CERTAIN PHYSICAL PROPERTIES OF DIVINYL ETHER FRANCIS T. MILES
AND
ALAN W. C. MENZIES
Frick Chemical Laboratory, Princeton University, Princeton,
New Jersey
Received February 16, 1988
Divinyl ether has recently (1) been proposed as an anesthetic. A knowledge of some of its physical properties, and especially of its vapor pressures, was obviously desirable, and a study of certain of these properties is here recorded. THE MATERIAL USED
A method of preparation of this substance has recently been worked out by Ruigh and Major (2) in the Laboratory for Pure Research of Merck and Company, Inc. They suggested the present work, and we are indebted to them for a sample of their purest product, it being the middle fraction, boiling over a range of O.O2"C., of a freshly prepared and purified batch of over a liter. These investigators show (2) that the product obtained by earlier workers,has been of lower purity. VAPOR PRESSURE MEASUREMHNT
This was carried out by the static isoteniscope (3) method of Smith and Menaies. The pressure gauge consisted of a U-form Pyrex glass tube of 13-mm. bore, containing triple-distilled mercury, one limb of which was evacuated to a pressure of less than 0.01 mm. of mercury as measured, by a McLeod gauge. The mercury levels were read off against a vertical mirror by means of a truly horizontal hair line ruled on a glass microscope slide fixed in a carrier which could slide the whole length of a graduated vertical steel bar 24 meters long. The graduation of this bar is nowhere in error by over 0.01 mm. The reduction of the pressure readings t o millimeters of mercury at 0°C. and g = 980.66 was carried out as described elsewhere (3). At Princeton, g = 980.18. Temperature measurement above 0°C. was made by a mercurial thermometer graduated in tenths of a degree and certificated at the Reichsanstalt t o the nearest =tO.O2"C. a t each 10°C. interval. The ice-point of this thermometer was of course redetermined. Below 0°C. another thermometer graduated to tenths was used, and its readings were corrected, through the courtesy of a colleague, by comparison with a platinum resistance thermometer whose readings are believed good to hundredths of a degree. 425
426
FRANCIS T. MILES AND ALAN W. C. MENZIES
The temperature bath was a 4-liter beaker, containing either water or else carbon tetrachloride, adequately stirred by a rotating vertical shaft carrying three propellor-like agitators. By adding solid carbon dioxide the temperature could readily be lowered t o -20°C. In preparing the isoteniscope, we took due precaution t o remove, by heating and exhausting, the moisture film from the surface of the glass. TABLE 1 V a p o r pressures of divinyl ether determined experimentally OBSERVATION NUMBER
I
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
T (observed)
PRESSURE
degrees C.
mm.
-19.70 -19.69 -16.55 -16.19 -10.02 -9.18 -0.39 -0.04 4.06 13.58 14.01 14.39 20.22 20.22 20.56 20.65 21.45 21.79 21.88 22.25 23.66 28.35 28.64 35.31 35.64 43.74 43.77 43.91 49.33 49.56
(observed)
85.7 86.0 101.5 103.5 143,7 150.0 230.0 233.4 282.4 426,6 433.9 440.5 557.2 557.5 564.0 566.7 584.7 592.8 595.8 602.9 636.5 759.2 767.0 971.1 985.2 1294.2 1296.2 1311.5 1551.0 1565.7
T
_- (calculated) - 19.673 -19.610 - 16.595 -16.235 -9.986 -9.142 -0.373 -0.060 4.089 13.608 14.017 14.382 20.205 20.218 20.513 20.635 21,434 21.787 21.917 22.223 23.636 28,322 28.600 35.183 35.597 43,693 43.741 44.101 49.361 49.664
- ,027
- .080
,045 .045 - ,034 ,038 - ,017 .020 - ,029 ,028 ,007 ,008 ,015 .002 ,047 ,015 ,016
-
-
,003
- ,037
,027 .024 .028 ,040 .127 ,043 .047 ,029 .191 - ,031 .lo4
-
EXPERIMENTAL RESULTS O F VAPOR PRESSURE MEASUREMENT
These are tabulated in table 1, in which the first three columns are selfexplanatory. In order to obtain a smooth curve through our experimental points, we
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PHYSICAL PROPERTIES OF DIVINYL ETHER
chose a three-constant equation of the Rankine-Kirchoff-Dupr6-Hertz type, and evaluated the constants as follows: loglop,,,
= 21.73592 - 2085.11
- 4.81530 10gloTsb..
(MI
Tabs.
The fourth column in table 1 shows the temperatures calculated for the observed pressures by means of this equation. The fifth column serves t o show (1) the closeness of fit, since the algebraic sum of the differences between calculated and observed temperatures is O.O42"C., and (2) the degree of consistence of the observations, for the sum of all the differences, each taken as positive, divided by the number of observations is O.04O0C., which may be considered as the average error of a single observation. TABLE 2 Vapor pressure of divinyl ether calculated from equation M 2
-30 -20 - 10 -0 0 10 20 30 40 50 60
46. 88 84.16 143.6 234.1 234.1 366.3 552.7 807.3 1145. 1682. 2134.
76. l r 129.5 213.0 256.8 398.8 597.7 867.8 1224. 1685.
4
67.0* 116.6 193.5 281.3 433.6 645.4 931.6 1307. 1788.
6
69.64 104.8 177.5 307.6 470.8 696.4 999.1 1395. 1898.
8
62.88 94.0' 158.9 325.9 511'.5 750.2 1070. 1486. 2014.
Extrapolated values are in italics.
