V O L U M E 2 7 , NO. 9, S E P T E M B E R 1 9 5 5
1435 proposed method, indicating the presence of 0.38 X 5.44 = 2.07% of ferberite. Additional tests indicated no errors when small amounts of ilmenite and columbite were added to scheelite. H~BNERITE
No methods are described in the chemical literature to distinguish manganese of hubnerite from that of other manganese minerals. Based on experiments indicating that hiibnerite is only slightly soluble in dilute acetic acid containing a small amount of oxalic acid, manganese from most manganese minerals was found to be soluble in the above medium.
I
XFEtt
Figure 3. Oxidation rate of iron(I1) in 50 to 50 mixture of pyrite and siderite at various temperatures
Oxidized iron minerals-such as hematite or limonite-do not interfere with the proposed method in the absence of reducing agents. Occasionally, ferrous-iron minerals other than pyrite or siderite, occur in small quantities in scheelite as gangue material. They are usually silicates, mainly garnets,'with either part of the soluble iron in the oxidized form or easily oxidizable by the roasting procedure a t 400" C. Such a garnet suspected to contain 2% of wolframite was obtained through the cooperation of the Wah Chang Smelting and Refining Co., Glen Cove, X. Y., from the weakly magnetic fraction of a high-grade scheelite concentrate (73oJ, tungst,ic oxide) which was passed through a laboratory magnetic separator. Part, of the iron [1.42y0 iron(II)] was found to be in the ferrous state using the hl-drofluoricsulfuric acid-permanganate titration method (4). Hoviever, after roast'ing, t'he iron(I1) content dropped to 0.38% using the
Experimental. One-gram samples of wolframite concentrates were heated for three 1-hour periods (with intermittent filtration) with 50-ml. portions of 2% acetic acid containing 100 mg. of oxalic acid. The filtrates, after addition of sulfuric acid, were evaporated separately by fuming and the manganese was determined by using the silver nitrate-ammonium persulfate method ( 2 ) . The data (see Table 111) indicate that the solubility of manganese of wolframite in the medium chosen amounts to about 0.4 mg. per 50 ml., and, that none of the wolframites tested contained more than 3% of the manganese in a nonhubnerite form. Since scheelite rarely contains more than 0.20% of manganese, the assumption is that all the manganese round exists in this mineral as hubnerite. REFERENCES (1) Dome, J. D., and Dana, E. S.,"The System of Mineralogy," T'ol. 11, pp. 1064-8, Wiley, New York, 1951. (2) General Servires Administration, U. S.Government Specification P-57R, S o . 53-8482 (1953).
(3) Hillebrand, W. F., Lundell, G. E. F., Bright, €1. A.. and Hoffman, J. I., "Applied Inorganic Analysis," 2nd ed., pp. 446-9, Wiley, Kew York, 1953. (4) Ibid., pp. 912-20. (5) Li, K. C., and Wang, C. Y.. "Tungsten," A.C.S. Monograph No. 94, pp. 284.-95, Reinhold. Sew York. 1947. (6) "Scott', Standard Methods of Cheniical Analysis" (W. H. Furman, editor), pp. 561-2, \-an Kostrand, Xew York, 1939. RECEIVED for rei.ier September 21, 1 9 . X
Arceyteri l i a y 17, 1955.
