collected and measured. T h e quant i t y of hydrogen sulfide formed corresponded to a t least 90% of t h e theoretical amount based on complete conversion of t h e thioacetamide initiallv present to H2S. T h u s a n y side reactions t h a t d o not lead t o t h e formation of hydrogen sulfide occui to an extent no greater than 10%. In a similar experiment with a n excess of thioacetamide over hydrazine, hydrogen sulfide evolution stopped when the hydrazine had been consumed but started again upon the addition of more hydrazine. Also within =tlOgl, one mole of H2S was formed per mole of hydrazine. A product of the reaction bettr-een thioacetamide and hydrazine was isolated from the reaction mixture. The procedure consisted of allowing 25 grams of thioacetamide and 16 grams of hydrazine hydrate in 100 ml. of water to react a t UO’ C. for several days. The solution was constantly purged with nitrogen to remove the hydrogen sulfide being generated and to remore any oxygen from the reaction solution. The solution was evaporated under vacuum a t 50’ C. JT‘hite crystals formed after the solution had been evaporated down to a fe\y milliliters. On e\posure to air the crystals slowly turned red. Upon recrystallization from ethyl alcohol long, thin crystals were obtained that appeared stable. 7‘he cryqtals rnc1tc.d a t 199’ to 201’ C. Microanalysis and a n approximate molecular weight detwmination indicated the formula C4H8N4. Nuclear
magnetic resonance measurements showed that the ratio of exchangeable to nonexchangeable hydrogens was 1 to 3. -4compound fitting the above data is the IT-aminotriazole:
s-s
ACKNOWLEDGMENT
The authors are grateful to E. H. Swift for many helpful suggestions, and to the National Science Foundation and E. I. d u Pont de Semours & Co. for grants in support of this work. The NRIR experiments were performed by Gideon Fraenkel.
LITERATURE CITED
Its reported melting point is 199’ C.
(1) Bowersox, D. F., Smith, D. M., Swift, E. H., Tulunta 2, 142 (1959). (2) Bowersox, D. F., Swift, E. H., ANAL.
( 8 )’ Qualitative experiments Kith hydroxylamine, urea, and N,N-dimethylhydrazine and thioacetamide showed t h a t all of these substances lead to much slower rates of hydrogen sulfide evolution than is obtained with hydrazine. Analytical Applications. T h e application of t h e thioacetamide hydrazine system to t h e precipitation of metal sulfides should enable homogeneous precipitations t o be made from weakly acid solutions. Preliminary experiments have shown t h a t readily coagulated precipitates are obtained; even in t h e case of nickel t h e precipitate obtained under these conditions consists of large particles that are readily filtered. The possibility that the thioacetamide-hydrazine combination could be used to effect separations, some of which are impossible with thioacetamide alone, is a t present iinder investigation.
RECEIVED for review September 21, 1960. Accepted December 21, 1960. Contribution KO.2626, Gates and Crellin Laboratories of Chemistry.
CHElf. 30, 1288 (1958). (3) Bush, D. G., Zuehlke, C. W., Ballard, A. E., Zbid., 31, 1368 (1959). (4) Butler, E. A., Swift, E. H., Ibid., 28, 146 (1956); Butler, E. -4., Peters, D. G., Swift, E. H., Ibid., 30, 1:79 (1958). (5) Clark, C. C., “Hydrazine, pp. 55-7, Mathieson Chemical CorD., Baltimore, Md., 1953. (6) DeFord, D. D., Abstracts 133rd Meeting, ACS, San Francisco, Calif., 1958. (7) Gould, E. S., “Mechanism and Structure in Organic Chemistry,” pp. 543-4, Henry Holt, Kew York, 1959. (8) Herbst, R. h4., Garrison, J. A., J . Org. Chem. 18, 872 (1953). (9) Penneman, R. A Audrieth, L. F., ANAL.CHEhL 20, lOS8 (1948). (10) Welcher, F. J., “lnalytical Uses of Ethylenediamine Tetraacetic Acid,” Chap. VIII, Van Nostrand, X ~ TYork, V 1958. (11) Yost, D. M., Ruseell, H., Jr., “Systematic Inorganic Chemistry,” PrenticeHall, New York, 1944.
