LITERATURE CITED
Browning, L. C., Watts, J. O., AXAL. CHERI. 29, 24 (1957). Fair, F. V., Friedrich, R. J., Zbid., 27. 1886-8 (1955). Jager, A., Ilattwinkel, O., Brennstof-Chem. 31, 65-79 (1950). Jones, B. IT,, Neumorth, 11. B., I n d . Eng. Chem. 44, 2872 (1952). Iiarr, Clarence, Jr., Brown, P. lI., Abstracts of Papers, 130th RIeetin5, ACS, rltlantic CitT-, 3966, p. 41%.
(6) Karr, Clarence, Jr., Brown, P. M., Estep, P. A., Humphrey, G. L., Fuel 37, 227-35 (1958). ( 7 ) Iihalturin, A . I., I a e s f . A k a d . .vauk Kaiakh. S.S.R., Ser. Khim. KO.8, 154-65 (1'355). (8) Ozaki, T., Coal Tar (Tokyo) 3, 11217 (1951). (9) Parant, A , , Cornpt. rend. congr. i n d . gat. 65. Congr., Paris, 409-21 (1948).
(10) Pound, G. S., Coke a n d Gas 14, 35562, 401-7 (1952).
(11) Watson, G. H., Williams, -1.F., A n n . mines Belg. 1957, 154-67. (12) Kiebe, 8.K., J. Phys. Chem. 60, 685
11956).
(13) Woolfolk, E. O., Golumbic, C., Frie-
del, R. A4., Orchin. AI., Storch, H. H., U. S. Bur. Mines, Bull. 487 (1950). ~ ~ C E I V Efor D review SeptPniber 19, 1957. .4ccepted April 4, 1958. Division of Gas and Fuel Chemistry, Symposium on Modern Techniques in Research on Coal and Related Products, 132nd LIeeting, ACS, Sew York, 3.T., September 195i.
Analytical Reactions of tert-Butyl Hypochlorite CLAYTON
E.
VAN HALL' and
K. G.
STONE
Kedzie Chemical Laboratory, Michigan State University, East Lansing, Mich.
b In searching for an organic oxidizing
APPARATUS A N D REAGENTS
agent to use in nonaqueous solvents, the properties and reactions of tertbutyl hypochlorite, which i s stable in the pure form, were investigated. Acetic acid solutions are decomposed b y mineral acids; slowly decomposed b y water, b y reducing substances in the acetic acid, or b y light; and rapidly converted to solutions of chlorine b y inorganic chlorides. Acetic acid solutions can be standardized b y iodidethiosulfate or oxalate-cerate procedures. fert-Butyl hypochlorite itself reacts only slowly with olefinic unsaturation. Direct titrations with the reagent as a source of chlorine using chloride solutions were possible in limited cases. Applications of tert-butyl hypochlorite to quantitative nonaqueous oxidations are limited.
Potentiometric titrations xere carried out \Tit11 a Sargent potentiometer and platinum. fiber-trpe calomel, and silversilver chloride electrodes. Amperometric titrations were made with a Sargent Model 111 manual polarograph and a Beckman t n in inlay platinum electrode. All titrations with tert-butyl hypochlorite required an amber buret with a nylon stopcock unit. Small liquid samples .were w i g h e d with a hypodermic qyringe. -411 inorganic chemicals were reagent grade. Phenol was 99.8% pure by bromination (12). Hydroouinone assayed 100.5% v-ith ceric sulfate (6). Cnsaturated hydrocarbons were analyzed by acid-catalyzed bromination (3). Reagent grade glacial acetic acid (99.7y0) was used TT ithout pnrification unless othernise stated. To free acetic acid of reducing impurities, 1 liter wxs refluxed with 20 grams of chromic acid for 2 hours and distilled ilcetic acid was made anhydrous by refluxing 1 liter with 50 ml. of acetic anhydride for 4 hours and then distilling. The method of Teeter and Bell (14) JTas used to prepare tert-butyl hypochlorite. The crude product was distilled and then stored in amber bottles. By iodometric analysis, the fresh material \yas 96.3% tert-butd hypochlorite. and after 8 months in the amber bottle it was 95.47,. The 0 1.Y solution of tert-butyl hypochlorite for titrations was prepared by diluting 5.4 ?rams of purified material to 1 liter TI ith glacial acetic acid and was stored in an amber bottle out of direct sunliqht. Standard solutions of sodium thiosulfate, ceric sulfate, silver nitrate, potassium bromate-potaqsium bromide, dichlorofluorescein indicator, and starch indicator \yere prepared by customary procedureq.
