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The synthesis of new derivatives of cellulose and other polysaccharides—XXV. The effect of the structure of organophosphorus derivatives of cellulose on the flammability of cellulose materials
POLYBENZYLIDENEBENZOATE AND POLYBENZYLIDENEALCOHOL*t S. L. SOSIN and V. V. KORSHAK Institute of Hetero-organic Compounds, U.S.S.R. Academy of Sciences
(Received 13 September 1961) IT WAS shown previously [1] that when benzyl benzoate is treated with tert.-butyl peroxide, as a result of the polyrecombination reaction a polymer of the following structure is formed:
I I
[C.H,COO--C--C.H,]
[
(I)
J-
The object of the present work was a more detailed study of the conditions of preparation of this polymer, the isolation of certain intermediate and side products and also an investigation of the conversion of the polymer to polybenzylidenealcohol. The polymer was prepared by the method described previously [2] and it consisted of a yellow powder of m.p. 180-205 °, readily soluble in benzene and insoluble in alcohol. The relationship between the molecular weight of the polymer and the intrinsic viscosity is expressed by the equation [7]----3"39 × 10-a M 0"$17 which we obtained experimentally. The composition and structure of the polymer is supported by the results of elementary analysis, by the infrared spectra with absorption maxima in the 1100, 1180 and 1250 cm -1 regions, assigned to aromatic esters, and in the 700, 770 and 1000 cm -1 regions, assigned to monosubstituted benzene (Fig. 3a), and also by conversion of the polymer to polybenzylidenealcohol. The dependence of the yield of polymer on the molar ratio of peroxide benzyl benzoate is shown in Fig. 1, and the curve of the variation in molecular weight in Fig. 2. I t is seen from Figure 2 that a rapid rise in molecular weight occurs at a peroxide ratio in the region of 2 moles per mole of benzyl benzoate and the maximum ( ~ 540,000) is reached at a ratio of 2.35 moles of peroxide per mole of benzyl benzoate. The curve of the variation in molecular weight with peroxide concentration is of the same type as those for diphenylmethane and other compounds studied previously [1], which indicates that the mechanism of chain propagation is the same. * Vysokomol. soyed. 5: No. 4, 499-505, 1963. ~f B. A. Antipowa assisted in the experimental work. 1167
1168
S.L. SosIN and V. V. KORSH),K
The formation of the polymer passes through the stage of formation of the dimer, diphenylethylene glycol dibenzoate (II), which was separated from the polymer b y dissolving the latter in benzene. We also isolated it from the low-molecular reaction products. This dimer was obtained earlier by Rust, Seubold and Vaughan [3] b y treating benzyl benzoate and benzaldehyde with tert.-butyl peroxide. In addition to the meso form of the dimer, of m.p. 244 °, they obtained a resinous residue, not further investigated, and presumably consisting of a mixture of stereoisomers of this dimer. The low-molecular portion of the reaction products obtained in our work also consisted of a transparent resin-like mass of m.p. ~ 60 °. B y treatment with acetic acid and subsequent precipitation b y methanol this mixture was separated into three parts: the dimer (meso form), a polymer fraction of low molecular weight (Mo]. wt. 600-800) and a resinous, low melting residue consisting of a mixture of Mol~w~.
o
///
,oo,ooo_ 5~ooo
N 0"5 1"0 1.5 2,a Peeoxlde Benzyl benzoafe
04 0'8 1.2 1.8 2.0 2.4 Peroxide Benzy/ benzoate
FIG. 1.
FIG. 2.
FIG. 1. Dependence of yield of polymer on molar ratio of peroxide: benzyl benzoate. /--quantity of benzyl benzoate in reaction product, 2--yield of polymer calculated on total benzyl benzoate, 3--yield of polymer calculated on benzyl benzoate reacted. FIG. 2. Dependence of molecular weight of polymer on molar ratio of peroxide: benzyl benzoate. methylphenylcarbiny] benzoate (III) and the dibenzoate of ~-methylhydrobenzoin (IV). Saponification of these esters with alcoholic alkali yielded methylphenylcarbinol (V) and a-methylhydrobenzoin (VI). The latter was in the form of an oil~hat could not be crystallized [4]. The discovery in the reaction products of a-methyl derivatives of benzyl benzoate and of the dibenzoate of hydrobenzoin indicates that in addition to the direct polymer-formation reaction C6HsCOOCH=CsH5 --~ C6HsCOOCHCeH5 --~ [CeHsCOOCHCeHs]=--~ I I.
I
_l.
Polybenzylidenebenzoate and polybenzylidenealcohol
1169
there occurs even if only to a small extent, cross recombination reactions of radicals of the original ester and its dimer, with methyl radicals (formed by decomposition of the peroxide), the compounds formed taking no further part in chain growth, for example CH3 CeHsCH2COOC~H
R" ~ --> CeHsCHCOOCeH5
.CH, I --> CsHsCHCOOC6H
(III) 5.
Reduction of polybenzylidenebenzoate with lithium aluminium hydride yielded polybenzylidenealeohol,
....
OH L C
OH I
OH I
C
C ....
