hydrocarbon derivatives with one or more hydrogen atoms in the molecule, substituted on -OH group (a hydroxyl group or a hydroxy group), - it alcohols.The chemical properties determined by a hydrocarbon radical and a hydroxyl group.Alcohols form a separate homologous series, it representative of each subsequent differs from the previous member for homology difference corresponding = CH2.All agents of that class can be represented by the formula: R-OH.For monatomic limit chemical compounds of general formula is CnH2n + 1OH.According to the international nomenclature names may be formed by adding a hydrocarbon closure ol (methanol, ethanol, propanol, etc.).
This is a very diverse and large class of chemical compounds.Depending on the number of -OH groups in the molecule, it is divided into one, two and so on trihydric - polyhydric compound.Chemical properties of the alcohols also depend on the content of hydroxyl groups in the molecule.These materials are neutral and do not dissociate into ions in water, such as strong acids or strong bases.However, there may be both weakly acidic (decrease with an increase in the number molecular weight alcohols and branched chain hydrocarbon chains) and basic (increase with increasing molecular weight and branching of the molecule) properties.
chemical properties of alcohols depend on the type and the spatial arrangement of atoms: molecules are chains with isomers and positional isomers.Depending on the maximum number of single bonds of the carbon atom (hydroxy group bound to) with the other carbon atoms (with the 1 st, 2 or 3) distinguish primary (normal), secondary or tertiary alcohols.Primary alcohols have a hydroxyl group attached to a primary carbon atom.In secondary and tertiary - to secondary and tertiary, respectively.Since propanol appear isomers that differ in the position of the hydroxyl group: C3H7-propyl alcohol and isopropyl alcohol OH CH3- (CHOH) -CH3.
necessary to name a few main reactions which describe the chemical properties of the alcohols:
- When interacting with alkali metals or hydroxides (reaction deprotonation) formed alcoholates (the hydrogen atom is replaced by a metal atom), depending on the hydrocarbon radical obtained by methoxide, ethoxide,propoxide and so on, for example, sodium propoxide: 2CH3CH2OH + 2Na → 2CH3CH2ONa + H2 ↑.
- In conjunction with concentrated hydrohalic acids formed halogenated hydrocarbons: HBr + CH3CH2OH ↔ CH3CH2Br + H2O.This reaction is reversible.This results in nucleophilic substitution of a halogen ion, a hydroxyl group.
- Alcohols can be oxidized to carbon dioxide, up to aldehydes or ketones.Alcohols burn in the presence of oxygen: 3O2 + C2H5OH → 2CO2 + 3H2O.Under the influence of a strong oxidizing agent (chromic acid, potassium permanganate, etc.) primary alcohols are converted into aldehydes: C2H5OH + H2O → CH3COH, and secondary - ketones: CH3- (CHOH) -CH3 → CH3- (CHO) -CH3 + H2O.
- dehydration reaction proceeds upon heating in the presence of dehydrating agents (zinc chloride, sulfuric acid, etc.).This produces alkenes: C2H5OH → CH2 = CH2 + H2O.
- esterification reaction also proceeds upon heating in the presence of dehydrating compounds, but, in contrast to the previous reaction at a lower temperature and to form ethers: 2C2H5OH → C2H5-O-C2H5O.With sulfuric acid, the reaction occurs in two stages.First, an ester of sulfuric acid: C2H5OH + H2SO4 → C2H5O-SO2OH + H2O, followed by heating to 140 ° C and an excess of alcohol produced diethyl (often called sulfuric ether): C2H5OH + C2H5O-SO2OH → C2H5-O-C2H5O + H2SO4.
chemical properties of polyols, by analogy with their physical properties depend on the type of hydrocarbon radical, forming a molecule, and of course, the amount of hydroxyl groups therein.For example, ethylene-CH3OH CH3OH (boiling point 197 ° C) is 2 atomic alcohol is a colorless liquid (sweetish taste), which is mixed with H2O, and lower alcohols in all proportions.Ethylene glycol, as well as the higher homologues, enter all the reactions characteristic of monoalcohols.Glycerol CH2OH-CHOH-CH2OH (boiling point 290 ° C) is the simplest representative of 3 atomic alcohols.It is a thick sweet-tasting liquid that is heavier than water, but it is mixed in any ratio.Soluble in alcohol.For glycerin and its homologues are also characterized by all the reaction of monohydric alcohols.
chemical properties of alcohols determine the direction of their application.They are used as fuel (ethanol or butanol, etc.), as solvents in a variety of industries;as raw material for production of surfactants and detergents;polymeric materials for synthesis.Some representatives of this class of organic compounds widely used as lubricants or hydraulic fluids, and also for the manufacture of medicaments and biologically active substances.