[CONTRIBUTION FROM
THE
RESEARCH LABORATORIES OF THE UNIWRSALOIL PRODUCTS Co.]
THE ALKYLATION OF PARAFFINS WITH OLEFINS. THE IDENTIFICATION OF THE PARAFFINS FORMED’ ARISTID V. GROSSE
AND
VLADIMIR N. IPATIEFF
Received June 16, 1943
In our previous paper (1) we described a new catalytic reaction between paraffins and olefins, consisting of the direct addition of an olefin to a paraffin according to the equation CmH2m+2
+ CnH2n
-+
Cm+n&(rn+n)+2
The identification of the reaction products is highly desirable per se and should give some very important information on the mechanism of the reaction. Their unambiguous identification is made difficult (a) because of the large number of possible isomers of the primary product; (b) because of their further alkylation to secondary products and (c) because of the possibilities of side reactions, such as auto-destructive alkylation (2). It should be stressed that in catalytic reactions the lowering of the energy barrier of the desired reaction brought about by the particular catalytic mechanism, markedly increases also the probability of undesired reactions. This is particularly true for reactions among hydrocarbons. Furthermore the energy given off by the desired reaction stimulates the undesired reactions by providing the necessary activation energy. The cumulative effect is such that it is highly optimistic to expect the simple reaction mixture encountered in most inorganic or organic reactions. In the field of catalytic hydrocarbon reactions one can hope to surmount these difficulties only by picking the simplest hydrocarbons or developing highly selective catalysts and allowing them to work under carefully selected conditions. In the reaction mentioned above the simplest hydrocarbon pair studied so far was i-butane and ethylene, leading by alkylation first to hexanes, which are then further alkylated to oclanes: at the same time some autodestructive alkylation (2) to pentanes, heptanes, and nonanes also takes place. The hexane fractions obtained both with a boron fluoride (1) and aluminum chloride (3) catalyst were investigated and found to consist mainly (in quantities of 90-70% of the total hexanes) of 2,S-dimethylbutane and much smaller quantities (10-25%) of 2-methylpentane. The presence of the expected reaction product 2,2-dimethylbutune could be definitely established, but only in minute amounts (3% or less). The two other possible hexanes, 3-methylpentane and n-hexane, could not be detected and may have been present only in traces if at all. The identification proceeded by two independent but parallel methods, one Presented before the Petroleum Division of the American Chemical Society a t its Rochester, N. Y . , meeting, Sept. 1937; see “Papers presented before the General Meeting,” pp. 1-12. A few additional data, particularly on the identification of 2,2-dimethylbutane, were added subsequently. 438
ALKYLATION O F PARAFFINS WITH OLEFINS
439
supporting the other, namely, preparation of chemical derivatives on one hand and comparison of Raman spectra of the hexanes (see Table V) on the other. Possibilities of errors were ruled out by a detailed analysis of the chemical and physical properties of the other isomers and their derivatives. The 2 , S-dimethylbutane was definitely identified by its Raman spectrum and the beautifully crystallizing needles of 2 ,3-diloromo-2,%-dimethylbutane,which could be obtained in yields corresponding to about 80% of the hexane fraction. The presence of %methylpentune was definitely proved by the preparation of its derivative, 2 ,3,3-trinitro-2-methylpentane, and checked by its Raman spectrum. DISCUSSION
The presence of 2,3-dimethylbutane as the main reaction product is unexpected. In view of the presence of the tertiary C-H bond in i-butane, we expected (1) 2,2-dimethylbutane to be the primary product of the reaction: (CH3)sCH
+ CH2:CHz
-4
(CH3)3CCHzCHa 2,2-Dimethylbutane
That this assumption is a t least partly correct is shown by the presence of small quantities of this hexane (Experimental, part 3), and by the interesting experiments of Frey and Hepp (4). These workers were able to repeat our reaction of i-butane alkylation with ethylene, without the use of catalysts, by performing the reaction at much higher temperatures (ca. 500") and pressures. Under their conditions the main portion of hexanes consisted of the expected 2 ,2-dimethylbutane. The preponderance of 2,3-dimethylbutane in our product is most probably a result of the isomerization of the primary product according to the equation: CHa
I
CHaCCHzCHa
I
CH3 CH3
I I -+ CHs CH-CHCHa Catalyst
