ACTION O F RADON ON POLYMETHYLENES: CYCLOPENTANE AND CYCLOPENTENE G. B. HEISIG School of Chemistry, University of Minnesota, Minneapolis, Minnesota Received February 13, 1936
In a previous paper ( 5 ) the action of radon on cyclopropane was reported. The study of the action of radon on this type of hydrocarbon was continued to permit comparisons of their behavior with that of the aliphatic hydrocarbons to be made and to study the relation of the values of the - M / N , the heats of formation, and the
The procedures and methods of calculation of the - M / N values were those used in a previous paper (4). The results of the present work are summarized in the upper part of table 1. The lower figures are given for purposes of comparison. A comparison of the values of -M / N and A(H2
+
CHd)100 -AHC
for cyclopentane with the corresponding values for the saturated aliphatic5 and those of cyclopentene with those of ethylene show a very striking similarity-in fact the values are practically identical. In a previous paper (6) the writer pointed out the fact that the - M / N values for compounds with positive heats of formation from diamond and hydrogen are low-ordinarily about 2. The values of - M / N for those compounds whose heat of formation was negative were larger than 2, and the va,lues increased with the increase of the negative heat of formation. The heat of formation of cyclopentane from diamond and hydrogen was calculated from the heat of combustion by means of the general expression mCdiamond
+ n2 Hz
4
C,H,
+ 92.1 wa + 34.2n - heat of combustion
The heat of combustion of cyclopentane is 783.6 (9), and the heat of formation is 18.9 kg-cal. The value of the - M / N is 1.7. The heat of com1067
1068
G . B. HEISIG
bustion of cyclopentene has not been determined experimentally, but was calculated by the method of Kharasch (10) and was found to be 735.9. The heat of f o r m a ~ o nfrom hydrogen and diamond based on this value is - 1.8 kg-cal., and the - M / N is 4.5. The correlation of these values of the heats of formation and the -M / N is very satisfactory. Inasmuch as very pure samples of these substances were available, their vapor pressures were determined.
P I R CENT HYDROCARBON
Cyclopentane. .. Cyclopentene., . Methane.. ...... Ethane. . . . . . . . . Propane. . . . . . . . Ethylene. .......
- ~pHc
*C" + C H ~ )~2%
I N MM.
CALCULATION
32.9 91.0
100 97.0
HEAT OF FORMA-
PRODUCT
+ Hd -~
73.7 19.2 75.7 91.1 82.3 16.0*
1.7 4.5 2.2 1.7 1.7 4.8
(DI?Z&D
18.9 -1.8 20.4t 25.5 30.3 -6.4
Light colored mobile liquids Light colored liquids
* During the first part of the reaction. The ratio increases, owing to action on the product. t Calculated from heats of combustion given in International Critical Tables Vol. V, p. 163 (1929). EXPERIMENTAL
Preparation of cyclopentane This substance was prepared by the reduction of (a) cyclopentadiene and (b) cyclopentene in an Adams hydrogenation apparatus using a platinum oxide catalyst. Since these methods of preparation have not been previously described, they are given in some detail. Dicyclopentadiene (60 cc.) was depolymerized by heating the polymer in a Clarke flask contained in a metal bath at 185°C. The temperature was gradually increased t o 215°C. at the end of the process. Thirty cc. of cyclopentadiene dissolved in 175 cc. of 95 per cent ethanol to which 0.5 g. of platinum oxide catalyst (prepared according to the directions in Organic Syntheses, Vol. VIII, p. 92) were reduced in the Adams hytlrogenation apparatus. Only 80 per cent of the calculated amount of hydrogen was taken up. The portion distilling to 78"C., but chiefly between 40-45"C., was thoroughly agitated successively with water, concentrated sulfuric acid, and dilute sodium hydroxide, and then dried over fused calcium chloride. The sample distilled between 49-50°C. On treating the alcohol used as a solvent with water, an oily solid separated which was identified as tetrahydrodicyclopentadiene by its melting point. This
ACTION OF RADON ON POLYMETHYLENES
1069
compound had been described by Eijkman (1). Its formation undoubtedly accounts for the low absorption of hydrogen. Forty cc. of cyclopentene dissolved in 150 cc. of ethanol was hydrogenated using 0.25 g. of the oxide catalyst. The calculated amount of hydrogen was absorbed in about an hour. The product was removed by distilling at 78°C. and was purified as described previously. Any traces of unsaturated impurity were removed by thoroughly agitating with an alkaline permanganate sdution until a portion did not decolorize a very dilute solution. After drying over calcium chloride, the sample distilled a t 48.8"C. a t 738.4 mm. The boiling point a t 760 mm. was calculated to be 49.6"C. (3). The boiling point given in the International Critical Tables is 49.5"C. (8).
