INDUSTRIAL AND ENGINEERING CHEMISTRY
2604
00-
I
CHsCCICHa
[
?OH ] + HBr +[CHtCCICHl + Br
(12)
]+
?OH
CH&C1CH3 2HBr + (an over-all reaction for the reduction of hydroperoxide to alcohol) (13)
Vol. 41, No. 11
TABLE x. ISOPROPYL CHLORIDE OXIDATION AT 160’
c.“
[Conditions: flows (cc./min.): iso-CaH~Cl,185; 0 2 , 185; Nz,186; HBr, 461 Moles/100 Moles Consumed of Products 02 EBrb Iso-CaHiC1 Acetone 28.6 26.8 ... Bromoacetone 12.0 11.3 23.Zb Acetic acid 25.5 23.8 ... 2-Chloro-2-bromopropane 0.8 ... 18.Sb Propylene 12.0 ... ... Carbon dioxide 14.1 13.2 Carbon monoxide 27.8 26.1 ..* Water ... 59.2 ... 48% isopropyl chloride consumed, 51% oxygen consumed, 3.2% input isopropyl chloride unaccounted for, and 0.6% input oxygen unaccounted for. b Moles/lOO moles of HBr input.
...
[
-+- CHsCOCH8 + HC1
CHs!:lCHJ
(14)
FOR Z-CIiLoRo-2-RRo\rorHoP~sE F ~ R V A T I OTlle S : reaction involves the same chloroisopropyl radical produced in Equation 10:
I CHsCCICHs + Brz --+-CH3CBrCICH3
+ Br
The near equality of the molar amounts of acetic acid and carbon monoxide (see Table X) suggests a common origin and the oxidation leading to this result is expressible as follows: CHaCHClCHs
HBr + 202 --+ CHICOOH + CO + H20 + HC1 (16)
However, the steps leading to this end result are obscure and no comparable phenomena have been observed with other compounds. Attempts were made to find methyl chloride and methyl alcohol, but results were negative or at best inconclusive. It would be predicted from Equation 13 that an increase in the hydrogen bromide input should increase the acetone yield a t the expense of that of the acetic acid and actually such a trend is observed. That methyl radicals are formed in the reaction is indicated by the considerable amount of methane found when operating with higher hydrogen bromide inputs. CH,
+ HBr --+ CH4 + Br
LITERATURE CITED
(15)
(17)
With lower hydrogen bromide inputs, as under conditions of the balance run (Table X), oxygen would be expected to compete more successfully for methyl radicals and actualIy somewhat larger amounts of carbon monoxide are found. This apparent ability of isopropyl chloride to generate methyl radicals under oxidizing conditions may be responsible for its sensitization of hydrogen bromide-catalyzed oxidations.
Barnett, B., Bell, E. R., Dickey, F. H., Rust, F. F., and Vaughan W. E., IND. E m . CHEW., 4 1 , 2 6 1 2 (1949).
Dickey, F. H., Raley, J. H., Rust, F. F., Treseder, R. S., and Vaughan, W. E., I b i d . , 41, 1673 (1949). Htlckel, W., “Theoretisohe Grundlagen der Organischen Chemie,” Vol. 11,p. 86, Leipzig, Akad. Verlags., 1935. Mayo, F. R.,and Walling, C., Chem. Revs., 27, 372 (1940). Milas, N. A., and Harris, 8 . A,, J . Am. Chem. SOC.,6 0 , 2434 (1938).
Milas, N. A., and Surgenor, D. M., I b i d . , 68, 205 (1946). Ibid.,p. 643. Raley, J. H., Rust, F. F., and Vaughan, W. E., Zhid., 70, 88 (1948).
Rieche, A., “Alkylperoxyde und Ozonide,” Leipzig, Steinkopff
I
1931.
Rossini, F. D., J. Research Natl. Bur. Standards, 15, 357 (1935). Rust, F . F., Seubold, F. H., and Vaughan, W. E., J . A m . Chem. Soc., 70, 95 (1948). Rust, F. F., and Vaughan, Wr.E., IND. Eiw. CHEM.,41, 2596 (1949).
Vaughan, TI7. E., and Rust, F. F., C. S. Patent
2,395,523
(Feb.