(VII)
©©© in the form of a white powder of m.p. 125-130 °, readily soluble in alcohol and other organic solvents but insoluble in benzene. This polymer has not been described previously. The infrared spectrum of this polymer contains absorption bands characteristic of the hydroxyl group in polymers, in the 3200-3400 cm -1 region [6] (Fig. 3a and b). In attempts to produce this polymeric alcohol directly from benzyl alcohol by the polyreeombination reaction we found that with a molar ratio of peroxide: benzyl alcohol 2 : 1 polybenzylidenebenzoate is formed instead of polybenzylidenealcohol. We had obtained the former polymer from benzaldehyde by the polyrecombination reaction, which passes through the stage of formation of diphenylethylene glycol [3]: CeHsCHO -> CeHsC= O O O C6H 5-
[
II
H
C" + O = CH-- C6H~ --> Cells-- C -- 0 -- CH-- Cell 5 -+ O1,
--> C.Hs--C--O--CH--C.H5
1
[
OIt
,
i--> [CsHs--C--0--C--C.Hs]~"
1
I It was therefore natural to suppose that benzyl alcohol is first converted to benzaldehyde, subsequently reacting according to the above scheme. In fact when benzyl alcohol was treated with the peroxide in the ratio 1 : 1 we isolated benzaldehyde and hydrobenzoin. The latter also could not serve as an intermediate product in the conversion of benzyl alcohol to polybenzylidenealcohol because special experiments showed that on further treatment with the peroxide the hydrobenzoin is dehydrogenated to benzil. On the basis of these results the following scheme for the conversion of the substances under consideration to polybenzylidenebenzoate and polybenzylidenealcohol can be put forward.
1170
S.L. SosI~ and V. V. KORSHAK fO0
I00
89
88
oT
60.~
2O
20
0
0
20 I
0
FIG. 3. Infrared spectra: a--polybenzylidenebenzoate, b--polybenzylidenealcohol from polybenzylidenebenzoate. CeH5
O6Hs
CeH5
I C=O 0
I C=O
I C--O
)
• C6H5 l
--
C6Hs--
] ~----0 )
I
l
C6Hs
CeH5
_
CIH,_
CsHsCHO
T
CeHsCH'OH~ OH
H-~ I
C6H5
/
/
~'[
OH
~-~--~.H,cococ.~, ~,H,
....
(vii)
P o l y b e n z y l i d e n e b e n z o a t e and p o l y b e n z y l i d e n e a l e o h o l The conversion dehydrogenation
of benzyl alcohol to benzaldehyde
is e v i d e n t l y
1171 the result of
a n d is n o t d u e t o t h e a c t i o n o f o x y g e n f r o m t h e p e r o x i d e , b e c a u s e
even on decomposition
of the latter directly in the readily oxidizable benzaldehyde
no benzoic acid was detected.
EX PERIMENTA L T r e a t m e n t of benzyl b e n z o a t e w i t h tert.-butyl p e r o x i d e a n d isolation of the p o l y m e r (I) were carried o u t b y the m e t h o d s described p r e v i o u s l y [1, 2], w i t h various peroxide: b e n z y l b e n z o a t e ratios a n d a t e m p e r a t u r e of 200 °. The results o f these e x p e r i m e n t s are g i v e n in the Table a n d in Figures 1 a n d 2. T A B L E 1. POLYRECOMBII~ATION OF BENZYLBENZOATE
Reaction products obtained * Molar ratio of peroxide: b e n z y l benzoate
0.167:1 0.25:1 0.5 :1 0.75 :l l:I 1-5 :1 1-66:1 1.75:1 1.84:1 1-89:1 1-9 :1 2.02:1 2.21:1 2.35:1
Dimer
4.9 5-97 7-28 6-35 4.7 --
-
-----
-
---
Lowmolecular polymer 20.1 25.7 46.7 35.7 29.2 16-6 18.1 14.9 21.4 22-9 15.1 22.11 24.3 17.85
Polymer (%)
---19.6 37.0 63.5 69.7 73.6 65.6 67.0 67.0 62-5 60-0 42-0
Molecular weight o f polymer ---800 1 410 2 480 2 760 3 380 4 420 8 680 6 800 12 600 140 000 540 000
M.p. of polymer (°C) ---108--115 108--116 108--120 142--153 134--142 161--175 172--185 171--184 176--187 187--200 189--205
Recovery of benzyl benzoate (~/o) 73.7 66-8 48.1 31.9 25-4 20.5 15-8 13.9 15.3 7.1 18.6 12.3 11.70 7.45
• % calculated on benzyl benzoate taken.
Polybenzylidenebenzoate (I) after two reprecipitations b y m e t h a n o l f r o m benzene solution was e b t a i n e d in the f o r m of a yellow p o w d e r of m.p. 180-205 °. The highest m o l e c u l a r weight, of 540,000, was o b t a i n e d w i t h a ratio o f peroxide: benzyl b e n z o a t e of 2-32 : 1. Molecular weights below 30,000 were d e t e r m i n e d ebulioscopically and for p o l y m e r s of higher m o l e c u l a r weight the light s c a t t e r i n g m e t h o d was used. F o u n d , ~/o: C 80-37; H 6.03. Calculated for a p o l y m e r w i t h a r e p e a t i n g u n i t of composition C14 H100~, %: C 79-98; H 4.79.
