16 Sucrose Benzoate—The Unique Modifier
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E. P. LIRA and R. F. ANDERSON Velsicol Chemical Corp., 341 East Ohio St., Chicago,Ill.60611
Sucrose benzoate, prepared via our industrial process, has a typical assay of approximately 7.4 benzoyl groups per sucrose molecule. This is about the optimum degree of substitution for the conditions imposed upon the reactants. It should be noted that, although sucrose benzoate is a discrete molecule, i t has a molecular weight approximating that of many oligomeric systems. Figure 1 depicts sucrose benzoate. Please note that the outer surface, or shell, is composed either of aromatic benzene rings or ester groups. This then is the type of surface which w i l l interact with the conditions imposed upon i t .
Figure 1. Sucrose benzoate—the unique mo 223 In Sucrochemistry; Hickson, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.
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SUCROCHEMISTRY
T h e r e i s one s i g n i f i c a n t a r t i c l e i n t h e r e c e n t l i t e r a t u r e o n t h e p r e p a r a t i o n o f s u c r o s e b e n z o a t e (1_) . Ness and F l e t c h e r d e s c r i b e d t h e p r e p a r a t i o n o f t h e octabenzoylated d e r i v a t i v e by use o f benzoyl c h l o r i d e i n p y r i d i n e , f o l l o w e d by a work-up procedure which involved a carbon t e t r a c h l o r i d e - m e t h a n o l treatment. T h i s r e s u l t e d i n a c r y s t a l l i n e adduct c o n t a i n i n g s u c r o s e b e n z o a t e and two moles o f c a r b o n t e t r a chloride. A l l p r e v i o u s and subsequent r e p o r t s o f s u c r o s e o c t a b e n z o a t e d e s c r i b e o n l y an amorphous p r o duct. T h i s N e s s - F l e t c h e r adduct r e t u r n e d t o t h e amorphous s t a t e a f t e r r e m o v a l o f t h e c a r b o n t e t r a c h l o r i d e u n d e r vacuum. T h i s amorphous s t a t e i s a second important c h a r a c t e r i s t i c o f sucrose benzoate. I n a d d i t i o n t o t h e above method o f p r e p a r a t i o n , a t t e m p t s h a v e b e e n made w i t h o u t s u c c e s s t o make b e n z o i c acid react d i r e c t l y with sucrose. The p r o c e s s w h i c h t h i s paper o u t l i n e s f o l l o w s t h e c l a s s i c a l S c h o t t e n Baumann t e c h n i q u e a s i l l u s t r a t e d i n F i g u r e 2.
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Manufacturing Process (Schotten-Baumann Technique) S u c r o s e (Aqueous) Caustic Solution Benzoyl Chloride Toluene
Ambient Temperature
Sucrose Benzoate i n Toluene Toluene Sucrose
Process Advantages:
Figure 2.
Benzoate
Lower C o l o r Higher Yields Less Contamination
Manufacturing process (Schotten-Baumann technique)
The r a w m a t e r i a l s a r e pumped i n t o a r e a c t o r a n d s t i r r e d v i g o r o u s l y , s i n c e t h e system i s heterogeneous. After a s u i t a b l e r e a c t i o n p e r i o d , t h e phases a r e separated and t h e t o l u e n e removed f r o m t h e s u c r o s e b e n z o a t e . The s o l v e n t - f r e e p r o d u c t t h e n i s p r e p a r e d i n a f l a k e d form. T h i s process y i e l d s a product which has l e s s c o n t a m i n a t i o n and c o l o r t h a n o t h e r methods and a l s o g i v e s c o n s i s t e n t l y good y i e l d s . T a b l e s I a n d I I l i s t some t y p i c a l p h y s i c a l p r o p e r t i e s and/or s p e c i f i c a t i o n s f o r t h e p r o d u c t o f t h e above process. As i n d i c a t e d b e f o r e , i t i s an amorphous m a t e r i a l w h i c h m e l t s o v e r t h e 95-101°C r a n g e . Ash and a c i d i t y a r e l o w a n d i t s f l a s h p o i n t h i g h . Its
In Sucrochemistry; Hickson, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.
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SuCTOSe BeîlZOdte
A.P.H.A. c o l o r i s v e r y loty i n f a c t , t h e p r o d u c t i s water-white. Other d a t a o f i n t e r e s t , and which s t r o n g l y i n f l u e n c e t h e use p a t t e r n s , a r e the r e f r a c t i v e i n d e x , UV absorbancy and v i s c o s i t y . E s p e c i a l l y note t h a t t h e v i s c o s i t y i n a t o l u e n e s o l u t i o n does n o t i n crease r a p i d l y u n t i l the c o n c e n t r a t i o n i s q u i t e high. T a b l e I.