26, 1946). Zhid., 2,403,771
(July 9, 1946). Wiles, Q. T., Bishop, E. T., Devlin, P. A., Hopper, F. C., Schroeder, C. W., and Vaughan, W. E., IND.ENG.CHEM.,41, 1678 (1949).
RICEWEOAugust 17, 1948. Presented in p a r t a t the meeting of the Gordon Research Conferences of the American Association for the Advancement of of Science, Colby Junior College, New London, N. H., June 1948.
(Oxidation of Hydrocarbons Catalyzed by Hydrogen Bromide)
OXIDATION OF STRAIGHT-CHAIN COMPOUNDS P. J. NAYXOCICI, J. H. RALEY, F. F. RUST, AND W. E. VAUGHAN Shell Development Company, Emeryville, Calv. T h e hydrogen bromide-catalyzed oxidation of propane, butane, and related compounds containing secondary carbon atoms produces ketones in high yield. The reaction-a free radical chain probably involving intermediate hydroperoxide formation-is profoundly affected by the inclusion of certain organic compounds which serve as chain branching agents-for example, isopropyl chloride-or chain initiators-for exampIe, ditert-butyl peroxide,
S DISCUSSED in the preceding papers of this series (1, 7 ) the hydrogen bromide-catalyzed oxidation of branched chain hydrocarbons produces organic hydroperoxides through attack at the tertiary position. The analogous oxidation of straight-chain compounds, in which a secondary carbon atom is involved, results in the formation of ketones ( 5 ) . For example,
the hydrogen bromide-catalyzed oxidation of propane produces acetone in yields as high as 7575, based on consumed hydrocarbon, under conditions where 75% of the latter is reacted. Despite the difference in final product, the two oxidations are believed t o follow similar mechanisms, the distinction being the relative behaviors of tertiary and secondary alkyl hydroperoxides. Thus, for the propane oxidation the chain may be represented as follows and the relationship to Equations 1 to 4 of the preceding paper is to be noted: HBr
+
CHaCH&H3
0 2
+Br
+ (HO,. . . . .?)
I + Br ---+ HBr + CH3CHCHs
(1) (2)
02-
CHJ!X3CH8
+
I
0 2
-+-CHdCHCH3
(3)
November 1949
INDUSTRIAL AND ENGINEERING CHEMISTRY R
2605
M + Br + RBr
(6)
which would result in chain termination, or by Br
b
Contact Time-Minutes
Figure 1. Propane Oxidation, Effect of Contact Time Temperature, 189O C.; 3-liter reaetor; CaHs:Oa:HBr.= 2:2:1
02-
c
CH3 HCH3
+ HBr +[CH3CHCH3 (?-OH] + Br
(4)
(5) The hypothetical intermediate, isopropyl hydroperoxide, has not been isolated; in fact, in none of the experiments on straightchain hydrocarbons have more than traces of peroxidic components been detected. However, hydroperoxides of this type are very reactive and decompose under the reaction conditions by elimination of water; aldehydes are among the major products of decomposition of n-alkyl hydroperoxides ( 2 , 4 ) . Propane is the simplest of the series containing a secondary carbon atom and has been extensively used for determining the effects of various fourth components in the reaction mixture which act as sensitizing agents. The effects of operating variables on the oxidation of this compound have also been studied. The oxidation of primary carbon-hydrogen linkages will be treated in the following paper which deals with ethane and related compounds. OXIDATION OF PROPANE
Summary and Product Balance. The catalyzed oxidation of propane occurs under conditions somewhat different from those for isobutane. To obtain comparable oxygen consumptions the temperature required for propane oxidation is somewhat (approximately 30" C.) higher, and higher partial pressures of the catalyst are necessary. However, even these temperatures (approximately 175' to 200' C.) are far below those necessary t o react propane with oxygen in the absence of hydrogen bromide. Furthermore, a t the temperature required in the latter case (of the order of 325' C.) the carbon chain is extensively degraded and the liquid product is relatively complex. A material balance for a typical oxidation is given in Table I. The acetone accounts for 72% of the consumed hydrocarbon and is in tenfold greater abundance than the next product, propionic acid. Small amounts of acetic acid, as well as bromoacetone and alkyl bromides, are also produced. The mechanism of propionic acid formation, which involves a primary carbon-hydrogen bond, will be discussed in the following paper. At present the reaction follows the same initial steps as for both tertiary and secondary bonds. The alkyl bromides can be accounted for either by an association step, such as