The dimer (diphenylethylene glycol dibenzoate) (II), filtered off f r o m t h e benzene solution of I, h a d m.p. 243 ° (from alcohol); q u o t e d in the l i t e r a t u r e 243-244 ° [3]. F o u n d , ~o: C 79.66; H5.37. CisHs2Od. Calculated, %: C 79-60; H.5.25.
1172
S . L . S08IN and V. V. KORSHAK
Saponification of the dimer With 2~o alcoholic K O H solution yielded hydrobenzoin, m.p. 133 ° (from alcohol): m.p. quoted in the literature 134 ° [7]. Separation of the low-molecular mixture. The benzene and methanol was evaporated from the filtrate after precipitation of the polymer, leaving a yellow, transparent, ~lassy mass of m.p. ~60 °. When this mass (57.19 g) was treated with acetic acid (200 ml) an insoluble precipitate of the dimer I I separated, m.p. 243-244 ° (5.06 g or 8.85~o). After evaporation of the acetic acid filtrate to one third of its volume methanol was added, which precipitated the low-molecular fraction of polybenzylidenebenzoate (19.31 g or 33"8~o), mo]ecular weight 600-800 (cryoscopie). Evaporation of the acetic acid and methanol from the the filtrate yielded a dark-yellow, viscous oil (31.87 g or 55-78~o) of molecular weight 290 (cryoscopic, in benzene), which solidified slowly in air, could not be crystallized a n d consisted of a mixture of methylphenylcarbinyl benzoate (III) and the dibenzoate of ~-methylhydrobenzoin (IV). Methylphenylcarbinol (V). Saponification of the yellow oil (20.4 g) with 2~o alcoholic K O H solution (4 hour reflux) after evaporation of the alcohol (100 ml) yielded a solid, yellow residue which was treated with water to remove sodium benzoate. The oil remaiuig after treatment with water was extracted with ether, dried over NaaSO 4 a n d distilled i~ vacuo. From 10.27 g of the oil 1.54 g of methylphenylcarbinol boiling at 97-100°/15 m m was obtained. The boiling point given in the literature is 95-96°/15 m m [7]. By oxidation of methylphenylcarbinol with chromic mixture acetophenone was obtained, a n d from this its 2,4dinitrophcnylhydrazone. Found, ~o: N 19.20, C14H12Oa~. Calculated, ~o: N 18.86. a-Methylh~drobenzoin. After removal of methylphenylcarbonal by distillation a residue was obtained in the form of a viscous, slowly solidifying oil (7 g) that could not be crystallized [4]. Found, ~/o: C 79.96; H 6-76. C15HlsOI. Calculated, ~o: C 78.94; H.5.61. The infrared spectrum contained an absorption b a n d at 3400 cm -1, assigned to the OH-group. On acidification of the alkaline extract after saponification of the benzoates (III) and (IV), benzoic acid precipitated, m.p. 119 ° (from water). Acid number found 79.33, calculated 81.88. Polybenzylidenealcohol (VII). Polybenzylidenebenzoate (5 g, 0.023 mole), dissolved in 100 ml of tetrahydrofuran, was poured, with stirring, into a solution of lithium aluminium hydride (0-09 mole) in 34 ml of tetrahydrofuran a~ 27-30 ° over a period of 1 hour. The mixture was then kept at 60 ° for 4 hours [5]. The reaction mixture was poured into a mixture of ice a n d dilute hydrochloric acid. The precipitate was separated, dissolved in methanol and reprecipitated b y water. Yield 2-46 g or 50%. :YIolecular weight 37,000 (osmometric), m.p. 127-137% Found, ~o: C 79-46; H 7.37. C~HHeO. Calculated, ~/o: C 79-30; H 5.65. Comparison of the infrared spectrum of the polymer (Fig. 3a) with the spectrum of the reduced polymer shows the presence in the latter of the b a n d at 3400 cm -~ characteristic of the OH-group (Fig. 3b), which supports the suggested structure. The polyrecombination reaction with benzyl alcohol. After treatment of benzyl alcohol (10.8 g, 0.1 mole) with tert.-butyl peroxide (14.6 g, 0.1 mole) at 200 ° a mixture of unreacted benzyl alcohol and benzaldehyde was isolated from the reaction mixture by vacuum distillation (46-47 °/3 ram). The benzaldehyde (2 g, 0.2 mole) was separated from the mixture
Polybenzylidenebenzoate and polybenzylidenealcohol
1173
