ANALYTICAL CHEMISTRY
996 ~~
Table X.
~
~~
~
~
Comparison of Riicro (1-Ml.) and Macro (100-Ml.) Vacuum Distillations” Wax Distillate
h e a n of 1Iacro Results Sone
Method Boiling aid
Initial boiling point, O C . 2% vol. distilled a t , ’ C. 570 vol. distilled a t , O C . 10% vol. distilled a t , O C. 20% vol. distilled a t , C. 30% voi distilled at 40% vol: distilled at: 50% vol. distilled a t , ’ C. 55% voi. distilled at, O C. 60% vol. distilled a t , O C. 70% vol. distilled a t , ‘ C. 80% vol. distilled a t , ’ C.
‘ g:
-~
Boiling aid
295.5 308,s 322 336 362 387 412.5 437 448.5 459.5 481 503
Boiling Stick Diff. from Results macro
....
3i o
+1.5
317 331 357 389 415 435 444
-- 52 -5
+2 +2.5
-2 -4.5
.. .. ..
h-one
....
Uicro Results ~-
Sickel Foil Diff. from Results macro 303 +7.5 311 +2.5 318 -4 320 -7 3311 -6 383 -2 412 -0.5 436 -1
....
4ii’l
fl.5 +3 +1
48-1
501
Nickel Foil
Nickel Foil Diff. from Results macro 279 -16.5 302 - 6.5 - 13 309 - 5 331 360 - 2 388 + 1 410 - 2.5 431 - 6
.4trnosplieric Residue _ K x e l Foil_
+
~
..
-
5.5 - 7 - 9
454 -171
494
Sickel Foil ~
+
+
-4.5 -1
-!.!
-a,> -4.5
+0.5 nil -3 ..., -2 -2 -4
457.5 479 499
232 265 +25 Initial boiling point, O C. 225 - 7 219 33 263,s 274 2% vol. distilled a t , C. +18.5 +10.5 263 - 0.5 273 286 303 5% vol. distilled a t , C . i17 296 + 8 297 10 312.5 325 1.5 f12.5 10% vol. distilled at, C. 323 +10.5 320 308 - 5.5 358.5 + 9 5 20% vol. distilled a t , C. 3R0 1.5 360 402 405 - 7 30% rol. distilled a t , O C. + 3 - 4 398 399 - 7 5 447.5 440 -20.5 40% 1-01, distilled a t , C. 437 -10.5 434 494 480 -11 - 14 50% voi. distilled at O C. 475 - 19 479 549 60% vol. distilled at: C. - 16 .... 530 - 19 531 a Temperature readings are boiling points a t atmospheric pressure which correspond to boiling points observed under vacuum.
’ ’
Difference between macro and micro results
Mean of micro results 29 1 307.5 314.5 330.5 357.5 387.5 412.5 434
+
~
~
~~
5 5 5 5 5 5
5
f 17 9.5 fll.5 + 8 + 2 - 2.8 - 13 -14.5 -17.5
+
__
The precision of the micro vacuum distillation results on the wax distillate and atmospheric residue (Table X and Figure 8) may be summarized as follows:
possible t o compare the accuracy of initial boiling points obtained by the micromethod with published data because these are not given in standardized macro methods.
Precision of Micro Vacuum Distillation Results
Difference from mean (repeatability) Average Maximum (95% probability level) Difference from 100-ml. test Average Maximum (95% probability level)
Wax Distillate, i. c.
ACKNOWLEDGMENT
The authors are indebted to the chairman of the British Petroleum Co., Ltd., for permission to publish the results of their work.
Residue, Z t 0 C.
3 8
3.5 10
3.5 9.5
8 23
REFERENCES (1)
The micromethod has a repeatability equal to about one third of that of the macro test and it is to be noted that the precision of the microresults on the wax distillate is better than the corresponding value for the residue. This is to be expected because the steeper distillation curve given by the latter will accentuate errors in temperature and distillate readings. It has not been
Bm.SOC.Testing Materials, Philadelphia, Pa., “-4STM Standards
on Petroleum Products and Lubricants,” 1953. (2) Institute of Petroleum, London, England, “Standard Methods for Testing Petroleum and its Products,” 13th ed., 1953. (3) Sommer, J. V., and Wear, G. E. C., “Some Microphysical Apparatus and .Methods for Inspection of Petroleum Products,” American Petroleum Institute Symposium on Rapid Methods of Analysis, April 1949. RECEIVED for review May 26, 19.54. Accepted February 1, 1955. Presented before the American Petroleum Institute, Houston, Tex., 1954.
