CHEMISTRY GLOSSARY

keto-enol tautomerism    →   keto-enolna tautomerija

See Tautomerism

ketose    →   ketoze

Ketose is any monosaccharide sugar that contains a ketone (carbonyl) group.

ketal    →   ketal

Ketals are organic compounds formed by addition of an alcohol to a ketone. If one molecule of ketone (RR’CO) reacts with one molecule of alcohol (R"OH) then a hemiketal is formed. The rings of ketose sugars are hemiketals. Further reaction produces a full ketal (RR’C(OR")₂). This term, once abandoned, has been reinstated as a subclass of acetals.

ketone    →   keton

Ketones are compounds in which a carbonyl group is bonded to two carbon atoms: R₁R₂C=O (neither R may be H). They are derived by oxidation of secondary alcohols. The simplest member of the series is acetone, (CH₃)₂CO.

acetal    →   acetal

Acetals are organic compounds having the structure R₂C(OR’)₂ (R’ ≠ H). They are organic compounds formed by addition of alcohol molecules to aldehyde or ketone molecules. Originally, the term was confined to derivatives of aldehydes (one R = H), but it now applies equally to derivatives of ketones (neither R = H ). Mixed acetals have different R’ groups. The formation of acetals is reversible; acetals can be hydrolysed back to aldehydes (ketone) in acidic solutions.

Acetal, 1,1-diethoxyethane (CH₃CH(OC₂H₅)₂), is an organic compound, pleasant smelling, formed by addition of ethyl alcohol to ethanal (acetaldehyde). It is used as a solvent and in synthetic organic chemistry.

anomer    →   anomer

Anomers are diastereoisomers of cyclic forms of sugars or similar molecules differing in the configuration at the anomeric carbon (C-1 atom of an aldose or the C-2 atom of a 2-ketose). The cyclic forms of carbohydrates can exist in two forms, α- and β- based on the position of the substituent at the anomeric center. Anomer are designated α if the configuration at the anomeric carbon is the same as that at the reference asymmetric carbon in a Fischer projection. If the configuration differs the anomer is designated β. For example, α-D-glucopyranose and β-D-glucopyranose, the two cyclic forms of glucose, are anomers.

carbonyl group    →   karbonilna skupina

Carbonyl group is a functional group common to all ketones and aldehydes.

Fehling’s test    →   Fehlingova otopina

Fehling’s test is a chemical test to detect reducing sugars and aldehydes in a solution, devised by the German chemist Hermann Christian von Fehling (1812-1885). Fehling’s solution consists of Fehling’s A (copper(II) sulphate solution) and Fehling’s B (sodium tartarate solution), equal amounts of which are added to the test solution. After boiling, a positive result is indicated by the formation of a brick-red precipitate of copper(I) oxide. Methanal, being a strong reducing agent, also produces copper metal; ketones do not react. The test is now rarely used, having been replaced by Benedict’s test.

non-Newtonian fluid    →   nenewtonski fluid

Non-Newtonian fluid is a fluid whose viscosity changes when the gradient in flow speed changes. Colloidal suspensions and polymer solutions like ketchup and starch/water paste are non-Newtonian fluids.

oxime    →   oksim

Oximes are organic compounds of structure R₂C=NOH derived from condensation of aldehydes or ketones with hydroxylamine. Oximes from aldehydes may be called aldoximes; those from ketones may be called ketoximes.