Table VII.
Effect of NHlClO4 Particle Size on the Product Distribution for a Toluene Solution of 1-Benzoyl-2-ethylaziridine and Propionic Acid at 60’ C.a for 5 Hours Constituents, y;, of Totalb Polymer w t . yc Particle CaHjCOOH Ariridine Oxarolined Ester6 UnidentGed Size, / r c ... 7.4 25.5 5.35 25.9 33.9 405 6.4 12.7 23.7 25.7 26.0 1.6 180 1.o 19.5 24.8 24.0 2.0 26.0 130 9.6 18.4j 22.4 19.5 2.2 ... 10 a 7 nil. of toluene solution per 5 grams .YH4ClOd (approx. 85% AVH~C104): acid and aziridine concn., each 0.5M. * Constituent chromatographic area Average particle size X 700/total Chromatographic area (marker and solcent excluded); p o h m e r is pPr cent of material not passing through column. micromerographic anabsis. d 5-Ethyl isomer; concn. of $-ethyl isomer did not change significantlq.. e Product of aziridine and oxazoline ring opening by acid. J Based on ualue of 26.0 for C z H j C O O H .
Table VIII. Concentration of Reactants and Products for a Toluene Solution with 4- or 5-Ethyl-2-phenyl-2-oxazoline, Propionic Acid, and NHdCIOd at 79’ C.“ Constituents, 7 of Totalb Time, Hldroxp Hr. C ? H j C O O H Oxazoltne Estere amided
5-Ethyl Isomer 0 1 5 3 0 30 0 34 0 59 6 91 2 163.3 330.0
40 7 43 1 40 7 36 6 41 6 42 5 40 2 43.2 43.6
56 0 53 2 52 7 44 7 42 6 41 7 38 6 37.5 36.7
1 9 2 0 2 2 3 0 2.7 6.7
3 4 5 4 6 2 11 8 13 8 13 5 18 3 16.4 12.9
4-Ethyl Isomer
and fluoborate all favor formation of the 5-ethyl isomer. While more study is necessary, it is tentatively concluded that the acidity of the salt, and not the surface structure, is the cause of the specificity of the rearrangement. Reaction of Oxazolines with Carboxylic Acids in the Presence of NHICIO~. Oxazolines will undergo - ringopening reactions with carboxylic acids, the products being similar to those resulting from ring-opening of the parent aziridine T h e rate of reaction of the two oxazoline isomers with propionic acid in the presence of NH4ClOa was very slow a t 80” C. T h e 4-ethyl isomer reacted about 3 times faster than the 5-ethyl isomer (Table V I I I ) . Both isomers undergo some hydrolysis from water contained by the ammonium perchlorate.
-
literature Cited
61.3 1.5 1.1 30.0 36.2 61.2 1.5 1.6 35.0 37.3 59.1 2.9 1.4 60.6 36.6 57 3 5 9 1 4 92 2 35 5 52 7 9 7 4 2 164 3 33 2 47 9 20 0 0 0 330 0 32 1 a 7 mi. of toluene solution per 5 grams .YHdClOa (approx. 85% ,2‘H~C104); oxaroline and acid, each 0.5.M. Constituent chromatographic area X 700/total chromatographic area (marker and soluent excluded). e Product of ring opening by acid. Product of ring opening by water.
Boyd, R. N., Hauser, R. H., J . A m . Chem. Soc. 75,5896 (1953). Cornforth, J. \V.,“Heterocyclic Compounds,” R. C. Elderfield, ed., Vol. 5 , p. 383, Wiley, New York, 1957. Fruton, J. S., “Heterocyclic Compounds,” R. C. Elderfield, ed., Vol. 1, p. 61, \Viley, New York, 1950. Goldstein, A , , “Encyclopedia of Polymer Science and Technology,” Vol. I, p. 734, Interscience, New York, 1964. Heine, H. \V., Angew. Chem. Intern. E d . 1, 528 (1962). Pittman, A. G., Lundin, R. E., J . Polymer Scz. 2A,3803 (1964). Schlitt, R. C., Anal. Chem. 35, 1063 (1963). RECEIVED for review May 16, 1967 ACCEPTED September 28, 1967 DOD Public Release Approval, RA/SA-AFRPL, 17 April 1967.