as the bisulphide compound. After decomposition of the latter the 2,4-dinitrophenyl-hydrazone of benzaldehyde was prepared, m.p. 235 °, according to the literature m.p. 237 ° [7]. After the benzyl alcohol a n d benzaldehydo, hydrobenzoin (1.94 g, 0-01 mole) distilled over at 177-180°/3 mm, m.p. 122-124 ° (from alcohol; according to the literature, m.p. 122 ° [7]. Found, e/o: C 79.35; t t 5.73. C14H1402 (hydrobenzoin). Calculated, %: C 78.47; H 6.58. The residue after vacuum distillation was a yellow oil of molecular weight 253. I n another experiment, for the t r c a t m n e t of benzyl alcohol (0.1 mole) with tert..butyl peroxide (0-2 mole) the reaction mixture was dissolved in benzene and reprocipitated b y methanol. This yielded 2.33 g of polymer, m.p. 134-143 °, molecular weight 930. F o u n d , %: C 79.95; H 4.86. Polybenzylidenebenzoate C14H1002 (I). Calculated, %: C 79.98; t t 4.79. The infrared spectrum of this polymer coincides with that of polybenzylidenebenzoate (I) prepared from benzoyl benzoate. Reduction of this material (2 g) with lithium alum i n i u m hydride yielded a n alcohol-soluble powder (1.2 g, 60 % yield),* of molecular weight 935 (ebullioscopic) a n d m.p. 132-146 °. The infrared spectrum of this product corresponded to polybenzylidenealcohol (VII). When hydrobenzoin (0.05 mole) was treated with tert.-butyl peroxide (0.1 mole) at 200 ° no poly mer was obtained b u t benzil was isolated by recrystallization of the reaction mixture Found, %: C 79.63; I-1 4.86. C14H1009.. Calculated,~/o: C 79.98; H 4.79. The 2,4-dinitrophenylhydrazone prepared from this melted at 187°; according to the literature, m.p. 189 ° [7]. Found, %: N 14-97. C~6H2~NsOs . Calculated, ~o: N 14.86.
The polyrecombination of benzaldehyde. By treatment of benzaldehyde (10.6 g, 0.1 mole) with tert.-butyl peroxide (14.6 g, 0.1 mole) the hydrobenzoin dibenzoate dimer (1.1 g) and a polymer (2.72 g) (molecular weight 800, m.p. 162-175°), corresponding in analysis and infrared spectrm~n with polybenzylidenebenzoate (I). The dibenzoate of hydrobenzoin had m.p. 241 °; according to the literature m.p. 243-244 ° [3]. For the dimer C~sH2aOd: Found, %: C 79.94; I-I 5.32. Calculated, %: C 79.6; H 5-25. For the polymer with repeating unit C1~ I-IloO2 (I) Found, %: C 78.73; I-I 5.57. Calculated, %: C 79.98; H 4.79. Reduction with lithium a l u m i n i u m hydride of the polymer (2 g) obtained from benzaldehyde yielded 1.13 g (yield 57%) of a polymer of m.p. 134-143 °, soluble in alcohol and having a n infrared spectrum coinciding with that of polybenzylidenealcohol (VII). * I n addition to this 0.57 g of a product insoluble in alcohol was obtained, of m.p. 205-206 °, with a n infrared spectrum also indicating the presence of a n OH-group.
1174
Z.A. ROGOVINet al. CONCLUSIONS
(1) The polyrecombination of benzyl benzoate has been studied and the dependence of the yield and molecular weight of the polybenzylidenebenzoate on the molar ratio of peroxide: benzyl benzoate has been determined. (2) The side products of the reaction, a-methylcarbonyl benzoate and a-methylhydrobenzoin dibenzoate have been isolated and indentified. (3) Polybenzylidenealcohol has been prepared and a reaction scheme for the polyrecombination of benzyl benzoate, benzyl alcohol and benzaldehyde is
suggested.
Translated by E. O. PHILLIPS REFERENCES
1. V. V. KORSHAK, S. L. SOSIN and V. P. ALEKSEEVA, Dokl. Akad. Nauk SSSR 132: 360, 1960 2. V. V. KORSHAK, S. L. SOSINand M. V. CHISTYAKOVA, Vysokomol. soyed. 1: 937, 1959 3. F. F. RUST, F. H. SEUBOLD and W. E. VAUGHAN, J. Amer. Chem. Soc. 70: 3258, 1948 4. I. H. BREWSTER, J. Amer. Chem. Soc. 78: 4061, 1956 5. R. C. SCHULZ and P. ELZER, Makromol. Chem. 42: 205, 1961 6. A. D. GROSS, Introduction to Practical Infrared Spectroscopy, London, 1960 7. E. H. RODD, Chemistry of Organic Compounds, IIIb, 1162, 1959
THE SYNTHESIS OF NEW DERIVATIVES OF CELLULOSE AND OTHER POLYSACCHARIDES--XXV. THE EFFECT OF THE STRUCTURE OF ORGANOPHOSPHORUS DERIVATIVES OF CELLULOSE ON THE FLAMMABILITY OF CELLULOSE MATERIALS* t Z. A. ROGOVIN, U. ]~IFI-YAN', M. A. TYUGANOVA, T. YAI ZHAROVA and E . L. GEFTER Moscow Textile Institute (Received 13 September 1961)
ONE of the interesting and practically i m p o r t a n t fields of study in the developm e n t of the general problem of the modification and improvement in properties of cellulosic materials is the production of fireproof materials t h a t do not catch fire or propagate flame. A large a m o u n t of research has been devoted to imparting * Vysokomol. soyed. 5: No. 4, 506-511, 1963. t The ll4th communication in the series "The study of bhe structure and properties of cellulose and its derivatives".
