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Synthesis and study of carbohydrate polyborates
Synthesis and study of carbohy(lr~te polyborates
1615
CONCLUSIONS
(1) The t e m p e r a t u r c - t i m e dependence of the s t r e n g t h of polymers has been studied on the example of k a p r o n fibres s i m u l t a n e o u s l y exposed to mechanical stress a n d UV radiation, a n d it has been f o u n d to d e p a r t from the o r d i n a r y r e g u l a r i t y defined b y f o r m u l a (1), a n d to be reflected b y families of broken lines in the coordinates log r - - a a n d log r - - 1/T. (2) E x p o s e d to U V radiation there is a gradual change in the s t r u c t u r e of k a p r o n fibres duc to a b r e a k d o w n of the chemical boncL~, a n d c o n s e q u e n t l y of the coefficient 7 in f o r m u l a (1). (3) Allowancc for the v a r i a t i o n in 7 is n o t sufficient to explain c o m p l e t e l y the effect of UV radiation on lifetime a n d the s t e a d y state creep rate. (4) An e x p l a n a t i o n has bccn suggested for the effect which UV radiation is f o u n d to have on the lifetime a n d creep rate of k a p r o n fibres. I t is based on the a s s u m p t i o n t h a t the following two processes are superimposed: d e g r a d a t i o n devcl()ping according to formula (1), a n d d e g r a d a t i o n due to the irradiatiom TraJ~sh~ted by/ V. AT,FORI) REFERENCES 1. S. N. Z H U R K O V and B. N. N A R Z U L L A Y E V , Zh. tekh. fiz. 23: 1677, 1953
2. 3. 4. 5. 6. 7. ~. •% 10. I 1.
S. N. ZHURKOV and E. Ye. TOMASHEVSKII, Zh. t~kh. fiz. 25: 66, 1955 S. N. ZHURKOV and T. P. SANFIROVA, Dokl. Akad. Nauk SSSR 101: 237, 1955 S. N. ZHURKOV, Vcstn. akad. imuk SSSR 11, 78, 1957 S. N. ZHURKOV and T. P. SANFIROVA, Fiz. tverd, tel~ 2: 1033, 1960 S. N. ZHI~KOV and S. A. ABASOV, Vysokomol. soycd. 3: 441, 196l S. N. ZHURKOV and S. A. ABASOV, Vysokomol. soyed. 3: 450, 1961 S. N. ZHURKOV and S. A. ABASOV, Fiz. tvcrd, tela, 4: 2148, 1962 V. R. REGEL' and N. N. CHERNYI, Vysokomol. soyed. 5: 925, 1963 G. B. TAYLOR, J. Amcr. Chem. Soc. 69: 635, 1947 S. R. RAFIKOV and HSUI CHI-PING, Vysokomol. soyed. 4: 851, 1962
SYNTHESIS
AND STUDY OF CARBOHYDRATE
V. V. GERTSEV a n d
YA.
POLYBORATES*
YA. MAKAROV-ZEMLYANSKII
Moscow Tochnological [nstiiuto of tho Light Industry
(Received 27 September 1963) T H E esters of boric acid a n d its derivatives are of considerable scientific and practical interst. This w o r k deals with the synthesis a n d s t u d y of the conversions of poly(alkyl)borates to tile c a r b o h y d r a t e series. As shox~71 b y published *Vysokomol. soy~(1. 6: No. 8, 1458 14(;2, 1964.
1616
V. V. GERTSEV and YA. YA. MAKAROV-ZEMLYANSKII
figures [1, 3], a variety of boron-containing monomers and polymers can be obtained from the esters of boric acid. Another aim for studies in the field of boron containing polymers is the production of compounds which are resistant to heat and the action of hydrolytic agents. This means that an investigation of the borates can follow the line of the synthesis of the borates of di- and polyhydroxy compounds and borates with different functional groups. At the same time, with the development of the hydrolysis industry some of the monosaccharides have become accessible and cheap raw materials [4, 5]. In view of this, and also the high reactivity of the monosaccharides, it can be assumed that these compounds could be a valuable starting material for various kinds of organic synthesis. But ways of using monosaccharides in the synthesis of macromolecular materials are not yet sufficiently clear since carbohydrates belong to the group of acidiphobic thermally unstable materials. This work deals mainly with the study of the transesterification of the lower alkyl borates with carbohydrates which is well known ibr simple alcohols [6] B(OR)3+ 3 R ' O H ~ B(OR')3 ~- 3ROH.
But since carbohydrates are labile polyfunctional compounds with a tendency to different conversions, it must be remembered that this could occur in the process of reactions known for simple compounds. For carbohydrates this w a y of conducting transesterification is with excess alkyl borate during boiling. In our experiments this excess was 0.6 mols per hydroxyl group of monosaccharide: R[OH]n -P 1 "6nB(OR')a~R[OB(OR')a]n -~ n R ' O H + 0'6nB(OR')a.
