Index
What is it?
Phenylamine, also known as aniline or aminobenzene, is an organic compound with C6H5NH2. The aniline is an aromatic amine consisting of a phenyl group attached to an amino group.
Like most volatile amines, it has the unpleasant smell of rotten fish. It ignites readily, burning with a smoky flame characteristic of aromatic compounds.
Aniline is colorless and is slightly soluble in water, and is easily mixed with most organic solvents.
Production
Phenylamine is produced in the industry in two steps from benzene. First, benzene is nitrated using a concentrated mixture of nitric acid and sulfuric acid that gives nitrobenzene; in the second step, nitrobenzene is hydrogenated. Alternatively, aniline is also prepared from phenol and ammonia.
In commerce, three brands of phenylamine are distinguished; aniline oil for the blue color, which is pure aniline; aniline oil for red color, a mixture of equimolar quantities of aniline and ortho and para-toluidines; and aniline oil for safranin, which contains aniline and ortho-toluidine.
Phenylamine derivatives
Many phenylamine derivatives can be prepared from nitrated aromatic compounds. Nitration followed by reduction of toluene provides toluidines.
There are three isomers of toluidine: o-toluidine, m-toluidine, and p-toluidine. The o- represents ortho-, m- means meta-, and p- means para-. All three are amines whose chemical structures are similar to aniline, except a methyl group is substituted in the benzene ring.
The difference between these three isomers is the position in which the methyl group (-CH3) is linked to the ring about the functional group.
Relationship with cancer
Ortho- and meta-toluidines are viscous liquids, but para-toluidine is solid. Toluidines are used in the production of dyes. There is the possibility of significant carcinogenic and genotoxic effects in the work environment.
The main signs of toxicity after acute short-term exposure to this chemical are methemoglobinemia and related effects in the spleen or bladder.
The risk of bladder cancer has increased among workers exposed to o-toluidine and aniline.
In 2004 an epidemic of bladder cancer was unleashed in workers exposed to ortho-toluidine in a chemical factory.
The related compound o-toluidine, used as a presumptive test for blood in forensic science, is two molecules of o-toluidine linked together.
Exposure and metabolism
The general population may be exposed to phenylamine when eating food or drinking water containing aniline, but these amounts are usually tiny.
If you work in a place that makes products such as dyes, varnishes, herbicides, and explosives, you may be exposed to aniline.
Aniline has also been detected in tobacco smoke, so people who smoke or breathe secondhand smoke may also be exposed to phenylamine.
People living near uncontrolled hazardous waste sites may be exposed to higher than normal levels of aniline.
How is it absorbed?
When people breathe air or consume food or water contaminated with aniline, it enters the body. It can also be absorbed through contact with the skin. It does not remain in the body due to its decomposition and elimination.
Aniline can evaporate when exposed to air. It dissolves when mixed with water. In philosophy, aniline is broken down into other chemicals.
Sunlight also breaks down phenylamine in surface water and soil. Microorganisms that live in water and dirt can also break down aniline.
Aniline is oxidized by p450 to P aminophenol and excreted in the urine as sulfate and glucuronic conjugate after 24 hours of exposure.
Sometimes, aniline is hydroxylated in an amino group to phenylhydroxylamine, considered one of the most toxic metabolites and causes organ damage.
Applications
In industry: Phenylamine is used to prepare methylene diphenyl diisocyanate used for the production of rigid polyurethane. These rigid polyurethane foams are good thermal insulators and are used in almost all freezers and refrigerators around the world and buildings.
Other industrial uses:
- Dust, fumes, and toxic gases in the industry.
- Herbicides (2%) and agricultural chemicals.
- Dyes and pigments (2%) are a precursor of indigo, the blue of the jeans, and ink for the tattoo. Other aniline dyes followed, such as fuchsine, safranine, and induline.
- Solvent and rubber.
In medicine: drugs prepared from phenylamine are paracetamol (acetaminophen), an analgesic drug.
As an antibacterial, a red azo dye was introduced in 1935 as the first antibacterial drug, prontosil.
O-toluidine for presumptive blood tests in forensic science. Toluidine blue is essential for detecting and documenting genital lesions after sexual assaults.