Puri$cation of cyclopentane The cyclopentane prepared from the cyclopentene was held over bright sodium under its own vapor. Fresh sodium was used each day. The surface was not coated after standing thirty-six hours. The sample was distilled three times under its own vapor pressure from a trap maintained a t 0°C. and condensed in a trap a t -8OOC. The vapor pressure was 107.3 mm. a t 0°C. and was unchanged by the distillations. After two distillations from -20°C. t o a trap a t -80°C. the vapor pressure at 0°C. was 107.3 mm. The vapor pressure of the first fraction and of the last fraction a t 0°C. was 107.3 mm. Action with radon Very shortly after mixing the cyclopentene with radon a fog appeared. The product collected as a mobile nearly colorless oil on the bottom of the reaction sphere, and was not appreciably affected by further action of radon as shown by the constancy of the ratio
+
A(H2 CH3 -AHC Typical data is given in table 2.
Preparation of cyclopentene Cyclopentene was prepared by the dehydration of cyclopentanol by heating with hydrated oxalic acid. The cyclopentanol was made by the reduction of cyclopentanone, using a Raney nickel catalyst and hydrogen under high pressure. Cyclopentanone (148.5 g. or 1.77 moles) from the Eastman Kodak Co. was reduced with hydrogen a t an initial pressure of 1600 Ibs., using 8 g. of Raney nickel catalyst but no solvent. After four hours a t 15OoC., 90 per cent of the calculated amount of hydrogen was absorbed. The contents of the b3mb were filtered through a sintered glass .
1070
G. B. HEISIG
crucible, and the residue was washed with a little absolute alcohol. The filtrate was distilled through a Widmer column with an electrically heated TABLE 2 Polymerization of cyclopentene by alpha rays f r o m radon CsHs+liquid. Temp. 25°C.; i s = 3.95; i = 1.23; s = 3.21. Reaction sphere: volume = 35.309 cc.; diameter = 4.070 em.; EO = 0.03395 Curie
I -
-
I
TIME
PRESSURE
,
RADON
Davi Hours
ApHz Total CsHs Hz+CH
+ CHI
A(HzfCH4) -ACbHa
----percent
1 1 1 2 2 3
3 4 5
6 6
-
1.03 3.15 7.18 9.32 14.6 Z3.65 3.57 9.40 12.73 0.23 5.23 1.38 5.98 9.11 0.37 0.10 8.15
mm.
mm.
100.000 168.7 168.7 99.231 166.9 163.9 97.665163.6163 6 94.757158.3152.3 93.260 155.6154.3 89.629 149.3 147.3 83.747140.0136.3 81.311 137.0 132.8 77.832 132.4 126.4 75.928129.8123.1 69.648 122.9 114.2 67.086120.2110.8 59.679111.8100.0 55.719110.3 97.9 45.461 103.0 88.3 40.546 99.9 83.8 33.935 96.1 77.7 31.947 94.8 75.1
Weighted average. . .
,@
ku/X
- M/N
--
mm.
1.0 1.3 2.0 3.7 4.2 6.0 6.7 8.7 9.4 11.8 12.4 14.7 16.1 18.4 19.7
1.o
0.3 0.7 1.7 0.5 1.8 0.7 1.o 0.7 2.4 0.6 2.3 1.4 2.3 1.3
... . . . . . , , . . . . . , , . . . . . . . . . . . . .