(Received 13 September 1961) IT WAS shown previously [1] that when benzyl benzoate is treated with tert.-butyl peroxide, as a result of the polyrecombination reaction a polymer of the following structure is formed:
I I
[C.H,COO--C--C.H,]
[
(I)
J-
The object of the present work was a more detailed study of the conditions of preparation of this polymer, the isolation of certain intermediate and side products and also an investigation of the conversion of the polymer to polybenzylidenealcohol. The polymer was prepared by the method described previously [2] and it consisted of a yellow powder of m.p. 180-205 °, readily soluble in benzene and insoluble in alcohol. The relationship between the molecular weight of the polymer and the intrinsic viscosity is expressed by the equation [7]----3"39 × 10-a M 0"$17 which we obtained experimentally. The composition and structure of the polymer is supported by the results of elementary analysis, by the infrared spectra with absorption maxima in the 1100, 1180 and 1250 cm -1 regions, assigned to aromatic esters, and in the 700, 770 and 1000 cm -1 regions, assigned to monosubstituted benzene (Fig. 3a), and also by conversion of the polymer to polybenzylidenealcohol. The dependence of the yield of polymer on the molar ratio of peroxide benzyl benzoate is shown in Fig. 1, and the curve of the variation in molecular weight in Fig. 2. I t is seen from Figure 2 that a rapid rise in molecular weight occurs at a peroxide ratio in the region of 2 moles per mole of benzyl benzoate and the maximum ( ~ 540,000) is reached at a ratio of 2.35 moles of peroxide per mole of benzyl benzoate. The curve of the variation in molecular weight with peroxide concentration is of the same type as those for diphenylmethane and other compounds studied previously [1], which indicates that the mechanism of chain propagation is the same. * Vysokomol. soyed. 5: No. 4, 499-505, 1963. ~f B. A. Antipowa assisted in the experimental work. 1167
1168
S.L. SosIN and V. V. KORSH),K
The formation of the polymer passes through the stage of formation of the dimer, diphenylethylene glycol dibenzoate (II), which was separated from the polymer b y dissolving the latter in benzene. We also isolated it from the low-molecular reaction products. This dimer was obtained earlier by Rust, Seubold and Vaughan [3] b y treating benzyl benzoate and benzaldehyde with tert.-butyl peroxide. In addition to the meso form of the dimer, of m.p. 244 °, they obtained a resinous residue, not further investigated, and presumably consisting of a mixture of stereoisomers of this dimer. The low-molecular portion of the reaction products obtained in our work also consisted of a transparent resin-like mass of m.p. ~ 60 °. B y treatment with acetic acid and subsequent precipitation b y methanol this mixture was separated into three parts: the dimer (meso form), a polymer fraction of low molecular weight (Mo]. wt. 600-800) and a resinous, low melting residue consisting of a mixture of Mol~w~.
o
///
,oo,ooo_ 5~ooo
N 0"5 1"0 1.5 2,a Peeoxlde Benzyl benzoafe
04 0'8 1.2 1.8 2.0 2.4 Peroxide Benzy/ benzoate
FIG. 1.
FIG. 2.
FIG. 1. Dependence of yield of polymer on molar ratio of peroxide: benzyl benzoate. /--quantity of benzyl benzoate in reaction product, 2--yield of polymer calculated on total benzyl benzoate, 3--yield of polymer calculated on benzyl benzoate reacted. FIG. 2. Dependence of molecular weight of polymer on molar ratio of peroxide: benzyl benzoate. methylphenylcarbiny] benzoate (III) and the dibenzoate of ~-methylhydrobenzoin (IV). Saponification of these esters with alcoholic alkali yielded methylphenylcarbinol (V) and a-methylhydrobenzoin (VI). The latter was in the form of an oil~hat could not be crystallized [4]. The discovery in the reaction products of a-methyl derivatives of benzyl benzoate and of the dibenzoate of hydrobenzoin indicates that in addition to the direct polymer-formation reaction C6HsCOOCH=CsH5 --~ C6HsCOOCHCeH5 --~ [CeHsCOOCHCeHs]=--~ I I.
I
_l.
Polybenzylidenebenzoate and polybenzylidenealcohol
1169
there occurs even if only to a small extent, cross recombination reactions of radicals of the original ester and its dimer, with methyl radicals (formed by decomposition of the peroxide), the compounds formed taking no further part in chain growth, for example CH3 CeHsCH2COOC~H
R" ~ --> CeHsCHCOOCeH5
.CH, I --> CsHsCHCOOC6H
(III) 5.
Reduction of polybenzylidenebenzoate with lithium aluminium hydride yielded polybenzylidenealeohol,
....
OH L C
OH I
OH I
C
C ....
