carbolic acid - one of the names of phenol, indicating his specific behavior in chemical processes.This material is easier than benzene enters into nucleophilic substitution reaction.The inherent properties of the compound are explained acid labile hydrogen atom in the hydroxyl group bonded to the ring.The study of the molecular structure and high quality response to the phenol compound to allow include aromatics - benzene derivatives.
Phenol (hydroxybenzene)
In 1834 a German chemist, Runge identified carbolic acid from coal tar, but was unable to decipher its structure.Later, other researchers have proposed a formula, and brought a new connection to the aromatic alcohol.The simplest representative of this group - phenol (hydroxybenzene).In its pure form, this material is a transparent crystals with a characteristic odor.In the air the color of phenol can change and become pink or red.For aromatic alcohol typical poor cold water solubility and good - in organic solvents.Phenol melts at a temperature of 43 ° C.Is a toxic compound, in contact with skin causes severe burns.The aromatic moiety is a radical of phenyl (C6H5-).Directly with one of the carbon atoms bound oxygen of the hydroxyl group (-OH).The presence of each particle shows the corresponding qualitative reaction to phenol.The formula showing the total content of atoms of chemical elements in the molecule - C6H6O.Structure reflect the structural formula, including cycle and Kekule functional group - hydroxyl.A visual representation of the molecule, an aromatic alcohol give sharosterzhnevye model.
avilable molecule
Interference of the benzene ring and OH group determines the chemical reaction of phenol with metals, halogens, other substances.The presence of the oxygen atom bound to an aromatic ring leads to a redistribution of electron density in the molecule.Communication O-H is more polar, which results in increased mobility of the hydrogen in the hydroxyl group.The proton may be replaced with metal atoms, which indicates the acidity of the phenol.In turn, the OH group increases the reactivity of the benzene ring.Increasing delocalization of the electrons and the ability to electrophilic substitution in the nucleus.This increases the mobility of the hydrogen atoms bonded to the carbon at the ortho- and para-position (2, 4, 6).This effect is due to the presence of an electron donor density - hydroxyl group.Due to its influence phenol active than benzene behaves in reactions with certain substances, and new substituents are oriented in the ortho and para positions.
acidic properties
The hydroxyl group of aromatic alcohols, oxygen gets a positive charge, weakening its connection with hydrogen.The release of the proton is facilitated, so phenol behaves as a weak acid, but stronger than alcohol.Qualitative reaction to phenol include test litmus test that in the presence of protons changes color from blue to pink.The presence of halogen atoms or nitro groups associated with the benzene ring leads to increased activity of hydrogen.The effect is observed in molecules nitro phenol.Lower acidity substituents such as an amino group and an alkyl (CH3-, C2H5- and others).Compounds that brings together a benzene ring, a hydroxyl group and a methyl radical, refers cresol.Its properties are weaker than carbolic acid.
reaction of phenol with sodium and alkaline
like acid phenol reacts with metals.For example, reacted with sodium: 2C6H5 + 2Na-OH = 2C6H5-ONa + H2 ↑.Sodium phenolate formed and hydrogen gas.Phenol is reacted with soluble bases.Neutralization reaction occurs with formation of salt and water: C6H5-OH + NaOH = C6H5-ONa + H2O.Capable of donating hydrogen in the hydroxyl group in the phenol is lower than the majority of inorganic and carboxylic acids.It displaces it from even the salts dissolved in water, carbon dioxide (carbonic acid).Reaction equation: C6H5-ONa + CO2 + H2O = C6H5-OH + NaHCO3.
reactions of the benzene ring
aromatic properties are due to the delocalization of the electrons in the benzene ring.Hydrogen from the ring is substituted by halogen atoms, nitro.Such a process per molecule of phenol is easier than that of benzene.One example - the bromination.Benzene acts in the presence of a halogen catalyst, a bromobenzene.Phenol is reacted with bromine water under normal conditions.As a result of the interaction of a white precipitate of 2,4,6-tribromophenol, whose appearance to distinguish a test substance from a similar aromatics.Bromination - qualitative reaction to phenol.The equation: C6H5-OH + 3Br2 = C6H2Br3 + HBr.The second reaction product - bromide.When reacting phenol with dilute nitric acid obtained nitro derivative.The product of the reaction with concentrated nitric acid - 2,4,6-trinitrophenol or picric acid is of great practical importance.
Qualitative reaction to phenol.List
The interaction of substances obtained certain foods that allow us to establish qualitative composition of the starting materials.A number of color reaction indicates the presence of particles of functional groups that are useful for chemical analysis.Qualitative reaction to presence of phenol prove molecule substances of the aromatic ring and OH-groups:
- The solution of phenol blue litmus paper turns red.
- Color reaction as phenols is carried out in a weak alkaline environment with diazonium salts.A yellow or orange azo dyes.
- reacts with bromine water brown, white precipitate appears tribromophenol.
- by the reaction with a solution of iron chloride obtained phenoxide ferric - substance blue, violet or green color.
producing phenol
production of phenol in the industry are in two or three stages.In the first stage of the benzene and propylene in the presence of aluminum chloride produced cumene (isopropylbenzene common name).Equation Friedel-Crafts reaction: C6H5 + C3H6-OH = C9H12 (cumene).Benzene and propylene in a ratio of 3: 1 was passed over an acidic catalyst.Increasingly, instead of the traditional catalyst - aluminum chloride - used clean zeolites.At the final stage of the oxidation is carried out with oxygen in the presence of sulfuric acid: C6H5-C3H7 + O2 = OH + C6H5-C3H6O.Phenol can be produced from coal distillation, are intermediates in the production of other organic substances.
phenol
aromatic alcohols are widely used in the manufacture of plastics, dyes, pesticides and other substances.Manufacture of carbolic acid, benzene is the first step in the creation of a number of polymers, including polycarbonates.Phenol is reacted with formaldehyde, phenol-formaldehyde resins are obtained.
Cyclohexanol is a raw material for the production of polyamides.Phenols used as antiseptics and disinfectants in deodorants, lotions.Used for phenacetin, salicylic acid and other drugs.Phenols are used in the manufacture of resins used in electrical products (switches, sockets).They are also used in the preparation of azo dyes, eg phenylamine (aniline).Picric acid, nitro derivatives of phenol which is applied for textile dyeing, manufacturing explosives.