The reaction was conducted with methyl- ethyl-, and n-propylborates. As the carbohydrate we used aldoses, ketoses and pentoses. The reaction started under heterogeneous conditions, and as the mixture was brought up to the boiling point of the alcohol, the monosaccharide started to decompose. As the reaction is reversible the only w a y to produce carbohydrate alkyl borates is by removing the alcohol formed as the product. According to our data the amount of alcohol in the distillation products corresponds to the total es~erification of all the hydroxyl groups of the monosaccharides, independent of their three-dimensional arrangement. Completion of the esterification was confrmed by using the I R spectra. There was no sign of a 3330 cm -1 absorption band, which is typical of the carbohydrate hydroxyl groups, in the I R spectra of the monose polyborates. The reaction of transesterification produces mixed carbon borates and simple alcohols. These monose poly(alkyl)borates are not subject to vacuum distillation, they do not crystallize but dissolve easily in organic solvents. When vacuum heated disproportionation occurs and as a result of this monose oligomeric polyborates are formed and the lower alkyl borates are separated. Solid, foamlikc, boron-containing polymers were produced on monose base, the corn-
xyloso
I'I~IFIn OSO
fructoso sorboso arabinos(,
lnanoso
ghlcoso galactoso
B(OCaH~)a 49 49 49 49 49 47 43 47
38 38 38 38 38 36 33 36
glucoso galactoso mo~noso fructoso sorboso arabinoso rarnnoso xyloso
B(OCH3)3
B(O('2Hs) 3
Amotmt of B(()R).~ in ml
8.0 8.0 8.0 6.0 ft.0 4-5 4.0 5.0
6.5 6.5 6.5 5.0 4.5 3.5 3-0 3.5
6.0 6.0 6-0 4-5 4.0 3.0 2.5 3.0
Reaction limo, h r ff
8.91 8.80 8.90 8-75 8.8O 8.50 8.60 8.5O
8-20 8.10 8.06 8.0 8.0 7.9 7.9 7-8
7.45 7.32 7-56 7.40 7.50 7-38 7.48 7.52
wt,
7.8 8.0 7-9 7.8 7-S 7.8 7.S 7.9
8-76 8.65 8.85 8.90 9.0 8.6 8.8 8.75
9-75 9.80 9.75 9.70 9.65 9.45 9.40 9.45
t)01'(}11, o' :O
37-32 37"25 37'30 37"35 37' 10 36'5 33"O 36"fi
28.15 28-00 28"20 28"25 28'2 28'0 25"2 27"9
18"9 18"8 18'95 19'0 18"9 19"1 17"1 19"3
w{, ~
4.47 4.46 4"44 4'47 2'47 4.46 4.45 4.46
5-73 5"80 5"76 5'76 5'74 5"75 5.73 5.77
8'16 8"14 8'I0 8"25 8"16 8"20 8"14 8"20
%
1~O1'OI1,
22"5 22-6 22"8 22 '5 22"4 22.6 22.5 22"7
22"7 22"6 22.6 22.5 22'7 22"4 22"7 22.5
21 '4 21'4 21'4 21 "4 21.4 21",~ 21"9 21"8
21.4 21.4 21'4 21 "4 21"4 21.8 21-9 21-8
21"4 21"4 21 '4 21 "4 21-4 21-9 21"9 21"9
t ical
22"2 22-2 22-3 21"0 22'0 21'6 22-0 21-4
t h(~Ol'O.-
mental
ah.ohol, 00 (~,XI }O|'i -
tlro
200-230 200 2 3 0 200-230 I S0-200 180-220 180 200 180-200 180 2O0
200 230 200.230 200-230 180 200 180 220 180 20O 180 2OO 180 200
200-230 200-230 200-230 180 200 180-230 180-200 180-200 180-200
(l) (2) (2) ( 1.5) (2) (1-5) (2) (1.5)
(1.5) (1.5) (1.5) (1) (1.5) (l) (1.5) 11)
( 1) (1) (1) (0.5) (l) (0-5) (l) (0-5)
rango of tho dL~proportionation ~g 5 10 ram, ~'C, hi"
T()mportd.
MOX()s.'t('t'IIAItII)ES
I)ro(hwts o f (listilb~tion of B(()R): I R O I I
<)l.' l,oWl.ilt+ .XI,KYL l~Ol{,,ITJ-.'~ W I T I I
l'olybor~Lt,
{,q." TIIJ.i T I t . ' t N S F S ' I ' E I { J I . ' I t ' A T I O N
25 25 25 25 25 24 22 24
Polyhydroxy COml)OUnd (Sg)
O1.' P I t o D I ' ( ' T . ' 4
glucoso gahv~toso manoso fructoso 8orboso arabinoso ramnoso xyloso
Alkyl borato B(()R) 3
(_]I).'0POSJ'I'It)N
O" 0
¢_
::e
o
r~
1618
V.V. GERTSEVand YA. YA. MAKAROV-ZEMLYANSKII
position being [CaHvOeB2,4(OR')~]~ :R[OB(OR')2],-*polymer+yB(OR')3; they had higher heat resistance than the original monosaccharides. They did not melt, and only decomposed with heating at 180-230°C for a long time. The mechanism of the transesterification of the lower alkyl borates ~4th monosaccharides can be represented as follows: - - C] - - O/H÷ f /OR
--C--o/H~oR [ : B-/--OR \OR (I)
C]--O--B
C
~C ~O
--C--O--B / ~OR [ (II)
--C --O I (III)
As we can see from this scheme, the transesterification proceeds via the coordination of the alkyl borate boron atom (Lewis acid) with a pair of hydroxyl group electrons of the carbohydrates, leading to the formation of the "acid" complex (1). As more alcohol is removed a mixed polyester of boric acid, carbohydrate and simple alcohol is formed (II). This kind of poly(alkyl)borate of monose can only exist where there is an excess of lower alkyl borates due to molecular association. When this excess is removed disproportionation occurs with formation of coiled structures where the three-dimensional arrangement of the OH group is suitable for coiling in the carbohydrate network of the monoses (III). This scheme for the mechanism of the re-esterification of the lower alkyl borates with carbohydrates is in very good agreement with the data obtained in a study of this reaction with hexoses, in which there are five completely esterifled hydroxyl groups in the different positions of a pyranose ring. The formation of the dimeric and oligomeric polyborates can be represented as the result of the further development of the disproportionation of cyclic and noncyclic structures of the monose alkyl borates [7]:
I -c--o\ 3 I
l --c--o\
I I I /o--c-B--OR ~ B--O--C--C--O--B +B(OR) 3 -c-o/ -c-o/ I I \o-el I I OR I 2----O--B ~--C--O / \O--C--+B(OR) 3.