(VII)
©©© in the form of a white powder of m.p. 125-130 °, readily soluble in alcohol and other organic solvents but insoluble in benzene. This polymer has not been described previously. The infrared spectrum of this polymer contains absorption bands characteristic of the hydroxyl group in polymers, in the 3200-3400 cm -1 region [6] (Fig. 3a and b). In attempts to produce this polymeric alcohol directly from benzyl alcohol by the polyreeombination reaction we found that with a molar ratio of peroxide: benzyl alcohol 2 : 1 polybenzylidenebenzoate is formed instead of polybenzylidenealcohol. We had obtained the former polymer from benzaldehyde by the polyrecombination reaction, which passes through the stage of formation of diphenylethylene glycol [3]: CeHsCHO -> CeHsC= O O O C6H 5-
[
II
H
C" + O = CH-- C6H~ --> Cells-- C -- 0 -- CH-- Cell 5 -+ O1,
--> C.Hs--C--O--CH--C.H5
1
[
OIt
,
i--> [CsHs--C--0--C--C.Hs]~"
1
I It was therefore natural to suppose that benzyl alcohol is first converted to benzaldehyde, subsequently reacting according to the above scheme. In fact when benzyl alcohol was treated with the peroxide in the ratio 1 : 1 we isolated benzaldehyde and hydrobenzoin. The latter also could not serve as an intermediate product in the conversion of benzyl alcohol to polybenzylidenealcohol because special experiments showed that on further treatment with the peroxide the hydrobenzoin is dehydrogenated to benzil. On the basis of these results the following scheme for the conversion of the substances under consideration to polybenzylidenebenzoate and polybenzylidenealcohol can be put forward.
1170
S.L. SosI~ and V. V. KORSHAK fO0
I00
89
88
oT
60.~
2O
20
0
0
20 I
0
FIG. 3. Infrared spectra: a--polybenzylidenebenzoate, b--polybenzylidenealcohol from polybenzylidenebenzoate. CeH5
O6Hs
CeH5
I C=O 0
I C=O
I C--O
)
• C6H5 l
--
C6Hs--
] ~----0 )
I
l
C6Hs
CeH5
_
CIH,_
CsHsCHO
T
CeHsCH'OH~ OH
H-~ I
C6H5
/
/
~'[
OH
~-~--~.H,cococ.~, ~,H,
....
(vii)
P o l y b e n z y l i d e n e b e n z o a t e and p o l y b e n z y l i d e n e a l e o h o l The conversion dehydrogenation
of benzyl alcohol to benzaldehyde
is e v i d e n t l y
1171 the result of
a n d is n o t d u e t o t h e a c t i o n o f o x y g e n f r o m t h e p e r o x i d e , b e c a u s e
even on decomposition
of the latter directly in the readily oxidizable benzaldehyde
no benzoic acid was detected.
EX PERIMENTA L T r e a t m e n t of benzyl b e n z o a t e w i t h tert.-butyl p e r o x i d e a n d isolation of the p o l y m e r (I) were carried o u t b y the m e t h o d s described p r e v i o u s l y [1, 2], w i t h various peroxide: b e n z y l b e n z o a t e ratios a n d a t e m p e r a t u r e of 200 °. The results o f these e x p e r i m e n t s are g i v e n in the Table a n d in Figures 1 a n d 2. T A B L E 1. POLYRECOMBII~ATION OF BENZYLBENZOATE
Reaction products obtained * Molar ratio of peroxide: b e n z y l benzoate
0.167:1 0.25:1 0.5 :1 0.75 :l l:I 1-5 :1 1-66:1 1.75:1 1.84:1 1-89:1 1-9 :1 2.02:1 2.21:1 2.35:1
Dimer
4.9 5-97 7-28 6-35 4.7 --
-
-----
-
---
Lowmolecular polymer 20.1 25.7 46.7 35.7 29.2 16-6 18.1 14.9 21.4 22-9 15.1 22.11 24.3 17.85
Polymer (%)
---19.6 37.0 63.5 69.7 73.6 65.6 67.0 67.0 62-5 60-0 42-0
Molecular weight o f polymer ---800 1 410 2 480 2 760 3 380 4 420 8 680 6 800 12 600 140 000 540 000
M.p. of polymer (°C) ---108--115 108--116 108--120 142--153 134--142 161--175 172--185 171--184 176--187 187--200 189--205
Recovery of benzyl benzoate (~/o) 73.7 66-8 48.1 31.9 25-4 20.5 15-8 13.9 15.3 7.1 18.6 12.3 11.70 7.45
• % calculated on benzyl benzoate taken.
Polybenzylidenebenzoate (I) after two reprecipitations b y m e t h a n o l f r o m benzene solution was e b t a i n e d in the f o r m of a yellow p o w d e r of m.p. 180-205 °. The highest m o l e c u l a r weight, of 540,000, was o b t a i n e d w i t h a ratio o f peroxide: benzyl b e n z o a t e of 2-32 : 1. Molecular weights below 30,000 were d e t e r m i n e d ebulioscopically and for p o l y m e r s of higher m o l e c u l a r weight the light s c a t t e r i n g m e t h o d was used. F o u n d , ~/o: C 80-37; H 6.03. Calculated for a p o l y m e r w i t h a r e p e a t i n g u n i t of composition C14 H100~, %: C 79-98; H 4.79.
