CHEMISTRY GLOSSARY

valence shell    →   valentna ljuska

Valence shell is the shell corresponding to the highest value of principal quantum number in the atom. The valence electrons in this shell are on average farther from the nucleus than other electrons. They are often directly involved in chemical reaction.

glycosidic bond    →   glikozidna veza

Glycosidic bond ia a bond between the glycosyl group, the structure obtained by removing the hydroxy group from the hemiacetal function of a monosaccharide, and the -OR group (which itself may be derived from a saccharide and chalcogen replacements thereof (RS–, RSe–). The terms N-glycosides and C-glycosides are misnomers and should not be used. The glycosidic bond can be α or β in orientation, depending on whether the anomeric hydroxyl group was α or β before the glycosidic bond was formed and on the specificity of the enzymatic reaction catalyzing their formation. Once the glycosidic bond is formed, the anomeric configuration of the ring is locked as either α or β. Specific glycosidic bonds therefore may be designated α(1→4), β(1→4), α(1→6), and so on. Cellulose is formed of glucose molecules linked by β(1→4)-glycosidic bonds, whereas starch is composed of α(1→4)-glycosidic bonds.

hydrogen bond    →   vodikova veza

Hydrogen is a bond formed by a hydrogen atom to an electronegative atom, and is denoted by dashed lines H-X---H-B. A hydrogen atom covalently bound to an oxygen (electronegative atom) has a significant positive charge and can form a weak bond to another electronegative atom.

ionic bond    →   ionska veza

Ionic bond is a strong force of attraction holding atoms together in a molecule or crystal. Typically chemical bonds have energies of about 100 kJ mol^-1. Ionic bond is a bond at which one of the participants, during the procedure of bonding, gives away its unpaired electrons to another atom so that both can achieve electron arrangement of the closest noble gas. In order to form an ionic bond one of the atoms must cross to the positively charged ion by losing certain number of electrons and the other atom must receive those electrons and cross to the negatively charged ion.

peptide bond    →   peptidna veza

Peptide bond emerges when two amino acid join in a way that the carbon atom from one connects with the nitrogen atom from the other (creating a C-N bond).

pi bond    →   pi veza

Pi bonds (π bond) between atoms are formed by the side-on overlap of the atomic orbitals on the different atoms.

valence electron    →   valentni elektron

Valence electrons are electrons that can be actively involved in a chemical change, usually electrons in the outermost (valent) shell. For example, sodium’s ground state electron configuration is 1s² 2s² 2p⁶ 3s¹; the 3s electron is the only valence electron in the atom. Germanium (Ge) has the ground state electron configuration 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p²; the 4s and 4p electrons are the valence electrons.

acceptor    →   akceptor

Acceptor is a compound, molecule or ion, to which electrons are donated in the formation of a coordinate bond

activator    →   aktivator

Activator is a substance that increases the activity of a catalyst; for example, a substance that - by binding to an allosteric site on an enzyme - enables the active site of the enzyme to bind to the substrate.

addition reactions    →   reakcije adicije

Addition reactions are normally occur with unsaturated compounds and involve the addition of one molecule (called the reactant) across the unsaturated bond (i.e. the double bond or the triple bond) of another molecule (called the substrate) to give a single product, formed by the combination of both reacting molecules.

For example, bromine adds across the double bond of ethene in an addition reaction to form dibromoethane.