Use of ~-(4=Ritrobenzyl)pyridine as Analytical Reagent for Ethylenimines and Alkylating Agents JOSEPH EPSTEIN, ROBERT W. ROSENTHAL, and RICHARD 1. ESS Sanitary Chemistry Branch, Chemical Corps M e d i c a l Laboratories, A r m y Chemical Center,
Procedures are described for colorimetrically estimating very low concentrations of ethylenimine and substituted ethylenimines in water and various alkylating materials in a nonaqueous solvent by the reaction of these compounds with y-(4-nitrobenzyl)pyridine followed by alkalinization. The procedure for ethylenimine and substituted ethylenimines is adaptable to routine analysis. Concentrations of ethylamine and ethanolamine (the hydrolysis product of ethy-lenimine) as much as 1000 times that of the ethylenimine do not interfere in the determination. Concentrations of the imines from 0 to 5 p.p.m. produce intensities in color in this reaction which adhere to the Beer-Bouguer law. In nonaqueous medium, the procedure has been applied to a-halogenated esters, diethyl sulfate, alkyl iodides, bromides, and chlorides; and various organic arsenic, phosphorus, silicon, and nitrogen chlorides. The procedure in nonaqueous solvents is recommended for estimation of reactive alkylating materials in the presence oE nonreactive alkylating material, but not vice versa. Development of optimum reaction conditions for individual compounds is recommended.
Md.
OESIGS a n d others ( 8 ) , reported that -y-(4-nitrobenzyl) pyridine, as well as 2- and +benzylpyridine, reacted with methyl iodide to form a salt which yielded a blue dye when treated with potassium hydroxide solution. The dye was assigned the following structure:
-
I \ l e - - S ~ = C H ~ N O I The application of this reaction to the detection of mustard gas \vas first discovered by Brown ( 3 ) . Gehauf ( 5 ) and Braun ( 1 ) utilized the general reaction to detect n number of organic alkylating compounds. The vapors of alkyl halides were adsorbed on silica gel impregnated with y-(4-nitrobenzyl)pyridine. Addition of alkali produced colors varying from blue to violet to brown. The group of compounds detected in this manner included a variety of examples such as diethyl sulfate, butyl thiocyanate, benzene sulfonyl chloride, diphenylchloroarsine, and diethyl phosphorofluoridate. Yo attempt was made to develop a procedure for quantitative estimation of the reacting compounds, or to determine the limits of sensitivity of the test. Swift and others (11)evpanded the qualitative studies of Gehauf and Braun
1436
ANALYTICAL CHEMISTRY
Organic molecules containing -COX, -CH?X, and -OCH2X groupings were found to react similarly. By qualitatively comparing the intensities of colors, the activity of functional groups as summarized as follows: RCH2CH2X > RCH?CHX? > RCHzCX,; ArCH2X > ArX, ROCHJ > ROCH?CH?X; and COCHsX > COX. N o attempt \vas made to correlate the concentration of the alkyl halide with the absorbance of the solution formed following reaction. Holzman ( 7 ) utilized this reaction for the estimation of 2,2'-dichlorodiethyl sulfide and 2,2',2"trichlorotriethylamine. Since a variety of alkylating agents had been shown to form a dye precursor when reacted with y(Cnitrobenzyl)pyridine, it was desirable to investigate these reactions further in order to develop procedures suitable for quantitative estimation. Two procedures are given in this publication. One is carried out in essentially nonaqueous medium and is generally applicable to a large number of organic solvent soluble alkylating materials; the other is carried out in essentially aqueous solution and is specifically for the estimation of ethylenimine and nitrogen or carbon substituted ethvlenimines in water. The procedure for estimation of concentrations of the alkylating material in nonaqueous medium is based upon studies with only one alkyl halide -viz., n-butyl bromide-and may not be the optimum one for other alkylating materials, especially with respect to the time of heating. For specific analyses, the analyst should determine the optimum conditions using the procedure given herein ~ t sa guide. SYMBOLS AND DEFINITIONS
The t e r m transmittance, T , absorbance, A , and molecular extinction coefficient, E,are used in this report as defined by Miller (6). The M301 for any compound is defined as the number of moles of that compound which will react with y(4-nitrobenzyl)pyridine (YBP) under the conditions of the relevant procedure to form a colored solution having 0.301 absorbance (50% transmittance) a t the wave length of maximum absorption in a cell of 1.3-cm. length.
Table I.