The dimer (diphenylethylene glycol dibenzoate) (II), filtered off f r o m t h e benzene solution of I, h a d m.p. 243 ° (from alcohol); q u o t e d in the l i t e r a t u r e 243-244 ° [3]. F o u n d , ~o: C 79.66; H5.37. CisHs2Od. Calculated, %: C 79-60; H.5.25.
1172
S . L . S08IN and V. V. KORSHAK
Saponification of the dimer With 2~o alcoholic K O H solution yielded hydrobenzoin, m.p. 133 ° (from alcohol): m.p. quoted in the literature 134 ° [7]. Separation of the low-molecular mixture. The benzene and methanol was evaporated from the filtrate after precipitation of the polymer, leaving a yellow, transparent, ~lassy mass of m.p. ~60 °. When this mass (57.19 g) was treated with acetic acid (200 ml) an insoluble precipitate of the dimer I I separated, m.p. 243-244 ° (5.06 g or 8.85~o). After evaporation of the acetic acid filtrate to one third of its volume methanol was added, which precipitated the low-molecular fraction of polybenzylidenebenzoate (19.31 g or 33"8~o), mo]ecular weight 600-800 (cryoscopie). Evaporation of the acetic acid and methanol from the the filtrate yielded a dark-yellow, viscous oil (31.87 g or 55-78~o) of molecular weight 290 (cryoscopic, in benzene), which solidified slowly in air, could not be crystallized a n d consisted of a mixture of methylphenylcarbinyl benzoate (III) and the dibenzoate of ~-methylhydrobenzoin (IV). Methylphenylcarbinol (V). Saponification of the yellow oil (20.4 g) with 2~o alcoholic K O H solution (4 hour reflux) after evaporation of the alcohol (100 ml) yielded a solid, yellow residue which was treated with water to remove sodium benzoate. The oil remaiuig after treatment with water was extracted with ether, dried over NaaSO 4 a n d distilled i~ vacuo. From 10.27 g of the oil 1.54 g of methylphenylcarbinol boiling at 97-100°/15 m m was obtained. The boiling point given in the literature is 95-96°/15 m m [7]. By oxidation of methylphenylcarbinol with chromic mixture acetophenone was obtained, a n d from this its 2,4dinitrophcnylhydrazone. Found, ~o: N 19.20, C14H12Oa~. Calculated, ~o: N 18.86. a-Methylh~drobenzoin. After removal of methylphenylcarbonal by distillation a residue was obtained in the form of a viscous, slowly solidifying oil (7 g) that could not be crystallized [4]. Found, ~/o: C 79.96; H 6-76. C15HlsOI. Calculated, ~o: C 78.94; H.5.61. The infrared spectrum contained an absorption b a n d at 3400 cm -1, assigned to the OH-group. On acidification of the alkaline extract after saponification of the benzoates (III) and (IV), benzoic acid precipitated, m.p. 119 ° (from water). Acid number found 79.33, calculated 81.88. Polybenzylidenealcohol (VII). Polybenzylidenebenzoate (5 g, 0.023 mole), dissolved in 100 ml of tetrahydrofuran, was poured, with stirring, into a solution of lithium aluminium hydride (0-09 mole) in 34 ml of tetrahydrofuran a~ 27-30 ° over a period of 1 hour. The mixture was then kept at 60 ° for 4 hours [5]. The reaction mixture was poured into a mixture of ice a n d dilute hydrochloric acid. The precipitate was separated, dissolved in methanol and reprecipitated b y water. Yield 2-46 g or 50%. :YIolecular weight 37,000 (osmometric), m.p. 127-137% Found, ~o: C 79-46; H 7.37. C~HHeO. Calculated, ~/o: C 79-30; H 5.65. Comparison of the infrared spectrum of the polymer (Fig. 3a) with the spectrum of the reduced polymer shows the presence in the latter of the b a n d at 3400 cm -~ characteristic of the OH-group (Fig. 3b), which supports the suggested structure. The polyrecombination reaction with benzyl alcohol. After treatment of benzyl alcohol (10.8 g, 0.1 mole) with tert.-butyl peroxide (14.6 g, 0.1 mole) at 200 ° a mixture of unreacted benzyl alcohol and benzaldehyde was isolated from the reaction mixture by vacuum distillation (46-47 °/3 ram). The benzaldehyde (2 g, 0.2 mole) was separated from the mixture
Polybenzylidenebenzoate and polybenzylidenealcohol
1173
as the bisulphide compound. After decomposition of the latter the 2,4-dinitrophenyl-hydrazone of benzaldehyde was prepared, m.p. 235 °, according to the literature m.p. 237 ° [7]. After the benzyl alcohol a n d benzaldehydo, hydrobenzoin (1.94 g, 0-01 mole) distilled over at 177-180°/3 mm, m.p. 122-124 ° (from alcohol; according to the literature, m.p. 122 ° [7]. Found, e/o: C 79.35; t t 5.73. C14H1402 (hydrobenzoin). Calculated, %: C 78.47; H 6.58. The residue after vacuum distillation was a yellow oil of molecular weight 253. I n another experiment, for the t r c a t m n e t of benzyl alcohol (0.1 mole) with tert..butyl peroxide (0-2 mole) the reaction mixture was dissolved in benzene and reprocipitated b y methanol. This yielded 2.33 g of polymer, m.p. 134-143 °, molecular weight 930. F o u n d , %: C 79.95; H 4.86. Polybenzylidenebenzoate C14H1002 (I). Calculated, %: C 79.98; t t 4.79. The infrared spectrum of this polymer coincides with that of polybenzylidenebenzoate (I) prepared from benzoyl benzoate. Reduction of this material (2 g) with lithium alum i n i u m hydride yielded a n alcohol-soluble powder (1.2 g, 60 % yield),* of molecular weight 935 (ebullioscopic) a n d m.p. 132-146 °. The infrared spectrum of this product corresponded to polybenzylidenealcohol (VII). When hydrobenzoin (0.05 mole) was treated with tert.-butyl peroxide (0.1 mole) at 200 ° no poly mer was obtained b u t benzil was isolated by recrystallization of the reaction mixture Found, %: C 79.63; I-1 4.86. C14H1009.. Calculated,~/o: C 79.98; H 4.79. The 2,4-dinitrophenylhydrazone prepared from this melted at 187°; according to the literature, m.p. 189 ° [7]. Found, %: N 14-97. C~6H2~NsOs . Calculated, ~o: N 14.86.