15.9 10.00 10 IO0 15.45 14.26 28.08 21.20 11.24 22.90 26.10 28.60 23.99 31.10 37.64 19.15
40.5 37.7 39.9 37.6 37.7 38.9 31.5 41.7 41 .O 35.2 34.9 32.1 31.8 29.6 31.5 33.6 50.5
5 .O 4.7 4.9 4.7 4.7 4.8 3.9 5.2 5.1 4.4 4.4 4.2 4.0 3.7 4.0 4.2 6.3
4.5 -
jacket. An oil bath was used to heat the sample. The following fractions were collected. Fraction Fraction Fraction Fraction
I . . , . . . . . . . . , . . . . . . . . . . . . . . 77-78°C. 11... . , . . . , , . . . . . . . . . . . . . . . 135-136°C. 111. . . . . . . . . . . . . . . . . . . . . . . . 136-137.5%. IV., . . , . . . . . . . . . . . . . . . . . . . . Above 137.5"C.
Solvent discarded Discarded Collected Discarded
Fraction I11 weighed 134.7 g. and 95 per cent of it boiled between 137137.5"C. The yield was 91 per cent. The reduction of cyclopentanone to the cyclopentanol has also been carried out by Godchot and Tabourg (2). They obtained some unreacted cyclopentanone, cyclopentane, 50 per cent of the weight of the sta.rting substance as cyclopentanol, and 40 per cent as a ketone having the formula CIoHlsO.
ACTION OF RADON ON POLYMETHYLENES
1071
Cyclopentanol (110 g. or 1.17 moles) and 600 g. o€ hydrated oxalic acid (4.8 moles) were placed in a l-liter Claisen flask. The flask was heated in a Wood's metal bath until the contents began to liquefy. A condensate began to appear in the condenser when the temperature of the mixture was 80°C. The heating was then gradually increased until no more solid was present (IlO"C.), and held a t that temperature for 30 minutes. The temperature o€ the distillate gradually increased to 8OOC. The temperature of the metal bath was increased until the temperature of the vapors distilling was 100°C. Very soon after this temperature was reached, the condensate was clear, indicating that no more product was being obtained: the heating was then stopped. The time of heating was about two hours. The cyclopentane was separated from the aqueous layer and dried over calcium chloride. The crude material weighed 55.5 g., making a yield of 70 per cent. The dried product was then distilled from sodium. The distillation started a t 43°C. and the temperature quickly rose to 433°C. When the temperature reached 45.5"C. the distillation was stopped. The 49.0 g. of the product (62 per cent yield) was mixed with the products obtained in preliminary runs, and allowed to stand overnight over sodium. On distilling, the material boiled between 435°C. and 433°C. A small fraction boiling between 43.8"C. and 44.1OC. was also obtained. The barometric pressure was about 740 mm. In order to dry it thoroughly and to remove any trace of unchanged cyclopentanol, a portion of the material was placed in a vessel previously filled with dry nitrogen containing bright pieces of sodium; after freezing in liquid oxygen the nitrogen was pumped off. After standing twelve hours under its own vapor a t 0°C. a brown sludge was formed; the sample was then distilled a t low temperatures into a second evacuated vessel containing a few pieces of bright sodium. After remaining three days in contact with the sodium no sludge was formed and the surface of the sodium was bright. Puri$cation of cyclopentene
The sample was then distilled from a trap maintained at 0°C. and was condensed a t -182°C. The first and last 1.5 cc. were discarded, A second distillation was made from O'C., and condensation took place a t - 182°C. Then the sample was cooled to - 182°C. and any non-condensable gases were pumped off. The temperature was raised to 0°C. and, after cooling, the pumping operation was repeated to remove any residual non-condensed gas. The vapor pressure of the sample at 0°C. was 131mm. The sample was then distilled two times from -30°C. to - 182°C. When two-thirds of the sample had distilled, the vapor pressure of the residue was found to be 131 mm. at 0°C. A second distillation under the same conditions was carried out. The vapor pressure of the low-boiling fraction was
.
