES AND VARIABLES IN THE REACTION OF THE CHLOROSULFONIC ACID - FORMAMIDE SYSTEM WITH STARCH

TYPE OF ACTION

TAB. 2




5

10 WATER

15

20wCVoJ

CONTENT

Figure 1. Lines of regression for the influence of the water content (w) of the starch on esterification (% S ) (v= S0 /AGU ratio) E

3

15

20 STARCH

25 s(%> CONTENT

Figure 2. Lines of regression for the influence of the concentration of the starch in formamide (s) on esterification (% S ) (w = water content, r = SO,/ AGU ratio) E



11.

scHiERBAUM A N D KORDEL


Acid-Formamide

179

r i f i c a t i o n decreases s l i g h t l y with i n c r e a s i n g conc e n t r a t i o n oi' starch i n a l l cases. The l i m i t i n g v i s c o s i t y number may be considered as a general measure f o r molecular degradation without using exact values f o r the molecular weight. Generally, s o l u t i o n s with excess e l e c t r o l y t e are used to eliminate p o l y e l e c t r o l y t e behavior. V i s c o s i t y measurements show a pronounced decrease of [»jj takes place with i n c r e a s i n g v/ater content ( f i g . 3 ) . A comparision of the values of [%] i n d i c a t e s that degradation u s u a l l y takes place under conditions which produce high degrees of ester i f i c a t i o n (high temperature and high SO3/AGU r a t i o ) and, i n v e r s e l y , t h a t s l i g h t l y degraded esters may be obtained under conditions f a v o r i n g low degrees of e s t e r i f i c a t i o n (lower temperature and lower SO3/AGU ratio). The high molecular weight p o r t i o n as determined i n the excluded volume through g e l permeation chromatography on SEPHADEX G 200 may be i n t e r p r e t e d s i m i l a r l y . There i s a strong tendency to decrease with i n c r e a s i n g water content at a SO3/AGU r a t i o of 4:1, both with 15 % and 25 % s, and a tendency to increase with an SO3/AGU r a t i o of 2:1 ( f i g . 4 ) . In t h i s case, however, the d i f f e r e n t p o l y e l e c t r o l y t e behavior of the v a r i o u s l y s u b s t i t u t e d polysaccharide esters could not be overcome by the solvent and t h e r e f o r e , a few r e s u l t s are i n c o n s i s t a n t with these tendencies. The apparent v i s c o s i t y ty) of 5 % aqueous s o l u t i o n s i s h i g h l y i n f l u e n c e d by the water content of the s t a r c h at 70 °C and decreases at a high SO3/AGU r a t i o ( f i g . 5 ) , The same tendencies have been observed at the higher v i s c o s i t y l e v e l at 50 °C. It i s s u r p r i s i n g , that high r a t i o s of SO3/AGU as w e l l as high concentrations of s t a r c h give r i s e t o higher v i s c o s i t i e s of the e s t e r . I t i s p o s s i b l e that the h y d r o l y s i s which i s accelerated by the higher water content of the s t a r c h may be reduced by higher amounts of formamide. I t i s , t h e r e f o r e , recommended to c a r r y out the r e a c t i o n at an SO3/AGU r a t i o of 4:1 and a s t a r c h concentration of 25 % at 70 °C i n order to obtain s t a r c h esters with higher v i s c o s i ties. With respect to the y i e l d of s t a r c h s u l f a t e , which i s s i g n i f i c a n t l y c o r r e l a t e d with process v a r i ables only at 50 °C, the same tendency i s observed as i n the dependency o f S-g on process v a r i a b l e s (see f i g . 1 ) . The tendency of the y i e l d value to i n crease with i n c r e a s i n g water content and i n c r e a s i n g SO3/AGU r a t i o , i s due t o a more complete e s t e r i f i c a t i o n . Thus, high degrees of e s t e r i f i c a t i o n c o i n c i d e




180

Figure 3. Lines of regression for the influence of the water content (w) of the starch on limiting viscosity number [η] (r = S0 / AGU ratio")

10 |_

3

nor) 5

10 WATER

15

CONTENT

Figure 4. Lines of regression for the influ ence of the water content (w) of the starch on the high molecular weight portion as excluded by gel permeation chromatography (SEPHA DEX G 200) (τ = SO /AGU ratio, s = starch concentration) 3


20wf%)

11.