(either a t the moment of formation or afterwards), similar to the isomerization of n-heptane into isomeric heptanes, n-pentane into i-pentane, or n-butane into i-butane ( 5 ) . Our second hexane, 2-methylpentane, is also an a priori not very probable product. It may be a primary product, according to the reaction
/"
(CH3)2 CHC-H
\H
+ CHZ :CHz
~
Catalyst -+ (CH3)zCHCHz CH2 CH3
2-Methylpentane
due to the greater availability (9: 1)or the more eacient activation of the primary C-H bond by the catalyst or, although less likely, it may be a product of isomerization of the original 2 ,2-dimethylbutane. The fruitful discussion of the reaction mechanism requires further experimental
440
A. V. GROSSE AND V. N. IPATIEFF
material. It will be particularly important to study the isomerization of different hexanes in the presence of our catalysts. EXPERIMENTAL PART
The hexane fractions from a set of alkylations made under identical conditions were combined and refractionated 2-3 times on a high-temperature Podbielniak column (at a reflux ratio of 5-1O:l and rate of 0.5-1.0 cc./min.) the fraction of a same starting boiling point being added to the still when the temperature of the distillate reached it. The distillates were all absolutely stable to nitrating mixture and potassium permanganate solution, proving the absence of aromatic and unsaturated hydrocarbons. Two sets of hexane fractions (A-1, A-2, and B) were investigated. Set A was prepared according to our procedure by Dr. Carl B. I h n using boron fluoride (I) as a catalyst, set B by Dr. L. Schmerling using aluminum chloride (3) under the following specific conditions: Set A-I: A batch of 350 g. of i-butane was alkylated in the presence of 35 g. of boron fluoride, 10 g. of nickel powder, and 30 g. of hydrogen fluoride under stirring at 0-5" during 10-12 hours with 170 g. of ethylene at a maximum pressure of 10 atmospheres. Yield of liquid product (separated from unreacted i-butane), 380 g. Yield of hexanes, 45% of total liquid product. Set A-8: 341 grams of i-butane 190 g. of ethylene, 10 g. of nickel powder, 35 g. of hydrogen fluoride and 35 g. of boron fluoride were used. Temperature -30" to -40'; 340 grams of product; hexanes, 20% of total liquid product. Maximum pressure, 6 atmospheres. Time, 20-22 hours. Set B: A batch of 340 grams of i-butane was alkylated in the presence of 25 g. of aluminum chloride and 10-15 g. of hydrogen chloride under stirring at 25-35' during 4.0 hours with 90 g. of ethylene under a maximum pressure of 10 atmospheres. Yield of liquid product (separated from unreacted i-butane), 270 g. Yield of hexanes, 45% of total liquidproduct. In all three cases the ethylene reacted completely. The carbon and hydrogen analysis and molecular weight determinations of different fractions (Nos. 11 and 12 of Set -4-1and KO,8 of Set A-2, see Table 11) prove that only hexanes are present (calc'd for C8Hla:C, 83.61; H, 16.39; Molecular weight 86.1). The results of fractionations are given in Table 11; a typical result (of Set A-I) is further illustrated in Fig. 1. These results indicate the probable presence of 2,3-dimethylbutane (b.p. 58.05') and 2-methylpentane (b.p. 60.20'), whereas 3-methylpentane and particularly n-hexane seem t o be absent. I n the case of Set A-1 the presence of small quantities of 2,2-dimethylbutane (part 3, below) is indicated by the small hump a t 49-51'. The indices of refraction and especially the densities of (a) fractions 11-13 of Set A-1, (b) fractions 8 and 8a of Set A-2, and (c) fractions 7 , 8 , and 9 of Set B are consistentwith values for a mixture of the two first named hexanes (compare with Table I ) . 1. Zdentijication of 2,J-dimethylbutane. The identification, and also more or less quantitative determination of this hexane, is simple because i t is the only isomer that forms a solid bromide on direct bromination of hexanes. Nitro derivatives, particularly the solid 2,a-dinitro compound, are difficult t o prepare and the mononitro hexanes can hardly be separated and distinguished from one another. The bromination of the pure hydrocarbon or mixtures rich in i t takes place easily in the sunlight or in strong electric light a t room temperature, with copious evolution of hydrogen bromide; every drop of bromine is decolorized in the course of a few seconds and soon colorless needles of d,b-dibromoJ, 3-dimethylbutane, CH&H(Br)CH(Br)CHa, appear in feathery
+
I
I
CHB CHr growths on the sides of the reaction flask until practically everything solidifies t o a crystalline aggregate. Our dibromide may be further brominated, but much less rapidly than the hexane, t o the 1,,9,J,~-tetTabTOmO-d,J-dimethyZbutane of melting point 130-131".
