CHEMISTRY GLOSSARY

ortho position    →   ortho položaj

Ortho position in organic chemistry is the one in which there are two same functional groups, tied to a ring of benzene in the positions 1 and 2. The abbreviation o- is used, for example, o-Hydroquinone is 1,2-dihydroxybenzene.

oxidation number    →   oksidacijski broj

Atoms can give one or more electrons for bond forming. The valence of any atom, which comes from stechiometrical relation of interbonded atoms, is called an oxidation number or an oxidation degree. Oxidation number of atoms in elementary state is zero. An atom of greater electronegativity has a negative, and an atom of lesser electronegativity has a positive oxidation number.

para position    →   para položaj

Para position in organic chemistry is the one in which there are two same functional groups tied to a ring of benzene in the position 1 and 4. The abbreviation p- is used, for example, p-Hydroquinone is 1,4-dihydroxybenzene.

peptide    →   peptid

Peptides are amides derived from two or more amino acids (the same or different) linked by peptide bonds. These bonds are formed by the reaction between adjacent carboxyl (-COOH) and amino (-NH₂) groups with the elimination of water.

polypeptide    →   polipeptid

Polypeptides are peptides containing ten or more amino acid residues. The properties of a polypeptide are determined by the type and sequence of its constituent amino acids.

polystyrene    →   polistiren

Polystyrene is a vinyl polymer. Structurally, it is a long hydrocarbon chain, with a phenyl group attached to every other carbon atom. Polystyrene is produced by free radical vinyl polymerization, from the monomer styrene. Polystyrene or Styrofoam is used in the construction industry as insulating material and for production of containers.

resonance    →   rezonancija

Resonance is a stabilising quality of certain molecules that can be represented by considering the electron distribution in an ion or molecule as a composite of two or more forms, in those cases where a single form is an inadequate representation; for example, benzene and the carbonate ion. A various canonical structures can be drawn to show how electron delocalisation will explain the discrepancy, the difference in electron density

saturated fatty acid    →   zasićena masna kiselina

Saturated fatty acid is a fatty acid carrying the maximum possible number of hydrogen atoms (It doesn’t have any double bounds in the alkyl chain). The most important of these are:

serine    →   serin

Serine is neutral amino acids with polar side chains. It is one of two hydroxyl amino acids. Both are commonly considered to by hydrophilic due to the hydrogen bonding capacity of the hydroxyl group. Serine often serves as a nucleophile in many enzyme active sites, and is best known for its role in the serine proteases. Serine is a site of phosphorylation and glycosylation which is important for enzyme regulation and cell signaling. It is not essential to the human diet, since it is synthesized in the body from other metabolites, including glycine.

• Abbreviations: Ser, S
• IUPAC name: 2-amino-3-hydroxypropanoic acid
• Molecular formula: C₃H₇NO₃
• Molecular weight: 105.09 g/mol

silicon    →   silicij

Silicon was discovered by Jöns Jacob Berzelius (Sweden) in 1824. The origin of the name comes from the Latin word silicis meaning flint. Amorphous form of silicon is brown powder; crystalline form has grey metallic appearance. Solid form unreactive with oxygen, water and most acids. Dissolves in hot alkali. Silica dust is a moderately toxic acute irritant. Silicon makes up major portion of clay, granite, quartz and sand. Commercial production depends on a reaction between sand (SiO₂) and carbon at a temperature of around 2200 °C. Used in glass as silicon dioxide (SiO₂). Silicon carbide (SiC) is one of the hardest substances known and used in polishing. Also the crystalline form is used in semiconductors.