CHEMISTRY GLOSSARY

secondary alcohol    →   sekundarni alkohol

Secondary alcohol is one in which the hydroxyl group (-OH) is attached to a secondary carbon atom (i.e. a carbon atom which has one hydrogen atom attached to it).

tertiary alcohol    →   tercijarni alkohol

Tertiary alcohols are aliphatic alcohols in which the hydroxyl group (-OH) is attached to a tertiary carbon atom.

fructose    →   fruktoza

Fructose (fruit sugar) is a ketohexose (a six-carbon ketonic sugar), which occurs in sweet fruits and honey. Glucose and fructose have the same molecular formula, C₆H₁₂O₆, but have different structures. Pure, dry fructose is a very sweet, white, odorless, crystalline solid. Fructose is one of the sweetest of all sugars and is combined with glucose to make sucrose, or common table sugar. An older common name for fructose is levulose, after its levorotatory property of rotating plane polarized light to the left (in contrast to glucose which is dextrorotatory). The polysaccharide inulin is a polymer of fructose.

glutamic acid    →   glutaminska kiselina

Glutamic acid is an electrically charged amino acids. It is one of the two amino acids that contain a carboxylic acid group in its side chains. These acids play important roles as general acids in enzyme active centers, as well as in maintaining the solubility and ionic character of proteins. Glutamic acid is commonly referred to as glutamate, because its carboxylic acid side chain will be deprotonated and thus negatively charged in its anionic form at physiological pH. Glutamic acid is referred to as a non-essential amino acid because a healthy human can synthesize all the glutamic acid needed for normal body function from other amino acids.

• Abbreviations: Glu, E
• IUPAC name: 2-aminopentanedioic acid
• Molecular formula: C₅H₉NO₄
• Molecular weight: 147.13 g/mol

glucose    →   glukoza

Glucose (grape sugar, blood sugar), C₆H₁₂O₆, is an aldohexose (a monosaccharide sugar having six carbon atoms and an aldehyde group). An older common name for glucose is dextrose, after its dextrorotatory property of rotating plane polarized light to the right. Glucose in free (in sweet fruits and honey) or combined form (sucrose, starch, cellulose, glycogen) is is probably the most abundant organic compound in nature. During the photosynthesis process, plants use energy from the sun, water from the soil and carbon dioxide gas from the air to make glucose. In cellular respiration, glucose is ultimately broken down to yield carbon dioxide and water, and the energy from this process is stored as ATP molecules (36 molecules of ATP across all processes).

Naturally occurring glucose is D isomers (OH group on the stereogenic carbon farthest from the aldehyde group, C-5, is to the right in the Fischer projection). Although often displayed as an open chain structure, glucose and most common sugars exist as ring structures. In the α form, the hydroxyl group attached to C-1 and the CH₂OH attached to C-5 are located on opposite sides of the ring. β-glucose has these two groups on the same side of the ring. The full names for these two anomers of glucose are α-D-glucopyranose and β-D-glucopyranose.

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.

thermit welding    →   termitno zavarivanje

Thermit welding is a group of welding processes in which fusion is produced by heating with superheated liquid metal resulting from a chemical reaction between a metal oxide and aluminium.

van der Waals’ force    →   van der Waalsova sila

Van derWaals’ force is the weak attractive force between two molecules which arises from electric dipole interactions. It can lead to the formation of stable but weakly bound dimer molecules or clusters. They are named after the Dutch physicist Johannes van der Waals (1837-1923).

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.

halogens    →   halogeni elementi

Halogens are the elements fluorine (F) chlorine (Cl), bromine (Br), iodine (I), and astatine (At). They are non-metals, and make up part of the 17 group in the periodic table. Compounds of these elements are called halogenides or halides.

The halogens all have a strong unpleasant odour and will burn flesh. They do not dissolve well in water. The five elements are strongly electronegative. They are oxidising agents, with fluorine being the strongest and astatine being the weakest. They react with most metals and many non-metals.

Halogens form molecules which consist of atoms covalently bonded. With increasing atomic weight there is a gradation in physical properties. For example: Fluorine is a pale green gas of low density. Chlorine is a greenish-yellow gas 1.892 times as dense as fluorine. Bromine is a deep reddish-brown liquid which is three times as dense as water. Iodine is a grayish-black crystalline solid with a metallic appearance. And astatine is a solid with properties which indicate that it is somewhat metallic in character.