Effect of pH of Initial Sdution on Absorbance Initial p H 2.4 2.8 3.2 4.0 4.4 5.0
Absorbance
0.199 0,211 0.215 0.226 0.224 0.220 0.172
5.6 6.0
0.152
reagent. The solutions are mixed m-ell, heated in a boiling water bath for 20 minutes, and then cooled in an ice-water bath. The reaction mixture a t this point is stable for about 30 minutes and the remaining steps in the procedure (including the measurement of color intensity) should be carried out on each tube, one a t a time. Four milliliters of acetone, 1 ml. of potassium carbonate solution, and sufficient distilled water to make up to a volume of 10 ml. are added in rapid succession. The solutions are again mixed well and read immediately a t 600 mb against distilled -a-ater. The absorbance of a reagent blank (0 p.p.m.) is determined as above and subtracted from that of the other samples. The standard curve is constructed by plotting the net absorbances against the concentration of ethylenimine on arithmetic graph paper.
Procedural Notes and Results. The importance of initial pH of the solution containing the ethylenimine was evaluated by tests performed on solutions of ethylenimine in Clark and Lubs buffers ranging in pH from 2.4 to 6.0. The absorbances found after reaction are shown in Table I.
Table 11.
Absorbance of Solutions Heated for Different Periods Heating Period, Mn. 5 10
15 20 25 30
Absorbance
0 262 0 300 0 306 0 311 0 307 0 315
APPARATUS
Coleman Universal sDectroDhotometer (Model 11A). Matched square ~ou;ettes.~l.3-cm.light path length. PC-4 filter. R EAGEVTS
r-(4-,\;itrobenzyl)pyridine Reagent. Five per cent of y-( 4 nitrobenzyl)pgridine, recrystallized from cyclohexme, melting point 70" to 71" C., in methyl ethyl ketone or C.P. acetone. Potassium Carbonate Solution, 1-Tf aqueous. Triethylamine Reagent, 50% C.P. triethylamine in :tcetone. Alkylating Agents. All alkylating agents were either purchased as C.P. chemicals or synthesized by standard methods and distilled prior to use. The ethylenimines were obtained from 3Ionomer-Polymer Inr., Chicago, Ill. The materials were distilled prior to usc. The boiling Doints and refractive indices of the distilled compounds
Compound Ethylenimine 2-Ethylethylenimine 2,2-Dimethylethyleniniine N-Ethylet hylenimine Manufacturer's value.
Boiling Point. C./ca. 760 mm. 55.2-56.0 88.0-88.3 68.0-69.0 51 3-52.3
Refractive Index a t 250 1.4088 1.4165 1.4088 1 .3935a
c.
Solutions of the ethylenimine compounds were made up by diluting accurately weighed quantities of the distilled materials to the mark in a volumetric flask. hliquots of the solutions m r e further diluted to give stock solutions containing from 0 to 5 p.p.m. The stock solutions were stable for a t least 24 hours. Buffer Solution, pH 4.0, Clark and Lubs ( 4 ) . ESTIMATIOV O F ETHYLENI'MIUES
Preparation of Standard Curve. To each of a series of calibrated 10-ml. tubes are added 3 ml. of the stock solutions, 1 ml. of the buffer solution, and 1 ml. of the Y-(4nitrobenzyl)pyridine
The absorbances are, within eiperimental error, the same and a t a maximum in solutions of initial pH between 4.0 and 5.0. A maximum and constant absorbance was obtained by heating the ethylenimine nith y-( 4-nitrobenzy1)pyridine agent in a boiling water bath for approximately 15 minutes, but the heating period could be extended to 30 minutes without any definite effect upon the absorbance of the final colored solution (Table 11).
Table 111. Stability of Reaction Product of Ethylenimine and y-(4-Nitrobenzyl)pyridine No. of Detn. 5
5 5
Absorhanres h* aa 0.214 i 0.002 0.210 0.004 50.413 1- 0.004 0.424 i 0.009 0.558 5 0.02 0 . 5 7 5 =t0.02
*
Reaction product between ethylenimine and N B P made alkaline immediately after heated product had been cqoled t o room temperature. b Reaction product between ethylenimme and X B P cooled t o room temperature, allowed t o sit for 30 minutes, and then made alkaline.