Determination of Mixtures of Hydrazine and 1,l -Dimethyhydrazine HUGH E. MALONE Air Force Flight Test Center, Edwards Air Force Base, Calif.
b A method for determining mixtures of hydrazine and 1,l -dimethylhydrazine in a nonaqueous titration uses acetic acid as a solvent with perchloric acid in dioxane as the titrant. The method uses the selective action of salicylaldehyde which forms the neutral azine with hydrazine and a basic hydrazone with 1,l -dimethylhydrazine. and 1,l-dimethylhgdrazine are both rocket fuels which when blended in certain proportions, possess certain properties superior to those of the individual fuels. The high specific impulse of hydrazine and lower
H
YDRAZINE
freezing point of 1,l-dimethylhydrazine are present in mixtures of these fuels. Since perchloric acid was first used by Conant and Hall (1) to titrate organic amines in acetic acid, many papers have been written on nonaqueous titrations. Of interest here are those of Fritz and Keen (3) and Riddick (5). Siggia and Stahl (6) determined 13 aldehydes including salicylaldehyde with 1,l-dimethylhydrazine by forming a neutral hydrazone in methanol. They (6) also state that “aromatic aldehydes yield hydrazones which exhibit no detectable basicity.” This fact was verified b y the author using methanol as the solvent system. However, when the sol-
vent system is changed to acetic acid, the hydrazone formed titrates basic. Whitnack et al. (8) studied the polarographic behavior of benzaldehyde derivatives of hydrazine, l,l-dimethylhydrazine, and monomethylhydrazine. Wagner et al. ( 7 ) developed a procedure for determining secondary and tertiary amines using salicylaldehyde. Critchfield and Johnson (2) modified their procedure using salicylaldehyde for determining primary, secondary, and tertiary amines. Malone (4) analyzed mixtures of aniline, furfuryl alcohol, and hydrazine by separating the hydrazine from the mixture with salicylaldehyde. VOL 33, NO. 4, APRIL 1961
575
REACTIONS OF HYDRAZINE WITH SALICYLALDEHYDE
I n acetic acid medium, salicylaldehyde reacts with hydrazine and 1,ldimethylhydrazine in the following manner : Salicylaldazine in Equation 1: H O
I/
C
Determination of 1,l - Dimethylhydrazine. Pipette a 1-ml. aliquot of t h e prepared sample into a 150-ml. beaker containing 20 ml. of glacial acetic acid. I n t o this solution add 2 ml. of salicylaldehyde and heat for 10 minutes a t 50" C. The yellow H N-N
I//
C
salicylaldazine precipitates immediately on stirring. Add 6 drops of methyl violet indicator and titrate with 0.1N perchloric acid in dioxane until the amber color of the solution (yellow from the azine-purple from the indicator) changes to dark green (yellow from azine-blue from the indicator). Indicate this amount for value B in Calculations.
\A
H
Possible improvements may be made in the test procedure by using a potentiometer to detect the end points. The salicylaldazine precipitate complicates the titration somewhat, but this can be overcome by permitting the precipitate to settle before adding more perchloric acid. The visual titration, though requiring a few practice titrations to reproduce end points, lends itself to a possible field method where, with a minimum of equipment, untrained personnel can easily analyze mixtures of hydrazine and 1,l-dimethylhydrazine.
and salicylaldehyde 1,l-diniethylhydrazone in Equation 2: CH,
The salicylaldazine formed in Equation l is a yellow crystalline solid and is neutral when titrated with perchloric acid. The salicylaldehyde 1,l-dimethyl hydrazone in Equation 2 has the same basic strength as the original 1,ldimethylhydrazine and can be titrated with perchloric acid to the methyl violet indicator end point. Attempts to determine monomethylhydrazine in a mixture with hydrazine or 1,l-dimethylhydrazine were unsuccessful. The hydrazone produced by the reaction of salicylaldehyde with monomethplhydrazine was not completely formed after three hours a t 60" C. Figure I shows that approximately 95% of the hydrazone in acetic acid titrated neutral with perchloric acid whereas the salicylaldehyde 1,l-dimethylhydrazone titrated basic in acetic acid.
