Table IV.
Determination of Uranium in Diverse Materials
Uranium Found, PAR method, yo 0.30 0.30" 25.9 25.6a 16.1 16.2" 14.8 14.7" 8.42 8.48" 0.044 0.043" 0.026 0.0286 0.OlG 0.01@
Present,b Sample % 0.30 UOz-Th02-Be0 U-Al alloy 25.6 Uranium ore 1 15.9 Uranium ore 2 14.4 Uranium ore 3 8.50 Uranium ore 4 0.046 Uranium ore 5 0.025 Uranium ore 6 0.014 Direct spectrophotometric method. Determined by a.c. polarography, (6). c Samples decomposed with HClO, HZF2, and uranium separated by chelating resin. Vanadium reduced with ascorbic acid before spectrophotometric determination. Fuel element pellet.
+
zirconium, iron, chromium(III), and silicon. Zirconium may be effectively masked with meso-tartaric acid, and iron can be tolerated in reasonable amounts if absorbance measurements are made within 10 minutes of mixing. Vanadium may be reduced to the tetravalent state with ascorbic acid. Dowex A1 chelating resin is capable of removing trace metals from solutions of high salt concentration (4). In the presence of CyDTA a t pH 3, uranium is still quantitatively adsorbed by the
resin, but most other elements pass into the effluent (Table 111). Using this technique, uranium can be separated, if necessary, from many of the elements which interfere in the direct method (Table 11). Vanadium(V), however, is also retained on the column, and leads to high results. Applications. I n Table I V the PAR method has been applied to the determination of uranium in some materials commonly encountered in nuclear technology, and the results
compared with those obtained by a highly precise a.c. polarographic method ( 5 ) . In the authors' laboratories, a wide range of chemical engineering and processing samples are now analysed on a routine basis using the P.4R spectrophotometric procedure. The high sensitivity of the PAR method often allows uranium to be determined without a preliminary separation. This has resulted in a considerable saving of analytical time. LITERATURE CITED
(1) Busev, A. I., Ivanov, V. M., Vesfnik Muskov. Univ., Ser. Khirn. 1960, No. 3, 52. (2) Cheng, K. L., ANAL.CHEM.30, 1027
(1958). (3) Cheng, K. L., Talanfa 9,739 (1962). (4) Dow Chemical International Ltd., Midland, Mich. Dowex AI chelatingresin Manual (1959). (5) Florence, T. M., Shirvington, P. J., Australian Atomic Energy Commission Repf. TM/153 (1962). (6) Geary, W. J., Nickless, G., Pollard, F. H., Anal. Chim. Acfa 26,575 (1962). (7) Gill, H. H., Rolf, R. F., Armstrong, G. W., ANAL.CHEM.30, 1788 (1958). (8) Pollard, F. H., Hanson, P., Geary, W. J., Anal. Chim. Acta 20,26 (1959). (9) . , Sandell. E. B.. "Colorimetric Metal Analysis," 3rd ed., Interscience, New York, 1959. RECEIVEDfor review March 21, 1963. Accepted June 27, 1963.
Characterization of Alkyl and Aryl Halides by 2,4Dinitrophenylhydrazones of Aldehydes from Reaction of Their Grignard Reagents with Dimethylformamide JACOB G. SHAREFKIN and ALEX FORSCHIRM Brooklyn College o f the City University o f New York, Brooklyn, 70, N. Y.
b A wide variety of aliphatic and aromatic halogen compounds have been characterized by forming aldehydes having one additional carbon atom, which aldehydes are then converted to their 2,4-dinitrophenylhydrazones. The latter were purified by recrystallization from different solvents and their melting points determined and compared with literature values. The basic reaction, formylation of the Grignard reagent with dimethylformamide, is carried out in a test tube in 1 hour and does not require elaborate equipment. A number of compounds, not before characterized in this way, are reported. Reaction was not obtained with allylic halides, some tertiary halides, and halides with electron-attracting substituents. IDENTIFICATION of a compound in qualitative organic analysis requires the preparation of one or more solid derivatives that are raINAL
1616
ANALYTICAL CHEMISTRY
pidly prepared and purified, melt between 50' and 250' C., and are obtained in good yield with a minimum of side reactions (14). The derivatives now available are limited to either aliphatic or aromatic monohalogen compounds and a general reaction for both types using common reagents and simple equipment would be advantageOUS.