i
i
~,Vc observed the formation of oligomeric P B E in practice w h e n the viscous mass changed over to a solid superficially foamy state in a certain temperature range combined with a vacuum. The polymers broke d o w n on further rise of temperature, and this could be seen by the change of colour of white to brown. During the investigation of the transesterification reaction it was found that the formation rate of the homogeneous solution of monosaccharide in alkyl
Synthesis and study of carbohydrate polyboratos
1619
borates increases where there is a very small amount (less than 1 o / o f the monosaccharide weight) of moisture or orthoboric acid. Monose polyborates were also obtained with the transesterificatiou of chemically pure alkyl borates. The reaction rate probably increases due to the formation of incomplete lower alkyl })orates OHB(OR')e, (OH)2BOR', which means t h a t the reaction rate of condensation will be higher t h a n t h a t of esterification with polyhydroxy compounds: R[OH]. + nOHB(OR')2-> R[OB(OR')=]. + nI-I=0 etc.
Since moisture was involved in the reaction in our case, it is suggested t h a t the incomplete monose borate is formed according to
I
--c-o_\
I
-c--o\
2| CO/ B--OR + H,O ~:~ --( !--O/B--OH q-ROH.
I
I
To test this the polyborates obtained were analysed with the Fischer reagent [8]. In all cases the only thing found was traces of the incomplete boric acid ester and the monose. This means t h a t when the reaction is conducted with lowcr alkyl borates, which easily hydrolyse, the possibility of a product of hydrolysis being present in them must be taken into account. For our transesterification reaction we chose the conditions under which the interaction of the lower alkyl borates (Lewis acid) ~dth the monosaccharides would be accompanied by the formation of a homogeneous solution. Under these cirmnnstances conversion of the c~.rbons is highly probable due to exposure of the pyronosc ring. In this case the presence of the carbonyl group m a y mean the formation of the products of the recovery of the original monosaccharides as eas(,s are k n o ~ l where alkyl })orates have been used instead of aluminium isoprol)ylatc to reduce aldehydes and ketones [9J. To do this the product polyborates were saponificd or hydrolysed and the polyhydroxy compounds separated were analyzed by paper (;hromatography. To be able to distinguish the monosac(;harides and the possible products of their reduction better, the chromatography was carried out over a fixed layer of cellulose powder [10]. In all cases the original monosaccharides and traces of di- and oligosaccharides were fouud. EXPERIMENTAL
All thc monosaccharides used were first purified by recrystallization and dried to constant weight. Before using the alkyl borates were distilled over m(,tallic sodium. The results of the analysis were consistent with the published figures Ill]. Trimethylborate B(OCH3) 3, B 10.4~, m.p. 68-69 °, 7----0-932 g/cm3; triethylborate B(OC2Hs)a, B 7.41~o, m.p. 117-120 °, ~--~().86 g/cma; tripropylborate B(OCaH:)a, B 5.75~, m.p. 176-179 °, 7----0"86 g/cm 3. Trrmsesterification. 5 g monosaccharide were placed i71 a 250 ml round bottomed flask with an agitator and rcflux cooler and a calcium chloride tube,
1620
V. V. GERTSEV and YA. YA I~LtKAROW-ZEMLYANSKII
a n d 1.6 moles alkyl b o r a t e per O H g r o u p of the p o l y h y d r o x y l c o m p o u n d was added. The heterogeneous m i x t u r e was h e a t e d over an oil b a t h until the alcohol boiled. The r e a c t i o n was c o n d u c t e d until the solid residue dissolved. W h e n the solution b e c a m e t r a n s p a r e n t the excess alkyl b o r a t e a n d alcohol f o r m e d as a result of the transesterification were distilled off the reaction zone into a deep cold receiver. The distillation p r o d u c t s were a n a l y z e d for boron c o n t e n t a n d the alcohol c o n c e n t r a t i o n calculated. The viscous p r o d u c t was h e a t e d u n d e r a v a c u u m of 5-10 m m until the alkyl b o r a t e was c o m p l e t e l y distilled off. A white f o a m y solid p r o d u c t was obtained, the p o l y b o r a t e of the original, monosaccharide. The b o r o n was d e t e r m i n e d b y t i t r a t i n g a q u e o u s solutions of boric acid in 0-1 .X" N a O H in the presence of m a n n i t e . The polyesters were saponified in hot absolute n - p r o p y l alcohol. A f t e r cooling the carbons were crystallized out a n d t h e n a n a l y s e d to determine t h e m separately, using p a p e r c h r o m a t o g r a p h y .