441
ALKYLATION O F PARAFFINS WITH OLEFINS
Direct comparative experiments with a 1000-watt lamp, made by Dr. L. Schmerling showed that pure synthetic 2,2-dimethylbutane does not react with bromine, whereas pure synthetic 2-methylpentane absorbs bromine moat rapidly, but that its reaction products are liquid even a t -78". The results with pure synthetic 2,3-dimethylbutane were identical with those obtained in sunlight. The dibromide has a strong characteristic odor; i t is very easily soluble in ether, crystallizing in centimeter-long silky needles. It readily deteriorates in air (hydrolysis) and should be kept in a sealed tube or a phosphorus pentoxide desiccator. Analysis showed 65.46% bromine; calculated for CBH12Br2, 65.53%. The pure derivative sublimes without melting a t 165-175"when heated in an open tube or capillary. In asealed TABLE I
PHYSICAL CONSTANTS OF THE HEXANES(14) (Arranged in the Order of Increasing Boiling Point) BOILING 'OINT
"c
HEXANE
iy
760 MM.
"$0 D
OCTANE NUMBERS (BESEABCE METHOD 15
--
J.0.P.
DETER-
MINATION ON W E E SYNTHETIC W P L E S . CFR IOTOB METHOD
C
I I
C-C-C-C
49 * 77
649 1.3690 101
93.0
c c c I I c-c-c-c
58.00
661 1.3751 124
94.0
60.20
653 1.3717
69
71.5
63.20
664 1.3765
84
68.75
659 1.3751
29
c 1
C-C-C-C-C
2-Methylpentane
3-Methylpentane
c-c-c-c-c-c
n-Hexane
Average Values for Hexanes of: Atb.p./Ap = 0.042"/mm. H g An/At = -0.00055/°C Ad/At = - O . ~ 9 O / " c
capillary our purest crystals melted, with decomposition and gas evolution, at 166-168'; they showed no depression with an authentic sample of 2,3-dibrom0-2,3-dimethylbutane prepared from the pure synthetic hexane. Evidently, in a sealed tube the small quantities of decomposition products, accumulating gradually, lower the melting point; the latter depends, therefore, also on the rate of heating, which explains the wide differences recorded in the literature: for instance >140°, Pawlow (6) and 169-170°, Kaschirski (7). It was ~~
The melting point 192" given by H. L. Wheeler (8) for our derivative is identical with that of the isomeric pinacoline dibromide, (CHa)sCC(Brt)CHs; probably he had the latter compound in his hands, since i t could readily form by "pinacoline rearrangement" from pinacone with hydrogen bromide in glacial acetic acid. 2
442
A. V. GROSSE AND V. N. IPATIEFF
TABLE I1 SET A-1. THIRD DISTILLATION OF HEXANES OBTAINED WITH BORONFLUORIDEAT 0-5". ORIGINAL CHARQE, 350 cc. a t 25"
