Modified Apparatus for Determination of Groups Active to the Grignard Reagent PAUL M. MAGINNITE” WITH JOHN B. CLOKE, Rensselaer Polytechnic Institute, Troy, N. Y . Company and was of 99.570 purity. If further purification of the gas is desired, it may be passed also through Fieser’s solution to remove oxygen; through lead acetate solution to remove traces of hydrogen sulfide; and through sulfuric acid and phosphorue pentoxide, as described by Kohler.) The gage pressure of the nitrogen was maintained a t approximately 10 pounds per square inch. Blank Run and Standardization of Reagent. The apparatus i p thoroughly cleaned and dried, and the reagent is filtered through glass wool into flask D. Stopcock A is opened to the nitrogen source, stopcock B is closed, and stopcock C is turned to position I (Figure 1) permitting the nitrogen to pass into flask D, and creating a pressure therein. Cis then quickly turned 180”counterclockwise to position I1 and the pressure relieved by opening A to the atmosphere through stopcock R, which is turned to bypass the buret. The nitrogen valve is then closed. B is opened, allowing the reagent to pass into G. When a sufficient amount of the reagent has passed over, the excess remaining in the upper part of the apparatus can be pressed back into D by again turning A to connect with C, which has remained in position 11. B is then closed, and it remains in this position until it becomes necessary to refill buret G. Five milliliters of the butyl ether solvent are placed in flask S , and the flask is replaced. Dry nitrogen is swept into the flask and l o w r part of &e apparatGs throu?gh stopcock A and tube J When the air has been displaced, A is closed and R is turned to connect with the system. ( A t this point, it has been found advisable to lower the mercury reservoir below the level of the mercury in the buret to reveal the presence of leaks, if an: exist ) Khen the level of the mercury in the buret has been read. the reservoir is lowered to create a pressure less than atmosphrrir
HE so-called Zerevitinov method for the quantitative dtbTtermination of groups active to the Grignard reagent had it. inception in the work of Chugaev ( d ) , who notcd that many organic compounds, especially those containing hydroxyl groups, produced hydrocarbons when treated with alkylmagnesium halides. Hibbert and Sudborough (5) and later Zerevitinov (13) took up and expanded the work of Chugaev, applying it to quantitative work. Although Chugaev himself did not discuss any particular type of apparatus in his original paper, other investigators have described various designs. The apparatus of Hibbert and Sudborough and that of Zerevitinov consisted essentially of a device for mixing the Grignard solution with the solution of the sample in the same glass container and measuring the resulting gas. Other Grignard reactions, notably those involving addition to double-bonded atom groups, could be measured by the apparatus developed by Kohler and his associates (6, 7 ) ,which was designed to measure both the amount of reagent reacting to form a gas and the total amount of reagent consumed, Other types of apparatus have been described by hIoureu and 13ignonac ( 9 ) , Odd0 (IO), Larsen (8), Assaf and Gladding ( I ) , Evans, Davenport, and Revukas (S), and Fuchs, Ishler, and Sandhoff ( 4 ) . Micromethods have been reported by Roth (11) and Soltys ( 1 2 ) . The apparatus described in this paper involves the principle of Iiohler’s device, but is constructed of standard pieces of glassware, utilizing standard-taper joints. The original Kohler apparatus was essentially one single piece of equipment, with the exception of the reaction flask. This new device, made of standard items which can be duplicated, permits disassembly for cleaning purposes and easy repair of any broken part. DESCRIPTlON OF THE APPARATUS
E , F , and L in Figure 1 are standard “gas inlet” tubes with a 24/40 joint. A , B , and C are ordinary three- and two-way stopcocks. Flask D is of 300-nil. capacity. Buret K, for the addition
of water, has a capacity of 10 ml., graduated in 0.1 ml., and may be attached to a 24/40 joint or inserted through a tightly fitting rubber stopper. P is a standard type mercury-filled gas buret of 100-ml. capacity, graduated in 0.1 ml., with a three-way stopcock, R, a t the top. Buret G has a capacity of 10 ml., graduated in divisions of 0.05 ml. Reaction flask ,I’ and buret P may be jacketed so that water of any desired temperature may be passed around them. The lower portion of G is connected to the gas tube, L , by a rubber sleeve. The ends of connecting tube Q may be sealed directly to R and L or connected by rubber sleeves. The use of a suitable lubricant is usually advisable to ensure gastight connections, especially of the reaction flask and ronnecting tube M. Broken lines in Figure 1 represent rubber connections which may be substituted. OPERATION OF THE APPARATUS
Reagents. The Grignard solution was prepared in a typical run from 62.8 grams of methyl iodide, 10.8 gram. of magnesium, and 260 ml. of anhydrous butyl ether. Butyl ether was also used as the solvent for the sample to be analyzed. The nitrogen gas was commercial anhydrous nitrogen, which was passed through a calcium chloride drying tube before being passed into the apparatus. (The nitrogen used was supplied by the Air Reduction 1
Prcaent address, Department of Chemistry, Boston College, Chestnut
Figure 1.
