Nitrobenzene

Nitrobenzene (Nitrobenzolum, nitrobenzene, nitrobenzine), C₆H₅NO₂, a derivative of benzene, known in industry as "mirban oil" (Oleum mirbani), "mirban essence," and also as artificial oil of bitter almonds. Pure N. is a transparent, pale yellow liquid with strong light refraction and a characteristic odor of bitter almonds. It boils at 205-206-209°, distills easily with steam, freezes at +3°, forming a mass of needle-shaped crystals. Sp. gr. at 15° is 1.206-1.209. It is almost insoluble in water, dissolves in alcohol and ether, and mixes in all proportions with chloroform, carbon disulfide, gasoline, and most fatty oils. The purity of the preparation is determined by specific gravity: the purer the preparation, the higher the specific gravity (up to 1.209). Intense coloring characterizes impure preparations. Commercial preparations of N. usually contain impurities of nitrotoluene and nitrothiophene (?). When boiled with soda lye, the latter should not become colored. An alcoholic solution of completely pure N. should not become colored from one drop of caustic potash (dinitrothiophene).- Preparation. To obtain N. in small quantities in the laboratory, place 100 parts benzene in a flask and add through a dropping funnel in small portions with shaking and cooling a cooled mixture of 115 parts nitric acid with sp. gr. 1.42 and 160 parts concentrated sulfuric acid. The reaction is carried out at a temperature not exceeding 25-30°. When all the mixture has been added, the flask is heated for another 7 hours on a water bath with constant stirring. After cooling, the mixture is diluted with 300 parts water, the N. (lower layer) is separated, washed with water, and distilled with steam to separate it from dinitrobenzene. The distilled nitrobenzene is dried with calcium chloride and redistilled over a free flame. Industrially, N. is obtained by nitration of benzene with a mixture of 2 parts nitric acid with sp. gr. 1.4 and 3 parts sulfuric acid with sp. gr. 1.84 in iron kettles equipped with agitators. Depending on the degree of purification, two grades are distinguished: light N. (mirban oil), used mainly in perfumery, and heavy N., used for the manufacture of aniline. Determination. The volume under investigation is acidified with sulfuric acid and distilled with steam. The distillate is shaken with ether or chloroform, the extract is allowed to evaporate, the residue is dissolved in diluted alcohol and tested for N. The determination is based on the conversion of N. to aniline. To the alcoholic solution of N. is added diluted sulfuric acid and enough water so that the solution begins to cloud. 2-3 g of zinc shavings are added and heated for about 7 hours on a water bath. The liquid is decanted from the undissolved zinc, freed from alcohol by evaporation, again diluted with water, strongly alkalized with caustic soda, and a solution of bleaching powder is added dropwise, avoiding excess; a red-violet or violet-blue (depending on the amount of solution added) coloration is obtained, gradually passing into dirty red. If to this red-violet or dirty red liquid is added a diluted ammoniacal solution of carbolic acid, a pure blue coloration is obtained (sensitive indophenol reaction).- Uses. N. is the starting material for obtaining aniline and an intermediate product in the preparation of dinitrobenzene (see) and other nitro compounds; it is used in the production of explosives, in the production of dyes (alizarin, quinoline, benzidine dyes, nitrobenzene method for obtaining fuchsine). In the pharmaceutical industry it is used to obtain quinoline and some other pharmaceutical preparations. It is widely used in a number of small industries: in the manufacture of toilet and other soaps, lacquers and shoe polishes, chemical means for cleaning clothes, hair liquids, insect liquids, confectionery, liqueurs and fruit waters (instead of non-toxic but expensive benzaldehyde, see) etc. As a medicinal agent, N. was used externally for scabies, but due to its high toxicity it was soon abandoned and subsequently found no medical application. At present, it is of considerable interest from a medical point of view only from a toxicological standpoint. Poisonings from N. in aniline factories often occur due to malfunctioning of equipment, during accidents, as a result of careless handling by workers, or due to the impurity of the product used in production. Household poisonings are observed from accidental ingestion or out of curiosity of the above-mentioned perfumery liquids, when using adulterated confectionery, alcoholic beverages and fruit waters. Ullmann described poisoning by vapors of N. emanating from the surface of shoes just polished with a poisonous paste. Schultz described a case of poisoning of six German soldiers who used a lice-killing liquid. Children are particularly sensitive to the poison. Temming described five cases of poisoning of infants per respirationem by stamping ink for linen containing N. Several similar cases are described in the German literature. Cases of fatal poisoning of women who used N. for abortive purposes are described (Schnopihagen).