1. A Reactions Review FREE RADICAL SUBSTITUTION POLYMERIZATION
ELECTROPHILIC ADDITION ( types)
A) Hydration (add water, HOH)
B) Halogenation (add H2)
C) Bromination (add Br2)
D) Hydrohalogenation (add HCl, HBr,HI (acids)
ELIMINATION (Dehydrohalogenation)
NUCLEOPHILIC SUBSTITUTION (add :OH-,:CN-,H2O, 2:NH3)
OXIDATION
A) 10 ALCOHOLS TO ALDEHYDES THEN TO CARBOXYLIC ACIDS
B) 20 ALCOHOLS TO KETONES

2. REACTIONS OF ORGANIC COMPOUNDS
POLYMERS
DIBROMOALKANES
KETONES
ALKANES
ALKENES
ALCOHOLS
ALDEHYDES
HALOGENOALKANES
AMINES
NITRILES
CARBOXYLIC ACIDS
CONVERSIONS

3. 14 REACTIONS OF ORGANIC COMPOUNDS
POLYMERS
DIBROMOALKANES
KETONES P F C D
ALKANES E
ALKENES
ALCOHOLS M N A B L
ALDEHYDES G
HALOGENOALKANES O H I
AMINES
NITRILES
CARBOXYLIC ACIDS

4. Free radical substitution
Initiation Cl2 ——> 2Cl• radicals created
Propagation Cl• CH ——> CH3• HCl radicals used and
Cl CH3• ——> CH3Cl Cl• then re-generated
Termination Cl• + Cl• ——> Cl2 radicals removed
Cl• + CH3• ——> CH3Cl
CH3• + CH3• ——> C2H6
Summary
Due to the lack of reactivity of alkanes you need a very reactive species to persuade them to react. This is done by shining UV light on the mixture (heat could be used)
CONVERSIONS

5. ELECTROPHILIC ADDITION OF HBr
(Hydrohalogenation)
Reagent Hydrogen bromide... it is electrophilic as the H is slightly positive
Condition Room temperature.
Equation C2H4(g) HBr(g) ———> C2H5Br(l) bromoethane
Mechanism
Step 1: As the HBr nears the alkene, the Pi bond breaks
The δ positive H joins a carbon (hydrogenation)
The :Br ion forms.
Also a carbocation (positively charged carbon species) is formed.
Step 2 The bromide ion (halogen) is a nucleophile and attacks the carbocation.
Br across the double bond.
CONVERSIONS

6. ELECTROPHILIC ADDITION OF Br2
Reagent Bromine. (Neat liquid or dissolved in tetrachloromethane, CCl4 )
Conditions Room temperature. No catalyst or UV light required!
Equation C2H4(g) + Br2(l) ——> CH2BrCH2Br(l) ,2 - dibromoethane
Mechanism
It is surprising that bromine
should act as an electrophile
as it is non-polar.
CONVERSIONS

7. ELECTROPHILIC ADDITION with Water
(or HYDRATION)
Reagent steam
Catalyst Sand coated with sulphuric acid or phosphoric acid (BOTH WAYS)
Product alcohol OR Ethene (depending on direction with Chatelier's principle)
H2SO4, SiO2
Equation C2H4(g) H2O(g) C2H5OH(g) ethanol ⍙H = -45 KJ/mo
So it is no surprise that the mechanism for hydration of alkenes is identical to that of dehydration of alcohols, but in the reverse order of steps. D and M are the same mechanism, in reverse
CONVERSIONS

8. ELIMINATION OF WATER (DEHYDRATION)
Reagent/catalyst sulphuric acid (H2SO4) or conc.
Conditions reflux at 180°C
Equation e.g. C2H5OH(l) CH2 = CH2(g) H2O(l)
So it is no surprise that the mechanism for hydration of alkenes is identical (as it is a REVERSABLE reaction) to that of dehydration of alcohols, but in the reverse order of steps. D and M are the same mechanism, in reverse
Mechanism
CONVERSIONS

9. ELECTROPHILIC ADDITION OF H2
or HYDROGENATION
Reagent hydrogen
Conditions nickel catalyst - finely divided
Product alkanes
Equation C2H4(g) H2(g) ———> C2H6(g) ethane Ni
Use margarine manufacture (Hydrogenated fats for spreading
on bread)
CONVERSIONS

10. POLYMERISATION OF ALKENES
ETHENE
POLY(ETHENE)
PROPENE
POLY(PROPENE)
CHLOROETHENE
POLY(CHLOROETHENE)
POLYVINYLCHLORIDE PVC
TETRAFLUOROETHENE
POLY(TETRAFLUOROETHENE)
PTFE “Teflon”
CONVERSIONS