Quantitative Determination of Certain Sulfenyl Halides NORMAN KHARASCH and MILTON M. WALD Department of Chemistry, University of Southern California, Los Angeles 7, Calif.
+
An iodometric method, involving the reaction 2ArSCl 21- + -4rSS.h ii 2C1-, has been adapted for the analysis of certain aromatic sulfenyl halides. Titrations accurate to =!=lo/,were easily obtained if water was excluded. In anhydrous acetic acid, the magnitude of the required blank was proportional to the oxygen tension. The titration may be applied t o following the rates of reactions involving sulfenyl halides.
+ +
I
S STUDIES of the kinetics of reactions of sulfenyl halides
T\ ith various substances, suitable methods for determining this key group of sulfur derivatives became necessary. This paper reports a general procedure for the quantitative estimations of 2,4-dinitrobenzenesulfenyl chloride (I), the corresponding sulfenyl bromide (11) and thiocyanate (111), and 2-nitrobenzenesulfenyl chloride (IV).
I n earlier work, Bohme and Schneider (1) carried out the successful iodometric analysis of benzenesulfenyl chloride (via Reaction 1, Ar = phenyl), by treating the sulfenyl chloride, dissolved in carbon tetrachloride, with aqueous potassium iodide. 2ArSC1
+ 2KI --+-ArS-SAr + 2KC1 + 12
(1)
More recently, Foss (2’) has reported the determination of certain sulfenamides and sulfenyl thiocyanates by reaction of these substances with thiosulfate ions and measurement of the unreacted thiosulfate. The method of Bohme and Schneider was attempted in the present work for the analysis of 2,4-dinitrobenzenesulfenyl chloride (I), but the release of iodine never exceeded 93% of the amount required by Equation 1 (Ar = 2,4dinitrophenyl). Elimination of other sources of error suggested that water was interfering; and this proved to be the case, as satisfactory titra-
V O L U M E 27, NO. 6, J U N E 1 9 5 5
997
tions (accurate to 51%) resulted when dry acetic acid (or acetic acid mixed with solvents as ethylene chloride) was employed as the reaction medium. Similar methods suffice for compounds 11, 111, and IV, with about the same accuracy, although not as many check determinations were made in these cases as with compound I. Small corrections are required to offset air oxidation of iodide. For acetic acid, the magnitudes of these blanks depended on the partial pressure of dissolved oxygen and were reduced to negligible amounts by sweeping with dry nitrogen. The effect of hydrogen chloride concentration on the blanks was also determined, as this substance is frequently encountered as a product, or as an added substance, in kinetic studies. In acetic acid, saturated with air, the blanks increased with increasing hydrogen chloride concentration; while with nitrogen-swept acetic acid, the magnitude of the blank was not appreciably altered by changes in the hydrogen chloride concentration. For kinetic studies, it was desired to know whether the presence of certain added substances would interfere with the estimation of the amount of 2,4-dinitrobenzenesulfenyl chloride present in a solution a t a given time. For this purpose, the substance to be tested was added to the mixture during the course of the titration. The results shotv that, under these conditions, a considerable number of reactive compounds do not interfere. No doubt, interference m:iy be anticipated from substances Jvhich oxidize iodide ion readily or interact rapidly with iodine; but only two such cases (bromoacetone and “cyclohexene peroxide,” a term used to denote the mixture of oxidation products which result on exposure of cyclohexene to air) were noted in the present work. In accord with these observations, iodometric estimation has already proved useful in following the rates of reactions of compound I with olefins ( 1 0 ) and of I, 11, and I11 with acetone (11). Preliminary work also shows that 2,4-dinitrobenzenesulfenyl acetate can be determined by the above procedure, whereas triphenylmethanesulfenyl chloride cannot-the release of iodine in the latter case being too slow under the conditions prescribed.
remove all the iodine from the nonaqueous phase. If an organic solvent-e. g., ether or benzene-of density lower than water is present, it is useful to add (after the water has been introduced) sufficient carbon tetrachloride or ethylene chloride to make the organic phase more dense, thereby avoiding the troublesome operation of “titrating through” the organic phase.
