alcohols are derived from hydrocarbons, molecules of which one or more hydrogen atoms near saturated carbon atom is substituted with a hydroxy group - OH.It is experimentally proved that the number of hydroxyl groups per molecule of alcohol can not exceed the number of hydrocarbon atoms.Depending on the nature of the radical, distinguish acyclic (aliphatic) and cyclic alcohols;by the number of hydroxyl groups, - mono-, di-, tri- and polyhydric alcohols;saturation - saturated or unsaturated;localization site of the hydroxyl groups in the hydrocarbon chain - primary, secondary and tertiary alcohols.
polyols - alkane derivatives, molecules with more than three hydrogen atoms are replaced by hydroxyl groups - OH.For both polyhydric alcohols derivatives characterized monosaccharides optical isomers and position isomers in the hydrocarbon chain OH group.Optical isomerism relates to the ability of certain groups of organic compounds in the solutions exhibit optical activity.Optically active substance is determined using a polarimeter.
Qualitative reaction on polyols
The most common reaction to high-quality polyols is their interaction with the copper hydroxide.During the reaction, hydroxide dissolves, thereby forming a chelate purple.
polyols: key representatives
Chetyrehatomnye S4N6 alcohols (OH) 4 called tetritami, pentahydric S5N7 (OH) 5 - pentitols, hexahydroxyalcohols S6N8 (OH) 6 - hexitol.In each group of distinguished individual spirits, which have historical names: erythritol, arabitol, sorbitol, xylitol, dulcitol, mannitol, etc.
Preparation polyalcohols
These alcohols are synthesized by reduction of monosaccharides, aldehyde condensation with formaldehyde in an alkaline medium.Very often, polyols prepared from natural raw materials.Some alcohols extracted from the fruits of mountain ash.
polyols - optically active compounds are readily soluble in water.In the IR and UV spectra have absorption bands typical of OH groups of monohydric alcohols.Chemical properties of alcohols due to the presence of OH groups.The interaction of these substances with alkaline earth metal alcoholates are formed - saccharates.The oxidation of hydroxyl which is localized near the first carbon atom (C1) form monosaccharides.
polyols: key representatives
Erythritol HOCH2 (CHOH) 2SN2ON - crystalline substance melts at 121,5 ° C.The above alcohol was found in lichens and mosses.Erythritol can be obtained by recovering the 1,3-butadiene and erythrose.Said alcohol is used in the manufacture of explosive compounds, quick-drying inks, emulsifiers.
Xylitol HOCH2 (CHOH) 3SNON - sweet crystals, readily soluble in water, melt at a temperature of 61.5 degrees.Said alcohol can be synthesized by reduction of xylose.Xylitol is used in the food industry in the manufacture of foods for diabetics, as well as in the manufacture of alkyd resins, drying oils, and surfactants.
Pentaerythritol C (CH2OH) 4 - solid poorly soluble in water.Prepared by reacting formaldehyde with acetaldehyde in the presence of Ca (OH) 2.It is used in the manufacture of polyesters, alkyd resins, tetrapentaeritrita, surfactants, plasticizers for polyvinyl chloride, synthetic oils.Shows narcotic properties.
Beckons HOCH2 (CHOH) 4SN2ON - sweet-tasting substance that melts at a temperature of 165 degrees.Contained in mosses, fungi, algae, higher plants.Used as a diuretic and as a component of cosmetics (ointments).
D-Sorbitol HOCH2 (CHOH) 4SN2ON - melts at a temperature of 96 degrees.This mountain ash fruits are rich in alcohol.Sorbitol is obtained by restoring glucose.Said alcohol is an intermediate product in the synthesis of vitamin C, shows diuretic action, is used as a substitute for sucrose diabetics.
