Considering the average difference column in Table I, it appears that pyrohydrolysis determinations show a negative bias of about 0.1 absolute %. The recovery curves shown in Figure 2 indicates that results might be more quantitative if the reactor tube temperature could be increased to 1400" C. On the other hand, different catalysts and operating conditions might enable the efficient recovery of boron a t lower temperatures. Boric oxide undoubtedly is incorporated into the silica network in a glass while fluoride is present as a fluxing agent and as such is much less rigidly bound. T~ improve the method further, Some of the mechanism b y which boric oxide is
(6) Ibid., 18, 788 (1946). (7) Powell, R. H., Menis, O., .~NAL.CHEY. 30, 1546 (1958). (8) Susano, C. D., I%-hite,J. C., Lee, J. E., rbia., 27,453 (1955). LITERATURE CITED (9) Warf, J. C., National Nuclear Energy Series, Div. VIII, Vol. I, pp. 728 ff., ( I ) Adams, P. B., Williams, J. P., J. Am. "Analytical Chemistry of the ManCeram. ~S'OC.41,377 (1958). hattan Project," McGraw-Hill, New American Society for Testing MateYork, 1950. rids, Philadelphia, "Standards on Glass (10) Warf, J. c,,cline, p;.D,, ~ ~ ~ and Glass Products," C169-53 (1955). R. D., ANAL.CHEM.26, 342 (1954). (3) Gillies, G. M., Keen, N. J., Lister, (11) 34,Webster, 305~ (1951). P. A., J. A m . Ceram. S O C . B. A., R ~ D.,~ ~ ~ ,t E~~~~~ ~ R ~~ i G. Brit. C/M 255 (Oct. (12) Wherry, E. T., Chapin, W. H., J. Am. C h m . SOL 30, 1687 (1908). (4)Hiliebrand, F.,Lundell, G. E. F. (revised by Lundell, G. E. F Bright, RECEIVEDfor review Januarv 16, 1959. E[. A., Hoffman, J. I.), "Appiied Inorganic Analysis," 2nd ed., pp. 749 ff., Accepted April 28, 1959. Pittsburgh Conference on Analytical Chemistry and Wiley, New York, 1953. (5) Hollander, M., Rieman, W., IND. hpplied Spectroscopy, Pittsburgh, Pa., ENG.CHEM.,ANAL.ED.17,602 (1945). March 1959.
separated from the glass by pyrohydrolysis would be desirable.
g$5$:tab1. w.
Determination of Vinyl Ethers and Other Unsaturated Compounds Modified Mercuric Acetate Procedure JAMES B. JOHNSON and JOHN P. FLETCHER Development Department, Union Carbide Chemicals
A modified methoxymercuration method has been developed for the determination of vinyl ethers and other olefinic unsaturation. It is easier to perform and has a wider application than earlier methods. The sample is allowed to react with an excess of mercuric acetate in methanol to form the mercury addition compound and acetic acid, In the case of vinyl ethers, the reaction is conducted a t - 10" C. Solid sodium bromide is added to convert the excess mercuric acetate to the bromide, permitting direct titration of the acetic acid with alcoholic potassium hydroxide. Data for the determination of 15 vinyl ethers and 2 7 miscellaneous olefinic compounds are presented. The standard deviation of the procedure for the determination of purity is 0.207&.
A
procedures employing mercuric acetate for the determination of olefinic unsaturation (1-4) have been reviewed by Polgar and Jungnickel ( 5 ) . This paper describes a modified procedure which can be used for the determination of a large number of unsaturated compounds including the vinyl ethers which have been largely ipnnred in earlier papers NALYTICAL
Co.,Division of
Union Carbide Corp., Soufh Charleston, W . Va.
