aromatic compound Flashcards
aromatic compound
compound that contains a benzene ring
why delocalised model better
.it shows that all the carbon bonds are the same length and are between the lengths of a single and double carbon bond
.its shows that in enthalpy change of hydrogination benzene is less exothermic than expected(more stable)
.as it is stable, it dosent undergo electrophillic addition
benezene with carboxylic acid
benzoic acid
benzene and aldehyde
benzaldehyde
benzene and alcohol
phenol
benzene and amine(NH2)
phenylamine
electrophillic subsitution of benzene(halogens)
halogen + halogen carrier –> YX4- + X+
Y = halogen carrier
X = halogen
e.g. AlCl3 + Cl2 –> AlCl4- + Cl+
.arrow from ring to Cl+
.ring broken and positive with Cl attached with H
.arrow from bond between H and benzene to positive symbol from ring
.results in chlorobenzene and H+ ion
.H+ + AlCl4- –> AlCl3 + HCl
electrophillic subsitution of benzene(nitration)
HNO3 + H2SO4 –> H2NO3+ + HSO4-
H2NO3 –> H2O + NO2+
.arrow from ring to NO2+
.ring broken and positive with NO2 attached with H
.arrow from bond between H and benzene to positive symbol from ring
.results in nitrobenzene and H+ ion
.H+ + HSO4- –> H2SO4
benezene vs alkene
.benzene is less reactive:
.as its pi electrons are delocalised whereas alkenes pi electrons are localised between two C
.this means that pi-electron density is lower in benzene
.lower density = electrophiles are less attracted = less polarisation
.less reactive
phenol vs benzene
.lone pair on O is delocalised into the ring
.lone pair “activates” the ring
.electrophiles are more attracted(Br2 more polarised)
.higher electron density = more reactive
activating groups
.moves subsituted groups to 2,4,6
OH
R(methyl)
NHR
X(halogens)
NH2
OR
deactivating groups
.moves subsituted groups to 3 and 5
.RCOR(ketones)
.COOR(esters)
.SO3H
.CHO
.COOH
.CN
.NO2
.NR3
