Table I. Analysis of Synthetic Mixtures of Ferrocyanide and Ferricyanide Composition Species determined
Mixture
Ferrocyanide
1 2 3 1 2 3
Ferricyanide
Taken, M
Found, M
5.0 X IO-’
2.50 X lo-’ 5.0 x 10-3 1.18 X lo-’ 2.50 X lo-’ 7.50 X lo-*
4.62 X 2.50 X
lo-’
lo-’
5.0 x 10-3 1.10 X 2.50 X lo-‘ 7.42 X lo-‘
Table II. Results of Analysis of Commercial Bleach Solution Method
0.6
~
2800
2100
~
2000
Species determined
Sampie
Ferrocyanide, M
A
B
W a v en u rn b a r
cm Figure 1. Infrared spectrum of 8.0 X 10-’M potassium ferricyanide and 9.5 X 10-3M sodium ferrocyanide in water
C’
Ferricyanide, M
A B
C
The infrared method described possessed accuracy and precision which was acceptable for the intended application. Unfortunately, the analytical range could not be extended in either direction, for if the path length was increased beyond 50 km, the available energy was decreased markedly and if more concentrated solutions were used, no further information could be obtained from the ferrocyanide calibration curve because of non-adherence to Beer’s law. Since very few compounds absorb in the region near 2100 cm-1, it is likely that other applications involving water soluble compounds containing a CN group are well suited to this technique. For example, the method may be applicable to the determination of cyanide in electroplating baths, provided the concentration is large enough to fall into the analytical range suggested above. Initially, Irtran 2 (hot pressed zinc sulfide) cell windows
Infrared
1.34 X 1.03 X 4.75 X 3.04 X 4.99 x 4.04 X
10-1 lo-’
lo-’ 10-1 10-1
IO-’
Chemical
1.31 X 1.09 X 4.88 X 3.07 X 4.99 x 3.99 X
10-1
lo-’ lo-’ 10-l 10-1 10-l
were used, and it was found that the stronger potassium ferricyanide solutions attacked the surfaces leaving a white deposit which showed an absorption band a t 2090 cm-1. Zinc ferricyanide and zinc ferrocyanide were prepared in the laboratory, and the infrared spectra showed bands a t 2185 cm-1 and 2090 cm-I, respectively. It therefore appears that the white deposit was zinc ferrocyanide. Irtran 1, which is hot pressed magnesium fluoride, did not show any evidence of attack after six months of use in the ferricyanide solutions.
ACKNOWLEDGMENT The author wishes to thank J. T. van Gemert for his helpful discussions and suggestions during the course of the work. Received for review May 14, 1973. Accepted July 9, 1973.
Determination of Water Content in Toluenesulfonic Acid by Nuclear Magnetic Resonance Kiyoshi Mashimo and Tohru Wainai Department of Industrial Chemistry, Faculty of Science and Engineering, Nihon University, Tokyo, Japan
p-Toluenesulfonic acid, which is important as an acid catalyst for esterification, dehydration, and polymerization, is formed by sulfonation of toluene. However, this reaction always produces three isomers, the ortho, meta, and para forms, and the proportion of the products differs greatly according t o the reaction conditions. Because toluenesulfonic acid is very hygroscopic, its water content must be determined. The water content of toluenesulfonic acid can be determined by Karl Fischer titration, but the values obtained vary because of the compounds very strong hygroscopic property. The nuclear magnetic resonance (NMR) 2424
spectrum of toluenesulfonic acid in anhydrous dioxane provides a convenient handle on the water content of toluenesulfonic acid. In this NMR spectrum, the sulfonic acid proton is shifted appreciably to a low field, but with increasing water content it shifts to a higher field. Several examples have been reported for similar quantitative analyses utilizing the NMR chemical shift. These include accurate determinations of the water content of benzenesulfonic acid ( I ) , the water content of tributyl phos(1) T. Wainai and K . Mashirno, BunsekiKagaku, 19, 1629 (1970)
A N A L Y T I C A L CHEMISTRY, VOL. 45, NO. 14, DECEMBER 1973
8
7
6
5
4
3
2
1
0
PPfl(S)
Figure 1. N M R spectra of a 10.0 wt YO solution of toluenesulfonic acid in dioxane at 30 "C Upper: 2.84M water per mole of toluenesulfonic acid. Lower: 0.34M water per mole of toluenesulfonic acid
10
0
WT
20
30
%
Figure 3. Concentration dependence of OH proton shift of toluenesulfonic acid in dioxane at 30 "C ( 0 )0.39 H~O/CH~CGH~SO~H. (0)2.84
H20/CH3CsH4S03H
I
-0 15 I
0,90
-0,20
I
0,7#
-0,5
-0,3
-0,l
0,l
\
I
\o
0,65
oo3
LOGn
Figure 2. Relationship between the chemical shift of OH proton and water content in variously mixed toluenesulfonic acid dissolved in dioxane (10.0 wt %) ( n ) Moles of water per mole of toluenesulfonic acid, (6) Chemical shift of OH proton ortho meta para 0 0 0 @ Q
7.4 17.9 16.5 38.0 18.6
4.3 7.0 25.8 0.0 4.7
60
79
TEPPERATURE
90 ( O f )
Figure 4. Relationship between temperature and coefficient of calibration curve Y = a bX
+
88.3 75.1 57.7 62.0 76.7
Y : Log of the chemical shift of OH proton. X : Log of water content
phate ( 2 ) , and the amount of acetic acid in acetic anhydride ( 3 ) .In this paper we report a simple method for determining the water content of toluenesulfonic acid, based on the chemical shift of the OH proton, independent of the proportion of isomers.