OXAZOLINE ISOMERS FROM T H E REARRANGEMENT OF 1,3,5=TRIS(2=ETHYL-l= AZI RID1NYLCARB0NYL)BENZEN E AND OF 1-BENZOY L-2 -ETHY LA21RID I N E A Kinetic Method of Analysis D. E. JOHNSON, R . H.QUACCHIA, A N D A . J. D I M I L O Propellant Research and Development Diuision, Aerojet-General Corp., Sacramento, C a l i f .
difference in the rates of reaction of 4-ethyl- and 5-ethyloxazolines with acetic acid was used to determine the distribution of these isomers in a mixture. T h e rates of reaction of 4-ethyl- and 5-ethyl-2-phenyl-2-oxazoline were determined in acetic acid by both titration and gas chromatographic methods. The data were utilized to determine the isomer THE
composition of a mixture obtained from rearrangement of 1,3,5-tris(2-ethyl-1-aziridinylcarbonyl)benzene.I n sodium iodide-acetone and in dimethylformamide the aziridines were converted predominantly to the 4-ethyloxazoline. Ammonium perchlorate converted the aziridines almost exclusively to the 5-ethyloxazoline. VOL. 6
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DECEMBER 1967
273
~~
~~
The isomerizations of 1,3,5-tris(2-ethyl- 1 -aziridinylcarbonyl)benzene and 1 -benzoyl-2-ethylaziridine were studied in sodium iodide-acetone, in dimethylformamide, and in contact with solid ammonium perchlorate. The amounts of the 4- and 5-ethyloxazolines formed b y the benzoylaziridine were determined by gas chromatography. Chromatography was not applicable to the determination of the isomer composition formed by the ethylaziridine derivative of trimesic acid. For the rate of reaction of the isomeric oxazolines with carboxylic acid, the 4-ethyl isomer was faster than the 5-isomer, and, as a consequence, a mixture of the isomers could b e analyzed by its kinetic behavior in acetic acid. The kinetic method of analysis was investigated and successfully applied to determining the isomer mixture formed by rearrangement of 1,3,5tris(2-ethyl-1 -aziridinylcarbonyI)benzene. The results indicated that isomerization of aziridines in sodium iodide-acetone and in dimethylformamide gave predominantly the 4-ethyloxazoline, while isomerization in solid ammonium perchlorate formed exclusively the 5-ethyloxazoline.
in methanol. The solution was dried over sodium sulfate and filtered and the methanol evaporated, giving a 90% yield of a heavy gum which crystallized slowly (m.p. 130-32' C.). Attempted Preparations of 1,3,5-Tris [ (4- and 5-ethyl)-2oxazolinyl-:!]benzene. METHODI . A lOO-ml., 3-necked, round-bottomed flask, fitted with a stirrer and a thermometer, was charged with 5 grams of VI1 and 20 ml. of redistilled pyridine. The solution was cooled to 20' C. and 6.9 grams of p toluenesulfonyl chloride were added slowly with stirring, maintaining this temperature. After addition of the chloride, the solution was allowed to warm to room temperature and then heated to 50' C. for 2 hours. The reaction mixture was poured into distilled water and worked up. None of the trioxazolines was isolated. METHOD11. Two grams of VI1 were dissolved in 20 ml. Experimental of concentrated sulfuric acid and kept a t 60' C. for 1 hour. T h e reaction mixture was poured into distilled water, neu1-BENZOYL-2-ETHYLAZIRIDINE,I. T h e benzoylaziridine was tralized with dilute potassium hydroxide, and extracted with prepared by reaction of benzoyl chloride with 2-ethylaziridine ether. None of the oxazoline was obtained. (Quacchia et al., 1967). Calculated for C I ~ H I ~ N O C,: 75.4; METHOD111. Method I1 was carried out using polyH, 7.5; N, 8.0. Found: C, 74.6; H, 6.9; N, 7.7. B.p. phosphoric acid at about 75' C., hut no oxazoline was obtained. 