--Toxicology. Nitrobenzene is extremely poisonous: death can result from the ingestion of 4-5 g and even 8-10 drops of N. (Koelsch). N. is absorbed not only from the stomach but, due to its volatility, also through the lungs, and like benzene and aniline, it easily penetrates intact skin. Lehmann proved this by his experiments, in which 1 g of N. was sufficient to kill a cat in which all other paths of entry of the poison were excluded, and of the gram taken only part was absorbed. Children and the elderly, physically weak and exhausted persons, are much more susceptible to the action of the poison. Curschmann connects this with the development in adults and healthy persons of a subcutaneous fatty layer, which according to some experiments can retain half of all the poison that has penetrated through the skin and thereby slow down the rate of its entry into the blood. According to the observations of many authors, alcohol strongly increases sensitivity to the poison. Cases of severe poisoning occurring after drinking beer by previously perfectly healthy but persons in contact with N. are described (Curschmann). High temperature, hot time of the year, increasing the volatility of N., increases the danger of poisoning. Most poisonings from N. occur in summer. As a compound of the aromatic series, N. is a poison for the central nervous system, and as a nitro compound it is a blood poison, converting Hb into methemoglobin. Therefore, the picture of N. poisoning is in many ways similar to the picture of poisoning by other nitro derivatives of benzene (see), as well as to poisoning by aniline (see). Symptoms of acute poisoning are dizziness, headache, general weakness, nausea, often vomiting. Particularly characteristic are changes in the color of the skin and mucous membranes. Yellowish dirty or yellowish-brown dirty color of the skin (mulatto color), pale bluish to cyanotic coloration of the lips and other mucous membranes, as well as the nails, with general pallor of the face, are an early and prominent symptom of poisoning, often standing in contradiction to the satisfactory general condition of the victim. Changes in skin color depend on changes in blood color, which acquires a brown color (up to chocolate color) due to the formation of methemoglobin and on spectroscopic examination gives characteristic absorption bands. In severe cases, to the described symptoms are added disturbances of coordination, a staggering gait, a stuttering speech, difficult breathing, irregular arrhythmic pulse, changes in the width or immobility of the pupils, convulsions, drowsiness passing into a comatose state. An important sign of poisoning is the characteristic nitrobenzene odor of the exhaled air. Sometimes very soon after poisoning, sometimes only after several days, degenerative changes in the blood are found with subsequent regeneration. Inflammation of the optic nerve has been repeatedly observed. Lewin described a case of poisoning which manifested itself at first only in general weakness, severe pallor and blueness of the face; however, later severe disturbances of the nervous system, respiratory apparatus and general nutrition were found, which made the victim unable to work for a long time. In chronic poisoning, anemia, methemoglobinemia, general weakness and the characteristic yellowish or bluish coloration of the skin (icterus) come to the fore. Prevention should be carried out in the following directions. 1. Complete withdrawal of the use of N. in cases where its application is undoubtedly associated with a great danger of poisoning due to the known entry of the poison into the body and at the same time the use of N. is not dictated by necessity or where N. can be replaced by other harmless substances, e.g. in the preparation of perfumery and some pharmaceutical preparations, confectionery, alcoholic beverages, fruit waters etc. 2.

Protection of the body during industrial production and use of N. from contact with N. and its vapors by sealing technological processes, mechanizing various operations such as: pouring, transportation, cleaning of vessels and equipment, etc., and by providing appropriate ventilation, fume hoods, etc. 3. Systematic monitoring of the correct course of the technological process, the condition of the equipment and ventilation systems. 4. Hygienic standardization and preliminary biological testing along with the chemical testing of chemical products admitted to production. 5. Timely informing workers about the possibility of poisoning by N. Treatment of acute poisoning must first aim to stop the absorption of N., which is achieved by various measures depending on the routes of entry of the poison: in one case it is necessary to wash the stomach and give an emetic, in another - to remove the victim from the poisoned atmosphere to fresh air, in the third - to change the clothing and linen soaked with poison, to remove the poison from the surface of the body, paying special attention to the hairy parts. The second task is to promote excretion: mild laxatives and abundant drinking (hot black coffee, hot tea) usually achieve the goal; in severe cases, bloodletting should not be refused, followed by the administration of a physiological solution. Alcoholic beverages are strictly contraindicated; carbonated waters should also be avoided. Symptomatic treatment: oxygen inhalation should be started as early as possible, combining it in cases of severe respiratory disorders with artificial respiration. Cool baths, according to Kurschmann, are of great service both symptomatically and hygienically (removal of poison from the surface of the body). Hot baths, on the contrary, may worsen the patient's condition. Lipschitz presents a number of well-founded considerations that make it advisable to prescribe quinine in addition to the measures listed. In cases of collapse - usual stimulants. Avoid alcoholic tinctures.