experiments (Table I) show that dilution has little or no effect on the recovery of phosphine. Another set of experiments was carried out on known mixtures of phosphine and air to determine the effect of sample volume changes on the recovery of phosphine. The results in Table I1 show that changes in sample volume do not affect recovery. The phosphine recoveries given in Tables I and I1 were determined from a calibration curve previously constructed. The reproducibility of Beyer’s method (1) and of the proposed method were essentially the same, approximately *5% relative. Gases such as arsine and stibene interfere with this determination because they reduce silver ion to silver metal.
Table 1. Length of
Color Band, Cm. 1.12 1i 4 1 90 2 39 4 07
Table II.
Volume of
Sample, Liters 5
5 22
Effect of Dilution
PH,, Mg. Added Recovered 0.047 0 089 0 121 0 131 0 273
n
016
0 0 0 0
087 110 140 280
Effect of Sample Volume
Length of Color Band, Cm. 2.77 1 57 0 79
PHI, hfg. ReAdded covered 0.173 0.079 0.021
0.175 0.080 0.022
Hydrogen sulfide interferes because of the formation of black silver sulfide. LITERATURE CITED
(1) Beyer, K., 2. anorg. zc. allyern. Chem. 250, 312 (1943). (2) Kitagawa, T., Ogawa, T., J . Electrochem. SOC.Japan 19, 258 (1951). (3) &fellor, J. W., “Comprehensive
Treatise of Inorganic and Theoretical Chemistry,” Vol. VIII, p. 802, Longmans, Green Pt Co., New York,
1940. (4) Work, J. B., “Inorganic Synthesis,” Vol. 11, pp. 141-4, McGraw-Hill, New York, 1956.
RECEIVED for review September 21, 1956. Accepted June 8, 1957. Paper No. 205, Journal Series, Research Laboratories, General Mills, Inc.
Determination of Alpha-Epoxides Containing a Tertiary Carbon Atom via Catalytic Isomerization with Zinc Bromide A. J. DURBETAKI Becco Chemical Division, Food Machinery and Chemical Corp., Station 6, Buffalo 7, N. Y.
A method for the determination of a-epoxides containing a tertiary carbon atom makes possible the determination of a-pinene oxide, camphene oxide, 1,2-diisobutylene oxide, and a-methylstyrene oxide, which cannot be determined quantitatively by any direct or indirect method heretofore described. The a-epoxide is converted to its corresponding aldehyde by catalytic isomerization with zinc bromide in benzene; the resulting aldehyde is determined gravimetrically as the 2,4-dinitrophenylhydrazone,
T
HE REACTIVITY and properties of an oxirane oxygen containing a tertiary carbon atom vary from those of other epoxy groups. Among the properties which appear to be characteristic of epoxides containing a tertiary carbon atom are ease of hydration, ease of isomerization, and formation of easily hydrolyzable chlorohydrins (6, 13). The direct and indirect methods heretofore described and used in the determination of other epoxides are not generally applicable to a-epoxy groups containing a tertiary carbon atom (3,4,
9,11).
Metallic halides, especially those of magnesium, have been used extensively in the rearrangement of various epoxides ( I , 2, 6, 7, 12, IS). The use of
1666
ANALYTICAL CHEMISTRY
zinc bromide and a possible reaction mechanism in the isomerization of apinene and camphene oxides was first described by Arbuzov (1, 2). The ease of isomerization of a-pinene, camphene, a-methylstyrene, and lJ2-diisobutylene oxides in the presence of acid catalysts is used here as the basic principle of this method. a-Pinene oxide, camphene oxide, amethylstyrene oxide, and 1,a-diisobutylene oxide are isomerized in anhydrous benzene with catalytic amounts of zinc bromide to give campholenic aldehyde, camphenilanaldehyde, amethylphenylacetaldehyde, and 2,4,4trimethylpentanal, respectively, and the corresponding 2,4-dinitrophenylhydrazones are determined gravimetrically. REAGENTS
Benzene, analytical reagent grade dried and stored over sodium. Zinc bromide, fused. Place 0.1 gram of analytical reagent grade zinc bromide in a dry clean tube (inside diameter 4 mm., outside diameter 6 mm., 17 cm. long) sealed at one end. Heat the tube to about 200” C., to avoid condensation of moisture distilled from the zinc bromide during fusion. Hold the zinc bromide over a Bunsen flame and heat gently to melt (melting point 394’ C.)> and remove all water. Avoid excessive heating, as it decomposes the zinc bromide. Seal the tube immediately a t