Table I. Quantitative Determination of Certain Sulfenyl Halides Range of Av. % Sulfenyl Concns. Studied, 30.of ArSX Halide Molarity Detns. Founda 2,4-Dinitrobenzenesulfenyl 3 . 2 x 10-4 38 99.96 chloride, I 9 . 8 x 10-3 2,4-Dinitrobenzenesulfenyl 8 . 2 x 10-4 7 100.2G bromide, I1 1 . 5 x 10-3 2,4-Dinitrobenzenesulfenyl 5 . 9 x 10-4 7 100.06 thiocyanate. I11 7 . 4 x 10-4 2-Nitrobenzenesulfenyl 1 . 1 x 10-3 7 99.63 chloride, IV 1 . 7 x 10-3 Standard deviations are not recorded because of t h e rather small number of determinations reported. T h e individual titrations were, Iyith very few exceptions, well within & l % , and no particular trend t o low or high values was noted.
Table 11. Effect of Oxygen on Titrations of 2,4-DinitrobenzenesulfenylChloride I in I Found Aliquot by Titration (by Weight). (Corr. for Blank), Meq. Meq. 1.55 1.556 1.55 1.555 1.55 1.555 1.55 1.555
Blank, Me,q. Iodine 0.063b
Treatment of Aliquota Saturated with dry air 0.023 Swept with dry nitrogen 0.291b Saturated Tyith dry oxygen 0.023 Saturated with oxygen, then swept with nitrogen a Gases passed in a t fairly rapid rate for 15 t o 20 minutes in each case. b Values of blanks in these runs are in a ratio of about 1: 5 showing blank t o be proportional to the partial pressure of oxygen in the so1;ent. T h a t this behavior was not confined t o titrations of I xas shown by siniilar results with titrations of 2,4-dinitrobenaenesulfenylacetate and with I T , as well a s in t h e absence of sulfenyl halide.
Titrations in Presence of Other Substances. In various kinetic studies of the reactions of a number of substances with compound I, information was desired as to whether these substances might EXPERLMENTAL interfere with the determination in some manner which would not include the particular reaction with compound I which was under Reagents. Compounds I, 111, and IV were prepared by rekinetic investigation. The effect of these substances on the analycorded procedures (3, 6, 6) or minor variations of these. Carefully recrystallized and dried samples were used for the titrations. sis was, therefore, studied by adding them after compound I had Dry ethylene chloride was prepared by distilling the commercial been destroyed by the iodide reagent but before water was added. product, and the acetic acid was also distilled, after the glacial Thus, the determinations with various substances present were acid had been heated with excess acetic anhydride to remove the carried out by the general procedure, except that-after the water. The acid undoubtedly contains small amounts of the anhydride, but this does not interfere with the analysis. anhydrous mixture had been swirled for about 1 minute-there The sulfenyl bromide was obtained by reaction of compound I was added 3 ml. of the liquid (or 2 grams of the solid) whose and aluminum chloride ( 8 ) , giving a product identical with that from 2,4-dinitrothiophenol and bromine (4). Ethyl ~u-2~4- effect on the titration was to be tested. The mixture was swirled 1 minute more, and the titration completed in the usual dinitrophenylthio- p - ketobutyrate-CH3-CO-CH [-S-CBHI ( NOZ)~]-CO-OC~H~-~ previously unreported compound, was manner. The following pure substance (cf. preparation of reaprepared, in good yield, by reaction of I with ethyl acetoacetat;; gents, above) did not interfere with the analysis of compound yellow needles from absolute alcohol; melting point 112-113 . I: 2-pentene; absolute ethyl alcohol; dimethylaniline; benzyl Analysis (by J. V. Pirie). Calculated for Cl~H1~K;207S: C, alcohol: ethyl acetoacetate; acetone; cyclohexene; ethyl 43.90; H, 3.69. Found: C, 44.12; H, 3.81. 2-Chlorocyclohexyl 2’,4’-dinitrophenyl sulfide ( 9 ) , ethyl 2,4-dinitrobenzenesulfenate CY-2,Pdinitrophenylthio-p-ketobutyrate;2-chlorocyclohexyl 2’,( 7 ) , 2-chloro-2-phenylethyl 2’,4’-dinitrophenyl sulfide (IO), and 4’-dinitrophenyl sulfide; ethyl 2,4-dinitrobenzenesulfenate;2acetonyl 2,4-dinitrophenyl sulfide (9) were prepared. Other chloro-2-phenylethyl 2’,4’-dinitrophenyl sulfide; and acetonyl reagents were purified grades of the commercial products. 