Chromatographic analysis of the monosaccharides. "M" paper made by Leningrad factory No. 2 was used for the chromatography; the rising branches of the chromatograms were taken. The solvent systems were as follows: n-butanol-ethanol-water (4 : 1 : 5), propanel-ethyl acetate-water (7 : 1 : 2), butanol-acetic acid-water (10 : 2 : 2), n-butanolacetic acid-water (4 : 1 : 5). The spots wore revealed with a 1o~) solution of Agl~'O3 in acetone and an alcoholic 4°/o solution of NaOH. The thin-layer chromatography was conducted over a fixed layer of cellulose powder using the procedure described in [10]. The following systems of solvents wore used: tertiary butanol-n-propanol-wator (8 : 2 : 3), binary butanol-ethyl acetate-water (8 : 12 : 3), n-butanol-pyridino-wator (10 : 3 : 3). The monosaccharides wore detected with a mixture of reactants: anilinc-phthalic acid, and anilino-diphcnylamino-phosphoric acid. To detect the polyhydric alcohols we used sodium bonzidine periodato. Reference point chromatography was used. CONCLUSIONS (1) The transesterification of tim lower alkyl borates with monosaccharides h a v e been studied. The p o l y b o r a t e s of aldoses, ketoses a n d pentoses were synthesized. (2) Esterification of the h y d r o x y l groups of the m o n o s a c c h a r i d e s h a v e been f o u n d to occur completely, i n d e p e n d e n t of their configuration. (3) Monosaccharides do n o t u n d e r g o a n y change as a result of the transesterification with alkyl borates. (4) The rate of the reaction with m o n o s a c c h a r i d e s is f o u n d to increase in the presence of the p r o d u c t s of the hydrolysis of lower alkyl borates. Translated by V. ALFORD REFERENCES
1. B. M. MIKHAILOV, Usp. khimii 28: 1450, 1959 2. V. A. Z A M Y A T I N A a n d N. I. B E K A S O V A , Usp. khimii 30: 48, 1961
3. W. GERRARD, The Organic Chemistry of Boron, Academic Press, London and New York, 148, 1961 4. S. V. CHAPIGO, K h i m . prom. 177, 1960
Chloroacetals of polyvinyl alcohol
1621
5. 6. 7. 8. 9. 10.
H. HASS, La Sacrarcs Belg. 75: 185, 1956 H. WUYTS and A. DUQUESNE, Bull. Soc. Khim. Belg. 48: 77, 1939 H. I. HUBERT, B. HARGITAY and I. DALE, J. Chem. Soc. 931, 1961 D. MITCHELL and D. SMITH, Aquamctry, 1952 H. C. KUIVILA, S. C. SLACK and P. K. S~TERI, J. Amer. Chem. Soc. 73: 123, 1951 L. D. BERGEL'SON, V. V. VORONKOVA and E. V. DYATLOVITSKAYA, ])okl. Akad. Nauk SSSR 145: 325, 1962; 149: 1319, 1963 11. H. STEINBERG and D. L. HUNTER, In(iustrial and Engineering Chemistr.v 49: 174, 1957
SYNTHESIS OF THE CHLOROACETALS OF POLYVINYL ALCOHOL* S. N. USHAKOV ]nstituto of Macromolecular
and N. A. KASHKINA Compounds,
U.S.S.R. Academy
of Scionces
(Received 27 ,'~eptember 1963) VARIOUS m e t h o d s a r e k n o w n for t h e s y n t h e s i s of p o l y v i n y l a c e t a l s [1]. T h e n u m b e r of p a p e r s r c f e r r i n g t o t h e s y n t h e s i s o f c h l o r o a c e t a l s o f p o l y v i n y l a l c o h o l , a n d i n p a r t i c u l a r to p o l y v i n y l c h l o r o e t h y l a l s [2], is e x t r e m e l y l i m i t e d . T h e r e is, however, interest in the synthesis of these d e r i v a t i v e s of p o l y v i n y l alcohol (PVA). Tim chloroacetals of PVA, in comparison with the o r d i n a r y p o l y v i n y l a c e t a l s , w h i c h do n o t c o n t a i n h a l i d e s , h a v e a n i n c r e a s e d c h e m i c a l r e s i s t a n c e . A t t h e s a m e t i m e , b e c a u s e o f t h e p r e s e n c e o f a t o m s of c h l o r i n e w i t h a lfigh r e a c t i v i t y i n t h e p o l y m e r m o l e c u l e , t h e c h l o r o a c e t a l s arc o f i n t e r e s t as t h e s t a r t i n g p r o d u c t s for fl~rther c h e m i c a l t r a n s f o r m a t i o n s . :ks is w~,ll known, the presence of mosomcrism may be postulated for the carbonyl group in th(; alternative polar form: R
R
,,,
,:
/~c-o,, RL~(~-6 R1 / The ine,~omorism of the carbonyl group depends to a considerable extent on the nature of the sul)stituonts R and R I . I n chloracotahtohydo as distinct from acetaldehyde, on() substituen~ contains a chlorine atom (R:CH~CI, R I = H ) , because of the presence of which an atomic bond of a partially ionic character is formed. As a result of the unequal affinity tbr electrons shown by the carbon atom and by the chlorine atom, the bonding electron pair is more strongly hold by the halide. This asymmetry in the charge distribution gives rise to the phenomenon of polarity, which is however not limited only to the two atoms directly connected by the given bond, but is (listributo(t in the remainder of the. molecule as a result of which an induction effect appears at bonds situated in the immodiat(~ vicinity. *Vysokomol. soyod. 6: No. 8, 1463-1466, 1964.