M
OST quantitative oxidations and reductions of organic molecules in nonaqueous solutions have used inorganic reagents (5, 7 , 8, 11, 15, 16). These reagents are relatively insoluble in organic solvents and the solutions are irnstable. To find a soluble reagent 11 hich gave stable solutions, tests with tert-butyl hrpochlorite were carried out in glacial acetic acid as the solwnt. Thr preparation, properties, and reactions of pure tert-butyl hypochlorite have been summarized ( I ) . However very little information is available a t concentrations of 0.1111 or less, as would he used for analytical purposes. Frequently reactions n hich proceed qinoothly and in good yield are not satisfactory n-hen diluted with a solvent. For analytical use, acetic acid is convenient and readily availahle. 1 Present address, Dow Chemical Co., lIidland, llich.
1416
ANALYTICAL CHEMISTRY
STANDARDIZATION OF ACETIC ACID SOLUTIONS
Several investigators ( I , I S ) stated that tert-butyl hypochlorite oxidizes
iodide to iodine quantitatirely :
+
(CH$),COCl 2HI -t (CH3)aCOH
+ HC1 + I?
(1)
Because the rate of this reaction and the effect of air oxidation had not been . chrcked, a series of iodine flasks containing 50 ml. of n-ater. 3 granis of potassium iodide, and 25-ni1. aliquots of pither 0.l.Ytert-butyl hypochlorite solution or glacial acetic acid \vas prepared. Bfter standing for varying periods, the iodine was titrated with sodium thiosulfatr. -4ir oxidation of iodine is a serious factor, but if the iodine is titrated nit'hin 5 minutes, little error is found because the reaction is very fast. To show that the liberation of iodine n-as quantitative, some independent check 011 the concentration of the tertbutyl hypochlorite v a s required. Both sodium oxalate (8) and arsenious oxide ( l 5 ) , which have been used in nonaqueous solvents, are only sparingly soluble in glacial acetic acid, but sodium oxalate is soluble to 0.04AYin 4 to 1 acetic acidwater solution. Under this condition, the expected reaction is:
+
+ +
(CHs),COC1 NapC1OA CHICOOH + (CH),COH 2CO: KaC1 CH3COOSa (2)
+
+
As hypochlorites react \T-ith chloride to form chlorine, shaking is necessary t o keep any chlorine formed in contact vith the oxalate. TKOsets of analyses were designed to check this reaction. Aliquots of 25 ml. of tert-butyl hypochlorite solution were added to 0.2680 gram (4 meq.) of sodium oxalate dissolved in 20 ml. of water plus 55 ml. of glacial acetic acid in iodine flasks. The flasks were stoppered and allowed to stand n-ith frequent shaking. The hypochlorite not consumed vias determined iodometrically. The hypochlorite-oxalate reaction required a t least
45 minutes, and no detectable loss of oxidizing pon-er occurred in 60 minutes. \Yith higher chloride concentrations, chlorine is formed and lost. The second set of analyses was based on the titration of excess sodium oxalate with ceric sulfate. The expected oxidation products did not interfere in the cerium titration. Keighed 0.25-gram samples of sodiuni oxalate nere added to 20 nil. of distilled water plus 55 nil. of glacial acetic acid in 500-nil. iodine flasks. Then 25-nil. aliquots of tert-liutyl hypochlorite n ere added, and the flaqks n ere allon ed to stand a t least 1 hour v i t h frequent shaking. Tlie excess oxalate vas detcrniined by adding 120 nil. of n.ater, 30 nil. of concentrated hydrochloric acid, and 5 nil. of 0.005M iodine monochloride, heating to 50" C., and titrating n i t h ceric sulfate to a ferroin end point. The data in Table I show that tlie stoichiometry iq exact and suggest that no loss of the hypochlorite occurs in thi. oxalate method. STABILITY OF SOLUTIONS Several factors should affect tlie stability of tert-butyl hypochlorite solutions including the amount of water, the presence of reducing substances, acids, and bases, and light sensitivity. Approximately 0.1-Ysolutions of tertbutyl hypochlorite were prepared in glacial acetic acid (99.7%), acetic acid containing 10% water, and anhydrous acetic acid prepared b y treatment of acetic acid n i t h acetic anhydride. These solutions were stored in stoppered bottles of brown glass out of direct sunlight and were analyzed periodically by iodometry. Commercial glacial acetic acid solutions lost 3%) and the 90% acetic