about 3 cm. from the liquid zinc bromide with an oxygen gas torch and allow to cool in a slanted position, to prevent flow of the zinc bromide to the sealed end of the vial. A large number of these vials can be prepared in a short interval and stored in a desiccated jar for use as needed. Isopropyl alcohol, analytical reagent grade. Treat and distill over 2,4dinitrophenylhydrazine. 2,4-DinitrophenylhydrazineJanalytical reagent grade. 2,4-Dinitrophenylhydrazine Reagent. Heat gently, while stirring, 9 grams of 2,4-dinitrophenylhydrazine in 1 liter of 2N hydrochloric acid in distilled water until completely dissolved. Do not reflux the solution. 2,4-Dinitrophenylhydrazine that does not go completely into solution under the above conditions is not satisfactory and should be used only after recrystallization from carbonyl-free methanol. Stopper the flask and allow to cool to room temperature. Filter through glass wool t o remove any precipitated solid and store in a glass-stoppered reagent bottle. This reagent is fairly stable; however, decomposition occurs after long storage, resulting in the formation of a dark precipitate. Discard the reagent when it shows signs of decomposition. PROCEDURE
Weigh 2.0 to 3.5 grams of the oxide in a 50-ml. ground-glass-joint Erlenmeyer flask with a spout. Add 5 ml. of
dry benzene by means of a dry pipet, followed by anhydrous olefin a t least 10% by weight of a-epoxide taken for analysis, and stopper the flask. The olefin added could be the corresponding olefin or preferably any liquid olefini.e., a-pinene, a-methylstyrene, or diisobutylene-which can be delivered readily by a pipet. Do not add olefin if it is present in the sample to be analyzed. Break a vial containing the fused zinc bromide in two parts and immediately add the half containing the catalyst to the benzene solution. Attach the flask to an air-cooled condenser equipped with a drying tube containing calcium chloride. Lower the flask in an oil bath a t 98" i 0.1" C. and heat for 10 minutes with occasional stirring. The reaction is vigorous and proceeds almost instantaneously as soon as the solution attains the desired temperature. After 10 minutes remove the flask from the oil bath and cool to room temperature by immersing in a beaker of cold water. 'iVash the condenser with carbonyl-free isopropyl alcohol. Transfer the contents of the Erlenmeyer flask quantitatively to a 100-ml. glassstoppered volumetric flask by surcessively -washing both Erlenmeyer flask and zinc bromide vial with small portions of isopropyl alcohol and make up to volume. Add 3 to 4 ml. of this solution, measured accurately with a pipet, slowly to a 150-ml. beaker containing 25 ml. of carbonyl-free isopropyl alcohol and 50 ml. of 2,4-dinitrophenylhydrazine reagent. Stir the mixture constantly with a glass rod during addition of the aldehyde solution. Cover the beaker with a watch glass and heat a t 50" t o 60" C. in a water bath for 5 to 10 minutes, then place in an ice bath for 1 hour. Filter the solution through a preweighed dry 30-ml. medium-porosity fritted-disk crucible and transfer the precipitate quantitatively into it by washing with small amounts of ice-cold 2N hydrochloric acid solution. After complete transfer, wash the precipitate with 50 ml. of cold 2N hydrochloric acid solution. -4110~ air suction for a few minutes to remove any excess hydrochloric acid and then dry to constant weight in a vacuum oven a t 50" C.
Calculation. c;
a-epoxide =
Table
I.
Determination of a-Epoxides with a Tertiary Carbon Atom by Catalytic Isomerization
% a-Epoxide Found Compound a-Pinene oxide Camphene oxide a-Methylstyrene oxidec 1,2-Diisobutyleneoxide
Catalytic Isomerizations**
EtherHC1
99 9 7k 0 3 ( 6 )
33
100 0 =k 0 4 (3) 80 1 i 0 1 (3)d 99 8 & 0 2 ( 7 )
35 28
75
rlcetic acidHBr 34 35 28
PyriPyridinium dinium chloride- chloridechloroform pyridine
75
Compound a-Pinene oxide Camphene oxide a-Methylstyrene oxide 1,2-DiisobutyIeneoxide
Factor 0.458 0.458 0.427 0.416
RESULTS AND DISCUSSION
The a-pinene, oxide, camphene oxide, IJ2-diisobutylene oxide, and an 80% solution of a-methylstyrene oxide in a-methylstyrene used in the development of this method were prepared in the Becco Research and Development
27 -7
I I
Figures in parentheses represent number of determinations. Olefin 10% of weight of a-epoxide taken for analysis was added 80% in a-methylstyrene. No olefin added. Table 11.
Effect of Olefins on Recovery of a-Epoxides
Compound a-Pinene oxide Camphene oxide 1,2-DiisobutyIeneoxide 5
b
% a-Epoxide Found No olefin Correspondinga,* addeda olefin added 98 2 (4) 99 9 zI= 0 . 3 (6) 96.6 & 0 . 3 (3) 100.0 f 0 . 4 (3) 99.8 f 0.2 (7) 94.8 0 . 9 (5)
*
Figures in parentheses represent number of determinations. 10% of weight of a-epoxide taken for analysis.