1615
CONCLUSIONS
(1) The t e m p e r a t u r c - t i m e dependence of the s t r e n g t h of polymers has been studied on the example of k a p r o n fibres s i m u l t a n e o u s l y exposed to mechanical stress a n d UV radiation, a n d it has been f o u n d to d e p a r t from the o r d i n a r y r e g u l a r i t y defined b y f o r m u l a (1), a n d to be reflected b y families of broken lines in the coordinates log r - - a a n d log r - - 1/T. (2) E x p o s e d to U V radiation there is a gradual change in the s t r u c t u r e of k a p r o n fibres duc to a b r e a k d o w n of the chemical boncL~, a n d c o n s e q u e n t l y of the coefficient 7 in f o r m u l a (1). (3) Allowancc for the v a r i a t i o n in 7 is n o t sufficient to explain c o m p l e t e l y the effect of UV radiation on lifetime a n d the s t e a d y state creep rate. (4) An e x p l a n a t i o n has bccn suggested for the effect which UV radiation is f o u n d to have on the lifetime a n d creep rate of k a p r o n fibres. I t is based on the a s s u m p t i o n t h a t the following two processes are superimposed: d e g r a d a t i o n devcl()ping according to formula (1), a n d d e g r a d a t i o n due to the irradiatiom TraJ~sh~ted by/ V. AT,FORI) REFERENCES 1. S. N. Z H U R K O V and B. N. N A R Z U L L A Y E V , Zh. tekh. fiz. 23: 1677, 1953
2. 3. 4. 5. 6. 7. ~. •% 10. I 1.
S. N. ZHURKOV and E. Ye. TOMASHEVSKII, Zh. t~kh. fiz. 25: 66, 1955 S. N. ZHURKOV and T. P. SANFIROVA, Dokl. Akad. Nauk SSSR 101: 237, 1955 S. N. ZHURKOV, Vcstn. akad. imuk SSSR 11, 78, 1957 S. N. ZHURKOV and T. P. SANFIROVA, Fiz. tverd, tel~ 2: 1033, 1960 S. N. ZHI~KOV and S. A. ABASOV, Vysokomol. soycd. 3: 441, 196l S. N. ZHURKOV and S. A. ABASOV, Vysokomol. soyed. 3: 450, 1961 S. N. ZHURKOV and S. A. ABASOV, Fiz. tvcrd, tela, 4: 2148, 1962 V. R. REGEL' and N. N. CHERNYI, Vysokomol. soyed. 5: 925, 1963 G. B. TAYLOR, J. Amcr. Chem. Soc. 69: 635, 1947 S. R. RAFIKOV and HSUI CHI-PING, Vysokomol. soyed. 4: 851, 1962
SYNTHESIS
AND STUDY OF CARBOHYDRATE
V. V. GERTSEV a n d
YA.
POLYBORATES*
YA. MAKAROV-ZEMLYANSKII
Moscow Tochnological [nstiiuto of tho Light Industry
(Received 27 September 1963) T H E esters of boric acid a n d its derivatives are of considerable scientific and practical interst. This w o r k deals with the synthesis a n d s t u d y of the conversions of poly(alkyl)borates to tile c a r b o h y d r a t e series. As shox~71 b y published *Vysokomol. soy~(1. 6: No. 8, 1458 14(;2, 1964.
1616
V. V. GERTSEV and YA. YA. MAKAROV-ZEMLYANSKII
figures [1, 3], a variety of boron-containing monomers and polymers can be obtained from the esters of boric acid. Another aim for studies in the field of boron containing polymers is the production of compounds which are resistant to heat and the action of hydrolytic agents. This means that an investigation of the borates can follow the line of the synthesis of the borates of di- and polyhydroxy compounds and borates with different functional groups. At the same time, with the development of the hydrolysis industry some of the monosaccharides have become accessible and cheap raw materials [4, 5]. In view of this, and also the high reactivity of the monosaccharides, it can be assumed that these compounds could be a valuable starting material for various kinds of organic synthesis. But ways of using monosaccharides in the synthesis of macromolecular materials are not yet sufficiently clear since carbohydrates belong to the group of acidiphobic thermally unstable materials. This work deals mainly with the study of the transesterification of the lower alkyl borates with carbohydrates which is well known ibr simple alcohols [6] B(OR)3+ 3 R ' O H ~ B(OR')3 ~- 3ROH.
But since carbohydrates are labile polyfunctional compounds with a tendency to different conversions, it must be remembered that this could occur in the process of reactions known for simple compounds. For carbohydrates this w a y of conducting transesterification is with excess alkyl borate during boiling. In our experiments this excess was 0.6 mols per hydroxyl group of monosaccharide: R[OH]n -P 1 "6nB(OR')a~R[OB(OR')a]n -~ n R ' O H + 0'6nB(OR')a.