A heating period of 20 minutes (see procedure) is therefore not critical. I t may be inferred from these observations that the product of the reaction between ethylenimine and y(4-nitrobenzy1)pyridine is stable. By comparing the absorbances of solutions obtained in tests in n-hich the intermediate had been allowed to sit a t room temperature for zero and 30 minutes prior to alkalinization, the intermediate was found to be stable for a t least that length of time at room temperature (Table 111).
1437
V O L U M E 2 7 , N O . 9, S E P T E M B E R 1 9 5 5 The drop in absorbance over the 30-minute period indicatm a decomposition of 2 to 3%. Measurement of the absorbance immediately after color development is imperative, as the final color fades appreciably with time. However, if the procedure is followed, good reproducibility of absorbances is obtained, as seen by the average deviations from the mean shown in Table 111. Tests performed with the other ethylenimines mere limited to the preparation of standard curves using the recommended procedure. In all m e s , the curves adhered to the Beer-Rouguer law. Dilute solutions of diethylamine and ethanolamine (the hydrolysis product of ethylenimine) did not interfere with the determination of the ethylenimine in concentrations up to 1000 times that of the ethyIenimine. Absorbances obtained in the presence of diethylamine and ethanolamine did not vary from the expected values by amounts greater than those appraised in the absence of these substxxes.
between n-butyl bromide in aqueous solution and y-(4nitrobenzy1)pyridine were unsuccessful presumably because of the insolubility of n-butyl bromide in water in concentrations necessary to give a test. Other solvents, which overcame the solubility factor, were unsatisfactory for various reasons: Ether, cyclohexane, and methyl and ethyl Cellosolves gave colored solutions which faded too quickly; nitrobenzene and nitromethane gave colored solutions cvhen heated with y-(4-nitrobenzy1)pyridine in the absence of alkyl halides. Methyl ethyl ketone and acetone were satisfactory and the former was chosen because of its higher boiling point. Addition of varying quantities of acid quickly revealed that acid promoted the decomposition of y-(4-nitrobenzy1)pyridine without assisting the reaction between it and the alkyl halide. The color intensity of both the sample and the blank increased with increasing concentration of acid.
500
ESTIMATIOK OF ALKYLATING AGENTS IN NONAQUEOUS SOLUTIOX
Preparation of Standard Curve. To G ml. of a methyl ethyl ketone solution containing different quantities of alkylating agent in dry round-bottomed flasks is added 5 ml. of y-(Cnitrobenay1)pyridine reagent. (A significant amount of watere.&., 1 ml., was found to have an effect on the results, and whereas it was not necessary to keep reagent>sand equipment absolutely water-free, some care was taken to keep water out of the reaction.) Two glass beads are added to the flask, and the flask is connected to a condenser, refluxed for 45 minutes in a boiling water bath, and then cooled for 1 minute in an ice-water bath. Five milliliters of acetone is added through the condenser and alloJved to drain for 1 minute into the flask. The condenser is separated from the flask, 1 ml. of triethylamine reagent is added, arid the solutions are mixed well. The purple color, which appears immediately, is read within 2 minutes after addition of the triethylamine reagent a t 565 mp. A l l concentrations of the samples, including bltanke (no alk!-lating agent) are measured against distilled water. Procedural Notes and Results. The variation in reactivity of alkylating w e n t s e0 nitrogen compounds ( 2 , 9, I O ) is \vel1 known. This pi oredure was developed using a comparatively unreactive alkyl halide-via., la-butyl bromide --and henre may not be the optimum procedure for others .ittempts to cause the reaction