EXPERIMENTAL Apparatus. NMR measurements were made with a JNM-C60HL spectrometer at a frequency of 60 MHz and a RS-201DY recorder. The temperature in the spectrometer probe was kept at 30 "C during the measurements unless otherwise indicated. Reagents. o-Toluenesulfonic acid was prepared from o-toluenesulfonyl chloride. o-Toluenesulfonyl chloride was purified repeatedly from commercial o-toluenesulfonyl chloride (containing about 27% p-toluenesulfonyl chloride) by vacuum distillation. A fraction boiling at 140 "C (33 mm) was hydrolyzed with boiling water. The homogenous aqueous solution was shaken with carbon tetrachloride and the aqueous solution was evaporated in uacuo. Its anhydride was obtained under reduced pressure at 1 2 mm (2) B. B. Murray and R. C. Axtmann. Anal. Chem., 31, 450 (1959). (3) T. Oshima and T. Iwai, Nippon Kagaku Zasshi, 89, 1036 (1968)
(70 "Cj for 2 hr. m-Toluenesulfonic acid was obtained by the hydrolysis of n-toluenesulfonyl chloride prepared from m-toluidine, as described by Meerwein et al., bp 125 "C (12 mm) (lit. 146 "C (22 m m ) j ( 4 ) . p-Toluenesulfonic acid of a commercial, pure grade was further purified by recrystallization from benzene. Its anhydride was obtained under reduced pressure a t 8 mm 1105 "C) for 2 hr. The confirmation of each anhydride was made by titrating the sulfonic acid with a 0.1NNaOH solution. Technical grade 1,4dioxane was purified by the standard method and dried by distillation with sodium after refluxing for 24 hr. A fraction boiling a t 101.3 "C was used. Water was purified by the conventional method. Procedure. The chemical shift, 6, was defined by the separation in ppm of the OH proton resonance from the methyl proton peak of p-toluenesulfonic acid. All samples were carefully prepared by adding a known amount of water to the anhydride of toluenesulfonic acid.
RESULTS AND DISCUSSION To investigate the hygroscopicity of toluenesulfonic acid, each 0.2 g of isomeric anhydride was allowed to stand in the air at a relative humidity of 70%. After standing for a few (4) H . Meerwein, G . Dittmar. R. Goller, K. Hafner, F. Mensch, and 0. Steinfort, Chem. B e r . . 90, 841 (1957).
A N A L Y T I C A L CHEMISTRY, VOL. 45, N O . 14, DECEMBER 1973
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~~
Table I. Analysis of Water Content of Toluenesulfonic Acid Dissolved in Dioxane (10.0 wt %) Using the Calibration Curve at 30 "Ca Taken, mol
Found, mol
Deviation, %
0.28 0.34
0.29
+3.4
0.33
-3.0
0.39
0.38 0.72 1.05 1.25 1.31 1.48 2.84
-2.6
0.72 1.01 1.28 1.35 1.44 2.84
0.0 +3.8 -2.4 -3.1 +2.7
0.0
Mean deviation
2.3
nCalibration curve: Y = 0.7721 - 0.1906X: ( Y ) the log of the chemical shift of the OH proton, ( X ) the log of water content.