The reaction was conducted with methyl- ethyl-, and n-propylborates. As the carbohydrate we used aldoses, ketoses and pentoses. The reaction started under heterogeneous conditions, and as the mixture was brought up to the boiling point of the alcohol, the monosaccharide started to decompose. As the reaction is reversible the only w a y to produce carbohydrate alkyl borates is by removing the alcohol formed as the product. According to our data the amount of alcohol in the distillation products corresponds to the total es~erification of all the hydroxyl groups of the monosaccharides, independent of their three-dimensional arrangement. Completion of the esterification was confrmed by using the I R spectra. There was no sign of a 3330 cm -1 absorption band, which is typical of the carbohydrate hydroxyl groups, in the I R spectra of the monose polyborates. The reaction of transesterification produces mixed carbon borates and simple alcohols. These monose poly(alkyl)borates are not subject to vacuum distillation, they do not crystallize but dissolve easily in organic solvents. When vacuum heated disproportionation occurs and as a result of this monose oligomeric polyborates are formed and the lower alkyl borates are separated. Solid, foamlikc, boron-containing polymers were produced on monose base, the corn-
xyloso
I'I~IFIn OSO
fructoso sorboso arabinos(,
lnanoso
ghlcoso galactoso
B(OCaH~)a 49 49 49 49 49 47 43 47
38 38 38 38 38 36 33 36
glucoso galactoso mo~noso fructoso sorboso arabinoso rarnnoso xyloso
B(OCH3)3
B(O('2Hs) 3
Amotmt of B(()R).~ in ml
8.0 8.0 8.0 6.0 ft.0 4-5 4.0 5.0
6.5 6.5 6.5 5.0 4.5 3.5 3-0 3.5
6.0 6.0 6-0 4-5 4.0 3.0 2.5 3.0
Reaction limo, h r ff
8.91 8.80 8.90 8-75 8.8O 8.50 8.60 8.5O
8-20 8.10 8.06 8.0 8.0 7.9 7.9 7-8
7.45 7.32 7-56 7.40 7.50 7-38 7.48 7.52
wt,
7.8 8.0 7-9 7.8 7-S 7.8 7.S 7.9
8-76 8.65 8.85 8.90 9.0 8.6 8.8 8.75
9-75 9.80 9.75 9.70 9.65 9.45 9.40 9.45
t)01'(}11, o' :O
37-32 37"25 37'30 37"35 37' 10 36'5 33"O 36"fi
28.15 28-00 28"20 28"25 28'2 28'0 25"2 27"9
18"9 18"8 18'95 19'0 18"9 19"1 17"1 19"3
w{, ~
4.47 4.46 4"44 4'47 2'47 4.46 4.45 4.46
5-73 5"80 5"76 5'76 5'74 5"75 5.73 5.77
8'16 8"14 8'I0 8"25 8"16 8"20 8"14 8"20
%
1~O1'OI1,
22"5 22-6 22"8 22 '5 22"4 22.6 22.5 22"7
22"7 22"6 22.6 22.5 22'7 22"4 22"7 22.5
21 '4 21'4 21'4 21 "4 21.4 21",~ 21"9 21"8
21.4 21.4 21'4 21 "4 21"4 21.8 21-9 21-8
21"4 21"4 21 '4 21 "4 21-4 21-9 21"9 21"9
t ical
22"2 22-2 22-3 21"0 22'0 21'6 22-0 21-4
t h(~Ol'O.-
mental
ah.ohol, 00 (~,XI }O|'i -
tlro
200-230 200 2 3 0 200-230 I S0-200 180-220 180 200 180-200 180 2O0
200 230 200.230 200-230 180 200 180 220 180 20O 180 2OO 180 200
200-230 200-230 200-230 180 200 180-230 180-200 180-200 180-200
(l) (2) (2) ( 1.5) (2) (1-5) (2) (1.5)
(1.5) (1.5) (1.5) (1) (1.5) (l) (1.5) 11)
( 1) (1) (1) (0.5) (l) (0-5) (l) (0-5)
rango of tho dL~proportionation ~g 5 10 ram, ~'C, hi"
T()mportd.
MOX()s.'t('t'IIAItII)ES
I)ro(hwts o f (listilb~tion of B(()R): I R O I I
<)l.' l,oWl.ilt+ .XI,KYL l~Ol{,,ITJ-.'~ W I T I I
l'olybor~Lt,
{,q." TIIJ.i T I t . ' t N S F S ' I ' E I { J I . ' I t ' A T I O N
25 25 25 25 25 24 22 24
Polyhydroxy COml)OUnd (Sg)
O1.' P I t o D I ' ( ' T . ' 4
glucoso gahv~toso manoso fructoso 8orboso arabinoso ramnoso xyloso
Alkyl borato B(()R) 3
(_]I).'0POSJ'I'It)N
O" 0
¢_
::e
o
r~
1618
V.V. GERTSEVand YA. YA. MAKAROV-ZEMLYANSKII
position being [CaHvOeB2,4(OR')~]~ :R[OB(OR')2],-*polymer+yB(OR')3; they had higher heat resistance than the original monosaccharides. They did not melt, and only decomposed with heating at 180-230°C for a long time. The mechanism of the transesterification of the lower alkyl borates ~4th monosaccharides can be represented as follows: - - C] - - O/H÷ f /OR
--C--o/H~oR [ : B-/--OR \OR (I)
C]--O--B
C
~C ~O
--C--O--B / ~OR [ (II)
--C --O I (III)
As we can see from this scheme, the transesterification proceeds via the coordination of the alkyl borate boron atom (Lewis acid) with a pair of hydroxyl group electrons of the carbohydrates, leading to the formation of the "acid" complex (1). As more alcohol is removed a mixed polyester of boric acid, carbohydrate and simple alcohol is formed (II). This kind of poly(alkyl)borate of monose can only exist where there is an excess of lower alkyl borates due to molecular association. When this excess is removed disproportionation occurs with formation of coiled structures where the three-dimensional arrangement of the OH group is suitable for coiling in the carbohydrate network of the monoses (III). This scheme for the mechanism of the re-esterification of the lower alkyl borates with carbohydrates is in very good agreement with the data obtained in a study of this reaction with hexoses, in which there are five completely esterifled hydroxyl groups in the different positions of a pyranose ring. The formation of the dimeric and oligomeric polyborates can be represented as the result of the further development of the disproportionation of cyclic and noncyclic structures of the monose alkyl borates [7]:
I -c--o\ 3 I
l --c--o\
I I I /o--c-B--OR ~ B--O--C--C--O--B +B(OR) 3 -c-o/ -c-o/ I I \o-el I I OR I 2----O--B ~--C--O / \O--C--+B(OR) 3.
