All Organic

Topic Reference Reading from Solomons, Organic Chemistry 6th edition

Acid-Base Theory (Unit 1) 90-93, 96-101

Acid-Base Theory (Unit 2) 102-118, 320, 433-434, 795-796, 903-905, 970-972

Isomerism (Unit 1) 59-61

Isomerism (Unit 2) 178-185, 188, 193-198, 200

Nomenclature 41-47, 65-75, 128-137, 284-286, 288-289, 415-417, 615-617,

705-706, 792-793, 797-800, 899-900 Reaction Mechanism (Unit 1) - Introduction to Mechanism 87-90, 94-96

Reaction Mechanism (Unit 2) - Nucleophilic substitution 224-233, 238-252, 256-259 Reaction Mechanism (Unit 3) - Nucleophilic substitution 260

Reaction Mechanism (Unit 4) - Nucleophilic substitution 913-914 Reaction Mechanism (Unit 5) - Nucleophilic substitution 438-443

Reaction Mechanism (Unit 6) - Nucleophilic substitution 923-924, 926-927, 966

Reaction Mechanism (Unit 7) - Elimination 260-262, 265-268, 300, 302-305 Reaction Mechanism (Unit 8) - Elimination 308, 312, 318-319, 443-444 Reaction Mechanism (Unit 9) - Nucleophilic addition 719

Reaction Mechanism (Unit 10) - Nucleophilic addition 470-472, 716-719, 729-734, 759-761 Reaction Mechanism (Unit 11) - Nucleophilic addition 708-711

Reaction Mechanism (Unit 12) - Nucleophilic addition 805-817, 820-824 Reaction Mechanism (Unit 13) - Nucleophilic addition 919-921

Reaction Mechanism (Unit 14) - Nucleophilic addition 711, 825-827, 918 Reaction Mechanism (Unit 15) - Electrophilic addition 327-333

Reaction Mechanism (Unit 16) - Electrophilic addition 336-339, 346-351, 422-425 Reaction Mechanism (Unit 17) - Electrophilic substitution 617-618, 655-658

Reaction Mechanism (Unit 18) - Electrophilic substitution 658-664, 930-931, 974 Reaction Mechanism (Unit 19) - Electrophilic substitution 930-931, 974

Reaction Mechanism (Unit 20) - Radical reactions 334-335, 366-379, 393-397

Amino acids 1146-1148

Oxidation and Reduction 165-166, 473-475, 690-691, 915-916

Uses of compounds with different functional groups Structure determination (Unit 1)

Structure determination (Unit 2) 295-297

Structure determination (Unit 3) 359-360, 742

Structure determination (Unit 4) 541-547

Organic synthesis 169-171

Organic Laboratory Technique (Unit 1) Organic Laboratory Technique (Unit 2) Organic Laboratory Technique (Unit 3) Organic Laboratory Technique (Unit 4)

I. Alkanes

A. Cracking

very long alkane



heat catayst



,

→

long alkane + short alkene

B. Combustion

CxHy + (x + y_{4 ) O}2(g) → xCO2(g) + y_{2 H}2O(l)

C. Chlorination

Chain initiation (chain initiating step) +

Cl Cl

Cl Cl hυ Cl· radical is generated. Chain propagation (chain propagating step)

Cl H C H H H H Cl C H H H + Cl· radical is consumed. C H H H Cl Cl C H H H Cl Cl + Cl· radical is regenerated.

Chain termination (chain terminating step)

radical is destroyed. C C H H H H H H C H H H C H H H Cl C H H H C H H Cl H + Cl Cl Cl Cl +

Energy

II.

Alkenes and alkynes

A. Addition

reactions

1.

Reaction with bromine in CCl

4

C C R R R R Br2 R C C R R R Br Br + in dark in CCl4 _{1,2-dibromoalkane}

Note : Test for C=C or C≡C bond

2.

Reaction with bromine water

C C R R R R Br2(aq) R C C R R R Br OH + in dark halohydrin Note : Test for C=C or C≡C bond

3.

Reaction with hydrogen bromide

Br H C C C H H H H H H propene + C C C H H H H H H H Br 2-bromopropane C C C H H H H H H H Br 1-bromopropane major product minor product

Note : Follows Markownikov's orientation

4.