Effects of toluidine blue and decolorizing reagents used in sexual assault tests on the ability to obtain DNA profiles from postcoital vaginal smears.
Signs and symptoms
The effects of phenylamine on human health and the environment depend on the amount of aniline present and the duration and frequency of exposure.
Lips, tongue, and mucous membranes from navy blue to black (cyanosis); slate gray skin, all without signs of heart or lung failure.
Breathing large amounts of aniline for short periods decreases the ability of the blood to carry oxygen.
The lack of oxygen produces effects ranging from severe headache, nausea, sometimes vomiting, dry throat, and loss of appetite.
Other symptoms include:
Symptoms of the central nervous system: confusion, ataxia, vertigo, tinnitus, weakness, disorientation, lethargy, drowsiness, and finally, coma. Continuous exposure may cause difficulty breathing, dizziness, stupor, loss of consciousness, and seizures but may seem infrequent.
Cardiac effects: cardiac blocks, arrhythmias, and shock.
Death, although rare, is usually due to cardiovascular collapse and not respiratory paralysis.
Urinary signs and symptoms may include painful urination, hematuria, hemoglobinuria, and renal failure (usually mild). Exposure to high concentrations can cause damage to the kidneys and bladder.
Skin: this can cause excessive drying of the skin and irritation. Absorption is significant and may increase the severity of the symptoms listed in the inhalation.
Eyes: causes irritation, redness, and burns.
Toxicity
Splenic toxicity: Aniline and its implication in damaging oxidative reactions, especially during the progression of characteristic splenic lesions, is demonstrated in time-dependent subchronic studies performed in rats.
Oxidative modification: such oxidative modifications, directly or indirectly, could contribute to splenic toxicity leading to detrimental consequences, including capsular hyperplasia and fibrosis, as observed in this study, and possibly chronic tumorigenesis exposure conditions to aniline.
Also, exposure to aniline produces selective splenic toxicity that leads to splenomegaly, bleeding, capsular hyperplasia, fibrosis, and, finally, a variety of sarcomas.
Toxic oil syndrome: Aniline is also known to induce allergic and autoimmune reactions. In 1981 in Spain, many people succumbed to the toxic oil syndrome, a disease caused by the ingestion of cooking oil contaminated with aniline.
The disease was related to the consumption of rapeseed oil denatured with aniline. Among the phenylamine derivatives detected in the batches of oil generated by an uncontrolled deodorization procedure during the refining process, the fatty acid anilides were first postulated as causal agents.
T cells ignore aniline, a prohapten, but they respond to their reactive metabolites generated by phagocytes.
Hemolytic anemia: It is believed that hemolytic anemia after aniline and aniline-related drugs, such as dapsone and primaquine, is mediated by the active/reactive metabolite formed during hepatic clearance the parent compounds.
Phenylamine metabolites: Methemoglobinemia is a disorder that is characterized by the presence of a higher than average methemoglobin level (metHb, i.e., ferric [Fe3 +] instead of ferrous [Fe2 +] hemoglobin) in the blood.
Methaemoglobin is an oxidized form of hemoglobin with a decreased affinity for oxygen, resulting in a higher oxygen affinity to other heme sites (which are still ferrous) within the same red blood cell.
This leads to a reduced overall capacity of the red blood cells to release oxygen to the tissues. There is evidence of the contribution of aniline metabolites to aniline-induced methemoglobinemia.
Other toxic considerations
In food or some kitchen utensils used in food preparation or tobacco smoke, the migration of phenylamine from polyamide cookware was investigated.
It was discovered that aniline originates from applying black dye in the polyamide 66 raw material.
Phenylamine and its derivatives and coal tar, its natural mother substance, have demonstrated their ability to produce inflammatory and neoplastic reactions in the skin.
Intense inflammation and resulting necrosis and fluidization of the affected tissue are the invariable stages that lead to ulceration and extrusion of foreign dyes through the exudate.
Keratoacanthoma is a cutaneous neoplasm that commonly affects the sun-exposed areas of the elderly.
Most consider it a form of squamous cell carcinoma. Some reports of keratoacanthoma arise in trauma sites, such as scars from burns, etc.