i
i
~,Vc observed the formation of oligomeric P B E in practice w h e n the viscous mass changed over to a solid superficially foamy state in a certain temperature range combined with a vacuum. The polymers broke d o w n on further rise of temperature, and this could be seen by the change of colour of white to brown. During the investigation of the transesterification reaction it was found that the formation rate of the homogeneous solution of monosaccharide in alkyl
Synthesis and study of carbohydrate polyboratos
1619
borates increases where there is a very small amount (less than 1 o / o f the monosaccharide weight) of moisture or orthoboric acid. Monose polyborates were also obtained with the transesterificatiou of chemically pure alkyl borates. The reaction rate probably increases due to the formation of incomplete lower alkyl })orates OHB(OR')e, (OH)2BOR', which means t h a t the reaction rate of condensation will be higher t h a n t h a t of esterification with polyhydroxy compounds: R[OH]. + nOHB(OR')2-> R[OB(OR')=]. + nI-I=0 etc.
Since moisture was involved in the reaction in our case, it is suggested t h a t the incomplete monose borate is formed according to
I
--c-o_\
I
-c--o\
2| CO/ B--OR + H,O ~:~ --( !--O/B--OH q-ROH.
I
I
To test this the polyborates obtained were analysed with the Fischer reagent [8]. In all cases the only thing found was traces of the incomplete boric acid ester and the monose. This means t h a t when the reaction is conducted with lowcr alkyl borates, which easily hydrolyse, the possibility of a product of hydrolysis being present in them must be taken into account. For our transesterification reaction we chose the conditions under which the interaction of the lower alkyl borates (Lewis acid) ~dth the monosaccharides would be accompanied by the formation of a homogeneous solution. Under these cirmnnstances conversion of the c~.rbons is highly probable due to exposure of the pyronosc ring. In this case the presence of the carbonyl group m a y mean the formation of the products of the recovery of the original monosaccharides as eas(,s are k n o ~ l where alkyl })orates have been used instead of aluminium isoprol)ylatc to reduce aldehydes and ketones [9J. To do this the product polyborates were saponificd or hydrolysed and the polyhydroxy compounds separated were analyzed by paper (;hromatography. To be able to distinguish the monosac(;harides and the possible products of their reduction better, the chromatography was carried out over a fixed layer of cellulose powder [10]. In all cases the original monosaccharides and traces of di- and oligosaccharides were fouud. EXPERIMENTAL
All thc monosaccharides used were first purified by recrystallization and dried to constant weight. Before using the alkyl borates were distilled over m(,tallic sodium. The results of the analysis were consistent with the published figures Ill]. Trimethylborate B(OCH3) 3, B 10.4~, m.p. 68-69 °, 7----0-932 g/cm3; triethylborate B(OC2Hs)a, B 7.41~o, m.p. 117-120 °, ~--~().86 g/cma; tripropylborate B(OCaH:)a, B 5.75~, m.p. 176-179 °, 7----0"86 g/cm 3. Trrmsesterification. 5 g monosaccharide were placed i71 a 250 ml round bottomed flask with an agitator and rcflux cooler and a calcium chloride tube,
1620
V. V. GERTSEV and YA. YA I~LtKAROW-ZEMLYANSKII
a n d 1.6 moles alkyl b o r a t e per O H g r o u p of the p o l y h y d r o x y l c o m p o u n d was added. The heterogeneous m i x t u r e was h e a t e d over an oil b a t h until the alcohol boiled. The r e a c t i o n was c o n d u c t e d until the solid residue dissolved. W h e n the solution b e c a m e t r a n s p a r e n t the excess alkyl b o r a t e a n d alcohol f o r m e d as a result of the transesterification were distilled off the reaction zone into a deep cold receiver. The distillation p r o d u c t s were a n a l y z e d for boron c o n t e n t a n d the alcohol c o n c e n t r a t i o n calculated. The viscous p r o d u c t was h e a t e d u n d e r a v a c u u m of 5-10 m m until the alkyl b o r a t e was c o m p l e t e l y distilled off. A white f o a m y solid p r o d u c t was obtained, the p o l y b o r a t e of the original, monosaccharide. The b o r o n was d e t e r m i n e d b y t i t r a t i n g a q u e o u s solutions of boric acid in 0-1 .X" N a O H in the presence of m a n n i t e . The polyesters were saponified in hot absolute n - p r o p y l alcohol. A f t e r cooling the carbons were crystallized out a n d t h e n a n a l y s e d to determine t h e m separately, using p a p e r c h r o m a t o g r a p h y .