M + Br --+
Brz
(7)
from which the bromine molecule could enter into a chain substitution reaction with hydrocarbon, alkyl bromide, or acetone ( M represents the reactor wall or a third body). The degradation products, acetic acid, carbon oxides, and olefin, probably result from continued oxidation of acetone or from other modes of peroxide decomposition. No free bromine has been detected in these experiments, in contrast to those with isobutane. Method of Analysis. The total ketone was determined by titration of the acid liberated from an excess of hydroxylamine hydrochloride and the fraction of bromoacetone was determined by adding an excess of 0.5 N base to the sample and measuring the increase in bromide ion. I n some cases bromoacetone was estimated from a carbonyl group titration on the bottoms after acetone had been removed by distillation. The organic acid was taken as the difference between the total acid and free bromide ion. The salts of these acids were analyzed for sodium and carbon contents and the ratio used t o estimate the proportions of acetic and propionic acids. For the water determination a small sample of effluent product was collected in pyridine and the water content determined by the Fischer method (S02-Iz). Combustion of the alkyl bromide showed it to be almost entirely monobromopropane. Unless precautions are taken during collection of the product, the concentrated hydrogen bromide will cause condensation of the acetone. Mesityl oxide has actually been isolated from the crude propane oxidation product. This difficulty can be avoided by collecting the product in an alkaline medium, such as sodium carbonate solution (6).
Effects of Operating Variables. CONTACT TII\.IB.The effect of varied contact time in the propane oxidation (Figure 1) clearly illustrates the autocatalytic nature of the reaction. This autocatalysis is so pronounced that, although only approximately 30'% of the input oxygen is consumed in the first 2 minutes of cont,act the oxidation is virtually completed during the succeeding 2 d n u t e s despite decreasing reactant concentrations. SENSITIZATION OF H Y D R O ~ E BROMIDE-CATALYZED N OXIDATIONS (6). The finding of autocataIysis led to a search which
300
8
Y
05
IO
Fractwn of Reactor Length
Figure 2. Propane Oxidation, Sensitization by Isopropyl Chloride
-
CsHst 0 2 : HBr 2:2:1. 1, Sensitized with 2.5% isopropyl chloride; temperature, 168' C.; contact time, 1.5 min.; total flow rate, 1200 cc./min. 2, Sensitized with 2.5% isopropyl chloride: temperature, 164' C.; contact time, 3 rnin.; total flow rate 600 cc./min. 3, Unsensitized reaction. temperature 189.5' C. contact time, 1.5 rnin.; total flow raie 1200 cc./mcn. 4, Unsensitized reaction; t e m erature, 18d5' C.; contact time, 3 min.; totafflow rate, 600 cc./min.
i
INDUSTRIAL AND ENGINEERING CHEMISTRY
2606
I
50
100
I
I
150
200
I
250
H Br ( c u m i n )
Figure 3. Propane Oxidation, Influence of Hydrogen Bromide C o n c e n t r a t i o n on Sensitization by Isopropyl Chloride Contact time, 1.5 t o 1.8 min.; temperature, 189O C.; flaws (co./min.) (465 CnHs:480 0%). D,isopropyl chloride, 15; 0,isopropyl chloride, 60; A, unsendtized
resulted not only in the probable identification of isopropyl bromide as the agent, but also in the discovery of a number of other sensitizers for the reaction. When a mixture of 480 cc. per minute each of oxygen and propane and 205 cc. per minute of hydrogen bromide are passed through the 3-liter vessel a t 189' C., about 28% of the oxygen is consumed. However, the substitution of 18 cc. per minute of isopropyl bromide for an equivalent amount of propane results in a 71% oxygen consumption. A number of other compounds are even more effective than isopropyl bromide under certain conditions. Most notable of these is isopropyl