acid lost 6% in 28 days. Drying with acetic anhydride increased the rate of loss. Daily standardization n as adequate for glacial acetic acid solutions. The effect of reducing materials n as checked b y preparing solutions of tertbutyl hypochlorite in commercial glacial acetic acid, in acetic acid treated v i t h chromic acid, and in acetic acid plus acetic anhydride treated n ith chromic acid. Treatment t o remove reducing substances had little advantage compared t o coinmercial acid. The decomposition of tert-butyl hypochlorite in n a t e r is catalyzed by acids and bases (1). T o test this effect in acetic acid, solutions of tert-butyl hypochlorite n ere made 0.1S in perchloric acid, hydrochloric acid, p-toluenesulfonic acid, and sodium acetate. The qolutions were analyzed iodometrically after 15 and 60 minutes. Both perchloric and p-toluenesulfonic acids, which are ionized in acetic acid, catalyzed the decomposition. Hydrochloric acid mhich is only partially ionized had some effect, hut sodium acetate which is a base in acetic acid had only a slight effect. The
Standardization of Hypochlorite Solution by Sodium Oxalate Method Sa2C204 0.0981N Sa2Ce04,N e q . Taken, ROC1, Ce(SO&, 11eq. 111. RI1. Left Consumed S ROCP 3 970 24 97 17 84 1 750 2 220 0 0889 4 009 18 20 1 785 2 224 0 0891 4 217 20 35 1 996 2 221 0 0890 a 0.08895 by iodine-thiosulfate method.
Table I.
~
Table II.
Electrode S j stem Satd ea1 -I't dg-AgC1-Pt A g -AgC1-Pt
Potentiometric Direct Titration of Styrene
_~ Styrene, Gram Taken 0 1738 0 1990 0 1678
_.
Found 0 1733 0 1985 0 1657 ~~~
Table Ill.
By BY 09 5 99 5 98 9
~
Amperometric Direct Titration of Styrene
H J pochloiite 111. s 3 7 43 0 0978 42 80 0 1008 39 90 0 1014 a
76Styrene
By ROC1 99 7 99 8 98 7
S t j rene, Giam Taken Found 0 1912 0 1007 0 2250 0 2246 0 2113 0 2106
5% Stjrene" 99 7 99 6 99 7
99 sC%b j bromination
effect of hydrochloric acid is questioiiable, because some chlorine n as formed. Applications of tert-butyl hypochlorite are limited by the effects of acid and chloride ion. The light sensitivity of 0.1-Yfert-hutyl hypochlorite solutions n as checked hy &Tiding an acetic acid solution in half, storing one part in an amber glassqtoppered bottle and the other in a clear glase-stoppered bottle, keeping both out of direct sunlight, and periodically analyzing both solutions iodometrically. The normality decreased froin 0.0942 to 0.0843 in the clear bottle and from 0.0942 to 0.0870 in tlie amber bottle in 28 days. END POINT DETECTION
E n d points have been detected for redox titrations in glacial acetic acid potentiometrically with platinum-calomel (15, 16) and silver-silver chloride-platinun1 (8) electrodes and amperonietricall>- n i t h two active platinum electrodes (7, 8). Both methods can be used 11-ith tert-butyl hypochlorite. Some difficulties were found with potentiometric detection of the end point. For reactions n here tert-hutyl hypochlorite is taken up completely-i.e., where chloride is not a product--very small or no potential changes were observed. If the acetic acid contained 0.5111 sodiuni acetatr. a change of 500 niv. n as observed. If lithium chloride n-as prtsent, a change of 600 mv. was obser-ved because tlie chlorine-chloride system is formed. The potentials were not steady, but end point detection was po..ible. \Then tert-butyl hypochlorite is added t o acetic acid, no current is found amperometrically with applied potentials up to 3 volts. Addition of lithium
chloride, 11-liich forms chlorine, gave large currentq, depending on the concentration. Sodium and potassium clilorides are too inqolulilr. t o he useful. For 0.1J1litliium chloride. 50 niv. applied to the electrode. gave a large current nitli only l drop of 0.1-1- tert-butyl 11)-poclilorite solution added to 50 nil. of acctic arid. REACTION WITH UNSATURATES