86-87' C./0.6 mm.; n b 1.5351. By the above three methods neither VI nor VI1 gave the A'BENZOYL-l-AMINO-2-BUTAKOL, 11. 1-Amino-2-butanol reexpected oxazolines. acted with benzoic acid in xylene (Quacchia et al., 1967). 1,3,5 Tris(2 ethyl - 1 aziridinylcarbonyl)benzene, VIII. B.p. 74-75' C./0.5 mm. TRIOXAZOLINES FORMEDI N DIMETHYLFORMAMIDE, I x . T O a l!r-BENZOYL-2-AMINO-l-BUTAKOL, 111. 2-Amino-1 -butanol 500-ml., two-necked, round-bottomed flask were added 32 reacted with benzoic acid in xylene (Quacchia et al., 1967). grams of VI11 and 200 ml. of redistilled dimethylformamide. B.p. 230-31' C./lO mm. The flask was fitted with a thermometer and a reflux con4-ETHYL-2-PHENYL-2-OXAZOLINE, I v . 111 was converted denser, connected to a drying tube. The flask was heated to to 4-ethyl-2-phenyl-2-oxazolineby the method of Boyd and 50' to 60' C. for 3 days; then the dimethylformamide evapoHauser (195j). ' rated under vacuum to one fourth the original volume. Cool5-ETHYL-2-PHENYL-2-OXAZOLINE.v. The 9-tO~UeneSUlfOnate of I1 was converted to 5-ethyl-2-phe~yl-2-oxazoline ing caused the formation of a fine white precipitate (m.p. 77-79' C.), which was separated by filtration. Infrared (Quacchia et al., 1967). analysis showed it to be an oxazoline. The progress of some 1,3,5 - TRIS ['v- 2(1 HYDROXYBUTYL)CARBOXAMIDO]BENZENE, of the reactions was followed titrimetrically by the disappearVI. T o a 250-ml., three-necked flask, fitted with a therance of the aziridine and the appearance of the oxazoline. mometer and mechanical stirrer, were added 10.4 grams (0.117 U p to 90% yields have been obtained. mole) of redistilled 2-aminobutanol dissolved in 35 ml. of TRIOXAZOLINES FORMED BY NAI ISACETONE, X. T o a 300methylene chloride. Then 17 grams (0.123 mole) of potasml., round-bottomed flask were added 20 grams of V I I I , 100 sium carbonate (reagent grade) in 50 ml. of distilled water ml. of acetone (reagent grade), and 0.2 gram of sodium iodide. were added without stirring. T h e mixture was cooled by T h e flask was fitted with a reflux condenser and the solution ice to 10' C. without stirring. A syringe with a long needle refluxed about 16 hours. Usually after this time KCNS was charged with 10 grams (0.114 mole) of trimesoyl chloride titration indicated that all the aziridine functionality had dissolved in 30 ml. of dried methylene chloride. The acid disappeared. The acetone was evaporated, and a tan solid chloride was introduced below the water level with stirring (7570 yield by titration) remained. The residue was rewhile the temperature was maintained between 10' and 15' C. crystallized from n-heptane (m.p. 79-80' '2.). A white precipitate formed. After addition of the acid chloTRIOXAZOLINES FORMEDO N . 