100
b
140-
% unreacted
t
ANALYTICAL CHEMISTRY
1
I
I
I
I
1
r
I
o f time; 0.1 N perchloric acid in dioxane
z20w e
3
MMH as function MMH titrated with
; 0
I
I
I
20
40
60
Table I.
80 100 TIME -MINUTES
I
I
I
120
140
160
180
Results of Analysis C-f /a
Number
PROCEDURE
576
I
-\
Figure 1 . Reaction of monomethyl hydrazine (MMH) with salicylaldehyde in glacial acetic acid at 60" C.
1
Test each batch of acetic acid by titrating with O.1N perchloric acid to the blue end point of methyl violet indicator. Preparation of Samples. Add 2.0 grams of t h e hydrazine-1,l-dimethylhydrazine mixture to a cooled 50-ml. volumetric flask containing 40 ml. of glacial acetic acid. L4110w t h e flask to reach ambient temperature. Weigh to the nearest 0.0001 gram obtaining t h e sample weight b y difference. Dilute to volume with acetic acid and shake thoroughly. Determination of Total Alkalinity of Hydrazines. Pipette a 1-ml. aliquot of the prepared sample into a 150-ml. beaker containing 20 ml. of glacial acetic acid and 2 drops of methyl violet indicator. Titrate with O . 1 N perchloric acid in dioxane solution until t h e violet of the indicator turns blue. Indicate this amount for value A in Calculations.
80
\ I
\
2 3
4 5 6
Sample 1,l-Dimethylhydrazine Hydrazine Water 1,l-Dimethylhydrazine Hydrazine Water 1,l-Dimethylhydrazine Hydrazine Water 1,l-Dimethylhydrazine Hydrazine Water 1,l-Dimethylhydrazine Hydrazine Water 1,l-Dimethylhydrazine Hydrazine Water
Calcd. 78.99 19.22
Exptl. 79,32 18.78
1.79
1.90
69.57 28.76
70.05 28.61 1.34 58.84 38. 70 2.46 49,93 46.98 3.09 45.24 54.27 0.44 49.32 50.58
1.6i
58.77 38.87 2.36
50.23 47.18 2.59 45.89 54.11 0.00
49.45 50.55 0.00
0.10
% Av. Diff. 1,l-Dimethylhydrazine Hydrazine Water
Diff. 0.33 -0.44
0.11 0.48
-0.15 -0.33
0.07
-0.17 0.10 -0.30 -0.20
0.50 -0.65 0.16 0.49
-0.13
0.03 0.10
Std. Dev.
0.29 -0.36 0.09
0.11
0.26
0.19
-0.24
-0.33
0.19
70
CALCULATIONS
(B
- bz) x
A-
w
x
M,
x 100 -
yG1,l-dimethylhgdrazine
d(T1 = milliequivalent weight of 1,l( O O6Ol0) AI2 = milliequivalent weight of hydrazinc (0.03205) =
weight Of VALlClTY
100 - ( 7 0 hydrazine dimethylhydrazine =
+7096water 1,l-
where perchloric acid for total alkalinity titration B = nil. perchloric acid for aldehyde addition titration bl = ml. perchloric acid for blank of acetic acid and indicator bp = ml. perchloric acid for blank of acetic acid, indicator, and salicylaldehyde h’ = normality of perchloric acid A
= nil.
for their helpful suggestions and technical assistance in the preparation of this paper. LITERATURE CITED
OF RESULTS
T o check the validity of the reactions and of the procedure, over 30 samples of hydrazine and 1,l-dimethylhydrazine mixtures with varying amounts of each constituent were prppared and analyzed in triplicate. Table I shows the calculated and experimental results of typical analyses obtained using the dcscribed procedures. ACKNOWLEDGMENT
The author thanks E. L. Harris, Ivey G. Crow, Richard E. Barron, Robert A. Biggers, and Nerna Dawson
(1) Conant, J. I Chem. SOC.49, ( 2 ) . Critckfield, :
(6) Sig2a, S., Stahl, C. R., Zbid., 27, 1975 (1955). ( 7 ) Wagner, C. W., Brown, R. H., Peters, J., J . Am. Chem. SOC.69, 2609 (1947). (8) Whitnack, G. C., Young, J. C., Sisler. H. H.. Gantz. E.. ANAL. CHEM. 28, 835 (1956). RECEIVED for review May 9, 1960. ACcepted November 25, 1960.