Chromatographic analysis of the monosaccharides. "M" paper made by Leningrad factory No. 2 was used for the chromatography; the rising branches of the chromatograms were taken. The solvent systems were as follows: n-butanol-ethanol-water (4 : 1 : 5), propanel-ethyl acetate-water (7 : 1 : 2), butanol-acetic acid-water (10 : 2 : 2), n-butanolacetic acid-water (4 : 1 : 5). The spots wore revealed with a 1o~) solution of Agl~'O3 in acetone and an alcoholic 4°/o solution of NaOH. The thin-layer chromatography was conducted over a fixed layer of cellulose powder using the procedure described in [10]. The following systems of solvents wore used: tertiary butanol-n-propanol-wator (8 : 2 : 3), binary butanol-ethyl acetate-water (8 : 12 : 3), n-butanol-pyridino-wator (10 : 3 : 3). The monosaccharides wore detected with a mixture of reactants: anilinc-phthalic acid, and anilino-diphcnylamino-phosphoric acid. To detect the polyhydric alcohols we used sodium bonzidine periodato. Reference point chromatography was used. CONCLUSIONS (1) The transesterification of tim lower alkyl borates with monosaccharides h a v e been studied. The p o l y b o r a t e s of aldoses, ketoses a n d pentoses were synthesized. (2) Esterification of the h y d r o x y l groups of the m o n o s a c c h a r i d e s h a v e been f o u n d to occur completely, i n d e p e n d e n t of their configuration. (3) Monosaccharides do n o t u n d e r g o a n y change as a result of the transesterification with alkyl borates. (4) The rate of the reaction with m o n o s a c c h a r i d e s is f o u n d to increase in the presence of the p r o d u c t s of the hydrolysis of lower alkyl borates. Translated by V. ALFORD REFERENCES
1. B. M. MIKHAILOV, Usp. khimii 28: 1450, 1959 2. V. A. Z A M Y A T I N A a n d N. I. B E K A S O V A , Usp. khimii 30: 48, 1961
3. W. GERRARD, The Organic Chemistry of Boron, Academic Press, London and New York, 148, 1961 4. S. V. CHAPIGO, K h i m . prom. 177, 1960
Chloroacetals of polyvinyl alcohol
1621
5. 6. 7. 8. 9. 10.
H. HASS, La Sacrarcs Belg. 75: 185, 1956 H. WUYTS and A. DUQUESNE, Bull. Soc. Khim. Belg. 48: 77, 1939 H. I. HUBERT, B. HARGITAY and I. DALE, J. Chem. Soc. 931, 1961 D. MITCHELL and D. SMITH, Aquamctry, 1952 H. C. KUIVILA, S. C. SLACK and P. K. S~TERI, J. Amer. Chem. Soc. 73: 123, 1951 L. D. BERGEL'SON, V. V. VORONKOVA and E. V. DYATLOVITSKAYA, ])okl. Akad. Nauk SSSR 145: 325, 1962; 149: 1319, 1963 11. H. STEINBERG and D. L. HUNTER, In(iustrial and Engineering Chemistr.v 49: 174, 1957
SYNTHESIS OF THE CHLOROACETALS OF POLYVINYL ALCOHOL* S. N. USHAKOV ]nstituto of Macromolecular
and N. A. KASHKINA Compounds,
U.S.S.R. Academy
of Scionces
(Received 27 ,'~eptember 1963) VARIOUS m e t h o d s a r e k n o w n for t h e s y n t h e s i s of p o l y v i n y l a c e t a l s [1]. T h e n u m b e r of p a p e r s r c f e r r i n g t o t h e s y n t h e s i s o f c h l o r o a c e t a l s o f p o l y v i n y l a l c o h o l , a n d i n p a r t i c u l a r to p o l y v i n y l c h l o r o e t h y l a l s [2], is e x t r e m e l y l i m i t e d . T h e r e is, however, interest in the synthesis of these d e r i v a t i v e s of p o l y v i n y l alcohol (PVA). Tim chloroacetals of PVA, in comparison with the o r d i n a r y p o l y v i n y l a c e t a l s , w h i c h do n o t c o n t a i n h a l i d e s , h a v e a n i n c r e a s e d c h e m i c a l r e s i s t a n c e . A t t h e s a m e t i m e , b e c a u s e o f t h e p r e s e n c e o f a t o m s of c h l o r i n e w i t h a lfigh r e a c t i v i t y i n t h e p o l y m e r m o l e c u l e , t h e c h l o r o a c e t a l s arc o f i n t e r e s t as t h e s t a r t i n g p r o d u c t s for fl~rther c h e m i c a l t r a n s f o r m a t i o n s . :ks is w~,ll known, the presence of mosomcrism may be postulated for the carbonyl group in th(; alternative polar form: R
R
,,,
,:
/~c-o,, RL~(~-6 R1 / The ine,~omorism of the carbonyl group depends to a considerable extent on the nature of the sul)stituonts R and R I . I n chloracotahtohydo as distinct from acetaldehyde, on() substituen~ contains a chlorine atom (R:CH~CI, R I = H ) , because of the presence of which an atomic bond of a partially ionic character is formed. As a result of the unequal affinity tbr electrons shown by the carbon atom and by the chlorine atom, the bonding electron pair is more strongly hold by the halide. This asymmetry in the charge distribution gives rise to the phenomenon of polarity, which is however not limited only to the two atoms directly connected by the given bond, but is (listributo(t in the remainder of the. molecule as a result of which an induction effect appears at bonds situated in the immodiat(~ vicinity. *Vysokomol. soyod. 6: No. 8, 1463-1466, 1964.