4 M Y O N I U M PERCHLORATE, X I . ride, the temperature of the solution was allowed to rise slowly T o a 1-liter, round-bottomed flask, fitted with a reflux conto room temperature, after which stirring of the solution was denser and drying tube, were added 16 grams of V I I I , 32 continued for 4 hours more. T h e product was separated and grams of ammonium perchlorate (130 microns), and 500 dried (m.p. 283-86' C., yield 9570). ml. of dried, reagent-grade benzene. The mixture was 1,3,5-TRIS - [IT-(2 HYDROXYBUTYL)CARBOXAMIDO]BENZENE, refluxed and gently stirred for 5 days, at which time V I I . T o a 1-liter, three-necked, round-bottomed flask were the aziridine moiety had almost disappeared. A 50% yield added 21 grams (0.236) of 1-amino-2-butanol dissolved in 50 of oxazoline was obtained; the major portion of the reml. of methylene chloride. Then 35 grams (0.25 mole) of maining material was polymeric. potassium carbonate (reagent grade) in 150 ml. of distilled Reactions of Oxazolines with Acids in Toluene. V water were introduced without stirring. As above, 19.6 (4.3729 grams, 0.025 mole) and propionic acid (1.8485 grams, grams (0.222 mole) of trimesoyl chloride in 50 ml. of dried 0.025 mole) were weighed, transferred to a 25-ml. volumetric methylene chloride were carefully added. T h e preparation flask, and diluted with toluene, redistilled from sodium metal. was continued as directed above. During the reaction, the Aliquots (2.5-ml.) were put into 5-ml. ampoules, which were product separated as a viscous resin. After completion of the cooled with dry ice and sealed. The ampoules were placed in a reaction, the product was separated into a beaker and dissolved
T h e tendency of 1-acylaziridines to isomerize to 2-oxazolines is well known (Heine, 1962; Pittman and Lundin, 1964). When the aziridine is unsymmetrical because of a substituent in position 2, the isomerization will produce two isomers, the 4and the 5-substituted-2-oxazoline. I n the course of a study defining the behavior of 1,3,5-tris(2-ethyl-1-aziridinylcarbonyl)benzene (BITA), a curing agent for solid rocket propellants, the products of the rearrangement and the amounts of each product became of interest. T h e method used to determine the isomer composition of rearranged BITA is the subject of this paper.
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l&EC PRODUCT RESEARCH A N D DEVELOPMENT
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constant temperature bath and withdrawn periodically. T h e ampoule to be analyzed was cooled, and the top snapped off. A small aliquot was withdrawn for chromatographic analysis and two 1-ml. aliquots were taken for analysis by titration. T h e same procedure was followed for similar reactions of I V and the trioxazolines prepared from V I I I , except that the trioxazolines could not be analyzed by gas chromatography. I n some experiments, acetic acid and also redistilled dioxane were used. I n all of the reactions of oxazolines and acids in inert solvents, the oxazoline content decreased more rapidly than the acid during the first 24 hours, then both the oxazoline and acid disappeared stoichiometrically. T h e initial, more rapid loss of oxazoline was of the order of 7 equivalent %.