chloride. Only 15 cc. per minute of this compound (2.5% of the total gas flow) is sufficient to produce mild explosions in a 2 to 2 to 1 mixture of propane, oxygen, and hydrogen bromide at temperatures as low as 169" C. Controlled oxidation, with 76% oxygen consumption and high acetone yield, has been obtained a t 164" C., a temperature approximately 25" below that a t which comparable consumption is obtained in the unsensitized reaction. I n Figure 2 the amount of oxygen consumed is shown as a function of reactor length. The advantages of this sensitization in eliminating the induction phenomenon are particularly apparent a t high flow rates. It is possible to take advantage of this sensitizing effect by reducing the hydrogen bromide input at higher temperatures. Whereas an unsensitized 2 to 2 to I mixture of propane, oxygen, and hydrogen bromide gives 30% oxygen consumption at 186' C. (contact time, 1.5 minutes), it is possible to obtain 89% consumption in this same temperature region (190 C.) by incluof isopropyl chloride in a sion of 15 cc. per minute (about 1,3y0) 3 to 3 to 1 mixture of propane, oxygen, and hydrogen bromide. The rate of oxygen consumption a t 189" C. as a function of hydrogen bromide input is given in Figure 3 for two different concentrations of isopropyl chloride. The small effect of isopropyl chloride on the reaction when small flows of hydrogen bromide
Vol. 41, No. 11
are used is significant and substantiates the conclusion that the hydrogen halide catalyst is not entirely replaceable by some other material. This phenomenon will be more fully discussed in connection with the theory of sensitization. A number of related compounds sensitize reaction but usually to a lesser extent than isopropyl chloride. Among these are 2,3dimethylbutane, 2-chloropropene, n-propyl bromide, and diisopropyl ether. tert-Butyl chloride, carbon tetrachloride, trichloroethylene, acetaldehyde, and isobutane do not produce appreciable sensitization, while chloroform actually behaves as an inhibitor. DI-tert-BuwL PEROXIDE AS SENSITIZER.Of the sensitizing compounds investigated, di-tert-butyl peroxide is most effective. A t 165 ' C. and under conditions where no reaction would ordinarily occur, 15% of the oxygen input was consumed when as little as 0.2 mole % di-tert-butyl peroxide was added to the feed. Comparable results in the absence of sensitizer are not obtainable below approximately 189" C. The effect of varying amounts of peroxide upon the oxygen consumption is shown in Figure 4. The principal difficulty in the use of peroxide sensitizer is associated with that very property which is responsible for its effectiveness-namely, its ease of decomposition. For best results the peroxide should decompose uniformly throughout the length of the reactor, but in actuality most of the decomposition seems to be confined to the vicinity of the point of introduction. If too much sensitizer is added, the reaction goes out of control (carbon and gaseous products) but, by successive injections along the reactor a controlled, rapid oxidation may be achieved (Figure +5). MECHANISJI OF SENSITIZATIOX, In the preceding paper the mechanism for the oxidation of isopropyl chloride was discussed, and it was pointed out that methyl radicals are probably an intermediate. It is to these radicals that the sensitizing action of isopropyl chloride is attributed. Although not all compounds which have a carbon atom bonded to but one hydrogen atom show sensitizing action, a large number of those which are effective are so constituted. Presumably such compounds on oxidation form unstable intermediate peroxides which release radicals upon decomposition. The attachment of a hydroperoxy group to a secondary carbon atom can be followed b splitting to a ketone and water without formation of radicals gee A ) . On the other hand, in the case of a compound of the type RIRzXCH (where X is a halogen atom), the replacement of the hydrogen atom by a hydroperoxy group produces an unstable molecule which cannot undergo dehydration. Instead, more drastic splitting, with radical formation, is thought to occur (see B ) .
