CHEMISTRY GLOSSARY

glycoside    →   glikozid

Glycoside is one of a group of organic compounds in which a sugar group is bonded through its anomeric carbon to another group via a glycosidic bond. The sugar group is known as the glycon and the non-sugar group as the aglycon. According to the IUPAC definition, all disaccharides and polysaccharides are glycosides where the aglycone is another sugar.

In the free hemiacetal form, sugars will spontaneously equilibrate between the α and β anomers. However, once the glycosidic bond is formed, the anomeric configuration of the ring is locked as either α or β. Therefore, the alpha and beta glycosides are chemically distinct. They will have different chemical, physical, and biological properties. Many glycosides occur abundantly in plants, especially as flower and fruit pigments.

The term glycoside was later extended to cover not only compounds in which the anomeric hydroxy group is replaced by a group -OR, but also those in which the replacing group is -SR (thioglycosides), -SeR (selenoglycosides), -NR1R2 (N-glycosides), or even -CR1R2R3 (C-glycosides). Thioglycoside and selenoglycoside are legitimate generic terms; however the use of N-glycoside, although widespread in biochemical literature, is improper and not recommended here (glycosylamine is a perfectly acceptable term). C-Glycoside is even less acceptable. All other glycosides are hydrolysable; the C-C bond of C-glycosides is usually not. The use and propagation of names based on C-glycoside terminology is therefore strongly discouraged.

groups in periodic system of elements    →   skupine periodnog sustava

Periodic system of elements is divided into 18 groups of chemical elements. Elements belonging to the same group have a same number of valence electrons and similar chemical properties. Elements of main groups are in 1., 2., and in groups 13. to 18. Different groups of elements can be named according to the first element in the group (elements of boron group, elements of carbon group), or they have some special names (noble gases, halogenic elements, halyde elements, earthalkali and alkali metals).

haematite    →   hematit

Haematite is a mineral of iron(III) oxide Fe₂O₃. It is the most important ore of iron and usually occurs in two main forms: as a massive red kidney-shaped ore and as grey to black metallic crystals known as specular iron ore. Haematite is the major red colouring agent in rocks; the largest deposits are of sedimentary origin. In industry haematite is also used as a polishing agent (jeweller’s rouge) and in paints.

tempering    →   kaljenje

Tempering is a rapid cooling of metals (often steels) from a suitable elevated temperature, thus changing its properties, e.g. steel becomes harder. This is generally accomplished by immersion in water, oil, polymer solution, or salt, although forced air is sometimes used.

vapour pressure lowering    →   snižavanje tlaka pare

Vapour pressure is a colligative property of solutions. The vapour pressure of a solution is always lower than the vapour pressure of the pure solvent. Ratio of solution to pure solvent vapour pressures is approximately equal to the mole fraction of solvent in the solution.

half-life    →   vrijeme poluraspada

For a simple radioactive decay process, half-life, t_1/2, is defined as the time required for the activity of a given radioactive isotopes to decrease to half its value by that process.

The half-life is a characteristic property of each radioactive isotope and is independent of its amount or condition.

half-wave potential    →   poluvalni potencijal

Half-wave potential (E_1/2) is a potential at which polarographic wave current is equal to one half of diffusion current (i_d). In a given supporting electrolyte, the half-wave potential is unique for each element and its different valence states and chemical forms. Observation of a current peak at a specific half-wave potential therefore identifies the chemical species producing the current.

hybridization    →   hibridizacija

Hybridization is an internal linear combination of atomic orbitals, in which the wave functions of the atomic orbitals are added together to generate new hybrid wave functions. The new orbitals which are formed are hybrids of the originals and have properties (shape, size and energy) that are somewhere in between.

ion exchanger    →   ionski izmjenjivač

Ion-exchanger is a solid or liquid material containing ions that are exchangeable with other ions with a like charge that are present in a solution in which the material is insoluble. Ion-exchange resins consist of various copolymers having a cross-linked three-dimensional structure to which ionic groups have been attached.

kinetic energy    →   kinetička energija

Kinetic energy (E_k) is associated with the state of motion of a body. It is a scalar property and defined to be

Kinetic energy is most clearly exhibited in gases, in which molecules have much greater freedom of motion than in liquids and solids.