Reaction of a Mixture of IV and V (40:60) in Glacial Acetic Acid. Into a 25-ml. volumetric flask were weighed 1.7683 grams (0.0179 mole) of I V , 2.6397 grams (0.0266 mole) of V, and 1.003 grams of m-bromoanisole, internal standard for analysis by gas chromatography. This mixture was diluted to 25 ml. with glacial acetic acid and stirred. Two-milliliter aliquots of the solution were syringed into ampoules, which were sealed and placed in an 80' C. constant temperature bath. Periodically, ampoules were removed, cooled, and opened. A small sample was taken for analysis by gas chromatography and 1 ml. was titrated for the total oxazoline content. Reaction of a Mixture of IV and V (30:70) in Glacial Acetic Acid. Into a 25-ml. volumetric flask were weighed 1.3216 grams (0.00755 mole) of IV, 3.0833 grams (0.0176 mole) of V, and 1.003 grams of m-bromoanisole, internal standard for the gas chromatographic analysis. T h e reaction was followed as indicated in the previous paragraph. Reaction of Trioxazolines (IX, X, and XI) in Glacial Acetic Acid. T o a 25-ml. volumetric flask were added 4.5 to
Table 1. Oxazoline Isomer Distribution for Rearrangement of 1-Benzoyl-2-ethylaziridine by Various Methods Isomer Composition, yo Rearrangement Method 4-Ethyl 5-Eth~l 93 7 NaI-acetone .. Dime thylformamide 90 10
NHaC104
0
loo
100
5.0 grams of one of the trioxazolines and glacial acetic acid. Two milliliters of the solution were syringed into ampoules, sealed, and placed in an 80' C. constant temperature bath. Ampoules were removed periodically and titrated for oxazoline. Titrimetric Analysis of Oxazolines. STANDARD SOLUTION OF PERCHLORIC ACIDIN ACETICACID. I n a 2-liter flask were placed 32 grams of acetic anhydride and 1 liter of glacial acetic acid. T o this stirred solution were slowly added 15 grams of 70y0 perchloric acid. T h e solution was standardized with a known aziridine or tris(hydroxymethyl)aminomethane, a primary standard. PROCEDURE.T h e procedure used is a variant of that of Jay (1964) for aziridines or epoxides. Approximately 1-meq. samples were dissolved in chloroform or glacial acetic acid. To this were added 10 ml. of a solution prepared by dissolving 1 gram of tetrabutylammonium iodide in 10 ml. of chloroform. A few drops of methyl violet or crystal violet indicator (dissolved in chloroform) were added and the sample was titrated to a royal blue end point using the standard perchloric acid solution. With some oxazolines the indicator tended to fade and another drop or two was added near the end point. Gas Chromatographic Analyses. T h e analyses were obtained using an F&M-500 gas chromatograph equipped with a thermal conductivity detector and a Minneapolis-Honeywell
0
0
0
3LQ
200
I
1
400
500
Acetic Acid Oxazoline
Time, Hours Figure 1.
79.8"
c.
Rate of reaction of 2-phenyl-4-ethyl-2-oxazoline (1N) and acetic acid
VOL.6
1N) in toluene at
NO. 4
DECEMBER 1 9 6 7
275
Table II. Second-Order Rate Constants for the Reaction of Carboxylic Acids with Oxasolines in 1N Solutions Rate Constants, Temp., L . / E q . Hr. Oxazoltne
Acid
4-Ethyl-2-phenyl-
Acetic Propionic 5-Ethyl-2-phenyl Propionic NaI-acetone reAcetic arrangement of .icetic BITA Acetic DMF rearrangement Acetic of BITA Acetic Acetic Acetic a
Solvent
Toluene Toluene Toluene Toluene Toluene Toluene Dioxane Dioxane Toluene Toluene
O
c.
80 80 80 80 100 100 80 80 58 80
x
103
2.0 1.5 0.23 2.8 10
20" 0.3
0.58a 0.56 2
Contain 0.5C0 zirconium aceblacetonate.
Table 111. First-Order Rate Constants for Reaction of 4- and 5-Ethyloxasolines from Various Sources in Acetic Acid at 80' C. First-Order Rate Constant, Hr.-1 x 701
Oxaroline
4-Ethyl-2-phenyl-
19,7"* 18. 4ac
22bd 1 . 04ab 1 .09ac 1 ,14bd 1 9 . 7ae 1 . 09aE 1 ,4a
5-Ethyl-2-phenyl-
4-Ethyl (BITA rearranged with NaI-acetone) 5-Ethyl (BITA rearranged with NaI-acetone) 5-Ethyl (BITA rearranged on NH4C104) From 30: 70 (by weight) mixture of a Oxazoline loss by titration. 4-and 5-ethyl-2-phenyloxarolines. From 60: 40 (iy weight) mixture of 4- and 5-ethyl-2-phenyloxarolines. Oxazoline loss by gas chromatography.
e
From mixture of 4- and 5-ethyl isomers.
Table IV.