scHiERBAUM AND KÔRDEL

Starch and

Chlorosulfonic

Acid-Formamide

181

with high y i e l d s . The amount of formamide necessary f o r producing 1 g s t a r c h s u l f a t e i s shown i n f i g . 6 and appears to decrease with i n c r e a s i n g s t a r c h concentration ( s ) . An i n c r e a s i n g water content, p r e f e r a b l y with a SCh/ AGU r a t i o of 2:1, leads to a s l i g h t decrease of tne formamide amount a l s o . The amount of c h l o r o s u l f o n i c a c i d necessary f o r 1 g ester decreases only s l i g h t l y with i n c r e a s i n g water content ( f i g . 7 ) ; The reason probably i s the increase of S as w e l l as of the y i e l d . Of course, the higher l e v e l r e f e r s to a SO3/AGU r a t i o of 4:1. The nitrogen content of the e s t e r s , the p r i n c i pal contamination, r e s u l t s from formamide bound by the s u l f a t e group. Therefore, the n i t r o g e n content e x h i b i t s the same tendencies i n dependence from process v a r i a o l e s as the degree of e s t e r i f i c a t i o n , i . e . , the higher the degree of e s t e r i f i c a t i o n , the higher the contamination with formamide. Independent of t h i s , the y i e l d of ammonium s u l f a t e as a byproduct r e s u l t i n g from decomposition of formamide i s highest at 70 °C and an SO3/AGU r a t i o of 4:1 and i s i n c r e a sing considerably with the water content.


E

Discussion The mutual actions of the explanatory v a r i a b l e s w i t h i n the given l e v e l of numerical values chosen f o r t h i s process are summarized i n Table 3 with r e spect to high degrees of e s t e r i f i c a t i o n , high y i e l d values, low molecular d e s t r u c t i o n , and low s p e c i f i c amount of raw m a t e r i a l s . Among the explanatory var i a b l e s a f f e c t i n g the process, the temperature has the greatest i n f l u e n c e on the e f f e c t v a r i a b l e s . Therefore high degrees of e s t e r i f i c a t i o n w i l l r e s u l t only at the higher temperature l e v e l . At t h i s l e v e l the r e a c t i o n proceeds completely i n the homogeneous system, the s t a r c h being d i s s o l v e d i n the reagent. At the 50 °C l e v e l , on the other hand, the r e a c t i o n takes place i n a predominantly heterogeneous system, rendering some s t a r c h soluble and r e a c t i n g to a higher degree and l e a v i n g another part of the s t a r c h undissolved and unreacted. Consequently these r e a c t i o n products have a non-uniform d i s t r i b u t i o n ofi substituents and a wide rang of molecular degradation* The water content or the s t a r c h has twofold e f f e c t , (a) : i t r e s u l t s i n high degrees of e s t e r i f i c a t i o n and a high e f f i c i e n c y regarding raw m a t e r i a l s , and (b) i t leads t o - pronounced h y d r o l y t i c degradation of molecules. The increase i n r e a c t i v i t y i s due to a




182

s = 25% 5

10 WATER

15

20wC%)

CONTENT

Figure 5. Lines of regression for the influence of the water content of the starch on apparent viscosity (5% sol) (r = SO /AGU ratio, s = starch concentration) s

Figure 6. Lines of regression for the influence of the starch concentration on the amount of formamide needed for producing 1 g of starch sulfate (w = water content of the starch)




Acid-Formamide

5 (9)


51

5

10 WATER

15

20w(%)

CONTENT

Figure 7. Lines of regression for the influence of the water content of the starch on the amount of chlorosulfonic acid needed for producing 1 g of starch sulfate (r = AGU/SO ratio) 3


183


70

TEMPERATURE °C

: 1

25

4

STARCH CONCENTRATION %

3

S0 /AGU RATIO

20

WATER CONTENT %

E

S

HIGH

: 1

50

-

4

20

HIGH VIELD VALUE 5

50

-

2 : 1

V

HIGH

4

G

50

25

: 1

5

N

LOW

p

Q

50,70

2:1

20

50,70

25

2:1

20

LOW AMOUNTS OF FORMAMIDE CHLOROSULFONIC ACID

EFFECT OF PROCESS VARIABLES ON THE STARCH CHLOROSULFONIC ACID - FORMAMIDE SYSTEM WITH RESPECT TO HIGH DEGREES OF ESTERIFICATION ( S ) AND YIELD VALUES, SMALL MOLECULAR DESTRUCTION (HIGH f * J VALUES) AND BY - PRODUCTS ( N ) , AND LOW AMOUNTS OF RAW MATERIAL

EXPLANATORY VARIABLES

TAB. 3


C/3


11.