2,4-dinitrophenyl sulfide. (Melting points are not corrected.) When ordinary stock cyclohexene was used, in place of the Titration Results and Procedure. The following general propurified olefin, the titration values were 150 to 250% high, on cedure led to the results summarized in Table I and in subsequent the basis of the amounts of compound I known to he present in paragraphs. the titration aliquots. A hlank determination showed that this C.P. sodium iodide (4 to 6 grams, dried 1 hour a t 110’) was was undoubtedly caused by oxidant impurities in the olefin. placed in a 250-ml. glass-stoppered Erlenmeyer flask. Dry acetic Bromoacetone, one of the products obtained in reaction of I1 acid (10 to 20 ml.) was added, followed immediately by an aliquot with acetone ( 4 ) , also gave high results in the titration of 11. of the prepared solution of the sulfenyl halide. The flask was Separate titration showed that this effect is caused by release of stoppered and swirled briefly three or four times during a 1.5minute period. Distilled water (ca. 120 ml.) was added, followed iodine in the reaction of bromoacetone and sodium iodide under by an excess of standard sodium thiosulfate solution, added with conditions of the titration. gentle swirling. The excess thiosulfate was estimated by backEffect of Oxygen. In a typical experiment, a standard solution titration with standard iodine solution. If a water-immiscible of compound I in acetic acid was divided into four equal parts, solvent (such as carbon tetrachloride) is present, it is necessary t o shake the mivture vigorously after adding the thiosulfate to each containing 1.55 X equivalent of I. Each part was then
-
ANALYTICAL CHEMISTRY
998 treated a s shown in Table 11, and titrated by the general procedure. Effect of Hydrogen Chloride. This was observed by preparing a standard solution of hydrogen chloride in acetic acid (or ethylene chloride) and diluting with acetic acid to various concentrations. I n one series of runs, when acetic acid saturated with air was used, and the hydrogen chloride concentration was varied, in six steps, from 0 to 1.3 meq. (is the standard volume of solvent used for the titrations), the blanks rose progressively from 0.02 to 0.06 meq. of released iodine; with the nitrogen-swept solutions, a similar series of determinations did not reveal such a trend. ACKNOULEDGMEKT
The authors are indebted to the National Science Foundation for partial support, and to Ronald Swidler for developing the method of synthesis of 2,4-dinitrobenzenesulfenylbromide cited above.
LITERATURE CITED B o h m e , H . , a n d Schneider, E., Ber., 76, 483 (1943).
Foss, O., Acta Chem. Scand., 1 , 310 (1946). H u b a c h e r , &I. H . , "Organic Syntheses," Coll. Vol. 11, p. 455, Wilev. Piew York. 1943. K h a r a s c h , N., Buess, C. AI., a n d S t r a s h u n , S. I., J. Am. Chem.
SOC.,74, 3422 (1952). K h a r a s c h , S . , Gleason, G . I., a n d Buess, C. %I.,Ibid., 72, 1796
(1950). K h a r a s c h , N., a n d H a v l i k , A. J., I b i d . , 75, 3734 (1953). K h a r a s c h , N., LlcQuarrie. D . P., a n d Buess, C. hl., I b i d . , 75,
2658 (1953). K h a r a s c h , S . , a n d Swidler. K., unpublished work. K h a r a s c h , S . , Wehrmeister, H . L.. and Tigerman, H . , J . Am. Chem. Soc., 69, 1612 (1947). Orr, W . L . , a n d K h a r a s c h , S . ,Ibzd., 75, 6030 (1953). W a l d , Vi. &I.,a n d K h a r a s c h , iY., Division of Organic C h e m i s t r y , 126th Meeting ACS, New Y o r k , S. Y.. 1954.
xx
for review July 17, 1954. Accepted December 8, 1954. Part in the series "Derivatives of Sulfenic Acids." For preceding papers see J. O r y . Chem., 19, 1704 (1954). and J . Am. Chem. SOC.,Vols. 69 t o 77. REChIVED
Volumetric Determination of Fluorine Involving Distillation from a Sulfuric Acid Solution OLIVER
D. SMITH
and THOMAS
D. PARKS
Stanford Research Institute, Stanford, Calif.