Oxazoline Isomer Distribution for Rearrangement of BITA by Various Methods
Rearrangement Method
NaI-acetone Dimethylformamide NH 4C104
Oxaroline Isomers, 7c 4-Ethyl 5-Ethyl
86 75 2
14
25 98
0.1- to 1-mv. recorder. Helium was the carrier gas a t a flow of 100 ml. per minute. T h e gas flow rate was measured a t the outlet with a soap bubble flowmeter. T h e temperature of the injection port was 165' C. and the block temperature was 250' C. The bridge current was 150 ma. and the sample sizes were 0.4 to 10 pl. m-Bromoanisole was used as an internal standard. A 2 foot X '/4 inch stainless steel column packed with 5% ethylene glycol succinate on 60-80-mesh Diatoport-S was used for the analysis of the oxazoline-acid reactions. T h e column temperature was programmed from 75' to 140' C. a t 7.9' per minute. After elution of the oxazoline the column temperature was raised to 225' C. to elute high boilers. Discussion
BITA was isomerized in acetone containing a catalytic amount of sodium iodide and in dimethylformamide a t 60' C. 276
I h E C P R O D U C T RESEARCH A N D D E V E L O P M E N T
(no catalysts) with excellent yields of oxazolines. Although the oxazolines from the two sources appeared to be the same and had the same melting points, the material obtained in dimethylformamide did not dissolve in n-heptane, whereas the other did and could be recrystallized from heptane upon cooling. T h e BITA could also be isomerized in dimethyl sulfoxide; however, the product was not obtained pure. The isomerization in sodium iodide-acetone was shown to give the 4-ethyl isomer. Thus hydrolysis of the oxazoline formed in NaI-acetone gave a material which gave no melting point depression when mixed with and had an infrared spectrum similar to that of 1.3,5-tri- [.V-(l-hydroxy-2-butyl)carboxamidolbenzene. T h e latter (m.p. 284-87' C.) was prepared by the reaction of trimesoyl trichloride with 2-aminobutanol in a two-phase system, methylene chloride and aqueous potassium carbonate. Attempts to convert this material by treatment with p-toluenesulfonyl chloride to the 4-ethyloxazoline derived from BITA were not successful. Isomerization of i-Benzoyl-2-ethylaziridine. More insight to the isomerization products of BITA was obtained by a study of 1-benzoyl-2-ethylaziridine.This aziridine was isomerized by the methods used for BITA isomerization. The two possible isomers, 4-ethyl- and 5-ethyl-2-phenyl-2-oxazoline, were prepared and separated and identified by gas chromatographic techniques. By this method it was discovered that contact with solid ammonium perchlorate isomerizes 1-benzoyl2-ethylaziridine (in toluene solution) exclusively to 5-ethyl-2phenyl-2-oxazoline (Quacchia et al., 1967). BITA was also isomerized by this treatment, but the isomer composition was not known. Table I shows the isomer composition obtained from l-benzoyl-2-ethylaziridine by each of the isomerization methods. Gas chromatographic analysis of the BITA isomerization products was not feasible, since they were not volatile enough. Reaction of Oxazolines with Carboxylic Acids. Oxazolines react with carboxylic acids by a ring opening reaction (Fry, 1950; Wehrmeister, 1963). A study showed that the 4-ethyl2-phenyloxazoline reacted 7 times faster than the 5-ethyl isomer with propionic acid a t 80' C. in toluene. The reaction was stoichiometric after an unexplained. initially more rapid loss of oxazoline and obeyed second-order rate laws to over 50% reaction, as far as it was followed. A typical rate plot is shown in Figure 1. Some second-order rate constants are presented in Table 11. The oxazolines derived from BITA also reacted with acids and some rate constants for them are also included