Acid-Formamide

185

pronounced swelling of the s t a r c h that contains r e l a t i v e l y large amounts of water, but the amount of water that causes swelling and increases reactivityw i l l also cause an increased h y d r o l y t i c a c t i v i t y and r e s u l t i n cleavage of g l y c o s i d i c bonds. When the s u l f u r t r i o x i d e content, i . e . , the SO3/AGU r a t i o , that i s h i g h l y s i g n i f i a n t i n a l l actions observed i s increased, higher degrees of e s t e r i f i c a t i o n , high y i e l d s and higher molecular d e s t r u c t i o n are observed. With respect t o the e f f i c i e n c y , i t must be kept i n mind, however, that the amount of raw materials may be increased a l s o . The concentration of s t a r c h i n the formamide may be increased up to 30 ;5, but concentrations of s t a r c h between 15 % and 25 % are l e s s s i g n i f i c a n t than other explanatory v a r i a b l e s . I n creasing amounts of s t a r c h lead to a s l i g h t decrease i n degree of e s t e r i f i c a t i o n but also reduce the amount of formamide and by-products. As to the r e a c t i o n time between 15 and 30 min, i t has been pointed out already that the i n s i g n i f i c a n t i n f l u e n c e on e f f e c t v a r i a b l e s may be due to the small d i f f e rence between the temperatures used. I t can theref o r e be stated that the r e a c t i o n times are long enough f o r the e s t e r i f i c a t i o n s at 70 °C, but not f o r those at 50 °C. Conclusions The mutual actions described above lead to some d i f f i c u l t i e s with respect t o the s e l e c t i o n of proper conditions f o r producing starch s u l f a t e s with predetermined p r o p e r t i e s . I t must be r e a l i z e d , however, that the l i n e a r regression adopted i n the study of t h i s process g e n e r a l l y allows the predetermination of tendencies q u a l i t i v e l y , but does not produce q u a n t i t a t i v e r e s u l t s . A p r e d i c t i o n may be allowable only i f the steps i n the system are w i t h i n concrete l i m i t s and rather narrow. Within these r e s t r i c t i o n s , the s e l e c t i o n of r e a c t i o n conditions f o r the preper a t i o n of s t a r c h s u l f a t e s c o n s i s t s of a compromise oetween process v a r i a b l e s being e i t h e r p o s i t i v e or negative i n t h e i r a c t i o n . As an example f o r u t i l i z i n g the tendencies e l u c i d a t e d i n t h i s study, Table 4 shows the recommended process v a r i a b l e s f o r producing s t a r c h s u l f a t e s with a high degree of e s t e r i f i c a t i o n . Experimental General procedure. The c h l o r o s u l f o n i c a c i d - f o r mamide complex was formed by adding dropwise c h l o r o -


In Carbohydrate Sulfates; Schweiger, R.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978. 15 % 70 C 15 MIN

CONCENTRATION CP STARCH TEMPERATURE TIME CP REACTION U

\ : 1

12 %

WATER CONTENT OF STARCH SO^/AGU RATIO

PROCESS CONDITIONS PROPOSED

r

7

t~ APPARENT VISCOSITY SPECIFIC CONSUMPTION: FORMAMIDE CHLOROSULFONIC ACID

ESTER CONTENT CONTAMINATION G,5

%Ν

5 . 3 g/1* STARCH SULFATE, 2.4 f / l g STARCH SULF ATP.

2 - 11 cP ( 5 % SOL.)

3 0 ml g" 1

5 -

14 - 16 % S

RESULTING PROPERTIES OF RAW STARCH SULFATE

PROPOSED PROCESS CONDITIONS FOR PREPARING STARCH SULFATES WITH A HIGH DEGREE OF ESTERIFICATION AS DERIVED FROM INTERPRETATION OF THE EQUATIONS OF REGRESSION


Η M

>

X

w ο

>

ο

00


11.

scmERBAUM AND KÔRDEL


Acid-Formamide

187

s u l f o n i c acid t o formamide i n a round bottom f l a s k that was cooled t o maintain the temperature at below 40 ° C . The complex formed was d i l u t e d by a d d i t i o n of the amount of formamide required f o r d i s s o l v i n g the dry s t a r c h . Potato s t a r c h with a known moisture content was added t o the complex s o l u t i o n at 20 ° C with vigorous s t i r r i n g , the r e a c t i o n v e s s e l being immersed i n a temperature c o n t r o l l e d bath. The temperature of the bath was r a i s e d t o the desired value within 30 min and the mixture maintained at t h i s temperature f o r the desired r e a c t i o n time and immediatel y poured with vigorous a g i t a t i o n i n t o excess methan o l (1.5 1) « T^e p r e c i p i t a t e formed was f i l t e r e d o f f by s u c t i o n , washed with 100 ml methanol, and f i n a l l y d r i e d by i n f r a r e d r a d i a t i o n i n a stream of cold a i r . Reaction v a r i a b l e s . The general procedure des c r i b e d above was performed with the f o l l o w i n g var i a t i o n of r e a c t i o n conditions: 1. 2. 3· 4· 5·

r e a c t i o n temperature, 50 ° C and 70 ° C ( < * , / * ) time of r e a c t i o n at given temperature, 15 and 30 min ( t ) concentration of dry starch, 15, 20 and 25 % ( r e l a t e d t o formamide) ( s ) moisture content of potato s t a r c h , 5 and 20 % (w? molar r a t i o of SO3 t o AGU. 2:1 and 4:1 ( r ) (AGU anhydro glucose u n i t )

The s p e c i a l conditions, applied i n 48 r e s u l t i n g preparations are summarized i n Table 5· A n a l y t i c a l . The a n a l y t i c a l procedure used f o r c h a r a c t e r i z i n g r e a c t i o n products r e l a t e t o molecular as w e l l as to f u n c t i o n a l properties of the crude r e a c t i o n products. Further p u r i f i c a t i o n as may be necessary f o r p r a c t i c a l a p p l i c a t i o n of the esters has not been a p p l i e d . I t should be noted, hov/ever, that most of the ammonium s u l f a t e , the main by-product, p r e c i p i t a t e s l a t e r than the s t a r c h s u l f a t e . Therefore a r e l a t i v e l y pure starch s u l f a t e may be obtained by f i l t e r i n g i t o f f immediately a f t e r p r e c i p i t a t i o n . T h e f o l l o w i n g a n a l y t i c a l methods have been applied during the course of the complete program of i n v e s t i g a t i o n . (a)

T o t a l s u l f u r content, S Q %,by t o t a l h y d r o l y s i s with HCi, p r e c i p i t a t i o n with BaCl2 and gravimet r i c determination as BaSO^.; s u l f u r , bound i n ester groups, % c a l c u l a t e d by S 3 = S Q - S ^ ; s u l f u r i n anorganic compounds, %, by complexo9



EXPERIMENTAL CONDITIONS FOR ESTERIFICATION

CHLOROSULFONIC ACID

43,1 86,2 86,2 86,2

2 : 1

2 : 1

4 : 1

4 : 1

4 : 1 2

SAMPLE AMOUNTS OF STARCH: 31,6 g (5 % Η 0 ) ,

43,1 43,1

2 : 1

3

S0 /AGU

186,7

20 25

153,4 123,4 2

15

203,4

37,5 g (20 % H 0 )

25

20

15

106,7

136,7

OP STARCH

CONCENTRATION

OF POTATO STARCH BY MEANS OF THE

FORMAMIDE

CHLOROSULFONIC ACID - FORMAMIDE REAGENT

MOL. RATIO

TAB. 5


11.


Starch and

Chlorosulfonic

Acid-Formamide

189

metric t i t r a t i o n of the aqueous s o l u t i o n with CHELAPLEX

(b (c (d (e (±-


(g (h (i (3 (k

#

L i m i t i n g v i s c o s i t y number [η\ , i n 0,33 M NaCl. T o t a l nitrogen content, N Q % by steam d i s t i l l a t i o n of the a l k a l i n e s o l u t i o n and t i t r a t i o n according to the KJELDAHL semi-micro method. Reduction value, c a l c u l a t e d as glucose, R Q %, according to W i l l s t a e t t e r - Schudel. O p t i c a l r o t a t i o n value,/Vj , of 1 % s o l u t i o n s . Dynamic v i s c o s i t y , 1 (cP), of 5 % s o l u t i o n s i n the HOPPL^R Viscosimeter. Coldwater s o l u b i l i t y , derived from the r e f r a c t i v e index η of a 10 % d i s p e r s i o n . pH-value of 10 % s o l u t i o n . T u r b i d i t y of 1 % solution,8 weeks at 4 C; cuvettes 1 cm, transmittance at 650 nm. Reaction with i o d i n e , maximum aborbancejl with 1 0 " % iodine. Gel permeation chromatography, GPC, on Sephadex G 200, measuring the high molecular weight por t i o n ( r e s u l t i n g from the excluded volume). 9

m

a

x

The r e s u l t s f o r k } and [*] r e f e r to pure starch s u l f a t e and to AGU, r e s p e c t i v e l y and those f o r R Q to crude and pure starch s u l f a t e and to AGU, r e s p e c t i v e l y . The y i e l d values were c a l c u l a t e d with reference to pure s t a r c h s u l f a t e and ammonium s u l f a t e . Evaluations. The above r e s u l t s derived from determinations and c a l c u l a t i o n s lead to 20 e f f e c t v a r i a b l e s at two l e v e l s each

Reaction of Starch with the Chlorosulfonic Acid-Formamide Reagent

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