Table IV. Moles of Alkyl Halide Required to Produce Colored Solution Having 0.301 Absorbance Halide
Series
Iodide
h-ormal
Bromide
Normal
Alkyl Group Ethyl Butyl Amyl Propyl Butyl A111yl
Is0
Secondary Twtiary Chloride
Fluoride Cyanide Bromobenzeac
Xorrnal
Normal Nornial
Hexyl Heptyl Decyl Ally1 Benzyl-(=-bromo-toIuene) 2-3leti~ylbenayl Butyl Amyl Isopropyl Butyl Octyl Butyl Butyl Amyl Benzyl p-hiethylbenzyl p-Sitrobenzyl .4myl Amyl
31301 1 0 x 10-6 7 o x 10-7 3 7 x 10-7 8 . 2 X 10-6 5 . 3 x 10-4 3 . 3 x 10-4 1 . 3 x 10-E 7 . 4 x 10-5 2 . 8 x 10-7 3 . 0 x 10-7 1 . 5 X 10-7 1 5 x 10-7 8 1 X 10"
7 t i x lo-' 1 . 3 x lo-'
x x 2 o x 6 6 x 4 4 x 4 9 x 2 2 x 2 5 x
5.5 4.6
210-2 > 10 - 3 >10-a
10-6 10-4
10-4 10-4 10-4 10' 10-7
10.:
,400
300
E
z5 E2
f
,200
,100
0 1
2
3
MOLES
4
x
5
6
7
10;
Figure 1. Calibration curves of some organic halides
The concentration of y-(4-nitrobenzj-l)pyridinerecommended in the procedure was chosen because under the conditions of the esperinient-i.e. a 45-minute reflux-blank determinations using this concentration of y-(Cnitrobenzyl) pyridine gave transmittances of 95% or greater, and this concentration produced a maximum reaction with n-butyl bromide in 45 minutes. A linear absorbance us. concentration of alkyl halide was obt:iined even if 2 ml. of water was added to the reaction mixturci prior to reflusing. A slight increase in sensitivity was observed by addition of water, but was unnecessary, except in the cnse of the 2,2',2"-triehlorotriethylamine and arsenic halides, where omission of wat,er produced nonreproducible results (see Table VII). As alkalizing agenk, potassium carbonate, piperidine, and sodium bicarbonate gave colored blanks, while pyridine failed to produce a color with the samples. Ammonia solution formed colorless blanks and highly colored solutions with the ~
1438
ANALYTICAL CHEMISTRY
samples, but gave inconsistent results, probably due to the difficulty in reproduction of ammonia concentrations. In contrast, triethylamine, which is less volatile, gave intensities of color which were reproducible and stable for a t least 5 minutes. Figure 1 shows typical graphs of absorbances of solutions us. concentrations of various halides. The sensitivities of the various halides in this procedure are given in the last column of Table IV. From the data in Table IV it can be seen that in an homologous series the sensitivity of the test increases with increase in molecular weight, in a series of halides having the same halogen and number of carbon atoms, the sensitivity follows the order normal > is0 and secondarv > tertiary, and in a series of halides having the same alkyl groups, sensitivitv follows the order iodide > bromide > chloride. n-Amyl fluoride, n-amyl cyanide, and bromobenzene in concentrations as high as 10-2, 10-8, and 10-3 mole, respectively, failed to react under the test conditions.
Table V. Observed Absorbances from Mixtures of n-Amyl Bromide and n-.4myl Chloride Reacted with ?-(&Xi trobenzy1)pyridine Moles of n-Amyl Bromide Present
1.4 X 10-6 1.4 X 10-8
1.4 X 10-6
1.4 X 10-6 1.4 X 10-6
AIoles of n-Amyl Chloride Present
0.8'X'lo-~ 1.6 X 10-5 3.2 x 10-6 G . 4 x 10-6
Observed Absorbance
Absorbance" Increase Due t o n-.kmyl Chloride
0.163 0.164 0,192 0.211 0.232
0.029 0.048 0.069
0:001
a Figures should be directly proportional t o concentration of n-amyl chloride. Errors inherent in analysis are believed t o be responsible for deviations of observed from theoretical values.