REAGENTS
Mercuric acetate, approximately 0.12M solution in anhydrous, reagent grade methanol. Dissolve 40 grams of mercuric acetate (reagent grade) in sufficient methanol to make 1 liter of solution. Stabilize the reagent b y the addition of 3 to 8 drops of glacial acetic acid. Filter the reagent before using. When used in the procedure, 50 ml. of the reagent should have a titration of from 1 to 10 ml. of 0.1N potassium hydroxide. Standard potassium hydroxide, 0.1N solution in methanol. Phenolphthalein indicator, 1.0% methanolic solution. Sodium bromide, reagent grade crystals.
sample and the blank to stand in the bath at - 10" C. or lower for 10 minutes. To each flask add 2 to 4 grams of sodium bromide and swirl the contents to effect solution. Add approximately 1 ml. of the phenolphthalein indicator and titrate immediately with standard 0.1N methanolic potassium hydroxide to a pink end point. Do not permit the temperature of the solution to exceed 15' C. during the titration. Because the method is based upon an acidimetric titration, take the usual precautions t o avoid interference from carbon dioxide. Reaction time and temperatures for other compounds are shown in Table 11. DISCUSSION
PROCEDURE FOR VINYL ETHERS
Pipet 50 ml. of the mercuric acetate reagent into each of two 250-ml. glassstoppered Erlenmeyer flasks. If a sealed glass ampoule is specified, use heat-resistant pressure bottles containing a few pieces of 8-mm. glass rod. Cool the contents of the flasks between - 10' and - 15" C. (A bath of chipped ice and methanol can be maintained below -10' C. for more than an hour without difficulty.) Reserve one of the flasks for a blank determination. Into the other flask introduce an amount of sample containing from 3.0 to 4.0 mea. of vinv! ether Allow both the
The vinyl ethers and certain other compounds react n.ith mercuric acetate in methanol to form mercury addition compounds which are unstable a t room temperature. These compounds can be determined quantitatively if the solution temperature is maintained below -10" C. during the reaction and is prevented from esceeding 15" C. during the titration step. Tin!-1 ethyl ether may also be determined by both the Martin (4)and Dns ( 1 ) procedures if these conditions of temperature arr observed. Presumably othtr viny! ethers may also be determined b r . these t w o prucedures if the temoeraturt
~
b
Table 1.
Vinyl Ethers Determined by Modified Mercuric Acetate Procedure
Purity, Av. No. Wt. Devia- of % tion Detns.
Compound 1-Butenyl methyl ether. 97.7 Divinyl Carbitol 98.4 1-Propenyl ethyl ether 97.4 Vinyl allyl ether 99.0 Vinyl butyl Cell+ solve 100.0 Vinyl butyl ether0 98.9 Vinyl (%butylmercaDto)ethvl . , " 100.0 ether Vinyl Carbitol 100.8
0.0 0.1
2 2
0.0
0.4
2 2
0.1 0.2
2 3
0.1
0.1
2 2
Compound Vinyl 2-chloroethyl ether Vinyl ethyl ether0 Vin 1 hexyl drbitol Vinyl isobutyl ether0 Vinyl propyl ether Vinyl tetradecyl ether Vinvl undecvl eeher ~I
Purity, Av. No. Wt. Devia- of % tion Detns. 97.3 98.9
0.0
0.2
2 14
100.1
0.1
2
98.6 97.0
0.2 0.3
2
95.2
0.1
2
96.2
0.1
2
2
Use a sealed glass ampoule or an aliquot from a methanolic dilution of the sample.
Table 11.
Determination of Purity of Unsaturated Compounds by Modified Mercuric Acetate Procedure
Purity, Wt. % 98.8 98.8 99.1 100.1 95.4 97.4 98.5 99.7 94.1 97.6 97.0 97.1
Compound Allvl acetate A161 acetone Allyl alcohol 2-Ally1-3-methyl-2-cyclopenten-Pol-l-one Butyl chrysanthemum monocarboxylate 2-Chloro-1-propenyl butyl ether Cyclohexene Dichlorostyrene 2,SDimethyl-l,5--hexadiene 3,4-Epoxy-l-butene 2-Etho~y-3~4-dihydropyran 2-Ethoxy-5-methyl-3,4-dihydropyran 3-Ethoxy-4-propyl-5-e thyl-3,4dihydropyran 96.2 2-Formyl-3,4-dihydropyran 97.0 3-Hydrox 8nonen-2,5-dione 98.9 Methally Tihlonde 97.9 2-Methoxy-3-ethyl-3,4-dihydropyran 100.0 %Methoxy-3-ethyl-4-rnethyl-3,4-dihydropyran 96.1 %Methoxy-3-rnethyl-3,4-dihydropyran 101..5 %Methoxy-3-methyl-4-propyl-5-ethyl-3,4dihydropyran 97.2 4-Methyl-3,4-dihydropyran 98.7 4-Methyl-1-pentene 98.2 a-Methylstyrene 99.2 Styrene 99.6 Vinyl acetate" 99.0 N-Viny lpipendone 99.1 N-Vinylpyrrolidone 97.0
Av. No. Deviaof tion Detns. 0.0 2 0.i 2 0.1 4 0.0 2 0.0 3 0.4 2 0.1 4 0.2 3 0.1 0.0
3
0.1 0.2
2 4 4
0.0 0.0
4 4
Min. Time, Min. 60 20 1
10 60 15
1 I.20 15
60 30 30
30
30 ..