in Table 11. The difference in rates of reaction of the 4- and 5-ethyl isomers was magnified by running the rates under pseudo-firstorder conditions with acetic acid as solvent. The first-order rate constants are summarized in Table 111. T h e amounts of each isomer could be determined for mixtures of 4- and 5-ethyl-2-phenyloxazolinesfrom the kinetic behavior of the mixture during reaction with acetic acid. The rate was rapid a t first because of the reaction of the 4-ethyl isomer and then slowed to that of the 5-ethyl isomer. The extrapolation of the line for the slower isomer to zero time gave the 5-ethyl isomer content. T h e 4-ethyl isomer content was obtained by difference. Figure 2 shows the rate curves for the reaction of a 40:60 by weight mixture of 4- and 5-ethyl-2phenyloxazolines with acetic acid. The experimentally derived isomer ratio obtained by extrapolating the line of lower slope to zero time is 39: 61. T h e rate constants could be derived for each isomer: for the 5-isomer directly from the rate curve and for the 4-isomer after replotting the initial portion of the curve. An additional check was made with a 70: 30 mix-
ture of the 5- and 4-isomers. These results demonstrated the feasibility of determining the isomer distribution of isomerized BITA. Isomer Distribution of Rearranged BITA. BITA rearranged by sodium iodide-acetone, by dimethylformamide, and by ammonium perchlorate reacted in acetic acid a t 80' C. T h e rate curves are shown in Figures 3 to 5. The isomer distribution and the rate constants for each isomer are given in
Tables I V and 111, respectively, and were derived from analyses of Figures 3 to 5. Comparison of Tables I and IV indicates that both BITA and its model, 1-benzoyl-2-ethylaziridine,were isomerized essentially to the 4-ethyloxazoline by both sodium iodide-acetone and dimethylformamide. Further, ammonium perchlorate converts both these aziridines to the corresponding 5-ethyloxazoline with great efficiency.
1
I
I
I
1
1
1
I
1
10
20
M
40
M
to
I
I 70
Time. hours
Figure 2. First-order rate of reaction of 4- and 5-ethyl-2phenyloxazoline mixture (40:60, 1N) in acetic acid at 80' C.
TIM. hr 100
90 80 70 60
Figure 4. Rate of reaction of BlTA oxazoline (1N) from DMF in acetic acid at 80' C.
50
40 o
BASED UPON TOTAL OXAZOLIMS
0
CORRECTED RATE FOR 4 - I S M R
M
.I
\
\
7t-
32
21 0
I
20
I 40
I
I
60
80 TIM. hrr.
I
100
I 120
Figure 3. First-order rate of reaction of isomeric oxazolines in acetic acid at 80" C. BlTA rearranged on Nal-acetone
c 0
10
M
20
40
M
M
70
TIME, hrs.
Figure 5. First-order rate of reaction of isomeric oxazolines in acetic acid at 80' C. BlTA
rearranged on NHdClO4
VOL. 6
NO. 4
DECEMBER 1967
277
Conclusions
literature Cited
The isomer distribution obtained by rearranging aziridines (specifically BITA and 1-benzoyl-2-ethylaziridine)can be determined by a kinetic method. This method, which involves determining the pseudo-first-order rate of reaction of the isomer mixture in acetic acid, is easily carried out and is applicable to materials which cannot be analyzed by gas chromatography. T h e method was demonstrated for BITA, a n aziridine curing agent of interest to solid rocket propellant technology.
Boyd, R. N., Hauser, R. H., J . A m . Chem. SOC.7 5 , 5896 (1953). Fry, E. M., J . Org. Chem. 15,802 (1950). Heine, H. W., Angew. Chem. Intern. Ed. 1, 528 (1962). Jay, R. R., Anal. Chem. 36,667 (1964). Pittman, A. G., Lundin, R. E., J . Polymer Sci. 2A,3803 (1964). Quacchia, R. H., Johnson, D. E., Di Milo, A. J., paper in preparation, 1967. Wehrmeister, H. L., J . Org. Chem. 28, 2587 (1963). RECEIVED for review May 16, 1967 ACCEPTEDAugust 28, 1967 DOD Public Release Approval RA/SA-BSD-4/27/67.