1072
G. B. HEISIG
131 mm. a t OOC. The vapor pressure of the middle sample was also 131 mm. at OOC. A sample t o use in determining the vapor pressure a t various TABLE 3 Polymerization of cyclopentane b y alpha rays f r o m radon CsHro gas +liquid. Temp. 25°C.; is = 4.3; i = 1.24; s = 3.48. Reaction sphere: volume = 35.805 cc.; diameter = 2.045 cm.; E O = 0.03718 Curie
-
TIME
-
Days
1 1 2 2 3 4 4 7
PRESSURE RADON
Hours
CsHio
per cent
mm.
mm.
mm.
100.000 98.364 96.987 94.729 92.892 84.219 82.426 72,253 64.931 59.715 54.653 47.168 42.276 24.450
105.5 105.5 105.5 104.9 104.6 103.2 103.0 101.5 101.0 100.4 100.1 99.3 99.1 98.0
105.2 104.6 103.2 101.9 97.2 96.0 90.8 87.7 85.7 83.1 79.3 77.8 72.3
0.3 0.9 1.7 2.7 6.0 7.0 10.7 13.3 14.7 17.0 20.0 21.3 25.7
--
2.22 4.08 7.22 9.83 22.90 1.77 19.33 9.58 20.75 8.56 4.20 18.8 19.8
+ CHI
Total
Weighted average..
Hz
100.0 100.0 57.2 77.0 70.3 83.3 64.8 83.8 70.0 88.5 78.8 86.7 79.9
. . .. . , .. . . . ., . . .... .. . .. . . . .
kdX
- M/N
-
-
4.9 11.2 15.9 18.5 14.7 18.7 14.2 12.8 11.9 16.3 16.8 16.2 11.3
0.6 1.3 1.8 2.1 1.7 2.2 1.7 1.5 1.3 1.9 1.9 1.9 1.3
-
73.7
I
1.7
-
TABLE 4 Vapor pressures of cyclopentane and cyclopentene t
VAPOR PRESSURE OF CYCLOPBNTANE
t
VAPORPRESSUREOF CYCLOPENTENE
"C.
mm.
"C,
mm.
-52.0 -47.5 -38.8 -25.9 -14.4 0.0 6.0 13.6 18.4
4.4 6.1 12.1 27.3 53.0 107.4 140.7 197.6 241.8
-77.5 -50.8 -26.8 -9.2 0.0 f6.8 +12.3 15.0 19.9 43.5
1.o 6.1 31.0 81.9 129.3 178.1 226.6 253.1 309.4 731.2
temperatures and t o subject to the action of a-particles was taken, after about a third of the material had been distilled off. The vapor pressure of this sample was 131 mm. a t 0°C.
ACTION OF RADON ON POLYMETHYLENES
1073
Action with radon The action with radon was practically identical with that of cyclopentane. The data is given in table 3.
Vapor pressures The vapor pressures of cyclopentane and cyclopentene a t various temperatures were determined using the method and apparatus previously described (7). The results are given in table 4. SUMMARY
1. Pure cyclopentane and cyclopentene have been prepared, and the vapor pressures a t several temperatures have been determined. 2. The action of radon on these compounds has been studied. The - M / N va.lues are in agreement with the heats of formation and with
A(H2 + CHd)100 -AHC The writer wishes to acknowledge the grant from the Graduate School to aid in carrying out this work and the assistance of Lucille M. Heisig in determining the vapor pressures. REFERENCES (1) EIJKMAN: Chem. Weekblad 1, 7-12 (1903). (2) GODCHOT AND TABOURG: Compt. rend. 162, 881 (1911). (3) Handbook of Chemistry and Physics, 18th edition, p. 1132. The Chemical Rubber Publishing Co., Cleveland (1933). (4) HEISIG: J. Am. Chem. SOC. 63, 3245-63 (1931). (5) HEISIG: J. Am. Chem. SOC. 64, 2328-32 (1932). (6) HEISIG:J. Phys. Chem. 36, 1000-5 (1932). (7) HEISIGAND DAVIS:J. Am. Chem. SOC.67, 339 (1935). (8) International Critical Tables, Vol. I, p. 192. McGraw-Hill Book Co., New York (1926). (9) KHARASCH: Heats of Combustion of Organic Compounds, Research Paper No. 41 (reprint from the Bureau of Standards Journal of Research, Vol. 2), p. 374 (1929). (10) Reference 9, p. 377.
