aromatic chem

Question 1

delocalisation

Answer 1

the pi electrons are soread over several atoms

Question 2

explain the structure of benzene

Answer 2

6 c atoms in a hexagon planar ring arrangement with a ring of delocalised electrons

Question 3

define substitution

Answer 3

a reaction in which one atom or molecule is replaced by a different atom or molecule

Question 4

what are the physical properties of benzene

Answer 4

colourless liquid
low mp and bp
distinctive petrol like aroma
carcinogenic
immiscible in water but soluble in hexane

Question 5

why was kekule structure rejected

Answer 5

the benzene structure was more energetically stable than kekule formula suggest

Question 6

what gives benzene its energetic stability

Answer 6

delocalisation ( electrons are more spread out and so have fewer electron-electron repulsion)
(bond length is the same between c-c and c=c

Question 7

define electrophile

Answer 7

an ion or molecule which attacks regions of HIGH ELECTRON DENSITY

Question 8

conditions and equations of monobromination of benzene

Answer 8

room temp with an iron(iii) or aluminium bromide catalyst
FeBr3 + Br2 > FeBr4- + Br+
FeBr4- + H+ > FeBr3 + HBr

Question 9

condition and equation for mononitration of benzene

Answer 9

conc nitric acid and conc sulfuric acid refuxed at 50°c (nitrating mixture)
HNO3 + 2H2SO4 > NO2+ + 2H2SO4 + H3O+
H+ + HSO4- > H2SO4

Question 10

monoacylation

Answer 10

acylium cation
catalyst of aluminium chloride in anhydrous conditions (prevents hydrolysis)
CH3COCL + AlCl3 > CH3C+O + AlCl4-
AlCl4- + H+ > AlCl3 + HCl