Primary and secondary aliphatic and alicyclic halides have been characterized as their mercuric halides, N-alylphthalimides, anilides, toluidides, naphthalides, and a-naphthyl ethers, but these methods are too specific and also are accompanied by experimental difficulties. More recently, thiourea has been reacted with alkyl bromides and iodides to give S-alkylthiouronium salts that are precipitated 8s their picrates. Ethylene thiourea has been employed to form S - alkyl - 2 - mercapto - 4,5 - dihydroglyoxalinium salts that are identified by
their melting points and those of their picrates, as well as volumetric determination of their equivalent weights and those of their free bases formed by reaction with aqueous ammonia ( 5 ) . The carboxylate anion of methyl fluorene-9-carboxylicacid, readily generated from its methyl ester, reacts rapidly with alkyl halides to give good yields of 9-alkyl derivatives that have sharp melting points (1). Derivatives of aryl halides are more limited inasmuch as they are prepared by electrophilic ring substitution to form nitro or sulfamido compounds. Chloro- or bromo-substituted benzenes having alkyl side chains are generally oxidized to corresponding benzoic acid derivatives. The greater reactivity of iodobenzene has made possible the formation of polyvalent iodine derivatives that are aryl iododichlorides ( l a ) , and also iodoxy and iodoso compounds as well as iodoso diacetates (19). The Grignard reaction to characterize
alkyl halides by formation of an aldehyde was applied by Fales ( 6 ) , who added Grignard reagents to the double bond of 6-methyl-3-;olyl-3,4dhydroquinoline. The adduct gave aldehydes with one more carbon than the alkyl halide and the carbonyl compounds were characterized as the,r dinitrophenylhydrazones. Methods of converting alkyl halides to aldehydes with a Grignard reagent reviewed by Smith and Nichols (15) include the action of excess ethyl formate ( 7 ) , ethyl orthoformate (2, 16, 17:, ethoxymethyleiieaniline ( 1I ) , carbon disulfide and semicarbazide (18-21) and Bouveault's use of disubstituted formamides (4). Although the Bouvoault reaction (3) for forming aldehydes from the Grignard reaction with dialkylformamides is quite complex, it presented the opportunity to use inexpensive, commercially available, and relatively-pure dimethylformamide. The metl-od also seemed to be applicable to both aliphatic and aromatic halogen conipounds, and the aldehydes thus produced should be readily identified since their 2,4-dinitrophenylhydrazones are described in the literature. I
RX
+
ROR
I-ICON( CI&)2
Mg-RMgX
The reducing action of the Grignard reagent may also conivert the dimethylformamide to a tertiaiy amine, but this product does not reac:; with the reagent and is easily separated.
+
2RMgX HCO-N(C!HI)I -L R&H--N(CHr)* MgO
+
+ MgXi
Other side reaction:; may result from the presence of another functional group in the halogen compound which also reacts with the Grignard reagent. Allylic compounds also present problems because of their rapid coupliiig reaction to form diallyls when the Grignard reagent is formed. Thl? allylic Grignard reagents are usually prepared under special conditions that involve a large excess of magnesium, dilute solution, slow halide addition, and long reaction time in an inert atmosphere. The preparation of benzyl magnesium halides is usually accomplished with freshly distilled benzyl halides. Another limitation of the Grignard reagent is the incrtne:s of fluorine com-
pounds and vinyl-type compounds with the chlorine atom on an unsaturated carbon atom. However, chlorobenzene does react if tetrahydrofuran is used as a solvent in place of ether and the selective use of solvents makes it possible to prepare a Grignard reagent with a bromine or iodine substituent on the ring while a second chlorine substituent does not react. EXPERIMENTAL
Reagents. Halogen Compounds. All halogen compounds were Eastman Grade (highest purity) of Distillatioil Product Industries. They were used without further purification except as noted in the experimental section. Magnesium. The magnesium turnings were from Dow Chemical and were listed a t 99.9% pure. They were stored in a tightly-sealed bottle and used without further treatment. Ether. Anhydrous, -4CS grade was stored over calcium hydride in an amber bottle that was fitted with a drying tube containing Drierite. Tetrahydrofuran. This solvent was regular commercial grade from E. I. du Pont de Neniours & Co., and was used without further puri6cation. As with the ether, the residue was discarded and fresh material was used when the volume had decreased by one half. Dimethylformamide. hlerck reagent grade was used without further purification. 