Eec-ause tert-l)utyl li!-pochlorite adds t o ethylenic honds readily. attempt's lx-ere made to determine if tlie time of reaction were reasonable under analytical conditions. Excess 0.1-Y tert-butyl hypochlorite was added to known amounts of hydrocarbons in glacial acetic acid, and the excess n-as measured iodometrically after varying periods. K i t h cyclohexene and 2-octene the uptake was rapid, and with styrene and divinylbenzene the uptake x i s s l o ~ . -4s the uptake continued 11-ith time and n-ent beyond that calculated from bromine uptake (3) in all cases, this approach was unsatisfactory. Addition of Chlorine. Under ordinary conditions, chlorine adds t o unsaturation as well as oxidizing t h e h y d roc a r boil further. The c oiidi t i ons used for tcrt-butyl hypochlorite were tested for moderation of chlorine oxidation. Separate experiments s h o v e d t h a t t h e addition of 0.5 gram of lithium chloride gave a quantitative conversion of tert-butyl hypochlorite t o chlorine and that the loss of chlorine on standing in acetic acid was within t'he titration error. d series of samples of unsaturates iia acetic acid was run as in the previous experiments on the addition of tertbutyl hypochlorite, except that 0.5 gram of lithium chloride was added to VOL. 30, NO. 8, AUGUST 1958
1417
all samples. The rate of chlorine uptake was reasonably fast, but not instantaneous. I n all cases, more chlorine was absorbed than bromine. None of the compounds tested could be determined b y excess chlorine using this method. DIRECT TITRATION
Because chlorine adds rapidly to unsaturates, but oxidizes most of them a t the same time, a direct titration with tert-butyl hypochlorite might control the chlorine. Both chlorine and chloride would be present, and either potentiometric or amperometric end point detection should be possible. Styrene plus lithium chloride in acetic acid could be titrated potentiometrically with tert-butyl hypochlorite in acetic acid. Platinum and silver-silver chloride electrodes were used. The substitution of a saturated calomel electrode for the silver-silver chloride electrode was not satisfactory, as equilibrium was reached very slowly and the values were more erratic. The potentiometric titrations summarized in Table I1 were satisfactory. These titrations are much slower than usual aqueous titrations, and the curves are abnormal. For amperometric end point detection using two platinum electrodes, an applied potential of 50 my. was used. Samples were rreighed using a hypodermic syringe, and 0.5 gram of lithium chloride was added per 100 ml. of acetic acid solvent. The hypochlorite solution was added rapidly until a fleeting current was observed. The solution was then added slowly until a steady current v a s observed. A blank sholyed
that 0.02 ml. of hypochlorite solution gave a steady current. No physical attack of the electrodes was detectable b y either physical inspection or change in sensitivity. As a precaution, the electrode mas stored in dichromate cleaning solution. The results for styrene in Table I11 are a little higher than the bromine uptake indicated. Other unsaturated compounds a ere titrated to see if the method had any advantages. hIaleic acid, cinnamic acid, cinnamaldehyde, crotonic acid, crotonaldehyde, methyl acrylate, allyl chloride, 2-butyne-lj4-diol, and 2,5-dimetliy1-3-hexyne-2,5-diol were unreactive. Divinylbenzene gave fair results. The low results for cinnamyl alcohol and vinylacetic acid were caused by the slow rate near the end point which made it impractical t o complete the titration. The high results for cyclohexene, oleic acid, methyl undecenoate, allyl alcohol, mesityl oxide. allyl acetate, 1-octene, 2-octene. 3-heptene, 2,5dimethyl-1, 5-hexadiene, and vinyl acetate suggest that processes other than addition are occurring. Other workers reduced the temperature t o minimize substitution reactions (4). Addition of 10% tmter or 20% carbon tetrachloride permitted a temperature of 5” C. during the titration. KO improvement in results mas noted. The addition of bromine has been catalyzed by acids (3) and heavy metals. notably mercuric chloride (2,9,10). The use of acids is prohibited by the decomposition of tert-butyl hypochlorite, Titrations with mercuric chloride present were run on styrene, l-octene, 2-octene, 3-heptene, and vinyl acetate with various combinations of solvent mixtures, temperature, and cata-
lyst. A11 results were higher than with acetic acid alone. It must be concluded that the cases where chlorination is of great value are limited. LITERATURE CITED
(I) hibar, LI., Ginsberg, D.; Chem. Rezs. 54, 925-58 (1954). (2) L. 21, 1461-5 . . Braae, B., * ~ z N . ~ CHEII.