Determinuti on of Copolymer Corn position by Infrared Analysis PoIy (viny I Acetate) -Po Iy ( met hy I Acry 1 ate) SURESH N. CHINAI’ and ROBERT H. CAMPBELL Special Projects Department, Monsanfo Chemical Co., Boston, Mass.
b A rapid and accurate absorptimetric method for analyzing poly(methyl acrylate)-poly(viny1 acetate) mixtures or copolymers has been developed. The absorption maxima due to ester linkages in the region o f 8.0 and 8.55 microns have been found useful in determining the composition of mixtures and copolymers. The developed equation is: % PVA = 70.27 (1.92 A8.oP -
P
A8.Shp).
OLT(VINYL ACETATE) and poly(methyl acrylate) are prepared from isomeric monomers, and thus have relatively similar solubility parameters. I n connection with work at this laboratory on properties of copolymers, a rapid and accurate method of analysis was needed to determine the extent of copolymerization of vinyl acetate and methyl acrylate. d literature search did not reveal any such method. ‘The investigation of poly(viny1 acetate) and poly(methy1 acrylate) polymers (henceforth referred t o as PVA and PhIA) by infrared spectroscopy revealed a considerable difference in the spectra in the region of ester absorption. The infrared spectrum of PhfA contained maxima a t 7.9, 8.35, and 8.55 I Present address, American Cyanamid Co., Stamford, Conn.
niicroiis, while the spectrum of PVA had one very strong absorption maximum a t 8.0 microns. Although PMA absorbed at 8.0 microns, the application of simultaneous equations a t 8.0 and 8.55 microns made feasible the analysis for both components in the presence of one another. Several standard techniques have been described for quantitative analyses in the infrared. F r y et al. (1) has described the “cell in-cell out” method n-here the spectrophotometer is set nianuslly a t the desired wave length, and a radiant intensity, I & is measured through air and a n I“ measured through the least absorbing component. Xext. a n 1; is again obtained through air and I b found for the unknown mixture. The log of the ratio, &‘Ib divided by I6 ’I: gives the absorbance value. Heigl et al. ( 2 ) have described the “base line density” method where the reference Io is obtained by drawing a base line on both sides of the maximum t o be measured. I n the method employed, the absorbances (log were obtained by first scanning the infrared spectrum of the solvent to determine the I: values, then t o determine the I , values from the spectrum of the solutions contained in the same cell.
$)
OPERATING CONDITIONS AND REAGENTS
The Perkin-Elmer Model-21 double beam infrared spectrophotometer with sodium chloride optics was used in the procedure. The infrared data on the samples were obtained in a 0.1-mm. sodium chloride cell with a 0.5-inch sodium chloride block in the reference beam. The following instrument s c t tings were optimum: selector snitch, manual; slit width, 180 microns; gain, 5; response, 1; response time, 3 secondi;; suppression, 0 ; and scanning speed, 1.15 microns per minute. The acetonitrile used as solvent 11 ar reagent grade (Fisher Scientific (30.). Standard 27, (w. /v.) poly(viny1 acetate) and 27, (vv./v.) poly(methy1 acrylate) in acetonitrile were prcyared. Each solution was prepared by atldiiig 2 grams of pure polymer to a 100-ml. volumetric flask and diluting to volume with acetonitrile. DETERMINATION OF SIMULTANEOUS EQUATIONS
The infrared instrument was adjusted to the described settings. The 0.1mm. cell was filled with acetonitrile and the spectrum scanned from 7.7 to 9.5 microns. This spectrum (C in Figure 1) provided the I o values a t 8.0 and 8.55 microns. The acetonitrile was flushed out of the cell with dry VOL. 33, NO. 4, APRIL 1961
577