The differences observed in A1301 values of two halides having identical alkyl groups suggests the possibility of estimating the concentrations of one halide in the presence of another. As an example, the absorbances of mixtures of n-amyl bromide and namyl chloride, after reaction with y(4-nitrohenzy1)pyridine and subsequent color development, are shown in Table V. Several experiments with mixtures showed that the calculated sum of the absorbances due to the individual components and the observed absorbance were within experimental error-Le,, the absorbances were additive. If in the analysis for n-amyl bromide an increase of 0.008 (5% of 0.163) in the absorbance ip allowable, then between 0.8 and 1.6 x 10-6 mole of n-amyl chloride can be present without seriously interfering with the accuracy of the analvsis. Thus, it is possible to estimate the concentration of n-amyl bromide in the presence of a t least as much as five times the concentration of n-amyl chloride. The rmctivities of several alpha-halogenated ester* in this reaction may be compared by reference to Table VI.
Table VI. Moles of Ester of wHalogenated .4cicl Required to Produce a Colored Solution Having 0.301 Absorbance Compound Methyl fluoroacetate E t h y l chloroacetate E t h y l bromoacetate E t h y l trifluoroacetate
AI301 10-4 10-6 1 lo-' 2 1 10-3 2
c x 9 x 1 x ox
Although the number of compounds in the series tested is far too small to allow any general conclusions, it appears that the carboalkoxyl group activates the halogen-containing compound, as shown by a comparison of the M301 of methyl fluoroacetate (Table VI) with that of n-amyl fluoride (Tahle IV). It also appears that, just as was found in the alkyl halide series, the bromo compound has a lower 31301 than the chloro compound in
this reaction. The presence of more than one fluorine atom on the same carbon seemed to increase the 111301 of the compound, as is roughly shown by a comparison in the M301 of the methyl fluoroacetate and ethyl trifluoroacetate. I n Table VI1 are given the 11301 results of diethyl sulfate, benzoyl chloride, and organic compounds of nitrogen, phosphorus, arsenic, and silicon. The reaction with benzoyl chloride was almost instantaneous; a yellow solution, with an absorption maximum a t 457 mp, m s formed without the addition of base. The 45-minute heating period did not increase the color. This reaction could be used for spot test detection a8 well as quantitative estimation. With triethoxychlorosilane, diethoxydichlorosilane, trimethylchlorosilane, phenyltrichlorosilane, and methylt~ichlorosilane,a plot of the concentration of the silicon compound against the absorbance of the solution was not linear and hence the proceduie cannot be recommended for quantitative work. In the cases of diphenylchloroarsine, phenyldichloroarsine, dimethylchloroarsine, and methyldichloroarsine, the addition of a small quantity of n-ater to the reaction mixture and use of a 20-minute heating period increased the sensitivity of the test. Chloramine T was tested and gave no color, xheresa 20% dichloramine T in glyceryl triacetate gave a color which did not come from the solvent. p-Dibromo- and p-diiodoarsinobenzenesulfonamide gave light colors, but were not studied because of their insolubility in methyl ethyl ketone. 2,B-Dichloroquinonechlorimide gave no color in the reaction other than a red color caused by its own reaction Tvith base NATURE AND EXTEhT O F RE4CTION
Holzman ( 7 ) isolated and identified the intermediates of the reaction between 2,2'-dichlorodiethyl sulfide and y-( 4-nitrobenzy1)pyridine. He reported that the sequence of reactions are as given in the following equations: H+NBPC1-( CH?)?S-( CH,)--S