11. NUCLEOPHILIC SUBSTITUTION AQUEOUS SODIUM HYDROXIDEG
NUCLEOPHILIC SUBSTITUTION
AQUEOUS SODIUM HYDROXIDE
Reagent Aqueous* KOH or NaOH
Conditions Reflux in aqueous solution (SOLVENT IS IMPORTANT)
Product Alcohol
Nucleophile hydroxide ion OH¯(aq)
Equation e.g. C2H5Br(l) NaOH(aq) ———> C2H5OH(l) NaBr(aq)
Mechanism
* WARNING It is important to quote the solvent when answering questions.
Elimination takes place when ethanol is the solvent
The reaction (and the one with water) is known as HYDROLYSIS
CONVERSIONS

12. NUCLEOPHILIC SUBSTITUTION
AMMONIA
Reagent Aqueous, alcoholic ammonia (in EXCESS)
Conditions Reflux in aqueous, alcoholic solution under pressure
Product Amine
Nucleophile Ammonia (NH3)
Equation e.g. C2H5Br NH3 (aq / alc) ——> C2H5NH NH4Br
(i) C2H5Br NH3 (aq / alc) ——> C2H5NH HBr
(ii) HBr NH3 (aq / alc) ——> NH4Br
Mechanism
Notes The equation shows two ammonia molecules.
The second one ensures that a salt is not formed.
Excess ammonia is used to prevent further substitution (SEE NEXT SLIDE)
CONVERSIONS

13. NUCLEOPHILIC SUBSTITUTION
POTASSIUM CYANIDE
Reagent Aqueous, alcoholic potassium (or sodium) cyanide
Conditions Reflux in aqueous , alcoholic solution
Product Nitrile (cyanide)
Nucleophile cyanide ion (CN¯)
Equation e.g. C2H5Br KCN (aq/alc) ———> C2H5CN KBr(aq)
Mechanism
Importance it extends the carbon chain by one carbon atom
the CN group can then be converted to carboxylic acids or amines.
Hydrolysis C2H5CN H2O ——> C2H5COOH NH3 K
CONVERSIONS

14. ELIMINATION Reagent Alcoholic sodium (or potassium) hydroxide
Conditions Reflux in alcoholic solution
Product Alkene
Mechanism Elimination
Equation C3H7Br NaOH(alc) ———> C3H H2O NaBr
Mechanism
the OH¯ ion acts as a base and picks up a proton
the proton comes from a C atom next to the one bonded to the halogen
the electron pair moves to form a second bond between the carbon atoms
the halogen is displaced; overall there is ELIMINATION of HBr.
With unsymmetrical halogenoalkanes, a mixture of products may be formed.
CONVERSIONS

15. OXIDATION OF PRIMARY ALCOHOLS
Primary alcohols are easily oxidised to aldehydes
e.g. CH3CH2OH(l) [O] ———> CH3CHO(l) H2O(l)
it is essential to distil off the aldehyde before it gets oxidised to the acid
CH3CHO(l) [O] ———> CH3COOH(l)
OXIDATION TO
ALDEHYDES
DISTILLATION
OXIDATION TO
CARBOXYLIC ACIDS
REFLUX
Aldehyde has a lower boiling point so distils off before being oxidised further
Aldehyde condenses back into the mixture and gets oxidised to the acid
CONVERSIONS

16. OXIDATION OF ALDEHYDES
Aldehydes are easily oxidised to carboxylic acids
e.g. CH3CHO(l) [O] ———> CH3COOH(l)
one way to tell an aldehyde from a ketone is to see how it reacts to mild oxidation
ALDEHYES are EASILY OXIDISED
KETONES are RESISTANT TO MILD OXIDATION
TOLLENS’ REAGENT
Reagent ammoniacal silver nitrate solution
Observation a silver mirror is formed on the inside of the test tube
Products silver + carboxylic acid
Equation Ag e- ——> Ag
CONVERSIONS

17. OXIDATION OF SECONDARY ALCOHOLSP
OXIDATION OF SECONDARY ALCOHOLS
Secondary alcohols are easily oxidised to ketones
e.g CH3CHOHCH3(l) [O] ———> CH3COCH3(l) H2O(l)
The alcohol is refluxed with acidified K2Cr2O7. However, on prolonged treatment with a powerful oxidising agent they can be further oxidised to a mixture of acids with fewer carbon atoms than the original alcohol.
CONVERSIONS