1380
I N D U S T R I A L A N D ENGINEEMNG C H E M I S T R Y
Vol. 20, No. 12
Vapor Pressures of Fumigants I-Methyl, Ethyl, Isopropyl, and Secondary Butyl Chloroacetates' 0. A. Nelson INSECTICIDE DIVISION,BUREAUOF CHEMISTRY AND SOILS,WASHINGTON, D. C.
R
ECENTLY Roark and Cotton2 investigated the effectiveness of certain esters of monochloroacetic acid ' for use as fumigants. The results of their experiments were very encouraging. It was found, for example, that methyl monochloroacetate, used a t the rate of 1 pound per 1000 cubic feet, killed all the insects used in the experiments. The ethyl and isopropyl chloroacetates also showed high toxicity, although not quite as high as that of methyl chloroacetate. I n view of the prospective use of these compounds as practical fumigants, it was thought desirable to determine some of their physical constants. The results of vapor pressure determinations are reported here. Preparation of Samples
Methyl chloroacetate was prepared. in the laboratory from crystalline monochloroacetic acid and methyl alcohol, concentrated sulfuric acid being used as a dehydrating agent. The resulting ester was washed several times with distilled water, dried over calcium chloride for one night or longer, and repeatedly fractionated by distillation. A middle portion of a fraction whose boiling point was constant within 0.10' or 0.20" C. was taken for vapor pressure determination. A commercial sample of ethyl chloroacetate obtained from the Dow Chemical Company was washed several times with distilled water, dried over calcium chloride, and fractionated by distillation. A middle portion of fraction whose boiling point was constant to within 0.10-0.20' was used for vapor pressure determination. Isopropyl chloroacetate and secondary butyl chloroacetate were prepared in the laboratory from monochloroacetic acid and isopropyl and secondary butyl alcohols by the same method as that used for the methyl monochloroacetate. The method of purification and the criterion for purity were the same as those for the methyl and ethyl monochloroacetate. Procedure
The method followed was that devised by Smith and Menzies3 and used later by the writer in the determination of vapor pressures of a number of organic compounds.4 This method is one of the most reliable thus far devised, in addition t o being unusually rapid. A series of determinations can be made in a single day. The low pressure bottle to which the apparatus was connected was evacuated by means of a Hy-T'ac vacuum pump, whereby the pressure could be reduced to about 2 mm. To obtain pressures above atmospheric a small hand pump was used. The highest pressure that could be determined with apparatus used was about 925 mm., and the lowest pressure obviously was about 2 mm. The temperature in the bath surrounding the isoteniscope was determined by Anschutz thermometers that had been standardized by the Bureau of Standards and could be read to within 0.10" C. The liquids used in this bath were glycerol above 100" C. and water below 100' C. The pressures 1 Presented as a part of the Insecticide Symposium befoie the Division of Agricultural and Food Chemistry a t the 75th Meeting of the American Chemical Society, St. Louis, Mo., April 16 to 19, 1928. I N D . ENG.CHEX., 20, 514 (1928). 8 J . A m Chem. SOL,32, 1420 (1910). 6 Nelson and Senseman, J. IND. ENG. CHEM.,14, 58 (1922); 16, 382 (1923); Nelson and Wales, J . A m . Chern. Soc., 47, 868 (1925).
were read directly from the manometer, after which corrections were made for temperature, the coefficient for expansion of mercury and glass given in the Smithsonian tables being used as a basis for the calculations. Results
The results obtained after all the air had been withdrawn from the sample bulb are shown in Table I. Table I-Observed
Vapor Pressures of Methyl Ethyl, Isopropyl, and Secondary Butyl Chloroace&tes CHLOROETHYL
METHYL CHLOROACETATE
CHLOROACETATE
-E;::
Temp.