+ C1-
+ O - C H z o - S O 2 ~
/OH-
Table VII. Moles of J'itrogen, Phosphorus, and \Iiscellaneous Compounds Required to Produce Colored Solution Having 0.301 Absorbance Compound Nitrogen conipounds 2,2'.2"-Trichlorotriethylarninea n-Bromosuccinimide Phosphorns compounds Butoxydichlorophosphite !butvlphosphorodichloridite) h Cyclohexanephosphodicliluride (cyclohexy1phos:ihonic dichloride) b Phenyldichlorophosp!iine (p!ienylphosphonoue dicliloride) b Arsenic compounds Lewisite i d i c h l o r o ~ 2 - c h l o r o ~ 1 n ~ l ~ ~ r ~ i n e l Dipheny16hloroarsine Phenyldichloroarsine Methyldichloroarsine DimethylchloroarsineC Silicon compoundsd Triethoxyc lilorosilane Diet hoxydichlorosiiane Trimethylchlorosilane Pbenvltrichlorosilane hIetkiyltrichlorosilane
\I701 1.3 X 10-7 4.0
x
lo-:
S 0 X 10-6 1 5 x 10-5 5 .Y X 10-6
3.0 X 10-6 6.3 X 10-5 3 x 10-4
s
2.7 X 10-6 6 2
x
10-6
7 . 4 x 10-6 8 . 5 x 10-7 3.3 x 10-4 9 . 3 x 10-4 1 5 x 10-4
Miscellaneous cornpounds 1 1 x 10-7 Diethyl sulfate 2 1 x 10-7 Benzoyl chloridee 2 ml. of water added t o reaction mixture before heating period. b A.C.S. nomenclature. C 1 ml. of water was added t o reaction mixture and 20-minute heating period was used. d Approximate values only as plot of absorbance against concentration was not a straight line. Aleasured a t 457 m p .
1439
V O L U M E 27, NO. 9, S E P T E M B E R 1 9 5 5 where H = Cl-( CH&-S-(
CH2)2-C1
The colored materials formed in the reaction between butyl, heptyl, and dacyl bromides with y-(4-nitrobenzyl)pyridine were isolated by the present authors. Elemental analyses (by Analytical Branch, Chemical Corps Chemical and Radiological Laboratories, Army Chemical Center, R‘Id.) of the dyes for carbon and hydrogen a g r e l y well with those calculated for the
and Larsen and Kraus (9) in the study of the reaction of alkyl halides with tertiary amines. This discrepancy may be due to different temperature sensitivities of the reaction products n-ith y(4-nitrobenzy1)pyridine. It is well known, for example, that prolonged heating tends to destroy the dye precursor, resulting in less than masimnl color yields.
Table VIII. Dyes Formed from Reaction of y-(4-Yitrobenzyl)pyridine with Alkyl Bromides
7 ,
(R being butyl,
structure OtN---CH=(=_)N-R heptyl, or decyl) (Table VIII).
Alkyl Group Butyl Heptyl Decyl
-8-,
Analysis %C 7cH Calcd. Obsd. Calcd. Obsd. 71.0 G9.2 6.7 G.3 69.7 7.4 7.15 73.3 74.2 8 5 8 4 74.6
Molecular Extinction Coefficient, Cm. Mole/Liter 2 . 8 2 x 104 3.30 x 104 3 . 0 4 X 10‘
G E U E R A L APPLICABILITY AND L I M I T A T I O N S
I 350
4M
55c
650
750
WAVE L E N G T H ( M p )
Figure 2. Absorption spectrum of alkyl halide-y-(4-nitrobenzyl)pyridine D y e dissolved in solution containing 6 ml. of methyl ethyl ketone, 5 ml. of acetone, 5 ml. of 5% N B P in acetone, and 1 ml. of 50y0 triethylamine in acetone
The results of this work offer limited but interesting possibilities for the use of y-(4-nitrobenzyl)pyridine. It is limited by the fact that a trace of an impurity of high reactivity in an alkyl halide of comparatively low activity would introduce large errors in the analysis of low activity halides. The method should be applied to estimation of relatively reactive alkyl halides that are pure and of known identity, or to estimation of reactive halides in mixtures containing unreactive halides. Its use to analyze for a relatively unreactive alkyl halide cannot be recommended unless it is definitely knomi that no relatively reactive alkyl halides are