methods of K analysis (8), but they are, in most cases, adequate for ordinary K-Ar work. The accuracy of the determinations carried out by this method can be estimated by comparison with other independent techniques. Results obtained by gamma ray spectrometry and flame atomic absorption on minerals and rock samples from volcanoes of southern Italy and on one pegmatite are reported in Table 111. Determinations by flame atomic absorption have been carried out on three different aliquots of each sample. The reported error is the overall deviation from the mean value. Only one gamma ray spectrometry analysis has been run for each sample. The reported error is twice the standard deviation. Two to three grams of mineral sample and 15-20 grams of whole rock sample have been used. Counting times have been no longer than 24 hours. The agreement between the two methods is, in all cases, better than 3 . 7 x . It should be noted that for 83% of the samples the differences are within the error. K40 determinations can therefore be routinely carried out by gamma ray spectrometry with a satisfactory precision and
accuracy for most minerals ordinarily used for K-Ar work when at least 1-2 grams are available. The method could be still improved by increasing the sample counting rate/background counting rate ratio. This can be accomplished by decreasing the background by the use of crystals and phototubes with low potassium contents and by anticoincidence annuli. The use of the anticoincidence annuli would also decrease the Compton effect contributed by TlZo8and General experimental data on anticoincidence shielding are given in (9). It is not advisable to increase the sample counting rate by including the part of the spectrum below 1.46 MeV. In fact, when lower energies are considered, the increased probability of self-absorption would enhance the effect of differences in densities and atomic numbers between samples and standards thus reducing the accuracy of the method.
(8) P. E. Damon in “Radiometric Dating for Geologists,” E. I.
(9) J. M. Nielsen and R. M. Perkins in “Radioactive Dating and
Hamilton and R. M. Farquhar, Eds., Interscience Publishers, New York, N. Y., 1968.
Methods of Low Level Counting, Proc. of a Symposium,” I.A.E.A., Vienna, 1967, p 687.
RECEIVED for review February 24, 1969. Accepted April 17, 1969. This work was possible through a NATO fellowship to P. Gasparini and a Robert A. Welch Foundation C-009 Grant to J. A. S. Adams and J. J. W. Rogers.
Polarographic Determination of Hydroxylamines and Some Hydrazine Derivatives Palle E. Iversen and Henning Lund Department of Organic Chemistry, University of Aarhus, 8000 h h u s
ANODICPOLAROGRAPHIC WAVES of organic compounds at the dropping mercury electrode have not been used very much for purposes of quantitative analysis (1-4); in a recent review (5) of electrolytic oxidations only a few of such reactions are mentioned. The present method is based on the anodic waves of some hydroxylamines, hydrazines, and hydrazides in aqueous alkaline medium containing sulfite ions and was originally developed (4) for the determination of some electrolytically produced N-alkylhydroxylamines. The work has now been extended to other compounds to find the scope and limitations of this rapid, convenient procedure which offers an alternative to the rather scarce general methods (especially for the hydroxylamines) found in standard handbooks on organic analysis, e.g. (6-8). (1) H. Lund, Talanta, 12, 1065 (1965). (2) I. A. Avrutskaya, V. G. Khomyakov, and M. Ya. Fioshin, Zauod. Lab., 30, 28 (1964). (3) J. Krupicka and J. Zwada, Collect. Czech. Chem. Commun., 32,2797 (1967). (4) P. E. Iversen and H. Lund, Acta Chem. Scand., 19, 2303 (1965). ( 5 ) N. L. Weinberg and H. R. Weinberg, Chem. Reu., 68, 449 (1968). (6) N. D. Cheronis and T. S. Ma, “Organic Functional Group Analysis,” John Wiley & Sons, New York, 1964. (7) A. Steyermark, “Quantitative Organic Microanalysis,” Academic Press, New York, 1961. (8) M. Brezina and P. Zuman, “Die Polarographie in der Medizin,
Biochemie und Pharmazie,” Akademische Verlagsgesellschaft, Leipzig, 1956. 1322
ANALYTICAL CHEMISTRY
C,Denmark EXPERIMENTAL
Apparatus. A Radiometer PO4 polarograph was used with a capillary of m = 1.83 mg/sec and t = 4.35 sec (supporting electrolyte, open circuit) and a water-jacketed cell thermostated at 25 “C. Reagents. Most of the compounds tested were either commercially available or prepared by standard methods found in literature. Some of the hydrazine derivatives were kindly furnished by Dr. Alexander Senning of this laboratory. The N-alkylhydroxylamines were prepared by electrolytic reduction of the corresponding nitro derivatives following published procedures (4, 9), and the same method was adopted for the asymrn. di-substituted hydrazines from the corresponding N-nitrosamines (10). Procedure. Stock solutions were prepared by dissolving 25-35 mg of the substance in 25.0 ml of de-oxygenated water. An aliquot (usually 1.0 or 2.0 ml) is diluted to 25.0 ml with a solution containing 20 g of sodium sulfite and 9 g of potassium hydroxide per liter, the solution transferred to the polarographic cell, and the polarogram recorded at once. The solution to be analyzed is diluted to the same range of concentration before the preparing of the polarographic solutions, and the concentration is determined by means of a standard curve of which only a few points are needed, once a linear concentration dependence has been established. Our experience shows that the most reproducible results are obtained by
(9) P. E. Iversen and H. Lund, Tetrahedron Lett. 1967, (41), 4027. (10) P. E. Iversen, Acta Chem. Scand., to be published.