Temp. o C. 145.9 144.6 144.2 142.4 139.8 134.7 130.0 124.9 120.2 114.9 110.0 104.6 98.5 92.0 85.2 79.3 72.5 65.7 59.9 54.5 47.4 41.0 32.0 25.0
"C. Mm. 130.9 129.9 127.8 125.0 120.0 113.0 110.0 106.0 100.0 90.3 85.3 80.3 75.3 70.3 65.3 60.2 55.2 50.1 45.0 40.0 35.0 30.0 25.0
ISOPROPYL SECONDARY Ru-
ACETATE
793.4 765.0 721.2 662.8 565.3 485.7 406.5 345,.2 289.3 205.6 168.7 138.3 110.0 87.2 69.2 54.3 43.3 33.3 25.4 19.9 15.4 11.5 8.0
TYL CHLORO-
ACETATE Temp.
Mm. 806.4 787.9 766.0 730.0 679.8 586.7 509.5 435.3 373.5 312.8 263.4 217.0 172.8 130.5 98.6 77.7 60.3 43.3 31.9 24.4 17.0 12.5 7.0 5.0
C.
Mm.
152.6 151.6 160.6 149.6 148.7 147.7 144.8 139.7 134.9 129.9 125.0 120.0 110.0 100.0 95.2 90.2 85.3 80.3 75.3 70.3 65.25 60.2 55.15 50.0 45.0 40.0 35.0
877.8 847.0 818.1 785.7 758.2 730.0 674.5 577.3 497.7 424.4 350.2 305.9 215.7 147.4 121.5 104.6 83.6 67.2 52.2 44.3 34.3 26.9 20.9 16.4 12.0 10.0 7.5
O
O C. 171.5 170.5 169.3 168.5 167.7 166.5 164.5 159.5 154.8 150.0 145.1 135.2 125.2 119.2 109.4 105.0 100.0 95.0 90.2 85.3 80.3 70.3 60.2 ' 55.1 50.1 40.0 30.0
::Mm. 895.7 849.8 825.9 792.0 771.0 748.1 705.8 612.1 528.4 455.2 395.9 288.8 208.7 167.4 117.5 104.1 83.2 66.8 54.3 43.3 34.4 21.9 14.0 10.5 7.0 4.5 2.5
Table 11-Observed and Calculated Vapor Pressures of Methyl, Ethyl, Isourouyl. and Secondary Butyl Chloroacetates PERATURE TEM-
C. 20 25 30 35 40 45 50 55 60 65 70 75 80 85
90 95 100 105 110 115 120 125 130 135 140 145 150 155 160 165 170
I
__
ETHYL
METHYL CHLORO-
CHLORO-
ACETATE
ACETATE
Obsd. Calcd.
Obsd. Calcd.
Mm. 6.7 9.0
11.5 15.2 20.0 26.3 33.5 43.0 54.1 68.0 85.2 107.0 132.3 164.5 200.0 240.0 489.0 342.5 406.0 482.5 566.0 663.0 777.0 894.0
Mm. 6.7 8.9 11.8 15.6 20.3 26.3 33.7 42.9 54.2 68.0 84.8 105.0 129.5 158.5 193.0 233.7 281.6 337.7 402.9 478.7 566.0 666.0 782.0 913.0
Mm. 3.7 4.9 6.7
8.9 11.7 15.2 19.7 25.3 32.2 40.0 51.1 64.0 80.0 98.0 120.5 148.0 180.0 217.0 261.0 311.0 369.0 434.0 511.5 596.0 687.0 988.0
Mm. 3.7 4.9 6.7 8.9 17.1 15.2 19.7 25.3 32.2 40.7 51.1 63.7 79.0 97.3 119.4 146.3 176.0 212.7 254.6 304.2 361.6 428.1 504.6 592.4 692.8 807.4
ISOPROPYL CHLOROACETATE Obsd. Calcd.
Mm. 3.0 4.3 5.6 7.5 10.0 12.5 16.5 21.2 27.0 34.0 43.0 53.3 66.0 81.6 100.0 122.0 145.0 174.0 212.0 252.5 303.0 258.0 422.0 495.3 584.5 682.0 802.0
Mm. 3.1 4.2 5.6 7.4 9.7 12.7 16.5 21.1 26.9 34.0 42.7 53.3 66.2 81.6
100.0 121.9 147.3 174.2 214.0 255.8 304.3 360.3 421.5 499.2 584.1 680.9 815.0
~ECONDARY Bu-
TYL CHLOROACETATE
Obsd.
Calcd.
Mm.
Mm. 1.4
2.0 2.5 3.0 4.5 6.0 8.0 13.5 16.5 22.0 28.0 34.8 43.6 54.0 67.0 81.5 101.2 122.0 148.0 174.0 207.0 245.0 288.2 335.1 494.5 458.0 633.0 618.0 712.5 828.0
2.7
... ...
4.7
8.1 13.6 22.1 34.8 51.9 80.2 118.0 170.2 241.0 335.5 460.1 621.6 828.2
INDUSTRIAL A N D ENGINEERING CHEMISTRY
December, 1928
The results in Table I were plotted on sheets of millimeter coordinate paper, approximately 16 by 21 inches. Curves were then drawn through these points, and corrected pressures were read from the smoothed curves. Table I1 gives the corrected pressures. Interpolation formulas that are valid over the range of temperatures and pressures under consideration may be obtained by a number of methods. The author used Ramsay and Young's5 boiling point law as a basis for deriving equations that fitted the experimental results.
1381
METHYLCHLOROACETATE-1Og~o P = 8.4073
ETHYLCHLOROACETATE-1Ogio P SECONDARY
- 2298.6 T(abs.) 2291.6 = 8.3893 - T(abs.) P
CHLOROACETATE-1Ogio
ISOPROPYL
2222.2 -T (abs.
= 8.3321
BUTYL CHLOROACETATE--lOglm 'f 8.3210
=
- 2393.44 T(abs.)
The agreement between the observed and calculated results is shown in Table 11. -4s all the compounds considered in this paper are effective as fumigants, it is desirable to. know the amount (weight) that can vaporize in a closed chamber of known dimensions a t any given temperature. I n calculating the weight of a fumigant that will vaporize in n closed chamber, the following fundamental equation can be applied: P V = ~ R T M
where P = pressure in atmospheres V = volume in liters R = the gas constant, or 0.08204 T = absolute temperature orJ273 t ) , t being the observed temperature in C. M = molecular weight of the fumigant
+
Flgure 1-Vapor Pressures Plotted against Temperature
If the reciprocal of the absolute temperature is plotted against the logarithm of the pressure, a curve drawn through these points should be a straight line. Thus it becomes only a matter of deriving an equation for this line. Such a vapor pressure equation, however, does not hold very far beyond the boiling point and it cannot be used to calculate the critical temperatures or pressures of the,.e compounds. Other more complex equations would fit the experimental results somewhat better than the ones presented herewith, but it was thought advisable to use the simplest form. The equations derived for the four chloroacetates considered in this paper are as follows: 6
Phil. Mag., 21, 33 (1886).
Solving for x in the above equation,
E";: '
x=-
grams
or, expressing P as p in millimeters of mercury, the equation becomes
As the capacities of fumigating chambers are usually expressed in cubic feet and the weight of the fumigant in pounds, the above equation, converted into the English system, becomes
Table 111-Weight of Fumigant That Will Vaporize into a 1000-Liter or a 1000-Cubic Foot Chamber
TEMPERA-
C. 20 25 30 35
40 45 50
1
METHYL CHLOROACETATE
Mm. H g 6.7 9.0 11.5 15.2 20.0 26.3 33.5
E r m L
CHLOROACETATE
1
ISOPROPYL CHLOROACETATE
SECONDARY BUTYLCHLOROACETATE
vapor
I
Grams/ 1000 1.