3
0.1 0.0 0.0 0 1
4 7 6 6
10 15 30 30 30
0.1 0.0
3120
0.1 0.0
2 2 2 4 2 4 2
0.3
10
10
0.2
0.0
0.1 0.1
15
30 5 10 10 10
25
- 10 ~. 25
- 10
25 25 25 25 ~. 25 25
Compound Allyl acetate Allyl alcohol Cyclohexene a-Methylstyrene Vinyl acetate Vinyl ethyl ether Q
Purity, wt. 72 98.3 99.7 94.2 85.9 99.4 98.7O
0
25 25 - 10 25 25 25 25 25
- 10
~.
25
- 10 25 25 25 25
0.3
0.1 0.4 1.5 0.0
0.1
Modified by carrying out reaction below
1564
ANALYTICAL CHEMISTRY
No. of
Detns. 5 4 8
3
3
4
Punty, wt. yo 98.8 99.1 98.5 99.2 99.0 98.9
Like the other methoxymercuration methods, this procedure is most suitable for the determination of unsaturated compounds containing a terminal double bond or a n internal double bond with a cis configuration. +?-Unsaturated acids, aldehydes, esters, ketones, and nitriles do not react quantitatively under the conditions employed. Inorganic salts, especially halides, must be absent from the reaction mixture. Inasmuch as the method is based upon a n acidimetric titration, the sample must be neutral to phenolphthalein or a suitable correction applied. Care must also be taken to exclude carbon dioxide, which titrates as an acid.
0
LITERATURE CITED
Comparative Purity Data
Das Method Av. dev.
LIMITATIONS A N D INTERFERENCES
0
* Each mole of vinyl acetate results in consumption of two equivalents of KOH due to ease of saponification of reaction product.
Table 111.
is controlled. The vinyl ethers which have been quantitatively determined by the procedure in this paper are shown in Table I. Table I1 contains reaction conditions for some of the other compounds which have been determined by this method. T o establish the optimum conditions, each sample was first tried at 25" C. for various times and, if the results were low, the temperature was lowered to 0" or -10" C. and the times were varied again. If longer times than the minimum did not give the same results within the precision of the method, the compound was not included in Table 11. Allyl acetate and certain other unsaturated esters are not hydrolyzed under the nonaqueous conditions of this procedure, whereas vinyl acetate is saponified quantitatively. a-Methylstyrene, a compound whose mercury addition product is unstable toward halogen acids ( I ) , can be determined by this procedure. The accuracy of the method was compared with that of Das ( I ) by determining the purity of six unsaturated compounds (Table 111). For cyclohexene and a-methylstyrene, better results are obtained using the method in this paper.
This Method Av. No. of dev. detns. 0.0 2 0.1 4 0.1 4 0.1 4 0.1 4 0.2 14
- 10" C . for 10 minutes.
(1) Das, M. N., ANAL.CHEM.26, 1086 (1954). ( 2 ) Marquardt, R. P., Luce, E. N., Ihid., 20,751 (1948). (3) Ihid., 21, 1194 (1949). (4) Martin, R. W., Ibid., 21,921 (1949). (5) Polgar, A., Jungnickel, J. L., "Organic Analysis," Vol. 111, ed. by John Mitchell, Jr., I. M. Kolthoff, E. S. Proskauer, A. Weissberger, pp. 301-10, New York, Interscience, 1956. RECEIVED for review November 13, 1958. Accepted March 27, 1959.