(1949). (3) Byrne, R. E., Jr., Johnson, J. B., Ibid., 28, 126-9, (1956). (4) DuBois, H. B., Skoog, D. -L, Ibicl., 20, 624-7 (1948). (5) Freedman, R. W., Ibid., 28, 247-9 (1956). (6) Furman, ?;. H., Wallace, J. H., Jr., J . Am. Chem. SOC. 52, 1443-7 (1930). ( 7 ) Hinsvark, 0. S . , Stone, K. G., . I s a ~ CHEM. . 27, 371-3 (1‘355). ( 8 ) Ibzd., 28, 334-T (1956). (9) Le&, J. B., Bradstreet, R . B., ISD. ENG.CHEX, AXAL. ED. 12, 38790(1940). (10) Lucas, H. J., Pressman, D., I b i d . , 10, 140-2 (1938). Sovotny, ‘J., Chem. lzsty 4 8 , 1865-7 (1954). Stone, K. G., “Determination of Organic Compounds,’’ up. 123-4, McGraw-Hill, Yew York, 1956. (13) Teeter, H. M.,Bachman, R . C., Bell, E. \ICowan. .. J. C.. I n d . Eno. C h e m . 41, 848-62 (1949). Teeter, H. ll.,Bell, E. JT., Ory. Syntheses 32, 20-2 (1952). Tomicek, O., Heyrovsk?, A., Collect i o n Czechoslo< Chem. Communs. 15. 997-1020 11950). (16) Tomieek, O., Valcha; J., Ibid., 1617, 113-26 (1951-2). ~~
RECEIVEDfor review August 29, 1957. Accepted ilpril 2, 1958. Abstracted from thesis submitted by Clayton E. Van Hall to the School for Advanced Graduate Studies. Llichigan State University, as partial requirement for the degree of doctor of philosophy, 1956
Determination of Blood Alcohol Improvements in Chemical a n d Enzymatic Procedures PAUL L. KIRK, A. GIBOR, and KENNETH P. PARKER School of Criminology, Universify of California, Berkeley, Calif. A combination aeration and distillation procedure, which has the advantages of a double distillation method, is used for determination of alcohol by dichromate oxidation. The sample is held on a folded filter paper impregnated with acidic salts, which retain any basic components of the sample. Aldehydes and ketones, as well as organic acids, are retained by washing through an alkaline mercuric oxide suspension. A second procedure utilizes the enzyme liver al-
1418
ANALYTICAL CHEMISTRY
cohol dehydrogenase and coenzyme l to produce enzymatic oxidation of the alcohol. A simplified diffusion system allows multiple determinations with a minimum time and number of operations. Direct and comparative data show the utility of the two procedures.
T
determination of the alcohol content of blood has assumed great importance in recent years, especially in law enforcement, and secondarily in HE
research and practice dealing with rehabilitation of chronic alcoholics. -4 multiplicity of methods dates back to that of Kidmark (11), on which have been based nearly all subsequent chemical procedures. This method utilized oxidation of the separated alcohol by acid dichromate solutions; this, also, has been generally adopted by later investigators. Brief excursions into the use of permanganate, especially in alkaline solution (8),have been made but generally abandoned.
1