present as impurities. The analytical procedure may be used to follow the kinetics of a reaction of a particular alkyl halide. For analysis of concentrations of ethylenimine compounds in air, the gas might be collected in bubblers containing solutions of 0 01M potassium acid phthalate. The y-( 4-nitrobenzy1)pyridine reagent is then added directly to 4 ml. of the collected solution, followed by heat, cooling, etc. The ethylenimine compounds hydrolyze slowly in buffered media, but the extent of hydrolysis is such that changes are not appreciable for a t least 24 hours. ACKNOWLEDGMENT
The molecular extinction coefficients were calculated from absorbance measurements of dye solutions in solvents of the same composition and ratio as those used in the experimental procedure for alkylating agents in nonaqueous medium. The spectral curves of the isolated dyes (Figure 2 ) show the wave length of maximum absorption to be 565 mp. By visual inspection, all alkvlating agents except benzoyl chloride gave the same color. The color produced by the reaction of benzoyl chloride with y-( 4-nitrobenq 1)pyridine has a maximum absorbance a t 467 mw. Under the reaction conditions described for the ethyleninlines, the wave length of maximum absorbance is 600 mp. If it is assumed that the molecular extinction coefficients of the dyes are not dependent upon the alkyl adduct (Table VIII), then under the test conditions the theoretical M301 for any alkyl halide can be shown to be 1.3 X 10-7. For the most reactive halides, the M301 was 1.5 X 10-7. Therefore, for these halides the reaction was, for all practical purposes, complete. The less reactive compounds had M301’s of 10-3 to 10-6. I t is likely that the reaction of y(4-nitrobenzy1)pyridine with ethylenimines is also complete, inasmuch as similar calculations from absorbanceconcentration data show that their M301’s were approximately 1.5 X 10-7. The order of reactivity toward y-(4-nitrobenzyl)pyridine observed in a homologous series of alkyl halides is opposite of that found by Noller and Dinsmore (IO) in the study of the reaction of alkyl bromides with pyridine; Brown and Cahn ( 8 ) in the study of the reaction of alkyl iodides with 4-methyl pyridine;
The technical assistance of Mary M. Demek, William Spall, Jack Florence, and William Duff is acknowledged. LITERATURE CITED
(1) Braun, C. E., Seydel, P. V., Sauer, C. W., Dubin, I. M., Chao,
(2) (3) (4) (5) (6)
(7) (8)
(9) (10) (11)
Y. T., Lemley, J. D., Mass. Inst. of Technol., Cambridge, Mass., MIT-MR No. 177, September 21, 1945 (unpublished data). Brown, H. C., and Cahn, A., Abstracts of Papers of the 119th Meeting of the AM. CHEM.SOC., p. 8M, 1951. Brown, W.G., Office of Scientific Research and Development, OSRD 140, September 22, 1941 (unpublished data). Clark, W. M., “Determination of Hydrogen Ions,” 3rd ed. Williams and Wilkins, Baltimore, hId., 1928. Gehauf, B., Chemical Warfare Service, CWS Field Lab., Memo 1-2-8 (1943). Gilman, H., ”Organic Chemistry. -4n Advanced Treatise,” vol. 111, p. 127, Wiley, Xew York, 1953. Holzman, G., Office of Scientific Research and Development, OSRD 4288, October 27, 1944 (unpublished data). Koenigs, E., Kohler, K., and Blindow, K., Ber., 58B,933 (1925). Larsen, R. P., and Kraus, C. A . , Proc. Aratl. Acad. Sci. U.S., 40, 70 (1954). Koller, C. R., and Dinsmore, R. D., J . Am. Chem. Soc., 54, 1025 (1932). Swift, E. H., Gould, C. W., Holzman, G., Sease, J. W., and Siemann, C., Chemical Warfare Service, CWS Field Lab., LIemo 1-2-16, July 1944 (unpublished data).
RECEIVED for review December 27, 1954. .4ccepted M a y 13, 1955.