The use of sulfuric acid and distillation at 150" C. in the Willard and Winter method decreases the retarding influence of aluminum and silicon upon the volatilization of fluorides in analysis of vegetation, soils, and particulate materials. A modified steam tube minimizes contamination of the distillate.
T
HE Willard and Winter (6) method is widely accepted as
the most satisfactory means of estimating the concentration of fluorine in a wide variety of materials and over a large range of concentrations. I n the first publication the authors pointed out several limitations-for example, gelatinous silica, boron, aluminum, phosphates, and sulfates prevented the distillation of fluosilicic acid from a perchloric acid solution. Winter and Butler (7) obtained unsatisfactory results when they attempted to determine the fluorine content of a plant ash. Since the first announcement of the method a great deal of work has been carried out both by individual investigators and by committees sponsored by such organizations as the Association of Official Agricultural Chemists ( 1 , 5 ) . I t was found that when the temperature of distillation from a perchloric acid solution was increased above 135" to 139" C., decomposition products and perchloric acid were carried over, which interfered with the titration. For this reason a doubledistillation method was introduced for use on materials that were difficult to analyze by the standard method. The solution was distilled from sulfuric acid a t 165" C. to free as much of the fluorine as possible from the interfering substances, the distillate was then evaporated to a suitable volume, and a second distillation was made from perchloric acid a t 135" C. to free the fluorine from the interfering sulfuric acid carried over in the first distillation. Recently Remmert and Parks ( 3 ) and Rowley and coworkers ( 4 ) published methods for the determination of fluorine in plant materials, which overcame some of the difficulties encountered by Willard and Winter. They found that the ash from certain types of plants did not give satisfactory results, even when the AOAC double-distillation procedure was utilized. Introduction
of a sodium hydroxide fusion of the plant ash prior to distillation by perchloric acid a t 135" C. gave greatly improved recovery of fluorine. Subsequent work a t Stanford Research Institute has shown that certain samples do not yield satisfactory results by distillation with perchloric acid a t 135" C., even after a fusion Kith sodium hydroxide. The work described in this paper was carried out in an effort to improve the recovery of fluorine from samples containing silica and alumina, without a long and tedious procedure such as that involved in the double-distillation method. Two problems were immediately recognized in attacking the distillation with sulfuric acid. First, lime is normally added to samples in the field to prevent the loss of hydrogen fluoride. With a sulfuric acid distillation there tends to be precipitation of calcium sulfate nTith subsequent "bumping." The second problem is the carrying over of enough sulfuric acid to interfere with the titration m-ith thorium nitrate. Both problems have been overcome and a satisfactory working method has been developed for the determination of fluorine in the types of sample which yielded low results when perchloric acid was used for dietillation. RE4GENTS
-411 reagents must be tested for fluorine content, in order to assure low blank values. Analytical reagent chemicals were found suitable for all reagents except magnesium oxide. Magnesium Oxide, low fluorine content. Dissolve 750 grams
of magnesium sulfate in 2000 ml. of distilled water in a 4000-ml. beaker. Heat to SO" to 100' C. and add 50 grams of sodium carbonate dissolved in 200 ml. of hot distilled water. Remove from
the hot plate, stir occasionally, and let settle overnight. Filter through an 18-cm. S o . 1 Whatman filter paper, using a Buchner funnel and a suction pump. Discard the precipitate. Dissolve the precipitate adhering to the 4000-ml. beaker with a few milliliters of dilute hydrochloric acid and discard. Return the filtrate to the 4000-ml. beaker. Heat the filtrate again to 80" to 100" C. Dissolve 400 grams of sodium carbonate in 1000 ml. of distilled water, using heat to effect solution. Add the sodium carbonate solution to the magnesium sulfate solution with stirring. Remove from the hot plate, let stand for 30 minutes, stirring occasionally, and again filter off the precipitate through an 18-cm. Buchner funnel using a
