Aromatic compounds

what shape is benzene and what bond angles

hexagonal planar, 120 degree bond angle

what length are C-C bonds

all the same length, between a double and single carbon bond

why does the pi system mean benzene is stable

it has delocalised electrons which minimise repulsion and make the molecule more stable

what shape, bond angle and bond length does cyclohexatriene have

hexagonal planar, 120 degrees, but 3 single and 3 double carbon bonds 

why does the fact that benzene doesn’t undergo addition reactions support the benzene structure

shows it doesn’t contain any double bonds, doesn’t decolourise bromine water

why does the fact that benzene has a smaller enthalpy of hydrogenation support the benzene structure

we would expect the triene to react with 3H2 to form cyclohexane, releasing -360kjmol-1 of energy, however benzene only releases -208, 152kjmol-1 less exothermic, so it is more stable

electrophilic substitution - nitration conditions

conc HNO3 and conc H2SO, 50 degrees C

what happens during electrophilic substitution - nitration

a hydrogen on the benzene ring is replaced with NO2

what is the electrophile in nitration (nitronium ion)

NO2+

equation to generate nitronium ion

HNO3 + 2H2SO4 -> NO2+ + 2HSO4- + H3O+

what mechanism is friedel-crafts acylation

electrophilic substitution

what are the reactants in friedel-crafts and conditions

acyl chloride/acid anhydride and AlCl3, anhydrous

what is the electrophile in friedel-crafts

RCO+ (acylium ion)