-
FRACTION
SOILMG RANGE,
%C
760 MM.
1 2
35.0-37.0 37.0-39.0
1.8 3.0
3 4
39.0-41.0 41.0-43.0
3.4 4.0
43.0-45.0 45.0-47.0 47.0-49.0 49. 0-51.0 51.0-53.0 53.0-55 .O 55 .0-57 .O 57.0-59.0 59.0-61.0 61.0-63 .O 63.0-65.0 65.0-67.0 >67.0
4.4 4.8 4.4 16.0 5.0 18.0 53.0 81 .O 90.0 7.0 3.4 2.0 2
bOL. WT.
-
BEAUPIIS
n-Pentane
1.3646 1.3675 5 6 7 8 9 10 11 12 13 14 15 16 Residue
1.3668 1.3688 1.3686 1.3693 1.3709 1.3722 0,6545 1.3729 .6579 ,6579 1.3734 1.3735 1.3744 1.3754 1.3819
4% by Vol. 83.39 83.45
16.58 16.28
84
Heptanes or Octanes
Total . . . . . . . . . . . . . . . 07 Losses during 3 distillations . . . . . .. . . . , 43
SETA-2. PROPERTIES OF SIMILAR CUTSOF HEXANES OBTAINED WITH BORON FLUORIDE AT
1 2 3 4 5 6 7 8 8a 9 10 Residue
30.0-40.0 40.0-45.0 45.0-47.0 47 .0-49 .O 49.0-51 .O 51.0-55.0 55 . e 5 7 .O 57.0-58.8 58.8-59 .O 59.0-61 .O 61.0-70 .O >70.0
-30
TO
5.0 2.3 1.0 0.7 0.1 2.9 14.5 47.0 22.5 15.0 2.0 4
T o t a l . . . . . . . . . . . . . . 97.0 Losses during 2 distillations . . . . . . . . . . . 1.3
-40". ORIGINAL CHARGE, 210 cc. a t 25" SECOND DISTILLATION
1.3546 1.3566 1.3627 1.3621 -
1.3676 1.3718 1.3747 0.6600 1.3746 .6597 1.3750 1.3752 1.3790
83.42
16.39
443
ALKYLATION OF PARAFFINS WITH OLEFINS
TABLE 11-Continued SET B. PROPERTIER OF HEXANES OBTAINED WITH ALUMINUM CHLORIDE AT 25-35', ORIGINAL CHARGE, 575 cc. at 25' SECOND DISTILLATION FPACTION
1 2 3 4 5 6 7 8 9 10 11 12 13 Residue
VOLUME
%OILINGRANGE,
760 MAC.
I N CC.,
25'
10.0 9.0 13.0 15.0 72.0 63.0 85.0 153.0 44.0 50.0 12.0 5.0 12.0 5.0
30.0-40.0 40.0-48.0 48.0-50.0 50.0-52.0 52.0-54.0 54.0-56.0 56.0-58.0 58.0-59.0 59.0-60.0 60.0-61 .O 61.0-62.0 62.0-63.0 63.0-70.0 >70.0
Total . . . . . . . . . . . . . . . . . Losses during 2 distillations . . . . . . . . . . .
1,3546 1,3622 1.3655 1.3670 1.3693 1.3708 1.3724 1.3743 1,3748 1 .3740 1.3740 1.3744 1.3742 1.3821
%C
%H
moL. WT.
83.51
16.49
84
0.655
--
548.0 27
so
J
* d o
2
L
'O
u
60
T
(r
h
50
V l l o
f
30 CO /O
0
I O / f / N G W O E /N .C. A T 760 HM H G .