2,4-DinitrophenylhydrazineSolution, (0.05M in 234 hydrochloric acid in methanol). This was prepared by dissolving 10 grams of Eastman grade 2,P-dinitrophenylhydrazine in 850 ml. of methanol, adding 170 ml. of concentrated hydrochloric acid with stirring, and filtering the solution. Apparatus. Most of the reactions were carried out in a 25- X 150-nim. borosilicate glass test tube in which was inserted a water-cooled, 6-inch1 semimicro finger condenser. I n some cases, the bulb of a micro thermometer was kept in the reaction mixture and a 5-ml. hypodermic syringe used for slow addition of the solution of halide in ether. For allyl and cinnamyl halides, the syringe was replaced by a Teflon needle valve body to which was attached a hypodermic needle and a piece of glass tubing that permitted automatic dropwise delivery of the solution of halide in ether over a long time period. A combination magnetic stirrer and hot plate was used for simultaneous heating and stirring. Formation of the 2,4dinitrophenylhydrazones was carried out in a 250-ml. Erlenmeyer flask and their recrystallizations in a small test tube. Melting points were determined in open capillary tubes in a ThomasHoover Uni-Melt apparatus and all melting points are corrected values. Procedure. The object of thiq work was to devisea sinipleand rapid method that would yield sufficient solid derivatives for purification by crystallimtion. 'I'he methods outlined below
do not necessarily represent optimal conditions for maximum yield. Procedure A , Total Halide Addition in Ether. Into a clean 25- X 150-mm. borosilicate glass test tube that was thoroughly dried was placed 0.243 gram (0.1 gram atom) of magnesium turnings and 10 ml. of ether. A solution of 0.01 mole of the halide in 10 ml. of ether (0.1 mole) was added to the ether, together with a crystal of iodine. Crushing the magnesium with a flamedried glass rod generally induced reaction. Gentle heating was used when crushing did not initiate reaction. The test tube was stoppered with a clean, dry, watercooled semimicro h g e r condenser and the reaction was allowed to proceed until the vigorous boiling subsided. If considerable magnesium still remained, heating was continued until most of the magnesium reacted. After the reaction mixture had cooled to room temperature, 0.8 ml. (0.1 mole) of dimethylforniamide was added slowly with stirring. This initiated a very vigorous reaction and, in most cases, produced a gelatinous mass. This mass was transferred to a 250-ml. Erlenmeyer flask containing 200 ml. of the 2,4dinitrophenylhydrazine solution. Precipitation of the phenylhydrazone usually occurred immediately. This solution was filtered, the precipitate washed and dried in a desiccator at room temperature, and then weighed. A portion was recrystallized three times from suitable solvents and the meltingpoint determined. Procedure B, Total Halide Addition in Tetrahydrofuran. This was identical with Procedure A except that tetrahydrofuran was used instead of ether as the solvent, Procedure C, Slow Halide Addition in Tetrahvdrofuran. This Drocedure was preferred where equipmknt and time permitted and because it generally produced better yields and reaction with some halides which were inert in Procedures A and B. A 25- X 150-mm. borosilicate test tube was carefully flame dried, and cooled. In it was placed 0.243 gram (0.01 gram atom) of magnesium, a crystal of iodine, and a Teflon-coated magnetic stirring ball. The tube was clamped so that the bottom was about '/4 inch from the top of a magnetic stirrer-hot plate. Into the neck of the tube was inserted a rubber stopper having a micro thermometer whose bulb was immersed in the reaction mass, a semimicro cold finger condenser, and a hypodermic syringe. A solution of 0.01 mole of the halide in 8.1 ml. (0.1 mole) of tetrahydrofuran was drawn into the syringe. (In some experiments the molar ratio of tetrahydrofuran t o halide was 2 t o 1). The stirrer was started, a few drops of ethyl bromide added, and about 5 ml. of the halide solution delivered. Reaction generally started immediately with the temperature rising to about 70" C. The remaining halide solution was added over a period of about '/a hour, after which reaction was allowed to continue for an additional 30 to 45 minutes. The reaction tube was then cooled t o about VQL. 35, NO. 11, OCTOBER 1963
1617
Table I.
Data Obtained f r o m Reactions o f Aliphatic Halogen Compounds
-
__2,4Dinitrophenylhydrazone
Halide 1-Iodoethane 1-Iodopropane 1-Chlorobutane 1-Bromobutane 1-1odobutane 2-Chlorobutane 2-CliloroI~utanc 2-Bromobutnne 2-Iodobutane 1-Chloropentane 2-Chloropentane 2-Chloropentane 1-Bromohexane 2-Bromohexane 3-Bromohexane 3-Bromohexane 1-Chloroheptane 1-Bromoheptane 1-Iodoheptane 1-Chlorodecane 1-Bromodecane 1-Iododecane Allyl chloridef 1-Chlorooctadecane Isobutyl chloride Isobutyl chloride tert-Butyl chloride tert-Butyl bromide iso-Amyl chloride
Grignard product, Propanal Propanal Pentanal Pentanal Pentanal 2-Meth ylbutnnnl KO reaction 2-Rlethylbutanal Halide decomposed Hexanal 2-Methylpentanal No reaction Heptanal 2-Methylhexanal 2-Ethylpentanal 2-Ethylpentanal Octanal Octanal Octanal Undecanal Undecanal Undecanal No reaction Nonadecanal 3-Methylbutanal No reaction 2,2-DirnethylpropanaI 30reaction 4-bfrthylpentanal
R,I.P.,
c.
149 124 107-9 107-8
102-3 12'3-30
1iiL30
Yield, ri
/o
33
61.5 20.3 30 10 35.5 ...