measuring the height of the wave at the half-wave potential in the case of waves appearing rather near the oxidation potential of the electrode itself.
RESULTS AND DISCUSSION A rather wide variety of available hydrazine and hydroxylamine derivatives has been investigated by the procedure described above. All of the N-alkylsubstituted hydroxylamines investigated till now have shown very well developed waves in aqueous potassium hydroxide solution at pH 13 in the presence of 2 z sodium sulfite. This concentration of sulfite ions was originally (4) chosen because the wave heights of the lower N-alkylhydroxylamines were found to be rather insensitive to changes in the sulfite ion concentration around this value. On the other hand, 0-alkylhydroxylamines were not expected to give anodic waves as they are not reduced by the Fehling reagent (11); 0-methylhydroxylamine and 0-t-butylhydroxylamine have been included in the present study and found not to give an anodic wave. N-acylsubstituted hydroxylamines (hydroxamic acids) were also found to give no anodic waves; the following compounds were tried with negative results : benzhydroxamic acid, p-cyanobenzhydroxamic acid, phthalhydroxamic acid, and isonicotinohydroxamic acid. In Table I the half-wave potentials and diffusion current constants of the investigated hydroxylamines (C = 5 X 10-4M) at 25 "C in alkaline sulfite medium are given. The half-wave potentials of N-monosubstituted hydroxylamines vary only slightly with changes in substituent, but are distinctly different from that of dibenzylhydroxylamine and the unsubstituted parent hydroxylamine. As already pointed out in an earlier paper (4), this difference is great enough to allow simultaneous determination of hydroxylamine and a N-monosubstituted hydroxylamine if the concentrations are of the same order of magnitude. In Tables I1 and 111 the half-wave potentials and diffusion current constants at 25 "C of some hydrazines and hydrazides are given, whose anodic waves are sufficiently well developed in alkaline sulfite solution to be used in quantitative analysis. The half-wave potentials of the hydrazine derivatives are more sensitive toward changes in the structure of the substituents than the hydroxylamines. The differences between the halfwave potentials of the two classes of compounds are mostly great enough to allow a simultaneous determination. In some cases especially at low concentrations (ca. 1 x l O - 4 M ) the waves are extended a little into the cathodic region. The reason for this is not known in detail; however, by measuring the total height of the wave a linear dependence on the concentration was found in the range 10-4-10-3M for all the compounds in Tables I, 11, and 111. At higher concentrations the waves in most cases tend to be lower than expected (e.g., about 2 at 5 X 10-aM for N-benzyl-N-methylhydrazine), but a useful standard curve may still be constructed. For the hydrazine derivatives the picture is somewhat less clear-cut with respect to the applicability of the present procedure. With the exception of o-nitrophenylhydrazine, which in this medium forms 1-hydroxybenzotriazole, and benzylidenehydrazine, which is partially decomposed, all the investigated mono-alkyl- or-acyl-, dialkyl- and acylalkylhydrazines were found to give anodic waves in alkaline medium. Only the asymm.-dialkylsubstituted hydrazines and possibly the lower aliphatic carbohydrazides generally gave well
Table I. Half-Wave Potentials (V us. SCE) and Diffusion Current Constants (@A.I.. mMol-I. mg-*ia.seclla) of Hydroxylamines
2-Phenyl-2-hydroxylaminopropane
3-Methyl-3-hydroxylamino-2-butanol 2-Methyl-2-hydroxylamino-1-propanol 2-Methyl-2-hydroxylamino-l,3-pro-
panediol
Id
0.35 0.48 0.49 0.49 0.48 0.47 0.49 0.47 0.48 0.52 0.47
8.69 4.21 3.36
2.66 2.77 3.03 2.50 2.88
0.51
2.52
0.49
2.62
0.49
2.34
0.49 0.38
2.08 2.31
3.25
3.73 3.28
2-Hydroxymethyl-2-h ydroxylamino-
1,3-propanediol N,N-Dibenzylhydroxylanine