Kill. Mass.
978
Diagram of Apparatus
V O L U M E 20, NO. 10, O C T O B E R 1 9 4 8
979
Table I. Action of M e t h y l m a g n e s i u m Iodide on Organic Compounds Mole8 of Active Bydrogsn/iMole
Compound Di-n-butylamine Methylaniline Piperidine Myristyl 8lCOhOl n-Butyl alcohol 7-Chlorobutyronitrile n-Hexaldehyde Methyl n-butyl ketone .Methyl isobutyl ketone Methyl n-amyl ketone hoetophenone oxime Phenyl tolyl ketimine * Not measured.
0.99 0.96 0.99 0.97 1.01 0.01 0.00 0.02 0.03 0.01 1.02 0.98
Moles of Reagent Adding/Mole
f0.02 f 0.01 f 0.01 f 0.03 =t0 . 0 3 *0.01 f0.01 f 0.02 f0.02 f0.02 f 0.08 == ! 0.09
0.97 0.99 0.98 1.02 1.05 0.88 1.02
*f 00 ..0023 i 0.02
f0.04 f 0.03 f 0.08 f 0.05
in the system, and a measured volume, at)out 1 nil., of the reagent is run into flask N . (The contents of this flask are usually mixed by shaking, but stirring can be readily accomplished by the use of a small magnetic stirrer, externally operated. A device of this type is sold by Arthur H. Thomas Co.) ilfter gas evolution has ceased, the level of the mercury is again read and the difference between the two readings is equal to the blank value on the solvent. At this point, a measured volume of water, about 3 mi., is added from buret K , and when gas evolution has again ceased, a third reading is taken. [Although the use of water is suggested as the means of decomposing the Grignard reagent,, any suitable liquid of loiver vapor pressure may be used in t.his apparatus-for example, aniline, as recommended by .\ssaf and Gladding ( I ) . ] The total amount of gas evolved divided by the volume of Grignard solution used is equal to the “methane equivalent” of 1 ml.,of the reagent. Active Hydrogen Determinations and Measurement of Addition Reactions. Active hydrogen analyses are run in the manner described above, except that a solution of the sample in 5 ml. of but,yl ether is used instead of the solvent alone. Preceding each run, flask N , connecting tube M , and buret K are removed and
washed with 20% hydrochloric wid, water, alcohol, ether, and absolute ether in that order. Reactions involving consumption of the Grignard reagent without the formation of methane, as in the case of many addition reactions, are measured by adding a known volume of the reagent to a solution of the sample, allowing a definite time for the completion of the reaction, and decomposing the excess reagent by the addition of a measured volume of water. The difference between the amount of methane produced and the amount of methane calculated to be formed from the volume of the Grignard solution is a measure of the amount of the reagent consumed in the reaction. ACCURACY OF RESULTS
Table I includes some results obtained with the apparatus OD various types of organic compounds. The reproducibility of the results is sholvn by the indicated precision. In the case of methylaniline, for example, values of 0.96, 0.94, 0.99, and 0.96 were obtained. LITER iTURE CITED (1) Assaf and Gladding. ISD. E x . Casu., AXAL. ED.. 1 1 , 164 (1939). (2) Chueaev. Ber.. 35. 3912 (1902). i3j Evans, Davenport, and Revukas, IND. ESG. CHEM.,A N ~ LED.. . 11, 553 (1939); 12, 301 (1940). (4) Fuchs, Ishler, and Sandhoff, Ibid., 12, 607 (1940). (5) Hibbert and Sudborough. J. Chem. Soc.. 85, 933 (1904). (6) Kohler and Richtrneyei, J. Am. Chem. Soc., 52, 3736 (1930) (7) Kohler, Stone, and Fuson, Zbid., 49, 3181 (1927). ENG.CHEM.,ANAL.ED., 10, 195 (1938). (8) Larsen, IND. (9) Moureu and Mignonac,.Compt. rend., 158, 1395, 1624 (1914) (10) Oddo, Ber., 44, 2048 (1911). (11) Roth, Mikrochemie, 11, 140 (1932). (12) Soltys, Zbid., 20, 107 (1936). (13) Zerevitinov, Ber., 40, 2023 (1907); 41, 2233 (1908); 12, 4806 (1909) ; 43, 3590 (1910). RECEIVED-JU~Y 2, 1947.
