CHEMISTRY GLOSSARY

disaccharide    →   disaharid

Disaccharides are compounds in which two monosaccharides are joined by a glycosidic bond. A glycosidic bond to the anomeric carbon can be either α or β. For example, maltose, the disaccharide obtained by enzyme-catalyzed hydrolysis of starch, consists of two D-glucopyranose units joined by a 1,4’-α-glycoside bond. The "prime" superscript indicates that C-4 is not in the same ring as C-1. Unlike the other disaccharides, sucrose is not a reducing sugar and does not exhibit mutarotation because the glycosidic bond is between the anomeric carbon of glucose and the anomeric carbon of fructose.

EDTA    →   EDTA

Ethyldiaminetetraacetic acid (C₁₀H₁₆N₂O₈) or shortened EDTA is a hexadentant ligand, and it forms chelates with both transition-metal ions and main-group ions. EDTA is used as a negative ion - EDTA^4-. The diagram shows the structure of the ion with the important atoms picked out. The EDTA ion entirely wraps up a metal ion using all 6 of the positions. The co-ordination number is again 6 because of the 6 co-ordinate bonds being formed by the central metal ion.

EDTA is frequently used in soaps and detergents, because it forms a complexes with calcium and magnesium ions. These ions are in hard water and interfere with the cleaning action of soaps and detergents. EDTA is also used extensively as a stabilizing agent in the food industry and as an anticoagulant for stored blood in blood banks. EDTA is the most common reagent in complexometric titration.

monodentate ligand    →   monodentantni ligand

Monodentate ligand is a ligand that has only one atom that coordinates directly to the central atom in a complex. For example, ammonia and chloride ion are monodentate ligands of copper in the complexes [Cu(NH₃)₆]²⁺ and [CuCl₆]²⁺.

oligosaccharide    →   oligosaharid

Oligosaccharides are carbohydrates containing from three to ten monosaccharide units, each joined to the next by a glycoside bond.

electronegativity    →   elektronegativnost

Electronegativity is a parameter originally introduced by L. Pauling which describes, on a relative basis, the power of an atom to attract electrons. For example, in hydrogen chloride, the chlorine atom is more electronegative than the hydrogen and the molecule is polar, with a negative charge on the chlorine atom.

There are various ways of assigning values for the electronegativity of an element. Pauling electronegativities are based on bond dissociation energies using a scale in which fluorine, the most electronegative element, has the value 4 and francium, the lowest electronegative element, has the value 0.7.

enzyme    →   enzim

Enzyme is a protein that acts as a catalyst in biochemical reactions. Each enzyme is specific to a particular reaction or a group of similar reactions. Many require the association of certain nonprotein cofactors in order to function. The molecule undergoing a reaction (the substrate) binds to a specific active site on the enzyme molecule to form a short-lived intermediate: this greatly increases (by a factor of up to 10²⁰) the rate at which the reaction proceeds to form the product.

epoxy resin    →   epoksi smola

Epoxy resins are thermosetting resins produced by copolymerising epoxide compounds with phenols (e.g. epichlorohydrin and bisphenol A). They contain ether linkages (-O-) and form a tight, cross-linked polymer network. Toughness, good adhesion, corrosive-chemical resistance, and good dielectric properties characterise epoxy resins. Most epoxy resins are two-part types which harden when blended.

Fajans’ rules    →   Fajansova pravila

Fajans’ rules, formulated by American chemist of Polish origin. Kazimierz Fajans (1887-1975), indicating the extent to which an ionic bond has covalent character caused by polarisation of the ions. Covalent character is more likely if:

1. the charge of the ions is high;

2. the positive ion is small or the negative ion is large;

3. the positive ion has an outer electron configuration that is not a noble- gas configuration.

organometallic compound    →   organometalni spoj

Organometallic compounds are compounds in which there is a covalent connection between atoms of carbons and atoms of metal (C-Me).

oxonium ion    →   oksonijev ion

Oxonuim ion (H₃O⁺) is formed when a molecule of water binds with a proton.