CHEMISTRY GLOSSARY

relative mistake    →   relativna pogreška

Relative mistake is a relation between absolute mistake (O-μ) and the real value (μ). It is expressed in percentage (%).

monosaccharide    →   monosaharid

Monosaccharides are carbohydrates, with the general formula C_n(H₂O)_n, that cannot be decomposed to a simpler carbohydrates by hydrolysis.

Depending on whether the molecule contains an aldehyde group (-CHO) or a ketone group (-CO-) monosaccharide can be a polyhydroxy aldehyde (aldose) or a polyhydroxy ketone (ketose). These aldehyde and ketone groups confer reduction properties on monosaccharides. They are also classified according to the number of carbon atoms they contain: trioses have three carbon atoms, tetroses four, pentoses five, hexoses six, heptoses seven, etc. These two systems of classification are often combined. For example, a six-carbon polyhydroxy aldehyde such as D-glucose is an aldohexose, whereas a six-carbon polyhydroxy ketone such as D-fructose is a ketohexose.

The notations D and L are used to describe the configurations of carbohydrates. In Fischer projections of monosaccharides, the carbonyl group is always placed on top (in the case of aldoses) or as close to the top as possible (in the case of ketoses). If the OH group attached to the bottom-most asymmetric carbon (the carbon that is second from the bottom) is on the right, then the compound is a D-sugar. If the OH group is on the left, then the compound is an L-sugar. Almost all sugars found in nature are D-sugars.

Monosaccharides can exist as either straight-chain or ring-shaped molecules. During the conversion from straight-chain form to cyclic form, the carbon atom containing the carbonyl oxygen, called the anomeric carbon, becomes a chiral center with two possible configurations (anomers), α and β. When the stereochemistry of the first carbon matches the stereochemistry of the last stereogenic center the sugar is the α-anomer when they are opposite the sugar is the β-anomer.

mutarotation    →   mutarotacija

Mutarotation is the change in optical rotation accompanying epimerization. In carbohydrate chemistry this term usually refers to epimerization at the hemiacetal carbon atom. In general α- and β-form are stable solids, but in solution they rapidly equilibrate. For example, D-glucose exists in an equilibrium mixture of 36 % α-D-glucopyranose and 64 % β-D-glucopyranose, with only a tiny fraction in the open-chain form. The equilibration occurs via the ring opening of the cyclic sugar at the anomeric center with the acyclic form as the intermediate. Mutarotation was discovered by French chemist Augustin-Pierre Dubrunfaut (1797-1881) in 1846.

resin    →   smola

Resins are gumlike solid or semisolid substances used in making such products as paints, varnishes and plastics. A resin is not a plastic unless it has become solid in the finished state.

resolution    →   rezolucija

Resolution is a process by which a racemic mixture is separated into its two pure enantiomers.

reverse osmosis    →   reverzna osmoza

Reverse osmosis is the method used for obtaining freshwater from saltwater. The process uses a semi-permeable membrane through which pure water and not the salts will pass. The saltwater must be pressurised to approximately 25 bar, which makes it operationally expensive to produce large quantities of fresh water by this method.

naphtha    →   benzin

Naphtha is any of various volatile, highly flammable liquid hydrocarbon mixtures (petroleum ether, ligroin, benzine) used chiefly as solvents and diluents. In petroleum engineering, naphtha is defined as the fraction of hydrocarbons in petroleum boiling between 30 °C and 200 °C.

neodymium    →   neodimij

Neodymium was discovered by Carl F. Auer von Welsbach (Austria) in 1885. The origin of the name comes from the Greek words neos didymos meaning new twin. It is silvery-white, rare-earth metal that oxidizes easily in air. Reacts slowly in cold water, more rapidly as heated. Metal ignites and burns readily. Neodymium is made from electrolysis of its halide salts, which are made from monazite sand. Used in making artificial ruby for lasers. Also in ceramics and for a special lens with praseodymium. Also to produce bright purple glass and special glass that filters infrared radiation. Misch metal, used in the manufacture of pyrophoric alloys for cigarette lighters, contains about 18 % neodymium metal. (Typically composition of misch metal are Ce:Nd:Pr:La:Other rare earth=50:18:6:22:4). Neodymium is used to create some of the most powerful permanent magnets on Earth, known as NIB magnets they consist of neodymium, iron, and boron.

Nernst’s division law    →   Nernstov zakon razdjeljenja

Nernst’s division law states that a substance is divided between two solvents in a way that proportion of concentrations of that substance is at certain temperatures constant, under the condition that both solvents are in the same molecular state. Division coefficient is a proportion of substance concentration in solvents A i B at a defined temperature.

Appearance of division is used for substance extraction.

reverse reaction    →   povratna reakcija

Reverse reaction is a reaction in backward directions, reaction (in the reversible reaction) in which original reactants emerge again from a products. It goes from right to left.