HERMAN PINESAND R. 6.WACKHER
2518
Vol. 68
Summary
54% yield of 3-rnethyl-2,4-hexanediol,b . p. 109" (9 mm.) ; $OD 1.4450; d2'14 0.9588 was obtained. I t s identity was
1,1,2-Trirnethylcyclopropanewas prepared in shown by analysis for carbon and hydrogen. Calcd. for CiHI6O2: C, 63.54; H, 12.18. Found: C, 63.48; H, high yield from 2-methyl-2,4-dibromopentane by 12.17. the Freund reaction a t low temperatures. 3-Methyl-2,4-dibromohexane.-The method of prepaIn the ring closure reaction to form 1,1,2-triration here was the same as t h a t described for 2-methylmethylcyclopropane from 2-methyl-2,4-dibromo2,4-&bromopentane. A 90% yield of crude product of high purity was obtained. It was purified by distillation pentane the principal by-products were found to under diminished pressure. The purified dibromide had be 2-methyl-1-pentene and 2-methylpentane. the following physical constants, b. p . 71.5-72.5(1 mm.); These by-product hydrocarbons have the same #JD 1.4967; d204 1.4504. Analysis for bromine gave results in agreement with the formula assigned. Calcd. for carbon skeleton as the dibromide from which they were formed. CiHI4Brl: Br, 61.97. Found: Br, 62.07. 1,Z -Dimethyl -3-ethylcyclopropane .-This hydrocarbon 1,1,2-Trimethylcyclopropanewas obtained in a was prepared from the dibromide by the method described purity of about 95y0 by fractional distillation in a for 1,1,2-trimet'hylcyclopropane. A 90% yield of product, $OD 1.4048,was obtained. Analysis for carbon and hy- high efficiency distilling column. Infrared absorption spectra show that aqueous drogen gave results in agreement with the formula C7HI4. Calcd. for C7HII: C, 85.62;H, 14.38. Found: C, 85.51; potassium permanganate was not very selective H, 14.32. A spectral map was made of this product. for removing 2-methyl-1-pentene from 1,1,2-triA portion of this product was distilled in the vertical surface column. 'The distillation is shown in Fig. 6. The methylcyclopropane. 1,2-Dimethyl-3-ethylcyclopropane was preinfrared absorption spectra of the two plateau fractions were determined, Figs. 8 and 9. pared in high yield from 3-methyl-2,4-dibromoAcknowledgment.-We are indebted to the hexane. I t was separated into two fractions by Chemical Research Laboratory of the Standard distillation. An improved method is described for the prepOil Co. of Ohio for the use of the. infrared spectrometer and to Dr. Martval J. Hartig of the aration of secondary and tertiary organic broStandard Oil. Co. of Ohio for assistance in the mides from alcohols or diols. interpretation of infrared data. RECEIVED SEPTEMBER 20, 1945 CLEVELAND, OHIO
[CONTRIBUTION FROM THE RESEARCH AND DEVELOPMENT LABORATORIES, UNIVERSALOIL PRODUCTS COMPANY]
Isomerization of Alkanes. 1V.l Deuterium Exchange in the Isomerization of nButane2 BY HERMAN PINES AND R. C. WACKHER It was shown2athat under controlled conditions, aluminum bromide-hydrogen bromide catalyst does not cause isomerization of n-butane unless traces of olefins or their equivalent are present. On the basis of these results, a chain mechanism was ~ u g g e s t e d . ~It was postulated that isomerization of n-butane proceeds in the presence of a catalyst and traces of olefins or their equivalent by a sequence of reactions as represented by the following equations.
+
R-CH=CH,, HXa HX is HBr or HAlBr4.
[R-CH-CHB]
X-
+ R--bH-CHa CHI-- -CH: ----CH--CH3 + R--CHZ-CHa
CH3---CH2--C13.
(1)
CH,-("2----&H----C'
(2)
3 ---f f -
CI&-CH-CHT~
I
CH3 -~
CHa-&-CHa
I
I
CHI CH3-CH-CH3
+ CHJ -CH,
I
(3)
CH3
I_
CH3-CH=CH-CH3 H + xHX CHa-CH=CH-CH3 DX If CHa-CD=CH-CH3
+ +
f4 CHr--CHD-CHX-CH~
CHa
(1) For paper 111 of this series, see R. C. Wackher and H. Pines, THISJOURNAL., 68, 1642 (1946). (2) Presented before t h e Organic Division at the American Chemical Society Meeting, Atlantic City, April, 1946. (2a) H. Pines a n d R , C. Wackher, THISJOURNAL, 68, 595 (1946). (3) H , S. Bloctt, H. Pines and L . Schmerling, i b i d . , 68, 153 (1946).