hours, the three isomeric toluenesulfonic acids showed remarkable hygroscopicity. The moisture content of the ortho isomer did not vary much after 3 hr, but that of the meta and para isomers increased with time. Typical spectra of toluenesulfonic acid dissolved in dioxane are shown in Figure 1. In this figure, the peak a t the extreme right is due to the methyl protons of p-toluenesulfonic acid and rn-toluenesulfonic acid. The methyl proton peak of o-toluenesulfonic acid and the phenyl proton peaks appear a t 0.25 and 5.2 ppm, respectively. The OH proton of sulfonic acid exhibits a low-field shift for the strong proton donor. OH proton peaks for toluenesulfonic acid containing 0.34 and 2.84 mol of water content per mole of toluenesulfonic acid appear a t 7.24 and 4.85 ppm, respectively. A relationship between the number of moles of water and the chemical shift of the OH proton of toluenesulfonic acid is shown in Figure 2. From this linear relation, we conclude that the resonance position of the OH proton is not dependent on the proportion of isomers, but only on the water content. The concentration dependence of the OH proton shift for toluensulfonic acid in dioxane is shown in Figure 3. The OH proton peak appears a t 4.50 ppm in a 2.0 wt % solution of the solute containing 0.39 mol of water per mole of toluenesulfonic acid and a t 8.07 ppm in a 20.0 wt % solution. Furthermore, the OH proton peak appears a t 2.48 ppm in a 2.0 wt % solution of the solute containing 2.84 mol of water and a t 5.87 ppm in a 20.0 wt '70solution. The OH proton peak is shifted to a lower field with increasing concentration of toluenesulfonic acid, regardless of the water content, because it is thought that the association of the OH proton is very strong. However, the OH proton is also shifted to a lower field with decreasing water content; the differences
in the chemical shifts of samples containing various water contents were almost the same for more than 10.0 wt % solutions. Therefore, the concentration of 10.0 wt % of toluenesulfonic acid in dioxane was chosen as the standard for this procedure. Water was added to mixtures of anhydrous isomeric toluenesulfonic acid and solutions were diluted to 10.0 wt % in dioxane. The chemical shift of the OH proton resonance with respect to the methyl peak of p-toluenesulfonic acid was measured for nine samples whose water content ranged from 0.28 to 2.84 mol/mol of toluenesulfonic acid. When the results were plotted, a linear relation was obtained between the common logarithms of the chemical shift and the number of moles of water. By using this calibration curve, the water content of toluenesulfonic acid was determined. The OH proton was linearly shifted to a higher field with increasing temperature, and the magnitude of the chemical shift was proportional to the water content. A linear relationship between the slope of the calibration curve for various temperatures and the temperature of measurement and that between the logarithms of the calculated chemical shift for 1.00 mol of water from the calibration curve and the temperature of measurement is displayed in Figure 4. From this information, a relationship between the chemical shift and the number of moles of water was obtained from the two straight lines described above for any desired temperature of measurement. The numbers of moles of water obtained from the calibration curve a t 30 "C are shown in Table I. All values agree closely with the true values. When samples contained sulfuric acid, the chemical shift of the OH proton was shifted to a low field. The chemical shift of the OH proton of a sample containing sulfuric acid a t 9 wt % in toluenesulfonic acid having 0.34 mol of water content was 7.45 ppm. Using this value, the water content calculated from the calibration curve a t 30 "C was 0.30 mol (taken 0.33 mol). Consequently, it is thought that the OH proton is not appreciably shifted by a small amount of sulfuric acid. However, the presence of a large amount of sulfuric acid would make the analysis invalid because the position of the OH proton would be shifted. The method described here may be applied more rapidly and simply than other methods. Furthermore, the saturation phenomenon which has an effect on the peak height or the area need not be considered, but the presence of a large amount of sulfuric acid in the toluenesulfonic acid must be avoided, because it shifts the position of the OH proton. Received for review January 16, 1973. Accepted April 3, 1973.
Column Partition Chromatographic Determination of Sodium Alkane Monosulfonates Wahid R. Ali and Patrick T. Laurence Research Laboratory, Texaco Trinidad, Inc., Pointe-a-Pierre, Trinidad and Tobago
Considerable interest has been directed, in recent years, toward the production of sodium alkane sulfonates for detergent manufacture. This is due to the demand for more completely biodegradable detergents and also to the re2426
*
cent availability of high purity normal paraffins and a olefins. The sodium alkane sulfonates, as prepared, usually contain alkane monosulfonates, alkane di- and polysulfonates, and sodium sulfate. Although the amounts of so-
ANALYTICAL CHEMISTRY, VOL. 45, NO. 14, DECEMBER 1973