Table 2 shows the vapor pressures of divinyl ether as calculated by equation M for each 2°C. interval from -30°C. to +60"C. R e have extrapolated values for 10°C. beyond each end of our experimental range, and show these extrapolated values in italics. We publish these pressure values for such small steps of temperature so that interpolation, using p and t as variables, can be made directly without exceeding the experimental error of the observations. The normal boiling point of divinyl ether, according to equation M, is 28.35"C. +0.04". This is in concordance with the normal boiling point, 28.3"C. &0.2", reported by Ruigh and Major. DUHRING'S, AND RAMSAY AND YOUNG'S RULE WITH ETHYL ETHER AS COMPARISON SUBSTANCE
Before the present measurements were made, Ruigh had obtained approximate values for the vapor pressures of divinyl ether by comparison
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FRAKCIS T. MILES AND ALAN W. C . MENZIES
with diethyl ether. For very closely analogous substances, the ratio T v / T E of the absolute temperatures a t which two substances, V and E, have the same vapor pressure should remain approximately constant. A t the normal boiling point, this ratio for vinyl and ethyl ethers is 301.45/ 307.54 or 0.9802. If this ratio is used, employing the values for ethyl ether found in International Critical Tables, the temperature discrepancy from our values for divinyl ether for the pressure 112.3 mm. is -0.50"C. and for the pressure 1277 mm. is +0.12"C. Therefore, not the Duhring but rather the Ramsay and Young equation
is t o be preferred, where c = 0.00003. DENSITY AND SPECIFIC VOLUME
It is well-known that for ranges of temperature sufficiently removed from the critical temperature, the change of specific volume of a liquid with temperature may be represented satisfactorily by a quadratic equation in t, measured from a convenient point. For ethyl ether, such a n equation is said in I. C. T. to represent the facts in the range 0°C. to 70°C. t o one part in ten thousand. For our purposes, therefore, it was sufficient to measure the density of divinyl ether a t three known temperatures near 0", +13", and +25"C. This we did by means of a dilatometer. From the values so obtained, we determined the three constants in the following equation: dt = [d,
in which 1,
=
+ 10-3
cy*
(t
- t,) + 10-6.p. (t - t,)']
& 10-4.A
(D)
0°C.
d, = 0.79601
-1.14582
CY
=
p
= -2.5706
A =2. LATENT HEAT OF VAPORIZATION
True values for this can be obtained from the Clapeyron equation, provided dpidt and the specific volumes of both vapor and liquid are known. Although equation M above is an empirical equation, it nevertheless represents accurately the experimental facts, and we can, therefore, obtain true values of dp/dt by its use. We had already measured the densities of the liquid. It was, therefore, necessary to measure experimentally only the specific volume of the vapor. It is frequently forgotten that values obtained upon the assumption that a saturated vapor follows the simple gas laws may be in error by several per cent. Because the instability of
PHYSICAL PROPERTIES O F DIVINYL ETHER
429
divinyl ether makes it a difficult subject for precise vapor density work, we have contented ourselves with reporting its orthobaric density only a t one temperature, the normal boiling point. The measurements were made in a 100-cc. bulb sealed to a graduated capillary in which the condensed liquid portion could be measured with a n accuracy of f 0 . 0 3 per cent. The total content of divinyl ether in the apparatus was obtained by direct weighing. The orthobaric density of the vapor thus found was 0.002994 3 ~ 0 . 5per cent, a mean of two observations. This value is 5.1 per cent higher than the value computed by the simple gas laws. Substituting in the rigid Clapeyron equation the experimental values thus found, we obtain 6260 and 89.4 calories as the latent heat of vaporization of divinyl ether a t 28.35”C., per mole and per gram respectively, with an accuracy of k0.5 per cent. TROUTON’S CONSTANT
The value just reported yields 20.8 for this constant, as compared with 20.8 for diethyl ether using Mathews’ (4)value for the latent heat of vaporization. HILDEBRAND’S CONSTANT
It will be recalled that Hildebrand ( 5 ) found steadier constants than those given by Trouton’s rule when he considered entropies of vaporization for series of liquids a t temperatures chosen to yield vapors of the same concentration rather than the same vapor pressure. Using the concentration where log T - log p = 0.5, as in an example studied by Hildebrand, we find that, for divinyl ether, the appropriate temperature is near -21°C. and the constant is 14.2 instead of Hildebrand’s standard or average value 13.7. Using Taylor and Smith’s (6) values for the vapor pressure of diethyl ether, we find a value of 14.0 for Hildebrand’s constant, calculated likewise for the above boncentration, which is reached near - 17°C. SUMMARY
The vapor pressures of divinyl ether are reported in the range -30°C. to 60°C. An equation is given relating experimental values of the density of the liquid to temperature. The latent heat of vaporization a t the normal boiling point is evaluated from the vapor pressure curve with the help of an experimental determination of the orthobaric volume of the vapor. The constants of Trouton and Hildebrand are evaluated under standard conditions.
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FRANCIS T. MILES AND ALAN W. C. MENZIES
REFERENCES (1) LEAKEAND CHEN:Proc. SOC.Exptl. Biol. Med. 28, 151 (1930). (2) RUIGHAND MAJOR:J. Am. Chem. SOC.63, 3663 (1931). (3) SMITHAND MENZIES:J. Am. Chem. SOC.32, 1419 (1910). (4) MATHEWS: J. Am. Chem. SOC.48, 562 (1926). (5) HILDEBRAND: J. Am. Chem. SOC.37, 970 (1915). (6) TAYLOR AND SMITH:J. Am. Chem. SOC.44, 3450 (1922).