39.8 52.6 66.1 85.9 111.2 143.9 180.5
Lbs./ 1000 cu. p . 2.48 3.28 4.12 5.35 6.93 8.97 11.25
Mm. Hg 3.7 4.9 6.7 8.9 11.7 15.2 19.5
I
Grams/ 1000 1. 24.8 32.3 43.5 56.9 73.5 93.9 118.6
Lbs./
1000 cu. ft. 1.552.01 2.71 3.54 4.5s 5.85 7.47
1
Mm. Hg 3.0 4.3 5.6 7.5 10.0 12.5 16.5
I
pressure
Grams/ 1000 1. 22.4 31.5 40.5 53.3 70.0 82.5 112.2
Lbs./
l O O O c u . ft. 1.40 1.97 2.52 3.33 4.36 5.37 6.98
Mm. HE 1.4 1.7 2.0 2.5 3.0 4.5 6.0
1
I
Weight
Grams/
Lbs./
1000 1. 1000 cu. ft. 11.5 0.72 13.9 0.86 15.9 0.99 19.6 1.22 23.2 1.44 34.2 2.13 44.9 2.80
I N D U S T R I A L A N D ENGINEERING CHEMISTRY
1382 W =
p X 1.0015 X M 273
+t
which, in cases where extreme accuracy is not essential, may be written
'
w=-273 + t pounds per 1000 cu. ft. Table I11 gives the weights of the compounds that will vaporize into chambers of 1000 liters and 1000 cubic feet capacities. The formula applies to all pure chemical compounds.
Vol. 20, No. 12
Absorption of the fumigant by any materials within the chamber or adsorption by the walls of the chamber has not been considered. This must, of course, be kept in mind during fumigating and allowance made for this loss. The amount of fumigant absorbed will depend upon the nature as well as the amount of material within the chamber and upon the temperature, although this factor may in most cases be disregarded. It cannot be determined beforehand with any degree of accuracy.
Vapor Pressures of Fumigants 11-Methyl, Ethyl, n-Propyl, Isopropyl, n-Butyl, Secondary Butyl, and Isobutyl Formates1 0.A. Nelson INSECTICIDE DIVISION. BUREAU OF CHEMISTRY AND SOILS. WASHINGTON, D. C.
HE experiments conducted by Cotton and Roark
T
on the toxicity of a number of alkyl formates against different kinds of insects indicated a decided insecticidal action of all the compounds tested.2 It was found, for example, that the lethal dose in the vapor phase for methyl, 1 Presented as a part of the Insecticide Symposium before the Division of Agricultural and Food Chemistry a t the 75th Meeting of the American Chemical Society, St. Louis, Mo., April 16 t o 19, 1928. 2 IND.ENG. C H E M . , 20, 380 (1928).
secondary butyl, isobutyl, and allyl formates against rice weevils in a flask half filled with wheat ranged from 35 to 39 milligrams per liter. The high insecticidal potency of these formates, in addition to their reasonable cost, their safety in handling, and the ease with which they can be made practically noninflammable, makes these compounds appear promising as practical fumigants. It is therefore desirable to determine some of their physical constants. The results of vapor pressure determinations are reported here.
Table I-Observed Vapor Pressures of Methyl, Ethyl, n-Propyl, Isopropyl, n-Butyl, Secondary Butyl, and Isobutyl Formates
ETHYL
METHYL FoR M A TE
Temp.
C.
Temp.
Press.
ISOPROPYL
%-PROPYL
FORMATE
FORMATE
Press.
Temp.
Press.
c.
Mm.
C.
Mm.
525.8 624.5 647.2 654.7 663.0 678.1 711.4 722.9 760.8 767.7
25.4 28.9 33.6 35.5 38.2 40.1 42.9 44.2 47.8 50.9 52.2 53.4 54.2 55.4
259.0 300.8 362.0 389.9 439.2 462.1 531.9 540.3 616.5 689.2 721.1 753.0 772.4 818.6
Temp.
c.
Mm.
26.2 30.8 33.2 40.5 46.2 50.0 58.4 63.7 63.9 70.5 71.0 73.5 75.1 78.9 80.5 82.3
88.2 109.1 134.5 170.4 216.5 252.9 348.6 421.8 430 7 540.3 554.8 600.0 648.9 724,O 759.4 798.8
25,l 29.8 35.0 41.2 48.0 48.2 63.7 57.8 63.9 68.6 70.3 71.7 72.1
Press.