FIGURE 1. FRACTIONATION OF HEXANES
444
A. V. CROSSE AND V. N. IPATIEFF
further identified by conversion into tetramethylethylene, of boiling point 72" a t 760 mm. and n? 1.4155, by boiling with zinc granules and 95% alcohol; this compound was converted by Thiele's method (9) into the volatile blue crystals of the nitrosochloride, (CHs)&-C(CH&
I 1
NO C1 melting point 121'. The only other known solid mono- or dibromo-hexanes are: (a) the monobromo derivative of d,b-dimethyZbutane, CH&H(Br)CH&Hs, which seems t o be much more readily bromi-
I
I
CHa CHa nated than 2,3-dimethylbutane itself (so that i t does not accumulate in the bromination products of this hexane), and is more readily prepared by the addition of hydrogen bromide to tetramethylethylene; m.p. 24-25', and (b) 3,b-dibromo-2,b-dimethylbutane, TABLE I11 BROMINATION OF HEXANEFRACTIONS h
w
d
d SOURCE OX HEXANES
d
a
d
ui
9 e 3
d
?
3 P e
5 -
I A-1 (BFs a t 0') Fractions 11, 12 A-2 (BFI at -30') Fraction 8 B (AIClnat 25-30') Fractions 6,7, 8 , 9
CHaC-CCHs,
I I
100 755 55 26 26 5 5 4 0
17
2
100
1
5 2 0
160
I
100 32.5 3.5 J O
3:
:1
2
1I B 6
v
xm eu
c
-
165 164 162 160 162
33 7 0.1
163 160 160
mp. 191.5' (in sealed tube), prepared from pinacoline with phosphorus
CHs Br pentabromide and not by direct bromination of the hexane. Our quantitative bromination took place a t ordinary temperature, (25-35') in the bright sunlight, in a flask fitted with a stirrer, reflux condenser, and burette with bromine. The hydrogen bromide fumes were absorbed in a trap containing water. At the beginning the rate of bromine addition was so adjusted that there was only a slight excess of bromine and i t was usually stopped when the bromine absorption had slowed down to about one-tenth of its original value, t o avoid overbromination. Between 10 and 100 g. of hexanes was used per batch. The product was then refluxed until all the bromine disappeared, the unreacted hexanes distilled off, the residue cooled, the crystals sucked dry on a porous filter plate, weighed and recrystallized from ether.
ALKYLATION OF PARAFFINS WITH OLEFINS
445
The results obtained with different fractions are correlated in Table 111. The liquid bromides, of Table 111, still contained some dissolved 2,3-dibromo-2,3dimethylbutane, but consisted mostly of monobromides having the boiling point 75-85" a t 200 mm. and n: 1.45. These remained liquid even on prolonged standing a t -78" (solid carbon dioxide) and were free from the 25"-melting 2-bromo-2,3-dimethylbutane; evidently they represent monobromosubstituted 2-methylpentanes. 2. Identification of 2-methylpentane. The chemical identification of this hexane is much more difficult than that of the preceding one. Its bromine derivatives are not characteristic. Fortunately i t is, besides 3-methylpentane, the only hexane that gives a crystalline trinitro derivative, on nitration by the method of Konowalow (lo), although the yields are far from quantitative. The two trinitro compoundsa mentioned have the following properties : (a) d,S,S-trinitroNOzNOz
I
I 1
I-methylpentane, CH&-CCH,.CHg,
I
colorless plates or needles, m.p. 96", readily soluble in
CH, NO,
NO2 NO,
I I
alcohol, insoluble in alkalies; (b) B,d, 8-trinitro-3-methylpentune, CH&-CCHzCHs,
I 1
m.p. 85".