The sensitizing action of 2-chioropropene is explained by this hypothesis since the peroxide, l-bromo-2-chloro-2-hydroperoxypropane, would be an expected intermediate. Two compounds which accelerate the oxidation but which do not fall into the above class of compounds are n-propyl bromide and ethyl bromide (5). The first has demonstrated its effect on propane oxidation, whilc the second is beneficial in the ethane oxidation. T h e oxidation of ethyl bromide a t about 200 C. seems t o give free methyl radicals, which are evidenced by a substantial amount of methane in the products. Acetyl bromide is the postulated oxidation intermediate, and the degradation products found are those which would be expected from its decomposition in the presence of hydrogen bromide. The subject I 1 of ethyl bromide will be discussed in more detail later. It seems logical that both ethyl and n-propyl bromides function similarly. Whereas the halogen-containing compounds discussed above seem to exert their effect through the instability o€ intermediate oxidation products, di-tert-butyl peroxide sensitizes reaction by virtue of its own instability and degradation to *free radicals. Thus, the first mentioned compounds function by chain branching whereas the peroxide is a chain initiator. TEMPERATURE A S D CATALYST CONCENTRATION. It was stated in earlier paragraphs that autocatalysis is an outstanding feature of the propane oxidation. It is reasonable, therefore, to expect that the effects of changes in such an operating variable as catI ' I alyst concentration would be greatly influenced by this character2 4 istic. I n Figure 6 the effect of catalyst concentration is illusD i - t e r l - butyl Perox'de (cc/niln) trated. This curve bears a striking resemblance to that of Figure 1, since the oxygen consumption a t first rises nearly linearly but Figure 4. Propane Oxidation, Influence of then very rapidly, with increasing values of the abscissa. It is Di-tert-butyl Peroxide probable that autocatalysis is the common explanation for both Contact time 1.5 t o 1.8 min.; temperature, 189O C.; flows curves. The temperature profile of the oxidation of a 2 to 2 to 1 (cc./min.) (460 CsHa:480 On). A, HBr, 30; 0,HBr, 51; 0, HBr, 78; -, represents "cold flash" region mixture is given in Figure 7.
--
O
INDUSTRIAL AND ENGINEERING CHEMISTRY
November 1949
I
I
025 0 50 Fraction of Reactor Length
0
Figure 5.
2607
1
I
0 75
IO
Propane Oxidation, Sensitization by Di- tert -butyl Peroxide
Temperature, 189' C.; total contact time, 2.5 min.; CaHs: 0a:HBr = 8:8:1. Injection points at 0.26, 0.48, and 0.70 of reactor length. A , sensitized by 1 oc./min. peroxide a t inlet 1 cc+/ and only propane added at eaoh injection point; min. peroxide at inlet, 2 cc./min. peroxide (in CaHYLt 0.26 and propane only a t 0.48 and 0.70. 0, 1 cc./min. peroxide a t inlet, 2 cc./min. peroxide (in Cako) at both 0.26 and 0.48 and propane only a t 0.70; d , 1 oc./min. peroxide (in CaHs) a t each injection point
% HBr in Feed
Figure 6. Propane Oxidation, Effect of Hydrogen Bromide Concentration Temperature, 189' C.; contact time, 3min.; CsHs: Oz
-
1: 1
100
OXIDATION OF OTHER COMPOUNDS CONTAINING SECONDARY CARBON ATOMS
Oxidation of n-Butane. Normal butane is oxidized in good yields to methyl ethyl ketone, diacetyl, and organic acidsprincipally acetic. The results of a typical run are given in Table 11. The balance on reactants is affected by condensations of diacetyl and ketone although the product was collected in carbonate solution (6). CHs Oxidation of Neohexane.
I
Neohexane, CH~--C-CH~-C€L,
SO v
9
5 60 0
c a 21 cn
5 SP 40
I
CHs 20
TABLE I.
,
PROPANE OXIDATION AT 189" C."
[Conditions: flows (cc./min.): CaHsb, 245; 0 2 , 245; HBr. 1151 Moles/100 Moles Consumed of Products CaHs 0 2 HBr Acetone 71.6 63.8 ... 2.9 2.6 26.5 Bromoacetone 3.8 3.4 Acetic acid Propionic acid 6.7 5.9 Alkyl bromides 5.5 49.6 ... Ethylene 5.7 0.1 ... Propylene 2.1 Carbon dioxide 2.3 ... 4.9 Carbon monoxide 5.5 96.9 Water a 83% hydrogen bromide recovered, 73% propane consumed, 78% oxygen consumed, 3.2% input propane unaccounted for 3.5% input oxygen unaccounted for, 4.0% input hydrogen bromide unaccodnted for. b Purity, 97.2%.
...
... ... ... ... ...
I
I
I80 IS5 Temperature ("C)
I 3
Figure 7. Propane Oxidation, Effect of Temperature
-
Contact time, approximately 3 min.; C&: Oa: HBr 2:2:1
I..
...