Laboratories. All a-epoxides, except a-methylstyrene oxide, were purified by fractional distillation under reduced pressure through a Todd column 90 em. long. The a-methylstyrene oxide was used as an 80% solution. The isomerization reaction proceeds vigorously a t 98" C. with catalytic amounts of less than 1% by weight of fused zinc bromide in anhydrous benzene as solvent, to give the corresponding aldehyde. The cessation of vigorous reflux and bubbling could be used as a criterion of completion of the isomerization. The results are highly reproducible and the accuracy is usually within 1% (Table I). The results obtained by the ether-hydrochloric acid (1I), acetic acid-hydrobromic acid ( S ) , pyridinium chloride-pyridine (9), and pyridinium chloride-chloroforni (9) methods were considerably lower than theory and highly dependent on the rate of addition of reagent, sample size, and amount of
Applicability of this method to variable concentrations of a-epoxides was tested by preparing known concentrations of a-pinene oxide, camphene oxide, 1,2-diisobutylene oxide, and a-methylstyrene oxide ranging from about 11 to 90% in a-pinene, camphene, 1,2diisobutylene, and a-methylstyrene, respectively (Table 111). The gravimetric determination of the resulting aldehyde as the 2,4-dinitrophenylhydrazone in principle is that of Iddles and Jackson ( 8 ) . Substitution of isopropyl alcohol in place of ethyl alcohol and adjustment of the ratio of isopropyl alcohol to 2,4-dinitrophenylhydrazine reagent were necessary to obtain accurate and consistent results.
Table 111. Determination of Variable Concentrationsof a-Epoxides in Corresponding Olefins
weight of 2,4-dinitrophenylhydrazone X factor X 100 weight of sample used in aliquot
The following factors are used in the gravimetric determination of the aepoxides.
26 12
29 3 26 75
moisture present in t,he reagent, as the apparent properties of these compounds indicate (1, 2, 5, IS). As the reaction is carried out in the presence of air, the aldehydes are oxidized to their corresponding acids to an extent of 5 to 10%) unless about 10% by weight of the corresponding olefin is present. The inhibitory effect of the olefin on the air oxidation of the aldehydes is indicated in Table 11. No comparison on the isomerization of pure a-methylstyrene oxide with a-methylstyrene is given because of the unavailability of the relatively unstable, pure epoxide.
a-Epoxide, Wt.
$70
R P-
Compound
Camphene oxide
a-MethyMyrene oxide
Added covered
32.0 45.5 82.1 93 0
32.8 45.1 82.4 92.8
20.1 48.5
20.0 48.4
80.1
l,2-Diisobutylene oxide
11.9 36.3 52.5 66.4
92.5 VOL. 29, NO. 1 1 , NOVEMBER 1957
80.1 11.8
36.4 52.6 66.5 92.7
1667
Solvents like hexane, ether, and chloroform did not interfere nor indicate any slowing in the apparent reaction rate of the isomerization of these aepoxides when present in the sample. Sobrerol in concentrations up to 15y0 did not interfere when added to a-pinene oxide, but greater concentrations increased the isomerization reaction period from 10 to 20 minutes for a-pinene oxide. Water and alcohol interfere, as expected, because of hydration and alcoholysis as a side reaction, and the apparent isomerization reaction rate is retarded. The unepoxidized olefins in concentrations from 1 to 100% did not interfere. The purity of the 2,4-dinitrophenylhydrazine is important, as it affects the ease of formation and quantitative precipitation of the corresponding 2,4dinitrophenylhydrazones, especially in the case of the two terpene aldehydes. When 2,4-dinitrophenylhydrazine containing small amounts of impurities was used in preparation of the 2,4-dinitrophenylhydrazine reagent, determinations gave values only about 40 to 50% of theory. When the same batch of 2,4dinitrophenylhydrazine was recrystallized from carbonyl-free methanol and the reagent was prepared from it, recoveries of the 2.4-dinitrophenylhydrazones of campholenic aldehyde and camphenilanaldehyde were quan2,4-Dinitrophenylhydrazi11e titative. obtained from the Eastern Cheniical
Corp. did not require recrystallization. Other grades of Z14-dinitrophenylhydrazine tested necessitated recrystallization. a-Pinene oxide, camphene oxide, l,%diisobutylene oxide, and a-methylstyrene oxide were also isomerized by use of zinc chloride and ferric chloride; however, the reaction rate with these catalysts was slower. The catalytic effect of zinc bromide, zinc chloride, and ferric chloride on the apparent reaction rate of isomerization of these epoxides appeared to be of the following order: ZnBrz > ZnClz>> FeC13. The above method can be used in differentiation and determination of 1.2-diisobutylene oxide in 2,3-diisobutylene oxide, as the latter showed no isomerization to the corresponding aldehyde or ketone under the *conditions of the test. The 2,4,4-trimethylpentanal obtained from isomerization of the 1,2diisobutylene oxide, in this case, is determined by the free hydroxylamine method (IO),as use of the highly acidic 2,ldinitrophenylhydrazine reagent results in some isomerization of 2,3diisobutylene oxide. As this method does not differentiate between an aldehyde or ketone from the epoxide, a correction for the amount of aldehyde or ketone present in the sample to be analyzed is necessary. ACKNOWLEDGMENT
The author is grateful to Frank P.
