aromatic compounds
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main type of reaction benzene undergoes
electrophilic substitution
why is benzene less reactive then a phenol
• in phenol, lone pair of electrons from O of -OH are donated to the π system of the ring • increasing electron density • meaning electrophiles are attracted more easily
evidence for delocalised model of benzene (3)
• does not react like an alkene - much less reactive - doesn’t decolourise bromine water (alkene does) • the c-c bond length is between double and single • the hydration enthalpy is not as expected (less energy produced when hydrated)
are phenols acidic?
yes
explain solubility of phenols
less soluble in water than an alcohol because of non-polar benzene ring - does partially dissolve
reactions of phenol and: • strong base • weak base
• yes - (alcohol wouldn’t) - no
observations of reaction of bromine water by phenol (name products formed)
• decolourises bromine water - white ppt. - 2,4,6-tribromophenol
where does -NH2 direct to
2,4
where does -OH direct to
2,4
where does -NO2 direct to
3
conditions required for nitration of phenol
• no conc. H2SO4 needed - only dilute HNO3
alkylation
adding a haloalkane to benzene, lengthening carbon chain by adding alkyl group - by reacting w. a chloroalkane
special thing about alkylation
lengthens carbon chain
acylation
adding an acyl group to benzene, forming a ketone
-NO2 is: deactivating/activating?
deactivating
-NH3 is: deactivating/activating?
activating
what does activating mean?
the aromatic ring reacts more readily with electrophiles
explain ease with which benzoic acid attracts electrophile
• COOH is electron withdrawing group - hard to attract electrophile