Tetrachlorodinitroethane - Credit to Mega.pdf - Chemia Organiczna - chemia2010

TF(TRACHLORDINITROETHANE1

BY W. I,. ARGO, €$. M. JAMES AND J. I.,. DONNELLY

Tetrachlordinitroethane is a white, Crystalline solid, in-

soluble in water, soluble in alcohol, ether, and ligroin. In

ether and ligroin it decomposes at 60' with evolution of

brown fumes. It is also very soluble in liquid Nz04and some-

what less so in carbon tetrachloride. When pure, decomposi-

tion does not begin until the compound is heated about to its

melting point, 142-143 ". It is probable, though not proved

that the behavior in ligroin is due to a difference in reaction

velocity rather than to a difference in equilibrium. Tetra-

chlordinitroethane is toxic to mice at one-sixth the concen-

tration for chlorpicrin. It produces lachrymation in man at

one-eighth the concentration that chlorpicrin does. It is

not stable when exploded in a three-inch shell, but would proba-

bly stand up satisfactorily if dissolved in chlorpicrin.

The only method of preparation described in the litera-

ture is that of Kolbe2 who heated a mixture of nitrogen per-

oxide and tetrachlorethylene in a sealed tube at I IO "-1 20"

for three hours. The tube was opened, the excess N204 al-

lowed to boil away, and the crystals of C2C14(N02)2

collected

and analyzed. Biltz3 obtained a larger yield by heatingfor

the same length of time to IOO"-IIO'. We have obtained

the best results at about 80"; but, even at this lower tem-

perature, the pressure developed in the tube is apt to cause

a violent explosion except when tubes of very small cross-

section are used. The danger of explosion increases very

much if the nitrogen peroxide is not dried by distillation over

phosphorus pentoxide, as an oxidation takes place when mois-

ture is present, giving.rise to a high pressure even when the

tubes are cooled in ice before being opened.

the Director of

1 Published by permission of

the Chemical Warfare

Service.

Ber. deutsch. chem. Ges., 2, 326 (1869).

3 Ibid., 35, 1528(1902).

Tetrachlordinitroethane

579

Quantitative Study of the Reaction

The nitrogen peroxide was obtained by heating lead ni-

trate in a long, glass tube at about 400°, drying the evolved

gases with Pz05, and liquefying the nitrogen peroxide by

means of ice and hydrochloric acid. Liquid nitrogen per-

oxide was also prepared by the interaction of arsenic tri-

oxide and nitric acid, and was furnished to us by the small

Scale Manufacturing Section; but this had to be dried over

phosphorus pentoxide before it would give satisfactory re-

sults. The tetrachlorethylene was obtained by cracking car-

bon tetrachloride.

Six small tubes of about 2 cc capacity were made by

fusing ordinary 4 mm soda-glass tubing. Into each was intro-

duced known weights of N204and C2Cl4,so that three con-

tained an excess of the former, and three an excess of the

latter. In each case the volume of the liquid was approxi-

mately z/3 of the capacity of the tube.

The tubes were divided into pairs, and heated in the

water bath. The conditions and results of the experiment

are summarized in Table I.

TABLE

- -

Time of

heating

Yield

rey

80 O

Obs.

Theory

(I) N204excess

(2) c&14 excess

(3) N204 excess

(4) CzC14 excess

(5) N204 excess

(6) CzC14 excess

3 hrs.

6 hrs.

3 hrs.

0.867 g

1.472 g

1.085 g

1.563 g

0.716 g

1.152 g

0.311 g

0.317 g

0.486 g

0.524 g

35.9%

21.4%

44.8%

33.5%

79.5%

65.8%

In every.case a considerable pressure was observed on open-

ing the tubes.

Since the production of tetrachlordinitroethane involves

merely the addition of Nz04 to CzC4 and the opening of

0.570 g

0.758g

the

double bond as follows :

W. L. Argo, E. hf. James awd J. L. Downelly

580

it is logical to assume that a diminution of pressure should

result in the tube as the reaction progresses. This, as we

discovered, was not the case. Nitrogen tetroxide is inter-

mediate in composition between nitrous and nitric anhydride

and reacts as follows with cold water:

OzN - NO2 + HOH + HzNOz + "03

If the water is heated, however, the unstable nitrous acid

breaks down, giving nitric acid and nitric oxide.