Table 11. Half-Wave Potentials (V us. SCE) and Diffusion Current Constants (PA.1.. rnMo1-l. mg-*i3. ~ e c l / ~ ) of Hydrazines Compound -E112 Id 1,I-Dimethylhydrazine 0.38 3 . 16a 1 ,I-Diallylhydrazine 0.40 3.59 1,I-Diethylhydrazine 0.44 2.15 1,l-Di-n-butylhydrazine 0.48 1.58 1, I-Diisobutylhydrazine 0.49 1.79 N-Aminopyrrolidine 0.46 3.14 N-Aminopiperidine 0.41 1.83 N-Aminomorpholine 0.33 1 . 29a 1-Methyl-1-phenylhydrazine 0.38 4.29 1-Methyl-1 -benzylhydrazine 0.41 1.98 1,2-Dimethylhydrazine 0.39 1.81" 1,2-Di-n-butyIhydrazine 0.39 1 . 88a 2-Carboxyphenylhydrazine 0.47 6.14 4Carboxyphenylhydrazine 0.47 6.01 a
Value uncertain, caused by distorted wave.
Table 111. Half-Wave Potentials (V us. SCE) and Diffusion Current Constants (PA .I. .mMol-' mg-2/3. of Hydrazides Compound Acetyl hydrazine Propionylhydrazine ti-Butyrylhydrazine Chloromethanesulfonylhydrazine Benzenesulfonylhydrazine
Isonicotinoylhydrazine
z
(1 1) W. Theilacker and K. Ebke, Ang. Chem.,68,303 (1956).
-E112
Compound Hydroxylamine N-Methylhydroxylamine N-Ethylhydroxylamine N-Propylhydroxylamine N-Isopropylhydroxylamine N-r-Butylhydroxylamine N-t-Octylhydroxylamine N-Cyclohexylhydroxylamine N-Phenylhydroxylamine N-Benzylhydroxylamine
2-Thiazolecarboxyhydrazide
1-Methyl-2-acetylhydrazine 1-Phenyl-2-acetylhydrazine Semicarbazide Thiosemicarbazide a
-Riz
Id
0.28 0.29 0.30 0.38 0.45 0.32 0.33 0.39 0.36 0.33
5.30" 7.00" 6.05"
0.51
1 . 15a
2.61 6.11 6.30 1.40 5.05
5.74 13.08
Value uncertain, caused by distorted wave.
developed waves suitable for analytical purposes in the presence of sulfite ions; for the rest of the compounds no general trend has been found. Diacylhydrazines, however, gave no anodic waves at all; the following substances were tried with negative result : 1,2-diformylhydrazine, 1,2-diacetylhydrazine, 1,2-dipropionylhydrazine, 1,2-dibenzoylhydrazine, 1,2-di-
VOL. 41,NO. 10,AUGUST 1969
1323
carbethoxyhydrazine, l-benzoyl-2-(p-methoxybenzoyl)hydrazine, l-benzoyl-2-(p-nitrobenzoyl)hydrazine, 1-acetyl-2-benzenesulfonylhydrazine, 1-benzoyl-2-benzenesulfonylhydrazine, maleic hydrazide, and phthalic hydrazide. Trisubstituted hydrazines like l-acetyl-1,2-dimethylhydrazine,1,2dimethyl-1-isonicotinoylhydrazine,and 1,l-diethy1-2-phenylhydrazine also could not be oxidized at a mercury electrode in alkaline sulfite medium. The following compounds were found to give too distorted anodic waves by the present method : hydrazine, methylhydrazine, phenylhydrazine, 2-naphthylhydrazine, p-toluylhydrazine, p-nitrophenylhydrazine, 1,l-diphenylhydrazine, 1,2diphenylhydrazine, 1,2-dibenzylhydrazine, 3,3-pentamethylendiaziridine, benzhydrazide, thiobenzhydrazide, l-acetyl-lphenylhydrazide, carbohydrazide, and benzylsemicarbazide. For some of these compounds a quantitative polarographic determination may still be possible in a sulfite-free supporting electrolyte using conventional deoxygenation techniques. The waves of the investigated compounds seem to be diffusion controlled, at least for the three typical examples, N-t-butylhydroxylamine, N-benzyl-N-methylhydrazine, and N-butyrylhydrazine, where a linear dependence of the wave height on the square root of the corrected height of the mercury reservoir was found. The electrode reactions responsible for the anodic waves have not been explored in the present work and are not known '
in general. We have earlier suggested a 2-electron oxidation of N-alkylhydroxylamines (4) at a micro electrode, but the reaction is more complex at a macro electrode and has not yet been fully declared. In the case of N,N-dibenzylhydroxylamine, however, the 2-electron process has been proved (12). With some monosubstituted hydrazines (13), a 4-electron oxidation has been proposed, but a quite different 2-electron process appeared to be in operation with dialkylhydrazines (13). Isoniazide (14) was found to give a 4-electron anodic wave, but the course of the reaction is pH and concentration dependent. Clearly, more work is needed before a general picture of these anodic electrode reactions can emerge. ACKNOWLEDGMENT
Dr. Alexander Senning at this Institute is thanked for supplying some of the hydrazine derivatives and Mrs. K. Skov for technical assistance. RECEIVED for review October 30, 1968. Accepted May 9, 1969. (12) H. Lund, Acfa Chem. Scand., 13,249 (1959). (13) A. F. Krivis and G. R. Supp, Abstracts American Chemical Society Meeting, Division of Fuel Chemistry (No. 49), Miami Beach, Fla., 1967. (14) H. Lund, Acta Clzem. Scand., 17,1077 (1963).
Detection of Thioureido Groups in Open Chain and Heterocyclic Cornpounds by Hydrazinolysis R. G. Dickinson and N. W. Jacobsen Department of Chemistry, University of Queensland, Brisbane, Australia SIMPLE THIOUREAS are generally characterized by S-alkylation, oxidation to formamidino disulphides, acetylation, acetonylation, and the precipitation of picrate salts. These reactions provide useful derivatives for identification purposes, but they are essentially the classical reactions of the individual mercapto or amino groups, rather than being diagnostic of the thioureido moiety as a whole. Moreover, when the thioureido molecule is substituted by other dominant groups, or if the carbon atom and any two of the heteroatoms are part of a ring system, then the innate properties of the thiourea become less obvious and more difficult to detect. We are reporting a simple and reliable analytical procedure to detect the thioureido group (or precursors of such a group) irrespective of the remainder of the molecule, through a reaction with hydrazine to give the readily isolatable and recognizable 4-amino-3-hydrazino-5-mercapto-l,2,4-triazole (I).
- NI \ c//s I
/
N
\
or \
Thioureido group
7%
N*c/sI
N
hydrazine ___t
/ \
HSYNYN"H2 NN-
lsothioureido group
EXPERIMENTAL
General Method. The thioureido compound (0.005 moles or 0.5 gram) was mixed with 99-100% hydrazine hydrate (0.10 moles or 5.0 mi) in a small flask fitted with a reflux con1324
ANALYTICAL CHEMISTRY
denser and heated on a steam bath for two hours. The solution was chilled, filtered from insoluble products when necessary, and acidified to pH 6-7 with dilute hydrochloric acid. The precipitated 4-amino-3-hydrazino-5-mercapto-l,2,4-triazole (10-80z) was collected and washed well with water and ethanol. Ether, chloroform, ethyl acetate, dioxan, and many other solvents in which the triazole was insoluble, may be used to extract contaminating by products. Recrystallized from boiling water (700 parts) the triazole was obtained as long lustrous needles mp 231-233 "C [literature mp 228 OC ( I ) ] . Found C, 16.3%; H, 4.0%; N, 56.9%. Calculated for C&N& C, 16.45%; H, 4.15%; N, 57.5%. Modified Method (To Suppress Displacement of Sulphur). The thioureido compound (0.005 moles or 0.5 gram), hydrazine hydrate (0.10 moles or 5.0 ml) and ethanol (5.0 ml) were heated in a sealed tube at 125 "C for two hours. The solution was evaporated to dryness, the solid mixed with water ( 5 ml) and the triazole isolated at pH 6-7 as for the general method. RESULTS AND DISCUSSION
Identity and Characteristics of the Triazole. The identity of the triazole, first reported by Stolle and Bowles ( I ) , rested for some years on its analysis and functional derivatives (2). The NMR and mass spectral properties (3) and X-ray measurements (4) are now known to be consistent with the struc-
(1) (2) (3) (4)
R. Stolle and P. E. Bowles, Chem. Ber., 41, 1099 (1908). E. Hoggarth, J. Chem. SOC.,1952, 4817. R. G . Dickinson and N. W. Jacobsen, unpublished data, 1969. N. W. Isaacs and C . H. L. Kennard, unpublished data, 1969.
