OChem Reactions

Question 1

Electrophilic substitution of an arene bromine.

Answer 1

Anhydrous iron (III) bromide catalyst Catalyst made by adding iron filings, benzene and bromine into a reaction vessel

Question 2

Electrophilic substitution of an arene with chlorine.

Answer 2

Chlorine gas is bubbled through benzene at room temperature in the presence of a catalyst like iron (III) chloride or aluminium chloride.

Question 3

Formation of chloromethyl benzene

Answer 3

Chlorine gas is passed into boiling methylbenzene in the presence of uv light Methyl benzene + Cl2 -> chloromethyl benzene + HCl

Question 4

Oxidising the side chain in a benzene ring

Answer 4

Reflux with alkaline potassium manganate Then acidify with H2SO4/ K2Cr2O7 Forms a carboxylic acid side chain

Question 5

Friedel-Crafts reaction

Answer 5

Electrophilic substitution Introduction of a side chain AlCl3 catalyst 1. Alkylation: Alkyl side chain 2. Acylation: Acyl side chain HCl produced in both cases

Question 6

Nitration of benzene

Answer 6

Making NO2+ (insitu) HNO3 + 2H2SO4 -> NO2+ 2HSO4- + H3O+ Reflux with benzene @ 55 C Electrophilic substitution: Benzene + HNO3 -> nitrobenzene + H2O Deactivates 2,4,6 -> further activates 1,3,5

Question 7

Bromination of phenol

Answer 7

Bromine water readily reacts with the phenol [phenol] + 3Br2 -> 3 bromo phenol + 3HBr

Question 8

Nitration of phenol

Answer 8

Dilute HNO3 at room temperature [phenol] -> 2 nitro phenol + 4 nitro phenol With conc HNO3: 2,4,6 trinitro phenol

Question 9

Oxidising Methanoic acid

Answer 9

Fehling’s / Tollen’s. HCOOH -> CO2 + 2H+ +2e- HCOOH + [O] -> CO2 + H2O K2Cr2O7: Orange -> Green KMnO4-: 2MnO4- + 6H+ + 5H2C2O2 -> 2Mn2+ + 10CO2 + 8H2O

Question 10

Making acyl chloride

Answer 10

Carboxylic acid with the following reactants: PCl5: CH3COOH + PCl5 -> CH3COCl + POCl3 + HCl PCl3: 3CH3COOH + PCl3 -> 3CH3COCl + H2PO3 SOCl2: CH3COOH + SOCl2 -> CH3COCl + SO2 + HCl

Question 11

Reaction of a phenol with alkali

Answer 11

Salt is soluble [phenol] + NaOH -> phenoxide salt and water

Question 12

Hydrolysis of an acyl chloride

Answer 12

White fumes immediate reaction CH3CH2COCl + H2O -> CH3CH2COOH + HCl 2 stages: 1. Condensation and 2. Elimination

Question 13

Esterification with acyl chloride

Answer 13

With acyl chloride -> completion, no equilibrium Alcohol: CH3COCl + C2H5OH -> CH3COOC2H5 + HCl Phenol: CH3COCl + Na+[benzene] -> CH3COO[benzene] + NaCl

Question 14

Reaction of acyl chloride with an amine

Answer 14

• Attack by lone pair CH3COCl + CH3NH2 -> CH2CONHCH3 + HCl

Question 15

Preparing amines

Answer 15

Hot ethanol if ammonia Excess to prevent amine from reacting with H-Hal CH3CH2Br + NH3 -> CH3CH2NH2 + HBr

Question 16

Reduction of nitriles

Answer 16

-Reduce - Nitrile vapor and hydrogen gas passed over Ni catalyst/ LiAlH4 (in dry ether) -CH3CN + 4[H] -> CH3CH2NH2

Question 17

Reduction of Amides

Answer 17

LiAlH4 in dry ether CH3CONH2 + 4[H] -> CH3CH2NH2 + H2O

Question 18

Preparing phenyl amine

Answer 18

Reducing Nitrobenzene Tin & Sn [nitrobenzene] + 6H -> phenyl amine + 2H2O

Question 19

Reaction of Phenyl amine with Bromine

Answer 19

Aqueous bromine Phenyl amine + 3Br2 -> 2,4,6 tribromo phenyl amine + 3HBr

Question 20

Diazotination

Answer 20

• Must be kept below 10 C using ice (Diazonium is unstable) 1. Nitrous acid made insitu NaNO2 + HCl -> HNO2 + NaCl 2. Phenyl amine and nitrous acid Phenyl amine + HNO2 + HCl -> diazonium chloride + 2H2O 3. Coupling: Diazonium ion + phenol -> Azo Dye + H+