3Nz04 + 2HOH ----f 4HN03 + 2N0,

(heated)

Thus the presence of hot water vapor in the reaction

mixture will produce HN03 and NO; and an oxidation of

CaC14 with the production of phosgene becomes possible.

This would account for the pressure developed.

Four tubes were prepared from 4 mm tubing, and the

open ends drawn to a capillary, bent in the form of a U, so

that any gas resulting from the heating could be collected

over mercury. One cc of a mixture of equal volumes of NzO

and CZCl4was introduced into each. Two were carefully

kept dry, but two were allowed to absorb moisture until the

contents became blue when frozen.

The conditions of

the

experiments and results are summarized in Table 11.

TABLE

Volume of gas

evolved

Time

Temp

(I) Contents moist

3 hrs.

35 cc

(2) Contents moist

(3) Contents dry

3 hrs.

40 cc

3 hrs.

IjCC

(4) Contents dry

3 hrs.

20 cc

Tetrachlordivtitroethavte

581

One end was blown into a small bulb, and the whole carefully

dried. A little P205was placed in the bulb and covered

with equal volumes of C2C14and NZO4,previously dried over

P205. The openings in the tube were then sealed and the

liquid distilled to the second arm by gently heating the bulb,

and freezing thesecond arm with C02snow and ether. The

connecting arm was then sealed, and the tube heated to 60'

for three hours. It was cooled, opened, and the gases col-

lected over mercury. About 3-5 cc of an inactive gas was

evolved. This indicates that careful drying will eliminate

the high presstire caused by the side reactions noted above.

There remains then only the pressure of N204 to account for.

Its vapor pressure at various temperatures are given in Table

111.1

TABLE

I11

Temperature

Pressure, atmospheres

4. IO

7.3

54.2

70. I

79.7

87. I

101.4

110.8

IO. I

13.0

20.5

27.2

Autoclave Material

Since no porcelain-lined autoclave was available at first,

a run was made in a phosphor-bronze autoclave. Accord-

ingly 175 g. N204 and 320 g. C2C14were placed in a tall beaker

within the autoclave and the whole heated to 80" for three

hours. A yield of 195 g. was obtained, 40 percent of the

theoretical. The interior of the autoclave was badly cor-

roded and it seems probable that the low yield was due to the

nitrogen peroxide reacting with the metal.

We next attempted to use Bakelite varnish as a protec-

tive coating, but even when carefully baked it was almost

completely destroyed as soon as subjected to the Nz04vapors.

Zeit. phys. Chem., 81, 308.

W. L. Argo, E. M. James and J. L. Donnelly

582

We then tried placing the mixture of C2C14 in a large bottle,

the mouth of which was loosely covered with a beaker. The

whole was surrounded with sand and a top layer of iron

filings. This method had to be abandoned on account of a

very considerable loss of product by diffusion through the

sand surrounding the reaction bottle.

An attempt was next made to find a metal sufficiently

unaffected by N204. Small pieces of nichrome, copper, and

iron wire, and spirals of copper and iron oxide were placed in

tubes with N205 and P205,and heated to 80" both in the

liquid and thevapor for three hours at 80'. The copper and

copper oxide were badly attacked, and so heavy a pressure

was developed that an attempt to open the tubes resulted in

their being reduced to fragments No pressure was developed

in the tubes with the nichrome, and the iron and iron oxide,

The last two showed no evidence of being attacked, but the

nichrome was badly pitted.

Since iron is apparently unattacked by dry N204,the

following series of tests were made to determine the resistance

of various kinds of iron when heated in a mixture of

CZCl4

and N204 at 80" for three hours.

The results are summarized

in Table IV.

TABLE

Pressure

developed

Iron

Condition of

Condition of metal

(I) Steel

(2) Steel

(3) Wrought iron

(4) Cast iron

(5) Wrought iron

Mixture dry

Mixture moist

Mixture dry

Slight

Very high

High

Unattacked

Completely destroyed

Badly attacked

Unaffected

From the above results it seemed probable that a heavy-

walled wrought-iron autoclave would prove satisfactory.

Accordingly several runs were made using such a container

but the efficiency was never better than 50 percent. Even

with the most careful drying, the moisture absorbed by the

CzCl4-N2O4mixture was sufficient.to cause the walls to be

Tetrachlorodinitroethane - Credit to Mega.pdf

Plik z chomika:

Inne pliki z tego folderu:

Inne foldery tego chomika: