Benzene and phenol

• Benzene has 6 carbons, each one has 3 sigma bonds, and a spare electron which is in a p-orbital. These p-orbitals overlap above and below the plane of carbons to form rings of electron density, which is delocalisation
• kekules model of benzene has alternating single and double bonds. this is wrong. 1- it does not react with bromine, if it has double bonds it should. 2- the bond lengths are different. 3- actual benzene is less exothermic, so more stable than kekules.
• benzene goes through electrophilic substitution. an electrophile is a species that accepts electrons to form a bond
• benzene reacts to form nitrobenzene. concentrated HNO3 and H2SO4 is needed. to prevent further substitution, 50 degrees is used.
• halogenation adds a halogen to benzene. a catalyst, AlBr3 is used, as well as the halogen Br2. the electrophile is formed first before being substituted
• freida-crafts alkylation adds an alkyl group to benzene. a catalyst AlBr3 is used, and a haloalkane, to form the electrophile.
• acylation is addition of a C=O group to benzene. this may be an acylchloride or an acid anhydride. a catalyst AlBr3 is used.
• Ring activators and 2-4 directing. They have faster reactions and more substitution. They include NH2, OH, R, and halogens
• Ring deactivators and 1-3 directing. they are slower reactions with less substitution. They include COOH, NO2, CN, CHO
• Phenols have an OH group on a benzene. They are slightly soluble in water. They neutrile bases.
• testing between COOH, ethanol and phenol. ethanol does not react with NaOH or Na2CO3. phenol reacts with NaOH but not Na2CO3. carboxylic acids show effervescence with NaOH and Na2CO3.
• Phenol reacts with dilute nitric acid and at room temperature, whereas benzene reacts with concentrated Nitric acid and at a higher temp. H2so4 is not required with phenol
• phenol decoloursies bromine water and forms a white precipitate. a halogen carrier is not required unlike benzene. benzene is too stable, so needs a halogen carrier