Vapor Pressures for Six Aliphatic Nitro Compounds MM. OF MERCURY
CENTIGRADE
1000
E. B. HODGE
rooo
Commercial Solvents Corporation, Terce Haute, Ind.
:- 600
y 4 7 6 0
1-500 k . 0 0
p L
ITTLE information is available on the vapor pressures of the aliphatic nitro compounds (4, 6). Since they show promise of commercial importance, it was believed that such information would be of general interest. Data are given for nitromethane, nitroethane, 1- and 2-nitropropane, and 1- and 2-nitrobutane. The materials were prepared by the vaporphase nitration of propane and butane. Each compound was rectified through a 5 foot X 3/4 inch (152 X 1.9 cm.) glass column packed with '/*-inch (3.2-mm.) single-turn glass helices (6) until the boiling range was not over 0.2" C. for 75 per cent of the volume originally taken. The boiling ranges were determined in the apparatus described by Quiggle,Tongberg, and Fenske (S), and the determinations were stopped when about 75 per cent of the liquid had distilled. Vapor pressure measurements were made in an apparatus similar to that described by Pickett (2) but differing in the following respects: A 2-liter flask mas in the system; glass seals were used for all connections except from the vacuum pump to the apparatus; a bath of dibutyl phthalate was employed for heating; a copperconstantan thermocouple and a Leeds & Xorthrup portable precision potentiometer were used for temperature measurements; a cathetometer was employed for the vapor pressure readings. . TheThermocouple was calibrated at the freezing and boiling points of water and a t 150" C. against two thermometers recently standardized by the National Bureau of Standards. Determinations were made as described by Pickett (2). The results were plotted on semilogarithmic paper. Pressures, in mm. of mercury, were plotted on the logarithmic scale against reciprocals of the absolute temperatures on the linear scale. Smooth curves were drawn through the points, and three points were taken on each curve to evaluate the constants in the equation:
L
-200
0 0
0
NITROMETHANE
NITROETHANE 2-NITROPROPANE
0 1-NITROPROPANE 0 2-NITROBUTANE
0 1-NITROBUTANL
i, Compound Xitromethane Nitroethane 2-Nitropropane 1-Nitropropane 2-Nitrobutane 2-Nitrobutane
B. P. (760 Mm.),
C.
101.2 114.0 120.3 131.6 139.6 152.9
Calcd. Vapor Pressure, Mm. Hg 758 760 759 757
762 759
C
A nomograph is included from which values accurate enough for many purposes can be read. This was constructed according to the method of Killeffer (I), except that the temperature scale was averaged from scales of nitromethane and Znitrobutane, which were found to differ somewhat. Over most of the range, pressures for a given temperature can be read within about 2 per cent of the value calculated from the corresponding equation.
18.0571 32.803 29.752 28.879 25.591 34.701
(1) Killeffer, D. H., IND.Era. CHEM., 30,477 (1938). (2) Pickett. 0.A., Ibid., Anal. Ed., 1, 36 (1929). (3) Quiggle, D.,Tongberg, C . O., and Fenske, M. R., Ibid., 6,466
The accuracy to be expected from the equations may be judged by the vapor pressures calculated a t the boiling points:
(1934). (4) Thompson, H.W., and Purkis, C . H., Trans. Faraday SOC., 32, 674-80 (1936). (5) Williams, J. W., J.Am. Chem. Soc., 47,2644 (1925). (6) Wilson, Parker, and Laughlin, Ibid., 55, 2795 (1933).
logP = A / T
+ BlogT + c
The following table gives the constants found: Compound Nitromethane Nitroethane 2-Nitropropane 1-Nitro ropane a-~itrogutane 1-Nitrobutane
A -2423.7 - 3249.5 -3106.7 -3168.8 -3048.1 -3679.3
log - A 3.38447 3.51181 3.49230 3.50089 3.48403 3.56576
B -3.3821 -8.3188 -7.3128 - 6.9695 -5.8579 -8.817
log -B 0.52918 0.92006 0.86409 0.84320 0.76774 0.94532
Literature Cited
748
