i
SEPTEMBER, 1933
INDLSTRIAI, AND ENGINEERING CHEMISTRY
proper oxidation-reduction equilibrium in the beer before bottling. De Clerck, who conducted a series of experinients to inrestigate this phenomenon, found that beers redured rapidly by sunlight' had a distinct "light' taste" while check samples Tvhich had reduced slo~vlyin the dark were absolutely free from it. On the ot'her hand, light did not change the taste when reduction had been prevented by aeration. Beer which was partly reduced by standing for some time in the ljarrel or hottle was much more susceptible to light taste than beer which had heen filled up recently. These results were obtained by determining the reducing action of the beer on niethylene hlue. Becauqe of the high sensitivity of beer to air, the oxygen of which disturbs the once-established balance of the oxidation-reduction systems, it seems that every contact of the finished beer with air should be avoided; this is particularly true during the filling operation. Replacement of the air in this process by carbon dioxide gas can only prolong the keeping qualities of the heer.
Yeast Turbidities Biological tests have indicated that for the developnient of each microorganism a specific r H range represents the most favorable conditions. Considered from this point of v i e y the heretofore accepted classification between aGrobic and anaerobic microorganisms finds a different explanation. Experiments have been successful to grow so-called anaerobic bacteria in the presence of air after t'he r H of the nutrient medium was properly adjusted.
1045
Yeasts growonlyat a rather high r H (above 13)-that is, in well-aerated beers. Otherwise propagation stops and the yeast cells present precipitate, in the majority of cases forming only a minute sediment. The keeping quality of a beer, particularly where yeast turbidities are to be expected, depends therefore on the fact that reduction of the beer takes place to an r H below the range of the respectire yeast strain before propagation can start. Compared with this factor, the clegree of infect'ion is of minor influence. Assuming from the results obtained so far that the propagation of inicroiirganisms has a definite relationship to the rH, the control of this factor will be an effective means for combating yeast turhidities. Low fermentable sugar content of the beer and a limited contact of the beer with air during processing will minimize returns caused by yeast turbidities. The occasional use of minute quantities of an as sulfurous acid, t'o prevent yeast grom-th finds its explanation in the reducing action of the chemicals rather t,han in their germicidal effect, which is imperative in the concentrations used. Bacteria seem to be less sensitive to the rH, but undouljteclly further studies will also bring about a better underqtanding of their living conditions.
Literature Cited (1) De Clerck, J., TVochschr. Brazc., 51, 196-200. 204-7, 37s-81 (1934). ( 2 ) Mendlik, F., Ihid., 51, 305-7 (1934). RECEIVED .ipril 27, 1933
Reduction of Nitrobenzene with Dextrose in Alkaline Solution N1CHOL;IS OPOLONICK
V
OHL first carried out the reduction of
iiitrohenzene to aniline in alkaline solution (ii), and later a process of reducing nitrobenzene with molasses or sawdust was patented ( 2 ) . In recent years an exhaustive study of the influence of experimental conditions on the nature and yields of the reaction products fornied in the reduction of nitrobenzene has been in progress in the laboratory of Fordham University ( i ) . The present investigation deals with the yields of azoxybenzene, azohenzene, and aniline under varied conditions. I t has been found that the yields of reduction products are materially influenced by temperature, relative concentration of the reactants, hydroxyl-ion concentration, and the extent of dilution. The hydroxyl-ion concentration was varied in some of the experiments by substitution of sodium carbonate or calcium hydroxide for sodium hydroxide.
