simplest polyhydric alcohol wherein there are three OH groups, - glycerol.The formula for the compounds of this general type, - CnH2n - 1 (OH) 3.To better understand the properties and uses of glycerin and its homologues, consider a variety of formulas substances, each of which is used in certain situations.
Classification and nomenclature glycerols
in organic chemistry alcohol - a substance derived from hydrocarbons.Part of the hydrogen atoms in the molecule is substituted by one or more hydroxy groups.Alcohols differ in the number of OH groups (single, double, polyols).The lower members of the class with the number of carbon atoms from 1 to 12 - liquids, higher - solids.Alkantrioly or glycerols - a trihydric alcohols containing in its composition three hydroxyl associated with three different carbon atoms.Compounds belonging to this group exhibit amphoteric properties, due to the mutual influence and hydroxy radical.
simplest representative alkantriolov - 1,2,3-propanetriol (synonym - glycerol).Formula agents - C3H8O3.Systematic nomenclature involves mention of the name of the corresponding alkane with the word "triol", the use of Arabic numerals, which determine the position of the OH group.Numbering in the molecules of homologue of glycerol is from the nearest end of the chain hydroxyl.Possible types of isomerism: the structure of the carbon chain, the position of the hydroxy groups, Optical.
Opening glycerol
Swedish pharmacist Karl Scheele in 1779 when the saponification of fats for the first time got a new syrupy substance.33 years later the Frenchman M. Chevreul named the sweet liquid glycerin.
chemical composition set Pelouse in 1836.Significant contribution to the study of the structure made Berthelot (1854) and Wurtz (1857), continues to explore glycerol.The molecular formula, and the nature of the radical include glycerin allowed to limit alcohol.
demand for glycerin has increased considerably since 1847, when it was opened ester of nitric acid.Swedish engineer A. Nobel in 1875 managed to get by using glycerine explosives - dynamite.
composition, structure and the simplest formula glycerol
simplest recording composition of matter coincides with the true, and the empirical formula of gross-glycerol - C3H8O3.The carbon chain has three atoms, each of them is associated with a hydroxy group.Chemical symbols designated substances contained atoms: C - carbon, O - oxygen, H - hydrogen.The composition of glycerin reflect different formula (molecular, structural).Widely used in the study of matter and sharosterzhnevye hemispherical model.Two-dimensional and three-dimensional structures created by computer simulation - a spatial image of the glycerol molecule.They allow you to visualize the structure of mutual accommodation and the distance, the angle between the atoms.
Molecular and molar mass of glycerol
According to the formula can be found molecular and molar mass, the percentage of elements in the material.For the calculations you must use the values of the atomic weights of the elements listed in the periodic table.The empirical formula of glycerin: C3H5 (OH) 3.By multiplying the atomic weight (in a. E. M.) On each element, followed by the number of atoms obtained by adding the value is found molecular (Mr) and the molar (M) of the mass.For that kind of calculations it is more convenient to use the gross formula of glycerin - C3H8O3.
- Ar (H) = 1.00794;the number of atoms in the molecule - 8.
- Ar (C) = 12.0107;atoms - 3.
- Ar (G) = 15.9994;atoms - 3.
- Mr (S3N8O3) = 12.0107 * 3 + 1.00794 * 8 + 15.9994 * 3 = 92.09382 as well.e. m.
- M (S3N8O3) = 92.09382 g / mol /
- percentage of the elements in the molecule of the substance: N - 8.756% C - 39.125%, O - 52.119%.
rational and structural formula of glycerin
composition of matter and its molecules represent a rational and gross formula, but they do not show the arrangement of the atoms, which differ glycerol.Formula structure and computer models are better suited to studying the structure of the molecule, the bonds between atoms.
- rational formula glycerol - C3H5 (OH) 3.From the composition of the molecules isolated and enclosed in parentheses functional groups OH.Just beyond the closing parenthesis indicates the number of hydroxyl groups in the molecule.
- Polurazvernuty kind of rational formula - HOCH2CH (OH) CH2OH (glycerol).
- structural formula graphically shows the location of the molecule.Dash between the atoms represent chemical bonds.
- Lewis structure contains points, the valence electrons and couples involved in bond formation.
Certain images molecules occupy a lot of space, so often use the abbreviated formula, for example, HOCH2-CHOH-CH 2 OH, and the skeletal structure:
states of atoms in a molecule of glycerol
hydroxyl - polar particle to the same oxygenIt has a lone pair of electrons.The presence of three hydroxyl groups leads to further polarization of the OH bond.On the carbon atom appears partial charge "+" facilitating nucleophilic substitution of hydroxyl.Features of composition and structure, which reflects the structural formula of glycerin, are confirmed by the properties of the substance.For this connection characterized by numerous hydrogen bridges - the weak additional bond.Glycerin has a pronounced acid properties compared to ethanol and propanol.The most important derivative is glyceryl trioleate.Formula:
- simple - S57N104O6;
- polurazvernutaya rational - (S17N33SOO) 3S3N5;
- rational with elements of structural and skeletal -
Appearance glycerol
At room temperature, 1,2,3-propanetriol - a colorless or pale yellow liquid, odorless, sweet taste.Solidified melts at low temperatures glycerol at 17.8 ° C.Boiling substance followed by evaporation begins at 290 ° C.Glycerin is slightly heavier than water, calculate its density at 20 ° C gives a value of 1.2604 g / cm3.
Properties propanetriol-1,2,3
Chemical formula of glycerin does not provide information about the nature of the amphoteric compound.Weak acidic and basic properties of substances related to the influence of the atoms in the molecule, the polarization in the group G-H.In the presence of glycerol is reacted with an alkali hydroxide of copper (II), obtained blue colored complex (one value reactions).Acid reaction ends with the formation of glycerol esters.Reacting a trihydric alcohol with nitric acid in the presence of H2SO4 (conc.) Leads to the formation of nitroglycerin.
At home, from fats and oils with glycerol using ethyl alcohol and other ingredients is prepared soap.The cooking process requires careful heating of the mass in a water bath, a creative approach to the selection of components and finished product forms for soap making.
Glycerin and its derivatives are used in enamels, paints, many medicines, toiletries.Contained sweetener in various foods, including bakery products.International name of the sweetener and flavoring confectionery - E422.Along with other alcohols and esters of fatty acids, glycerol is regarded as a potential replacement fuel derived from petroleum.Economical methods of new varieties of biodiesel to fuel cars revolutionize the global transport sector.Improve the environmental situation of the world economy to reduce dependence on oil and gas.