Ci: -CX, (4)
If the isomerization steps as given above are correct, then, by substitutlng deuterium bromide for hydrogen bromide, one would expect an exchange reaction to occur between the deuterium of the catalyst and hydrogen of the butanes. This can be represented by the equations CHa--CH2-&H-CH3
- - ~CHa
+
+ CH3-CH2-CH,--CH,
CH3-6-CHs
-+-
Hf
(3a) (3b)
+ HX
[CH3--CHD--bH--CH3]
X-
(3c)
CHs-CHD-?H-CH3 CHx-CH-EHD
I
CH3
CH3--d-CHnD
I
CH3
(3d)
Dec., 1946
2519
CATALYTIC DEUTERIUM EXCHANGE WITH %-BUTANE
ISOMERIZATIOS OF 11-BUTANE IN
THE
Experiment no. Reaction time, hrs. Temp., "C. ( AlBra IlRr Charge, wButaiie inole , j i-Butaiie
TABLE I PRESESCE OF ALUMIXUM BROMIDE-DEUTERIUM BROMIDECATALYST 1 2 3 4 , 20 20 20 _~_____ 25 ,7
-
0.01171 0 . 0 to31 0.1170 .01045 ,1173 .lo60 0 0 ~r-~uteiies 116 x 10-6 98 x 10-6 9.4 8.1 Anal. of ,' DBr HBr 36.6 19.1 reaction Isobitane 53.0 i2.4 product, ! n-Butane 92.1 0 1.0 0 .4 mole yo \ Pentanes and higher Deuterium anal. a:id calc. %-Butane z-Butane i-Rtttanc 12-Butane ;-Butane %-Butane . 4 t O I n r; 1) i i i H;C of coii11)iistioii'~ 0.1352 0.1888 2.232 1,606 2.396 1.488 Averagc no. atoms of D i)er molecule of hutanes .nim .nm 0.2198 0.1572 0 . 2 4 ~ 2 0.1354 T;7 I ) orig. present as I)Rr found in butanes 5.97 9. .54 45.13 46.83 26.22 58.60 o f tieutcriuni osidc was subtracted from this coluiiiik for succeeding calculation, iiiasiriuch as this amount is (L 0.017', present in iiatural watcr. 0 * 0 1151 .01051 .1239 0 0 7.9 0.0
1,
+
CH3-~-CH211)
I
4-CHa---CH2--CH2---CH3
CHa CHa--CH---CH2D
+ CHa --CH2--CH~--CH, f
(3e)
CHJ
0 . 0 1021 ,00942 0 0.1156 0 6.3
F::
reaction, namely, from 92 to S3C;b, as indicated by experiment 4, Table 1. The deuterium tracer technique also was used to throw some light on the mechanism of the isomerization of n-butane in the presence of hydroxyaluminum dibromide.
TABLE I1 By applying the same reasoning as given above, i t becomes clear that deuterization of the n- KEACTIOX O F ALUMINUM BROMIDEWITH DEUTERIUM butane can also take place. The equations also OXIDE A N D ISOMERIZATIOI. O F %-BUTANEI N THE PRESENCE show the possibility of the existence of more than O F T H h KESCLTINC REACTION PRODUCT one atom of deuterium in a molecule of butanes. Part A 5 6 In order to test the validity of the postulated Fxperiment n o 10 17 iiiechanisni of isomerization, deuterium bromide- Reaction { At 23' time, hrs ( A t 100' 0 i 0 75 aluminum bromide instead of hydrogen bromideAIBra 0 01175 0 01137 aluminum bromide was used as an isomerization Charge, DKI o 01142 0 01177 catalyst, 'The reactions were carried out under Moles Lhc) per mole 1 AlBri 1 00 1 00 controlled conditions using a high-vacuum tech0 01179 0 01186 crated gen-' 3loles per mole nique as described p r e v i o u ~ l y . ~The ~ * ~ experi- DBr mental conditions are summarized in Table I. AlBri 1 00 1 04 I t was found that by treating either n-butane or Part R isobutane with :a 10 mole per cent. of deuterium Isomerization of 21-Butane in t h e Presence of t h e Catalyst Described bromide-aluminium bromide catalyst for twenty in P a r t A--Isomerization of %-Butane in t h e Presence of DOAIBn 20 42 hours at %", no isomerization of the butanes oc- Reaction time, hrs. 25.0 2.5.0 curred anti only 6 and 9.50/;, of the deuterium Reaction temp., 'C. charged, moles 0.1189 0.1179 exchanged with n-butane and isobutane, respec- n-Butane Anal. of product, mole % tively. it71ieri,however, 0. t mole per cent. of nHBr and I l B r 0 0 0 6 3.7 21.0 butenes was atlrlcd to n-butane arid the iso- ( ;-Butane 96.3 78.1 tnerizatiori reaction was carried out under the ~ ~ ~ higher ~ ~ ~0 . 0 ~ ~ 0 .s3 n d same rxperirnciital conditions, over 4076 of the L l e u t ~ r i u m anal and hutane isomerized to isobutane and 92% of the calc. i-Butane n-Butane i-Butane 11-Butane tleuteriuni uiitli.~went an exchange reaction. AtcBm %, 1) in IIzO o f combustion" b 11.1224 0.1604 0.1288 'I% results given above indicate clearly that olefins take an active part in isomerization, and Average nu. atunis (if D per molecule of the results, obtained are in agreement with the butanes .0088 ,0126 ,0094 proposed mechanism of isomerization. yo P orig. present as DOAIBrz iriund in It mas f80uridthat the decrease of the contact 4.32 1.44 3.99 butanes time between the catalyst :ind the hydrocarbons 0 , 0 1 7 5 of deuterium oxide was subtracted from this from twvcnty 'hours ti) seven hours, decreases for succeeding calculation, inasmuch as this only slightly the 11ytlrogc.11deutr.riuni exchange column amount is present i n natural watcr. Quantity too small
i
(
1
.
fl
(-4)
If. F'iiir\
:tiid
l i i'.1 4 k k I i ? r , 'l'nrs
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