Aliphatic And Aromatic Hydrocarbons

Aliphatic and Aromatic Hydrocarbons

Nadine Z. Villarin

In organic chemistry, compounds composed of carbon and hydrogen are divided into two classes: aromatic compounds - contain benzene rings or similar rings of atoms. aliphatic compounds - do not contain the benzene rings.

Halogenated Aliphatic Hydrocarbons These agents find wide use as industrial solvents, degreasing agents, and cleaning agents. Example: • carbon tetrachloride • chloroform, trichloroethylene • Tetrachloroethylene (perchloroethylene) • 1,1,1-trichloroethane (methyl chloroform)

Mechanism of Action These substances are depressants of the central nervous system in humans.  Halogenated hydrocarbons also cause liver injury, kidney injury, and some degree of cardiotoxicity.

Clinical Effects • Chloroform - widely used as an anesthetic agent, is the most potent. • Chronic exposure to tetrachloroethylene can cause impaired memory and peripheral neuropathy. • Hepatotoxicity is also a common toxic effect that can occur after acute or chronic exposures.

• Nephrotoxicity can occur with exposure to carbon tetrachloride, chloroform, and trichloroethylene. • Carcinogenicity has been observed in lifetime exposure chloroform, carbon tetrachloride, trichloroethylene, and tetrachloroethylene. • Studies show that margin of safety for humans is very large with respect to the potential carcinogenic effect of household exposure to chloroform or environmentally relevant concentrations of trichloroethylene.

Treatment

There is no specific treatment for acute intoxication resulting from exposure to halogenated hydrocarbons. Management depends upon the organ system involved.

Aromatic Hydrocarbons Benzene is widely used for its solvent properties and as an intermediate in the synthesis of other chemicals. Sources: -Lacquer Thinner - insecticides -Spray paints - Cleaners - Vehicle oils

• The acute toxic effect of benzene is depression of the central nervous system. • Exposure to 7500 ppm for 30 minutes can be fatal. • Exposure to concentrations larger than 3000 ppm: – euphoria, nausea, – locomotor problems, and coma

• Concentrations ranging from 250 to 500 ppm: - vertigo, drowsiness, headache, and nausea

• Chronic exposure to benzene unpredictable injury to the bone marrow: - aplastic anemia, leukopenia, pancytopenia, or thrombocytopenia.

• The early symptoms of chronic benzene intoxication may be headache, fatigue, and loss of appetite, though it can be vague. • No specific treatment exists for the toxic effects of benzene.

Toluene (methylbenzene) clear, water-insoluble liquid is widely used as an industrial feedstock and as a solvent. It does not possess the myelotoxic properties of benzene however, It is a central nervous system depressant. Toluene is readily absorbed from the lungs, and most exposures to toluene occur by inhalation. Exposure to 800 ppm can lead to severe fatigue and ataxia. 10,000 ppm can produce rapid loss of consciousness. There is no antidote for toluene. Treatment consists of support of respiratory and cardiovascular functions.