NO2 CHa The results of our nitrations are given in Table IV. I n every case the same crystalline melting a t 96.3-96.8" was obtained, trinitrohexane namely 2,3,3-trinitro-%-methylpentane, besides some unreacted hydrocarbon and some yellow oily nitro compounds, probably mononitrohexanes. No crystalline derivative of 3-methylpentane could be found. The nitrations of our fractions were carried out as follows: 20 cc. of the fraction was boiled under reflux (glass ground joints) with 60 cc. of 38% nitric acid for 6 hours. At the end of experiment the unreacted hydrocarbon was separated, the acid diluted with ice, any of the crystalline derivatives which usually appeared at this point were filtered off, the filtrate extracted with ether, the ether extract dried, and the ether allowed t o evaporate slowly. Any crystals were separated from the oil and recrystallized from ethanol. 3. Zdentification of 8,2-dimethylbutane. At first, indications for the presence of this hexane were available in the form of a peak (4 vol. %) in the boiling point curve a t 44-51' in the case of Set A-1, (see Fig. l ) ,and the value n: 1.3686 coinciding with the properties of 2,2-dimethylbutane, b.p.780 49.75', n: 1.3690. This fraction was exceedingly resistant towards nitration (2,2-dimethylbutaneis known to be the most difficult hexane to nitrate), and heating for 6 days with 37% nitric acid at 100" in a sealed tube failed to nitrate noticeable quantities of the hydrocarbon; a t slightly higher temperatures explosions occurred. Later, in working up another batch of AlClt-hexanes (obtained under similar conditions, as described under Set B), 3 vol. % (based on total hexanes) of a cut boiling at 49.2-49.9" a t 760 mm. with d? 0.6492 and n: 1.3689, was obtained. Its analysis gave C, 83.55; H, 16.45. Kitration by Konowalow's method yielded colorless crystals of 3-nitro-2,d-dimethylbutane (rn.p. ca. $40"). 3111 this connection i t should be mentioned that a third trinitro-2-methylpentane (with unknown positions of the nitro groups), m.p. 85', registered in "Beilstein" (see Vol. I, p. 149) is evidently identical with the 2,2,3-trinitro-3-methylpentane mentioned below under (b). In the original article [Francis and Young, J. Chem. Soc., 73, 930 (1898)l no mention is made that specifically 2-methylpentane was used for nitration, but only "light petroleum fractions." The best yields of the above nitro derivative were obtained from a cut boiling from 62.6-63.1'. This range is very near the present reliable value for the b.p. of 3-methylpentane (63.20"). Evidently the abstractor assumed the cut to be 2-methylpentane.
446
A. V. GROSSE AND V. N. IPATIEFF
Two cubic centimeters of hexane was heated with 6 cc. of 37% nitric acid in a sealed glass tube t o 120' for 8 hours (in a rotating autoclave under 15 atmospheres nitrogen pressure). After the reaction, the tube was cooled in dry ice, the nitrogen oxides released, the tube resealed and again heated for 8 hours at 180"; a t the end of the experiment a small quantity of colorless crystals floating a t the surface between the two layers was observed. AS the TABLE I V NITRATION OF HEXANE FRACTIONS NITROHEXANE FROM
(see Table 11)
Fraction
Set
A-1 (BFa, 0-5')
Set B (AlCl,, 25-30']
YIELD, % OF ORIGINAL FRACTION
MELTI!G OINT,
c
%N
PEMARKS
APPEARANCE
11 12 13
2 11 9
96.3 96.5 96.0
8
5
96.8
Larger quantities 18.61; Mixed melting point with Set of oily nitro 18.69 A-1, no depresproduct. sion
96.8
18.99
18.68
Colorless thin jagged plates
Some yellow oily nitro product obtained simultaneously. Mixed melting point of Cut 12 with 11 & 13. No depression.