TABLE 11. 12-BUTANE OXIDATION AT 183' C." [Conditions: flows (cc./min.): n-CpHmb, 240; 0 2 , 240; HBr, 1201 Moles/100 Moles Consumed of Products n-C&La 0 2 HBr Methyl ethyl ketone 42.2 29.0 Organic soid (acetio) 26.5 18.3 Diacetyl 9.6 6.7 ... Bromoketone 7.2 5.0 28.5 sec-Butyl bromide 6.0 4.2 23.8 Dibromobutane 3.6 ... 14.3 Olefin 3.6 ... Carbon oxides 14.5 10.0 ... Water 80.0 a 71% hydrogen bromide recovered, 53% n-butane consumed, 73% oxygen consumed, 5.7% input n-butane unaccounted for, 7.6% input oxygen unaccounted for, 5.5% input hydrogen bromide unaccounted for. b Purity, 99.8%.
... ... ...
...
...
was an interesting subject for oxidation because of the uncertainty as to the position of attack. (Neohexane, as well as the naphthenes discussed hereinafter, although not a straight-chain compound, is included here, as its products of oxidation are characteristic of attack on methylene groups.) Methyl groups attached to a quaternary carbon atom sometimes show considerable resistance to reaction. Whether such resistance would also be shown by the methylene group and would thus permit a primary attack on the adjoining methyl group to give tert-butyl acetic acid, was decided in the negative. The principal product was pinacolone, methyl tertiary butyl ketone (boiling point, 105.6' to 107.6' C.; literature value, 106.2' C.). (Derivative: pinacolone oxime, melting point, 75" C.; literature value, 74' to 75 C. and 77" t o 78" C.) Organic acid was produced but not identified. Table I11 shows a rough product distribution for several temperatures. The large amount of unaccounted-for oxygen has been attributed to ketone condensations inside the reactor wherein
INDUSTRIAL AND ENGINEERING CHEMISTRY
2608
balance given in Table V.
TABLE111. YIELDS ON OXYGENCONSUMEDIN NEOHEXANE Conditions: flows (cc./min.): neo-CeHln, 30. iiz, 30; 0 2 , 30; HBr 15. Reactor volume: 450'00.1 hIoles/100 Moles of Consumed 0 3 Products At 180a C. At 190° C. A t 1913' C. Organic acid Ketone Carbon oxides Unaccounted for5 Total % input oxygen consumed
76
48
25
I n these calculations 1 molecule of water is assumed to be formed concurrently with each molecule of ketone. a
TABLE Iv. YIELDS
ON OXYGEN CONSTJhlED BROUIDEOXIDATION
I N %-PROPYL
[Conditions: flows (cc./min.): n-CsH.iBr, 30: Nz, 30; 02, 30; HBr, 15 Reactor volume: 450 cc.] Moles/l00 Moles of Consumed On Products .4t 1800 At 1950 c. Organic acid 24a 226 26 14 Ketone (bromoacetone) Carbon oxides 26 27 Unaccounted forC 33 47 Total yo of input oxygen consumed 46 76
c.
Estimated as 44% propionic, 56Y0 acetic. Estimated as 78% propionic, 2 2 7 , acetic. I n these calculations 1 molecule of water ia assumed to be formed ooncurrentIy with each molecule of ketone. a 0
TABLE IT.YIELDSoh- CONSUMED OXYGENIN OXIDATION
n-BuTYL BROMIDE
[Conditions: flows (cc./min.): n-GHoBr, 30; Nz, 30; 0 2 , 30; HBr, 16. Reactor volume: 450 cc.] Moles/100 Moles of Consumed Os Products ilt 190' C. At 210' C. At 230' C. Organic acid 21 15 13 65 49 41 Ke?one 15 22 33 Carbon oxides 2 20 26 Unaccounted fora Total % of input oxygen consumed a
50
79
TABLE VI. ACID COMPONENTS IN n-BuTYL BROMIDE OXIDATION Temp., C. Average number of carbon atoms per molecule
II
190
210
230
3.0
2.7
3.1
a considerable amount of carbonaceous deposit was always found after an experiment. This conclusion is supported by the increase in the unaccounted-for material as the amount of total reaction increased. Oxidation of n-Propyl Bromide. Normal propyl bromide, nitrogen used as a carrier, oxygen, and hydrogen bromide in the ratio of 2 to 2 to 2 to 1 were passed through the 450 cc. volume glass reactor a t 180" and 195" C. (contact time approximately 3 minutes). No exhaustive analysis of the reaction products was attempted on these small scale runs, but a compilation of the data taken is of interest