VISCOSITY MEASUREMENTS ON CHEMICALLY MODIFIED CELLULOSES W . B . A C H W A L A N D T. V . N A R A Y A N Defartment of Chemical Technology, University of Bombay, Bombay 19, India
A large number of oxycelluloses were prepared and treated with chlorous acid and sodium borohydride and their degree of polymerization (DP) was determined in a number of alkaline solvents as well as in ethyl acetate after nitration. Comparison of DP values showed that differences in alkalinity of the solvents had practically no effect, but the values for different modified celluloses varied considerably, depending upon the acid and alkali sensitivity of functional groups formed. A pretreatment of degraded samples with sodium borohydride is recommended to get a more representative DP value in alkaline solvents.
of degree of polymerization (DP) of cellulosic materials by viscosity measurement involves either working with highly alkaline solvents or nitration under strong acidic conditions. Chemical modifications, particularly by oxidation, may introduce different functional groups such as carbonyl and carboxyl in various positions of the cellulose molecules and induce alkali or acid sensitivity resulting in apparently low degree of polymerization values. Such discrepancies between the viscosity measurements in alkaline solvents such as cuprammonium hydroxide (cuoxam) or cupriethylenediamine (CED) and nitrate viscosity have been reported by many workers (Davidson, 1941 ; Ellefsen, 1963 ; Sihtola et al., 1958; Virkola, 1958). Pronounced alkali sensitivity of oxycelluloses having reducing groups has been attributed by Davidson (1941) and Brownsett and Davidson, (1945) to the presence of carbonyl groups in certain positions which induce alkali sensitivity in 1-4 glucosidic linkages. Rogovin et al. (1949) and Davidson (1941) had observed that nitration of dialdehyde celluloses of a higher degree of oxidation gave poorly soluble nitrates and high viscosity values, which has been attributed to acetal cross linkages formed during the nitration between the individual cellulose molecules (Sihtola, 1960; Sihtola et al., 1958; Virkola, 1958). Acid and alkali stability of dialdehyde cellulose formed by periodate oxidation and stabilization caused by conversion into dicarboxylic and dialcoholic celluloses on further treatment with sodium chlorite and sodium borohydride have been studied (Betrabet et al., 1965; Meller, 1951, 195G; Rutherford et al., 1942). Ellefsen (1963) had suggested a treatment for pulp DETERMINATION
278
l&EC PRODUCT RESEARCH A N D DEVELOPMENT
samples with sodium borohydride to get comparable DP values in CED and on nitration. T h e effect of the presence of functional groups formed by oxidizing agents other than periodic acid on DP values in different solvents has not been thoroughly investigated and most of the D P measurements have been carried out in cuprammonium hydroxide and cupriethylenediamine and after nitration. With the development of iron-tartrate complex solvents a wide range of solvents of different alkalinities are available and variation in alkali content may also have a n effect on the extent of alkali sensitivity. A large number of oxycelluloses of different types were prepared by oxidation with various oxidizing agents a t different p H values. AI1 these samples were further treated with sodium chlorite and sodium borohydride under controlled conditions and D P values compared in three types of iron-tartaric acid complex (FeTNa) solvents, cuoxam, and CED as well as in ethyl acetate after nitration. Experimental
Preparation of Modified Cellulose Samples. Forty grams of standard cellulose was oxidized by the respective oxidizing agent a t room temperature a t a material-liquor ratio of 1 to 40. Oxygen consumption was determined wherever possible from the change in the concentration of oxidant and the samples were washed free from reagents, dried in air, and conditioned a t 65y0 R H a t 30' C. Periodate oxidation was carried out by 0.01M potassium metaperiodate for 17 hours and by 0.005M solution for 8 and 24 hours. Potassium dichromateoxalic acid oxycellulose was prepared by suspending the sample in 2M oxalic acid and adding 140 ml. of 2.ON potassium