Experimental Procedure The reductions were carried out in a three-neck flask equipped with a reflux condenser and a stirrer which could be driven at 600 revolutions per minute. The third neck of the flask served for introduction of the glucose. At the start the sodium hydroxide solution of the desired concentration was run into the flask, along with I/a mole of
Fordham UniFeeraity-,Sew York, N. l-.
nitrobenzene-i. e., 34.2 cc. or 41 grams (the amount used in a11 experiments). With the temperature of the hath at' 55" t o 60" C., the dextrose in solid form was introduced in small portions over a 1-hour period, and then a reaction temperature of 100" C. \Tas maintained for 2 hours. The process was carried out with continuous stirring. At the end of the operation, the aniline and unreduced nitrobenzene were separated from the nonvolatile azoxghenzene by steam distillation. The aniline was separated from the nitrobenzene by steam distillation after the former had been converted to hydrochloride. It was found that, with azobenzene present, there mas no unchanged nitrobenzene. The azobenzene and azoxybenzene were purified by recrystallization from methyl alcohol, and the aniline was converted to acetanilide. Boiling points or melting points, as well as the usual comparison with authentic samples, were made on all three products. It was observed in the case of strongly concentrated caustic solutions that the reduction proceeded with the greatest velocity in direct sunlight; accordingly all experiments were performed approximately under the same light conditions. Preliminary experiments showed that, when the temperature \vas held at 55" to 60" C. for 1 hour and then brought to 100' C. for 2 hours, maximum yields were obtained. These temperature conditions were maintained in all experiments. In the study of the effect of the concentration of sodium hy-
INDUSTRIAL AND ENGINEERING CHEMISTRY
1046
VOL. 27, NO. 9
TABLEI. EFFECT OF SODIUM HYDROXIDE CONCENTRATION 7 -
160 Grams NrtOH-
Water
Nitrobenzene
cc .
Grams
%
%
%
200 400 800 1200 1600 2000 3000 4000
16.2 9.0
40 58.1 72.7 59 54.5 42.4 39.3 33.9
None None
4.8 4.8 9.6 11.6 12.9 12.9 22.5 25.8
None None None None None None
Azoxybenzene
Azobenzene
I
Aniline
0.3 1.6 4.9 6.6 6.6 16.5
(Dextrose, 90 grams) 80 Grams NaOH NitroAzoxyAzobenzene benzene benzene Grams None None None None None None None None
%
%
%
71.5 69.6 60.6 50 39.3 37.8 29.0
0.3 0.9 1.9 6.6 5.9 7.2 9 2 21.1
6.7 12.9 16.1 20.9 25.1 27.7 37.0 45.1
None
droxide on the reduction of aeoxybenzene to azobenzene, a solution of 41 grams of nitrobenzene, 45 grams of dextrose, and 60 grams of sodium hydroxide in experiments 1 and 3, and 40 grams in experiment 2, in 400 cc. of water was kept at 55' to 60' C. for 1 hour and then at 100' C. for 2 hours; the solutions indicated in the following table were added and mixed; and the temperature was maintained at 100" C. for 2 additional hours: Expt. No.
Water
Dextrose
1 2 3
600 600 600
90 90 135
Sodium Hydroxide None
AZObenzene 79.5 46.5 10.5
40 40
15.1 60.6
6 0
d
Haber (3) showed that the reduction of nitrobenzene by chemical or electrolytic means in weakly alkaline medium proceeds in the following manner: nitrobenzene, nitrosobenzene, P-phenylhydroxylamine. The further reduction of phenylhydroxylamine is modified by the condition under which the reduction proceeds. Brand and hfahr showed that nitrosobenzene and phenylhydroxylamine in the presence of alkali form azoxybenzene (1). Tables I and I1 indicate that the yield of azoxybenzene is greatest in a concentrated solution of sodium hydroxide, and that in very dilute solution the azoxybenzene cannot be obtained. However, if the sodium
0
a
to# I
(Sodium hydroxide, 60 grams) Grams Dextrose- -90 Grams Dextrose--45 Grams DextroseAzoxyAzoAzoxyAzoAzoxyAzobenzene benzene Aniline benzene benzene Aniline benzene benzene Aniline
%
%
%
%
%
%
%
%
None None None None None None None None
24.7 26.4 47.8 46.2 41.2 24.7 24.4 4.9
19.3 20.9 24.1 32.2 35.4 48.3 48.3 51.6
71.2 57.5 42.4 26.6 18.1 3.0
0.9 3.0 11.5 14.5 14.8 17.1 22.4 17.1
9.6 17.7 22.5 37.0 40.3 43.5 58.0 59.6
83.0 81.8 76.3 73.3 70.6 68.4 63.6 55.7
None None None None None None None None
hydroxide solution is very concentrated, as shown in Table I, some nitrobenzene remains unreduced. With sodium carbonate, nitrobenzene reduces to aniline and no azoxy- or azobenzene is found. The effect of hydroxyl-ion concentration on the optimum yield of aniline, azobenzene, and azoxybenzene is apparent from Tables I and 11. However, to show that the reduction of nitrobenzene depends not only upon hydroxyl-ion concentration but also upon dilution, in one set of experiments the hydroxyl-ion concentration was kept approximately constant with a large quantity of calcium hydroxide, and the dilution was varied. Figure 1 shows that the yield of aniline, with constant hydroxyl-ion concentration, increases with dilution u p to 1200 cc., then the yield decreases. The two main factors in the reduction of nitrobenzene in aqueous alkaline solution either to aniline or azoxybenzene are the difference in hydroxyl-ion concentration and the quantity of water used.