The polyrecombination of benzaldehyde. By treatment of benzaldehyde (10.6 g, 0.1 mole) with tert.-butyl peroxide (14.6 g, 0.1 mole) the hydrobenzoin dibenzoate dimer (1.1 g) and a polymer (2.72 g) (molecular weight 800, m.p. 162-175°), corresponding in analysis and infrared spectrm~n with polybenzylidenebenzoate (I). The dibenzoate of hydrobenzoin had m.p. 241 °; according to the literature m.p. 243-244 ° [3]. For the dimer C~sH2aOd: Found, %: C 79.94; I-I 5.32. Calculated, %: C 79.6; H 5-25. For the polymer with repeating unit C1~ I-IloO2 (I) Found, %: C 78.73; I-I 5.57. Calculated, %: C 79.98; H 4.79. Reduction with lithium a l u m i n i u m hydride of the polymer (2 g) obtained from benzaldehyde yielded 1.13 g (yield 57%) of a polymer of m.p. 134-143 °, soluble in alcohol and having a n infrared spectrum coinciding with that of polybenzylidenealcohol (VII). * I n addition to this 0.57 g of a product insoluble in alcohol was obtained, of m.p. 205-206 °, with a n infrared spectrum also indicating the presence of a n OH-group.
1174
Z.A. ROGOVINet al. CONCLUSIONS
(1) The polyrecombination of benzyl benzoate has been studied and the dependence of the yield and molecular weight of the polybenzylidenebenzoate on the molar ratio of peroxide: benzyl benzoate has been determined. (2) The side products of the reaction, a-methylcarbonyl benzoate and a-methylhydrobenzoin dibenzoate have been isolated and indentified. (3) Polybenzylidenealcohol has been prepared and a reaction scheme for the polyrecombination of benzyl benzoate, benzyl alcohol and benzaldehyde is
suggested.
Translated by E. O. PHILLIPS REFERENCES
1. V. V. KORSHAK, S. L. SOSIN and V. P. ALEKSEEVA, Dokl. Akad. Nauk SSSR 132: 360, 1960 2. V. V. KORSHAK, S. L. SOSINand M. V. CHISTYAKOVA, Vysokomol. soyed. 1: 937, 1959 3. F. F. RUST, F. H. SEUBOLD and W. E. VAUGHAN, J. Amer. Chem. Soc. 70: 3258, 1948 4. I. H. BREWSTER, J. Amer. Chem. Soc. 78: 4061, 1956 5. R. C. SCHULZ and P. ELZER, Makromol. Chem. 42: 205, 1961 6. A. D. GROSS, Introduction to Practical Infrared Spectroscopy, London, 1960 7. E. H. RODD, Chemistry of Organic Compounds, IIIb, 1162, 1959
THE SYNTHESIS OF NEW DERIVATIVES OF CELLULOSE AND OTHER POLYSACCHARIDES--XXV. THE EFFECT OF THE STRUCTURE OF ORGANOPHOSPHORUS DERIVATIVES OF CELLULOSE ON THE FLAMMABILITY OF CELLULOSE MATERIALS* t Z. A. ROGOVIN, U. ]~IFI-YAN', M. A. TYUGANOVA, T. YAI ZHAROVA and E . L. GEFTER Moscow Textile Institute (Received 13 September 1961)
ONE of the interesting and practically i m p o r t a n t fields of study in the developm e n t of the general problem of the modification and improvement in properties of cellulosic materials is the production of fireproof materials t h a t do not catch fire or propagate flame. A large a m o u n t of research has been devoted to imparting * Vysokomol. soyed. 5: No. 4, 506-511, 1963. t The ll4th communication in the series "The study of bhe structure and properties of cellulose and its derivatives".