Benzene

Question 1

arenes

Answer 1

with one or more benzene

Question 2

halogenarene

Answer 2

benzene with halogen

Question 3

aryl compounds

Answer 3

compounds with bezene

Question 4

benzene + Cl2 or Br 2

e.g br2

Answer 4

electrophilic substitution
anhydrous AlBr3 catalyst
Br+ and electron rich benzene ring attracted
CH bond heterolytically break

Question 5

halogen carriers

Answer 5

AlBr3 and AlCl3

Question 6

methyl benzene with electron donating groups

Answer 6

at 2,4,6

Question 7

FRS with benzene

Answer 7

boil with UV light
CH3 becomes CH2Cl
in excess, all H are replaced with Cl atoms

Question 8

nitration of benzene

Answer 8

NO2+ is an electron withdrawing group so it has it at 3,5,7

conc nitric acid and conc sulfuric acid reflux 25C to 60C

Question 9

acylation/aklylation of benzene = Friedel-Crafts

Answer 9

halogen (X) forms dative covalent with AlX3
e.g
Cl–> AlCl3 = [AlCl4]-
AlCl3 regenerated when H+ reacts with it to form HCl

Question 10

acyl group

Answer 10

R-C=O

Question 11

oxidation of side chains in arene

Answer 11

alkane oxidised to COOH
methane produces benzoic acid when refluxed KMnO4 with 3[O] and acidified with H2SO4
produces H2O

Question 12

hydrogenation

Answer 12

similar to alkene to alkane
heating H2 with Ni/Pt catalyst
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also works with akyl

Question 13

make phenol

Answer 13

phenylamine with nitric aicd
ice = temp under 10`C
first make nitric acid
NaNO2 + HCl –> HNO2 + NaCl
sodium nitrate + hydrochloric acid –> nitrous acid + sodium chloride
phenylamine with HNO2
benzene-NH2 + HNO2 + HCl –> N+=_NCl- + 2H2O
forms a diazonium
benzenediazonium chloride + H2O(warm) –> phenol + HCl + N2

Question 14

pKa differences meaning

Answer 14

lower pKa means stronger acid

Question 15

acidity of phenol

Answer 15

weakly acidic, stronger than water and ethanol
lies on the right (strongly dissoacitated)
this is because the O atom overlaps with delocalised electrons in the benzene ring. The negative charge is spread throughout the structure.
ch3ch2–> o, negative charge concentrated on oxygen atom.
Attraction between o and h for benzene is not as strong.
completely dissoacioates, won’t reform again as attraction kinda weak

Question 16

phenol with base

Answer 16

benzene-oh + NaOh –> Benzene-o-na+ + H2O

product soluble inwater

Question 17

phenol and benzene reactivity comparison

Answer 17

phenol is more reactive with electrophiles
the lone pairs of electron of oxygen overlaps with the delocalised electron ring (pi bonding system) increases electron density
attracts electrophile (electron deficient groups)
the electron donating group of OH enables 2,4,6

Question 18

phenol nitration

Answer 18

don’t need conc nitric acid + sulfruic acid at 25C to 60C
readily undergoes at room temperature with dilute nitric acid (HNO3)
at 2 and 4
or conc = 2,4,6

Question 19

phenolic compound

Answer 19

OH acrivates the benzene ring, open to electrophilic substitution, attacking at 2 or 4