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Typical Physical Properties Non-Crystalline 95-101° 1.25 0.0J% maximum 500 L e s s than 0.1 0.9 150 30
Form S o f t e n i n g P o i n t (ASTM E28-67) Sp. G r . 25°/25°C Ash (ASTM E347-71) F l a s h P o i n t , TOC A c i d V a l u e , Mg. KOH/G. Hydroxy1 V a l u e , Meg./Gm. Saponification Equivalent APHA C o l o r (ASTM D1209-69)
1.577 230my >300my
N
25 XMax 100% T r a n s m i t t a n c e V i s c o s i t y (25 C) i n Toluene
Solid
25% 40% 60% 70%
1.30 Solids 3.7 Solids 35.1 Solids S o l i d s 530.0
Centipoises Centipoises Centipoises Centipoises
The s t a b i l i t y p r o f i l e d a t a i n T a b l e I I , g e n e r a l l y are q u i t e f a v o r a b l e . Sucrose benzoate i s r e s i s t a n t t o p r o l o n g e d t r e a t m e n t w i t h b o i l i n g water and has s u r p r i s i n g l y good s t a b i l i t y a g a i n s t b o t h a c i d and a l k a l i n e conditions. The r a t e o f h y d r o l y s i s appears i n i t i a l l y t o be f a s t e r i n base, b u t t h e n may t u r n o u t t o be s l i g h t l y s l o w e r than i n an a c i d treatment. Table I I Stability Hydrolysis
Profile
(100°C)
Water 5% Aq. HCl 5% Aq. Na C0 2
24 hours
96 hours
0 0 1.9%
0 0.6% 2.3%
In Sucrochemistry; Hickson, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.
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T h e r m a l s t a b i l i t y was f o l l o w e d b y c o l o r c h a n g e a n d i n c r e a s e i n a c i d i t y a s shown i n T a b l e I I I . The r a t e o f d e c o m p o s i t i o n i s v e r y s l o w a t 150°C. E v e n a t 175°C, i n a n a l u m i n u m d i s h , t h e i n c r e a s e i n a c i d i t y was o n l y f r o m .001 meg H+/g t o .007 meg H+/g. I t has been found t h a t e p o x y - c o n t a i n i n g a d d i t i v e s can i n c r e a s e the heat s t a b i l i t y of the product. Table I I I
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Stability Thermal
(150
C) Color
Hours
30 70 250
0 6 24 UV
Light
(Atlas
Profile
(APHA)
+
Meq.H /g .0025 .004 .009
U
(140 F)
Fade-O-Meter)
Film - No -
(4 m i l ) c o l o r change a f t e r 3000 h r I n f r a r e d unchanged a f t e r 3000 h r
UV s t a b i l i t y s t u d i e s i n d i c a t e v i r t u a l l y no c h a n g e i n t h e c h e m i c a l c o n s t i t u t i o n o f s u c r o s e b e n z o a t e when i t i s subjected t o prolonged exposure t o a f i l t e r e d , c a r b o n a r c l i g h t s o u r c e a t 140°F. The p r i n c i p a l m a x i ma o f t h i s l i g h t s o u r c e i s b e t w e e n 340 - 440 my. As n o t e d p r e v i o u s l y , t h e Xmax. o f s u c r o s e b e n z o a t e i s a r o u n d 230 my which i s w e l l below the wavelength which w i l l penetrate a i r . I t i s completely transparant a b o v e 300 my. A s m i g h t be e x p e c t e d o f a s t r u c t u r e w i t h a r o m a t i c and e s t e r c h a r a c t e r , t h e s o l u b i l i t y and c o m p a t i b i l i t y p r o p e r t i e s h a v e a p p r e c i a b l e l a t i t u d e , a s shown i n Table IV. Sucrose benzoate i s v i r t u a l l y i n s o l u b l e i n h y d r o c a r b o n s and w a t e r . I t has low s o l u b i l i t y i n lowe r m o l e c u l a r w e i g h t a l c o h o l s and g l y c o l s . Only the o l e f i n i c polymers are not compatible, w h i l e substances w i t h a l a r g e h y d r o c a r b o n p o r t i o n m i g h t be o n l y c o m p a t i b l e a t l o w l e v e l s ( e . g . 2%) (See T a b l e V ) . Examples of t h i s b e h a v i o r are c o t t o n s e e d o i l , corn o i l , s t e a r i c a c i d and t a l l o i l f a t t y a c i d s . This broad c o m p a t i b i l i t y makes s u c r o s e b e n z o a t e a p o t e n t i a l l y u s e f u l m o d i -
In Sucrochemistry; Hickson, J.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.
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f i e r i n many s y s t e m s a n d c a n be u s e d t o c a u s e c o m p a t i b i l i t y between " m a r g i n a l l y " compatible
"mutual" systems.
Table IV. Solubility
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Water
(20°C) (67°C) H e p t a n e (67 C) Ethyl Alcohol Most A c i d s , Amides, Aromatics, Ethers, Ether Alcohols, Esters, H a l o c a r b o n s , Ketones and N i t r i l e s Alcohols, Glycols
.001%
