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Heterocyclic compounds.






A heterocyclic compound is a cyclic compound that has atoms of at least two different elements as members of its ring(s). The counterparts of heterocyclic compounds are homocyclic compounds, the rings of which are made of a single element. Although heterocyclic compounds may be inorganic, most contain at least one carbon. Since in organic chemistry non-carbons usually are considered to replace carbon atoms, they are called heteroatoms, meaning 'different from carbon and hydrogen' (rings of heteroatoms of the same element are homocyclic). The IUPAC recommends the Hantzsch-Widman nomenclature for naming heterocyclic compounds.

Heterocyclic chemistry is the branch of chemistry dealing with synthesis, properties, and

applications of heterocycles. Heterocyclic compounds can be usefully classified based on their electronic structure. The saturated heterocycles behave like the acyclic derivatives. Thus, piperidine and tetrahydrofuran are conventional amines and ethers, with modified steric profiles. Therefore, the study of heterocyclic chemistry focuses especially on unsaturated derivatives, and the preponderance of work and applications involves unstrained 5- and 6-membered rings. Included are pyridine, thiophene, pyrrole, and furan. Another large class of heterocycles are fused to benzene rings, which for pyridine, thiophene, pyrrole, and furan are quinoline, benzothiophene, indole, and benzofuran, respectively. Fusion of two benzene rings gives rise to a third large family of compounds, respectively the acridine, dibenzothiophene, carbazole, and dibenzofuran. The unsaturated rings can be classified according to the participation of the heteroatom in the pi system.

Polyaromatic hydrocarbons (PAH s), also known as polycyclic aromatic hydrocarbons or

polynuclear aromatic hydrocarbons are potent atmospheric pollutants that consist of fused

aromatic rings and do not contain heteroatoms or carry substituents. Naphthalene is the simplest

example of a PAH. PAHs occur in oil, coal, and tar deposits, and are produced as byproducts of

fuel burning (whether fossil fuel or biomass). As a pollutant, they are of concern because some

compounds have been identified as carcinogenic, mutagenic, and teratogenic. PAHs are also

found in cooked foods. Studies have shown that high levels of PAHs are found, for example, in

meat cooked at high temperatures such as grilling or barbecuing, and in smoked fish.

32) билет Fundamentals of biochemistry. Types of biomolecules.

Biochemistry, sometimes called biological chemistry, is the study of chemical processes within and relating to, living organisms. By controlling information flow through biochemical signaling and the flow of chemical energy through metabolism, biochemical processes give rise to the complexity of life. Over the last 40 years, biochemistry has become so successful at explaining living processes that now almost all areas of the life sciences from botany to medicine are engaged in biochemical research. Today, the main focus of pure biochemistry is in understanding how biological molecules give rise to the processes that occur within living cells, which in turn relates greatly to the study and understanding of whole organisms.






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