and is shown in Table IV. The reaction at the higher temperature shows a 2.7-fold increase in total propionic acid output whereas the net acetic acid output shows a corresponding decrease of about 40%. The values for the acetic and propionic acid content of the organic acid were obtained from the ratio of carbon to sodium in the combined salts. The proportional yield of propionic acid is much greater than in the propane oxidation. Oxidation of %-Butyl Bromide. Both acid and ketone are produced in the oxidation of n-butyl bromide and the distribution between these two classes of compounds is indicated by the oxvgen
0
/I
from n-butyl bromide, C-C-C-C-Br and C-C-C-C-Br. Treatment of the ketone fraction with warm sodium hydroxide converted to bromide ion an amount of organic bromide equivalent t o between one third and one half of the ketone. This value was considered to be an estimate of the aniount of l-bromo-2-b~tanone present. Less than 1% of the oxygen was consumed in the formation of diketone. Analysis of the acids indicates that they are present as a mixture (Table VI). Oxidation of Naphthenes (8). Cyclopentane, methylcyclopentane, and cyclohexane were oxidized on a small scale and in general, the yields were low, either because of acid-catalyzed condensation reactions affecting the ketonic product or because oxygenated product was more easily oxidized than the parent hydrocarbon. Ketonic material, to be expected from such compounds containing secondary carbon-hydrogen bonds, was detected in each of the three cases tried. I n these experiments the 450-cc. reactor was used with flows of 30 cc. per minute each of the hydrocarbon vapor, nitrogen, and oxygen and 15 cc. per minute of hydrogen bromide. At 180" C. the oxidation of cyclopentane consumed 43% of the oxygen. Cyclopentanone was isolated from the product (n::' 1.4358, literature value, 1.4366; boiling point 130" t o 135" C., literature value, 129 O to 130 O C.; derivative: dibenzalcyclopentanone, melting point, 190" to 191" C., literature value, 189" C.) Methylcyclopentane reacted at 166' C., but the product for the most part was a tarry deposit. Some ketone was formed, but no individual compounds were isolated. When cyclohexane was subjected to oxidation a t 220' C., 40% of the input oxygen was consumed, and only 8% of the consumed oxygen appeared as oxides of carbon and concurrently formed water. Cyclohexanone (derivative: dibenxalcyclohexanone, melting point 116" to 117" C., literature value, 118" C.) and some diketones were obtained. LITERATURE CITED
7.5
See corresponding note for Tables 111 and IF'.
Two bromo-ketones are possible
0
OXIDATION
Vol. 41, No. 11
(1) Bell, E. R., Dickey, F. H., Raley, J. H., Rust, F. F., and Vaughan, W.E., IND.ENG.C H E M . , 2597 ~ ~ , (1949). (2) Harris, E. J.,Proc. Roy. SOC. (London),173A,126 (1936). (3) Raley, J. H., and Rust, F. F., U. 8 . Patent 2,391,740 (Dec. 25, 1945). (4) Rieche, A., "Alkylperoxyde und Ozonide," Leipsig, Steinkopff, 1931. (5) Rust, F. F., and Bell, E. R., U. S. Patent 2,380,675 (July 31, 1945). (6) Rust, F. F., Raley, J. H., and Vaughan, W. E., Ibid., 2,421,392 (June 3, 1947). (7) Rust, F. F., and Vaughan, W. E., IND.ENG.CHEM.,41, 2595 (1949). (8) Rust, F. F., and Vaughan, W. E., U. S.Patent 2,369,181 (Feb. 13, 1945). RECEIVED August 17, 1948. Presented in part a t the meeting of the Gordon Research Conferences of the American Association for t h e Advancement of Science, Colby Junior College, New London, N. H., J u n e 1948.
Correction I n the article by J. R. Bowman, "Distillation of an Indefinite Number of Components" [Ih-D. EKG.CHEW, 41, 2006 (1949)l errors were made in Equations 7 and 9, where the symbols J should be factors of the exponent. These equations should read:
(7)
JOHN R.B o m f m M ~ L L OIXETITUTE N PITTBBURQH. P h .