Temp.
Press.
c.
Mm. 136.5 169.4 217.2 281.5 368.0 372.1 458.3 530.0 658.0 768.1 812.9 853.8 873.3
SECONDARY BUTYL FORMATE
n-BuTuL FORMATE
FORMATE
Temp.
Mm.
29.1 34.3 41.5 49.0 57.8 65.3 71.1 75.5 80.5 85.7 93.2 100.4 102.0 106.0 106.7 109.3 109.8 111.3 112.4
C.
Mm.
29.7 35.7 41.7 46.5 52.9 58.1 61.8 65.8 71.3 76.8 83.5 88.5 95.0 97.0 98.5 99.8
58.8 81.2 108.0 139.9 172.8 212.2 246.5 309,8 340.6 427.3 534.4 635.5 798.4 857,7 907.5 945.0
a
34.8 45.8 65.7 93.1 134.9 184.2 229.0 266.8 323.1 397.8 505.0 641.9 683.5 770.9 787.3 828.1 872.4 903.3 941.1
Press.
ISOBUTYL
FORMATE
Temp.
Press.
c.
MVk. 59.3 79.2 103.1 136.5 195.2 243.4 301.7 393.3 483.3 611.7 708.8 735.2 767.6 792.9 824.2
31.7 38.7 43.7 50.3 58.6 63.6 69.9 77.5 82.8 90.2 95.0 96.6 98.2 99.2 100.5
Table 11-Observed and Calculated Vapor Pressures of Formates TEMPERATURE
c. 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110
ETHYL FORMATE
%-PROPYX. FORMATE
Calcd.
Ohsd.
Calcd.
Mm.
Mm.
Mm.
Mm.
206.5 255.0 312.0 382.0 462.3 558.0 668.0 791.0
204.8 253.6 311.8 380.9 462.3 557.6 668.8 797.6
64.5 85.0 107.0 134.0 166.2 203.5 248.0 303.5 269.5 343.5 531.7 634.5 747.5 877.6
67.1 85.2 107.3 134.0 166.3 205.0 251.0 305.4 369.5 343.3 531.7 633.0 749.7 883.9
Obsd.
ISOPROPYL FORMATE
%-BUTYL
FORMATE
SECONDARY BUTYL FORMATE
ISOEIJTYL
FORMATE
Calcd.
Obsd.
Calcd.
Obsd.
Calcd.
Obsd.
Calcd.
Mm.
Mm.
Mm.
Mm.
Mm.
Mm.
Mm.
Mm.
112.0 138.5 174.2 216.0 267.0 325.1 396.0 478.0 570.8 678.5 803.0
113.0 141.6 176.1 217.4 266.7 325.1 393.7 474.2 568.0 676.5 801.7
22.6 29.4 37.8 48.3 61.3 78.0 98.0 120.0 147.6 186.0 219.0 265.5 319.5 383.0 457.0 543.0 639.5 749.0 878.0
22.6 29.4 37.8 48.3 61.2 77.0 96.2 119.3 147.0 186.1 219.3 265.5 319.7 383.1 456.7 541.8 639.8 752.3 880.8
36.0 48.1 62.5 79.6 102.0 126.0 155.2 187.0 228.2 276.8 333.9 400.5 477.2 567.0 671.5 797.0 938.0
38.4 49.2 62.6 79.0 98.8 123.2 152.6 187.0 228.2 276.8 333.9 400.6 478.2 567.9 671.5 790.1 925.7
33.0 43.5 56.0 71.0 88.6 111.0 136.5 168.0 204.0 246.8 300.0 362.0 431.0 511.0 604.0 700.0 806.0
35.1 44.9 56.9 71.6 89.5 111.0 136.5 167.5 200.0 246.7 296.8 355.2 423.1 501.3 591.3 696.0 811.0
Obsd.