~
2,3,3-Trinitro-2-methylpen-
Colorless plates
tane, from synthetic 2methylpentane TABLE V RAMANSPECTROSCOPIC RESULTS SOURCE OF MATERIAL (see
Set
A-1 (BFs)
B (AICla)
1
I
I
Table 11)
Fraction
I I
l 8
AMOUNTS,
%
I
2,3-Dimethylbutane 2-Methylpentane l2 6
APPROXIMATE
HEXANES FOUND
10-20
2,3-Dimethylbutane 2-Methylpentane
100-90
2,3-Dimethylbutane 2-Met hylpentane
85-75 15-25
E O
results of two such experiments, the tube contents were extracted with ether, separated from the acid layer, washed with water, dried with calcium chloride, and fractionally distilled. Discarding the fractions of ether and unreacted hexane, a colorless liquid came over at 168'/760 mm., leaving a small quantity of higher-boiling residue (dinitrohexanes). The fraction a t 168' solidified t o white crystals and represented 3-nitro-2,2-dimethylbutane. It dissolved completely in 5% solution of sodium ethoxide in ethanol, forming a
ALKYLATION OF PARAFFINS WITH OLEFINS
447
sodium salt; this remained in solution on adding an equal volume of water, and was precipitated as an oil on saturation with carbon dioxide, all characteristic properties of the %nitro compound. The yield of crystals based on the hexane was 10-15%. 4. Identification and quantitative estimation by means of Raman spectra. The Raman spectroscopic work was carried out by one of us (A.V.G.) in conjunction with Dr. E. Rosenbaum at the University of Chicago. The method of investigation and details will be published separately (11). It is sufficient to mention here that first Raman spectra of the five pure synthetic hexanes (12)were taken. We owe these hexane samples t o the kindness of Dr. P. L. Cramer of the General Motors Corporation (13). These spectra were compared with the spectra of our different fractions; from the correspondence of the Raman lines and their intensity the presence of a particular hexane and its approximate quantity could be determined. Some of the most important results are shown in Table V. ACKNOWLEDGMENTS
The authors are indebted to Mr. R. W. Moehl for carbon and hydrogen analyses and to Drs. J. Mavity and L. Schmerling for their valuable help in various phases of the investigation. SUMMARY
From the combined results of the chemical and Raman spectroscopic investigation it may be concluded with certainty that the hexanes formed by the catalytic alkylation of i-butane with ethylene, in the presence of boron fluoride or aluminum chloride, are 2,S-dimethylbutane (90-70% of the total hexanes), d-methylpentune (10-2073, and traces of 2,d-dimethylbutane (3% or less). With both catalysts their relative amounts are approximately the same. The identification has been accomplished (a) chemically through their bromo and nitro derivatives and (b) by their Raman spectra. The two other hexanes can only be present in negligible amounts if at all. RIVERSIDE,ILL. REFERENCES
(1) IPATIEFF AND GROSSE,J . Am. Chem. Soc., 67, 1616 (1935). AND GROSSE,Ind. Eng. Chem., 28, 461 (1936). (2) IPATIEFF GROSSE,PINES,AND KOMAREWSKY, J . Am. Chem. Soc., 68, 913 (1936). (3) IPATIEFF, (4) FREYAND HEPP,Ind. Eng. Chem., a8, 1439 (1936). unpublished results. (5) GROSSE,PINES,AND IPATIEFF, (6) PAWLOW, Ann., 198, 124 (1879). (7) KASCHIRSKI,J . Russ. Phys.-Chem. Soc., 13, 84 (1881). (8) WHEELER,Am. Chem. J., a0, 150 (1898). (9) THIELE,Ber., 27, 456 (1894). (10)KONOWALOW, J . Russ. Phys.-Chem. Soc., 26, 498 (1893). (11) GROSSE,ROSENBAUM, AND JACOBSON, Ind. Eng. Chem., Anal. Ed., 12, 191 (1940). GROSSE,AND JACOBSON, J . Am. Chem. Soc., 61, 689 (1939). (12) ROSENBAUM, J . Am, Chem. SOC.,58, 373 (1936). (13) CRAMERAND MULLIGAN, “Physical Constants of P a r f i n Hydrocarbons,” U. 0. P. Book(14) GROSSEAND EGLOFF, let No. 219, 1938; see further, EGLOFF, “Physical Constants of Hydrocarbons,” Vol. I, Am. Chem. SOC.Monograph No. 78, 1939. (15) GARNER,EVANS, SPRAHE,AND BROOM,World Petroleum Congress Preprint No. 118, 1933, calculated from aniline equivalents, determined by LOVELL,CAMPBELL, AND BOYD,Ind. Eng. Chem., 23, 26 (1931).