Greenspan and Ralph J. Gall for their review and criticism of this work and to members of the Research Department who prepared the epoxy compounds. LITERATURE CITED
Arbuzov, B., Ber. 68B,1430 (1935). Arbuzov, B., Zhur. ObshcheZ Khim. 9. 2.55 - - - fl939). -
I
\ - - - - I
Durbetaki, A. J., ASAL. CHEM. 28,2000 (1956). Durbetaki, A. J., J . Am. Oil Chemists’ SOC.33, 221 (1956). Eltekow. A,. Be?. 16.395 f1883) Gasson,‘ E.’ J., Graham, A. R., Millidge, A . F., Robson, I., Webster, R., Kild, A. M., Young, D. P., J . Chem. SOC.1954, 2170. Gasson, E. J., Millidge,‘ A. F., Primavesi, G. R., Webster, W., Young, D. P., Ibid., 1954,2161. Iddles, H. A , , Jackson, C. E., IND. ENG.CHEIM.,ANAL. ED. 6, 454 (1934). (9) Jungnickel, J. L., Peters, E. D., Polgar, A,, Weies, F., “Organic Analyeis,” Vol. I, pp. 127-54, Interscience, Sew York-London, 1953.
(10) Knight, H. B., Sxern, D., J . Am. Oil Chemists’ SOC.26,366 (1949). (11) Swern, D., Findlep, T. W.,Billen, G. N.. Scanlan, J. T.. A 4 ~ ~ ~ . CHEV.‘19.414 f194i). (12) Tiffeneau, 61., Ann. chzm. [8] 10, 322 (1907). (13) Winstein, S., Henderson, R. B., “Heterocyclic Compounds,” Elderfield, Vol. I, pp. 1-60. Wiley, S e w York, 1950. RECEIVED for review January 19, 1967. Accepted June 13, 1957.
Simultaneous CompIexometric Determination of Copper and Mercury KElHEl UENO Research laboratory, Dojindo &
Co., ltd.,
A procedure has been developed for the complexometric determination of copper(l1) and mercury(l1) in mixtures. An excess of (ethylenedinitril0)tetraacetic acid (EDTA) is added to the sample; unreacted EDTA is back titrated with the standard copper solution using murexide as an indicator. Potassium iodide is added to the titrated solution to decompose the mercury-EDTA chelate, and the liberated EDTA i s again titrated with the standard copper solution. The first titer corresponds to the sum of copper and mercury, and the second titer to mercury. The method is simple and accurate, and is recommended for the routine control work. 1668
0
ANALYTICAL CHEMISTRY
Kumamotoshi, Japan
S
THE IA-TRODUCTION of complexometric titrations, most polyvalent cations can be determined by a volumetric method. Thus, copper(I1) can be titrated with (ethylenedinitril0)tetraacetic acid (EDTA) using murexide ( 5 ) , pyrocatechol violet (7, 8) or 1-pyridyl-2-azonaphthol (1) as indicators; mercury(I1) can be titrated USing Eriochrome Black T as an indicator (6). However, t o determine copper and mercury simultaneously, no complexometric procedure has been reported in the literature. One of the reasons may be the lack of a suitable indicator. Although Eriochrome Black T is a good indicator for mercury(II), copper(I1) seriously IKCE
interferes if present. hIurexide, which is suitable for the copper titration, is not sensitive to mercury(I1). Similarly, pyrocatechol violet and l-pyridyl-2axonaphthol are not suitable indicators for the mercury(I1) titration. This work reports the rapid complexometric determination of copper(I1) and mercury(I1) in mixtures. REAGENTS
Standard EDTA Solution, 0.01M. Dissolve 3.8 grams of disodium dihydrogen (ethylenedinitri1o)tetraacetate dihydrate (reagent grade) in distilled water and dilute t o 1 liter. Standardize the solution against the stand-