17
Lit.
A A A
Ce .A h
105-6 112-14
8.6 32
103-4
25
A C
124-5
70 18.1 7.2 5,5
55
h C A
122-6 1244 106 106 103 106 106 106
36 21 51.5 41.8 35 ...
104-6 122-3
9
...
,..
20'3
18.4
... 91
...
7.5
A
139-30 1ii-3,
...
CJ
A A
... 106 ..
106 b c
,4 A A A A A A
C.
O
1.55 123 106 106 106
A
A
...
...
m.p.
Procrdurc
..
...
... d
C
BandC A
a Yo literature value given. Calculated for C12Hi6NI01: C, 51.40; Found: C, 52.04; H, 5.91; N, 18.6. S o literature value eiven. Calculated for CIqH~INd)~: . . . . . . C., 53.10:, Found: C. 53.36: H. 6.34: N. 17.3. S o lit&ature'value given. ' Calculated for ClsH1,NdOd: C, 53.10; Found: C, 53.14; H, 6.37; N , 18.15. d No literature value given. Calculated for C?bHatNlOa: C, 64.90: Found: C, 66.39; H, 9.52; N, 11.0. 0 Ratio of moles of tetrahydrofuran to RX is 2 to 1. f Freshly distilled from calrium sulfate prior to use. Boiling point
106 106 106 106 106 106
123 .. 210 ... 99
H, 5.71; N, '20.0; H., 6.12: N. 19.0: H, 6.12; N, 19.0;
45' C.
2,4-Dinitrophenylliydrazone
~
Lit.
( I-Bromoethy1)-
benzene
Grignard product Cyclopentanal Cy clopentanal Cyclohexanal Cyclohexanal 3-Phenyl-1-propannl
M.P., a C. 162-4 162-3 174 173-4 154
Yield, Ci
31.5 26.5 30 243 20
Procedure ,4
A A .\
C
?.P.#
C. 160-2 160-2 173 172 149-50
S o reaction
...
...
B
...
No reaction
...
...
.A
...
31.5
A
149-50
3-Phenyl-1-propanal No reaction
Phenylacetaldehyde o-Tolylacetaldehyde S o reaction Azelaicdicarboxaldehyde S o reaction
154
l2&3 150-7
... 20.3 28.4
...
...
132-5 ...
5.5
...
DISCUSSION
H, 9.10; S , 12.1;
Table It. Data Obtained f r o m Reactions of Alicvclic and Side Chain Halogen Compounds
Halide Bromocyclopentane Chlorocyclopentane Broinocyclohexane Chlorocyclohexane (2-Chloroethy1)benzene (2-Chloroethy1)benzene ( 2-Chloroethy1)benzene (2-Bromoethy1)benzene Chlorophenetole Benzyl chloride o-Chloro-p-xylene Cinammyl chloride 7,5-Dichloropentane
50" C. and a solution of 0.77 ml. (0.01 mole) of dimethylformamide in 0.8 ml. (0.1 mole) of tetrahydrofuran was slob-ly added. Reaction was very vigorous and the temperature rose immediately to 70" C. &Yfteraddition was completed and the reaction had subsided, the reaction mass was transferred to 200 ml. of 2,4-dinitrophenylhydrazine solution in a 250-ml. Erlenmeyer flask. Precipitation of the hydrazone usually occurred immediately and purification was effected by Procedure A above. Gilman Color Test for Formation of Grignard Reagent. About 1 ml. of the reaction mixture from formation of the Grignard reagent was added to an equal volume of a 1% solution of Michler's ketone in dry benzene and the reaction product was then hydrolyzed by slow addition of 1.0 ml. of water. This was followed by addition of several drops of a 0.2% solution of iodine in glacial acetic acid, which gave a characteristic green-blue color as a sign of positive reaction (8). The data obtained are summarized in Tables 1-111, which list the various aliphatic, alicyclic, aromatic side chain and nuclear substituted halogen compounds used, the aldehydes formed as intermediates, the percentage yields of their 2,4-dinitrophenylhydrazones, and their observed melting points, as well as the values in the literature.
C
Cy C
c
C .1 and C
...
121
Examination of Tables 1-111 shows that characterization of different types of organic halides by synthesizing aldehyde 2,4dinitrophenylhydrazones was widely applicable but that it mas subject to some drawbacks. N o reaction occurred with some compounds, even with the preferred Procedure C (10). Reaction in Tables 1-111 refers to the nonformation of the Grignard reagent which was determined by the Gilman color test (9), and not the reaction with dimethylformamide or the conversion of aldehyde to dinitrophenylhydrazonc:. p-( CHB)&-C~H~
\
CsHsMgBr __+
/=O
p-( CHB)ZS-C~HI
-
C-CsH, / \
-12
CHaCOOIl
p-(CH3)2SC