Semimicrodetermination of Arsenic in the Presence of Antimony, Bismuth; Tin, and lead *
JA3IES H. FREEhIAN AND WALLACE &I. MCNABB Cniversity of Pennsylvania, Philadelphia, Pa.
r r H E material given in this paper is an extension of the method described by Sloviter, McNabb, and Wagner ( d ) for the semimicrodetermination of arsenic in organic compounds. The arsenic is precipitated as the element by action of hypophosphorous acid and determined iodometrically with the aid of Koppeschaar’s bromide-bromate solution. This method is applicable to the determination of arsenic in the presence of sntimony, bismuth, tin, and lead when present as the chlorides. Table I.
D e t e r m i n a t i o n of Arsenic
Arsenic Taken
Metals Present
.Ma.
MQ.
19.16 19.16 19.16 19.16 19.16 19.16 19.16 19.16 19.16 19.16 l9,16 19.16 19.16 19.16 19.16 19.16 j9.16 19.16 19.16 19.16 19.16 19.16 19.16 19.16
None None None None None None None None 100 Antimony 100 Antimony 100 Bismuth 100 Bismuth 100 Tin 100 Tin 100 Tin 150 Tin 100 Lead 100 Lead 100 Antimony, bismuth 100 Antimany, biqmuth 200 Antimony, bismuth, and tin lOOAntimony, biamuth, tin,and lead
Arsenic Found Mo. 19.18 19.16 19.22 19.18 19.26 19.15 19.07 19.10 19.13 19.12 19.01 19.01 19.13 19.15 19.24 19.09 19.12 19.07 1 9.08 19.10 19.17 19.17 19.19 19.20
Error % +0.1
0.0 f0.3
fO.l 4-0.5
-0.0
-0.4 -0.3 -0.1 -0.2 -0.7 -0.7 -0.1
0.0
f0.4 -0.3 -0.2 -0.5
-- 0 0 .. 34 4-0.1 +0.1 fO.2 f0.2
Results are given shoir-irig the percentage error obtained when arsenic is determined in the presence of these foreign ions. PROCEDURE
An aliquot portion of sodium arsenite solution containing approximately 20 mg. of arsenic was transferred to the flask of an all-glass decomposition apparatus with reflux tube, such as that described for use in the determination of arsenic or mercury in organic compounds ( 1 , a). Rieasured volumes of solutions of antimony chloride, bismuth chloride, stannous chloride, and lead acetate were added to the arsenic solution. To the solution in the flask were added and dissolved rapidly 3 grams of sodium hypophosphite (NaH2POzH&), and then sufficient concentrated hydrochloric acid was added to increase the acid concentration to a t least 6 iV. The condenser was attached, the flask heated with a small flame, and the analysis completed as described (2). The results obtained for the determination of arsenic alone gave an average error of 0.2% (Table I). Arsenic with antimony present gave an average error of 0.15%; with bismuth 0.7%; with tin 0.2%; and with lead 0.3%. Arsenic with antimony and bismuth present gave an average error of 0.3%; with antimony, bismuth, and tin 0.1%; and with mtimony. bismuth, tin, and lead 0.2y0. LITERATURE CITED
(1) Sloviter, McNabb, and Wagner. IND. ENG.CHEW,ANAL. ED.. 13, 890 (1941). :2) Ibid., 14, 516 (1942). RECZIVED December 20, 1947. Presented before the ~~eeting-in-hliniature of the Philadelphia Section of the AMERICAN CHEMICAL SOCIETY, January 22, 1948.
