CHEMISTRY GLOSSARY

Curie    →   Curie

Maria Sklodowska-Curie (1867-1934) Polish-born French chemist who went to Paris in 1891. She married the physicist Pierre Curie (1859-1906) in 1985 and soon began work on seeking radioactive elements other than uranium in pitchblende (to account for its unexpectedly high radioactivity). By 1898 she had discovered radium and polonium although it took her years to purify them. In 1903 the Curies shared the Nobel Prize for physics with Henri Becquerel, who had discovered radioactivity.

cyclic compound    →   ciklički spoj

Cyclic describing a compound that has a ring of atoms in its molecules. In homocyclic compounds all the atoms in the ring are of the same type, e.g. benzene (C₆H₆) and cyclohexane (C₆H₁₂). These two examples are also examples of carbocyclic compounds; i.e. the rings are made of carbon atoms. If different atoms occur in the ring, as in pyridine (C₅H₅N), the compound is said to be heterocyclic.

Dalton’s atomic theory    →   Daltonova atomska teorija

Dalton’s atomic theory is a theory of chemical combination, first stated by John Dalton in 1803. It involves the following postulates:

1. Elements consist of indivisible small particles (atoms).

2. All atoms of the same element are identical; different elements have different types of atom.

3. Atoms can neither be created nor destroyed.

4. ’Compound elements’ (i.e. compounds) are formed when atoms of different elements join in simple ratios to form ’compound atoms’ (i.e. molecules).

Dalton also proposed symbols for atoms of different elements (later replaced by the present notation using letters).

diastereoisomer    →   dijastereoizomer

Diastereoisomers (diastereomers) are stereoisomers of a compound having two or more chiral centers that are not a mirror image of another stereoisomer of the same compound. For example, in the structure below, 1 and 2 are enantiomers and so are 3 and 4; 1 and 3 are diastereoisomers, as are 2 and 4. Unlike enantiomers, diastereoisomers need not have closely similar physical and chemical properties

law of definite composition    →   zakon o određenom sastavu

Law of definite composition states that the elements in a given compound are always combined in the same proportion by mass. This law form the basis for the definition of a chemical compound.

Lewis acid    →   Lewisova kiselina

Lewis acid is an agent capable of accepting a pair of electrons to form a coordinate bond.

Lewis base    →   Lewisova baza

Lewis base is an agent capable of donating a pair of electrons to form a coordinate bond.

differential thermal analysis    →   diferencijalna termalna analiza

Differential thermal analysis (DTA) is a technique that is often used to analyze materials that react or decompose at higher temperatures. The difference in temperature between the sample and an inert reference material is monitored as both are heated in a furnace. Phase transitions and chemical reactions taking place in the sample on heating cause the temperature difference to become larger, at temperatures that are characteristic of the sample.

dioxin    →   dioksin

Dioxin is a general term that describes a group of hundreds of chemicals that are highly persistent in the environment. The most toxic compound is 2,3,7,8-tetrachlorodibenzo-p-dioxin or TCDD. The toxicity of other dioxins and chemicals like PCBs that act like dioxin are measured in relation to TCDD. Dioxin is formed as an unintentional by-product of many industrial processes involving chlorine such as waste incineration, chemical and pesticide manufacturing and pulp and paper bleaching. Dioxin was the primary toxic component of Agent Orange, found at Love Canal in Niagara Falls, NY and was the basis for evacuations at Times Beach, MO and Seveso, Italy.

Dioxin is formed by burning chlorine-based chemical compounds with hydrocarbons. The major source of dioxin in the environment comes from waste-burning incinerators of various sorts and also from backyard burn-barrels. Dioxin pollution is also affiliated with paper mills which use chlorine bleaching in their process, with the production of Polyvinyl Chloride (PVC) plastics, and with the production of certain chlorinated chemicals (like many pesticides).

dissociation    →   disocijacija

Dissociation is the process by which a chemical combination breaks up into simpler constituents as a result of either added energy (dissociated by heat), or the effect of a solvent on a dissolved polar compound (electrolytic dissociation). It may occur in the gaseous, solid, or liquid state, or in a solution.

An example of dissociation is the reversible reaction of hydrogen iodide at high temperatures

The term dissociation is also applied to ionisation reactions of acids and bases in water. For example

which is often regarded as a straightforward dissociation into ions