None None None None None
DEXTROSE 90 OM.
-120
None None
% 24.1 27.4 3.5.4 45.1 53.2 61.2 61.2 60.3
I SGDIUM HYDROXIDE 40 GU. 11 SODIUM CARBONATE 106 OM. 111 CALCIUM HYDROXIDE 55 GM.
8 1
TABLE11. EFFECT OF DEXTROSE CONCENTRATION
200 400 800 1200 1600 2000 3000 4000
% 4.0 3.0 8.5 8.9 13.2 7.9 6.6 5.2
% 6 3 1.5
7
Aniline
l p t v +
Azoxybenzene None 0 14 k .
cc.
Grama None None None None None None None None
40 Grams NaOHhoxyAzobenzene benzene
The maximum yield of azoxybenzene is obtained when 1 mole of nitrobenzene is reduced with 0.75 mole of dextrose in 7 . 5 molar solution of sodium hydroxide (600 cc.). The yield of azoxybenzene is 83 per cent.
Discussion and Summary
Water
Nitrobenzene
Aniline
I
11000 I
1
?om
2000
4ooo.
droxide (1200 cc.); 1.5 moles of dextrose in 1800 cc. water are added to reduce azoxybenzene to azobenzene. The vield is 79.5 oer cent.
Literature Cited
%
(1) Brand, K., and Mahr, J., J. prukt. Chem., 131, 119 (1931); 120,160 (1928). (2) Chemikalienwerk Griesheim, German Patents 225,245 (April 24, 1908) and 228,722(May 1, 1908). (3) Haber, F., 2. Elektrochem., 4, 509 (1898). (4) Hynes, W. A., doctor's thesis, Fordham University, 1927; Landau, S., and Baoharach, G., Ibid., 1929; Weber, F.. Ibid.,1930. (5) Vohl, H., Juhresber. Fortschr. Chem., 1863,410. 4.8 6.4 8.0 9.6 9.6 9.6 12.9 12.9
REcEIvm March 21, 1935.
**e
-*+a
COAL-TAR DYEEXPORT TRADEWELLMAINTAINED. United States foreign trade in coal-tar colors dyes, and stains was well maintained during the first half of the year with both imports and exports registering substantial value increases over the first half of 1934, according to the Commerce Department's Chemical Division. Exports of coal-tar colors, dyes, stains. and color lakes reached 9,274.500 pounds valued at $3,164,685 during the first half of the year, 'compared with 10,270,600 pounds valued at $2,905,600 for the corresponding period of 1934. American coal-tar dye exports enjoy wide distribution in world markets, with China, Canada, Belgium, Mexico, Japan, and Brazil the outstanding outlets. During June export shipments went forward to 49 foreign markets, according to preliminary figures. Imports of coal-tar products into the United States come almost entirely from Germany and Switzerland, with small quantities originating in England and elsewhere.