Reaction with conc. sulphuric(VI) acid

conc. H2SO4(l) C C R R R R C C R R R R H O S O O OH + alkyl hydrogensulphate(VI) Note : A reversible reaction

C C R R R R H O S O O OH H2O(l) R C C R R R H OH H2SO4(aq) + + alkyl hydrogensulphate(VI) alcohol Note : Laboratory preparation of alcohol

5.

Reaction with water

CH2 CH2+ H2O H_{300 ºC}3PO4 CH3 CH2 OH

ethane ethanol

Note : Industrial preparation of alcohol

6.

Catalytic hydrogenation of oil

B.

Ozonolysis of alkene

CH3CHCH CH2 CH3 CH3CH CH3 C O H + 3-methylbut-1-ene 2-methylpropanal (1) O3, CH2Cl2, -78 ºC (2) Zn / H2O H C H O methanal

Note : Can be used to determine the structure of the alkene with characterization of the derivatives of carbonyl compounds formed.

C.

Oxidation cleavage of double bond

propanone pentan-3-one + C CH3 O H3C CH3CH2 C CH2CH3 O 3-ethyl-2-methylpent-2-ene C C CH3CH2 CH3CH2 CH3 CH3 (1) KMnO4, OH-, hot (2) H+ 2-methylpropanoic acid 3-methylbut-1-ene + + CO2 H2O CH3CH CH3 C O OH CH3CHCH CH2 CH3 (1) KMnO4, OH-, hot (2) H+

Note : The outcomes are different from the ones from ozonolysis.

a)

Reaction with cold acidic or alkaline permanganate solution

C C H H H H C C H H H H O O H H cold KMnO4(aq)

H3O+ or OH -ethane ethane-1,2-diol

D.

Oxymercuration of alkyne

R C C H H H O keto-enol tautomerization Markovinkov orientation HgSO4(aq) H2SO4(aq) R C C H C R C H H O H terminal

E.

Polymerization of alkenes

Chain initiating step

2 R C O O O C O R R R C O O 2 Diacylperoxide + 2 CO2 alkyl radical heat

Chain propagating step

C C R H H H H R C C H H H H

long chain polymer etc. C C R H H H H C C H H H H R C C C C H H H H H H H H Chain terminating step

R (CH2 CH2)n C C H H H H R (CH2 CH2)n C C H H H H C C (CH2 CH2)n R H H H H C C (CH2 CH2)n R H H H H combination C C (CH2 CH2)n R H H H H R (CH2 CH2)n C C H H H H R (CH2 CH2)n C C H H H H C C (CH2 CH2)n R H H H H disproportionation

III. Aromatic

hydrocarbons

A.

Substitution reactions of benzene

1. Nitration

NO2 conc. HNO3(aq)

conc. H2SO4(l) 55°C

benzene

nitrobenzene

Note : No reaction if conc. H2SO4(l) is not added.

2. Halogenation

X X2 FeX3 or AlX3 benzene halobenzene

3. Sulphonation

benzene S O O O H conc. H2SO4 heat benzenesulphonic acid benzenesulphonic acid OH S O O O H O-Na+ NaOH(s) 350°C H3O+ phenol sodium phenoxide / sodium phenolate Note : Industrial preparation of phenol

4. Alkylation

benzene R RX and AlX3 alkylbenzene

B.

Oxidation of alkylbenzene

alkylbenzene R _{C OH} O 1) KMnO4, OH-, heat 2) H3O+ benzenecarboxylic acid

IV. Halogeno-compounds

A. Nucleophilic

substitution

1.

Reaction with sodium hydroxide

R OH R X haloalkane NaOH(aq) alcohol NaOH(aq) heat X OH halobenzene phenol

Note : Prolonged heating is required for the alkaline hydrolysis of halobenzene.

2.

Reaction with potassium cyanide

R X haloalkane

KCN(aq)

R CN nitrile

3.

Reaction with ammonia

R X haloalkane N H H H ammonia + H N H R + HX 1° amine R X haloalkane N H R H 1° amine + R N H R + HX 2° amine R X haloalkane N R R H 2° amine + R N R R + HX 3° amine R X haloalkane N R R R 3° amine + R N R R R X -quaternary ammonium halide Note : A mixture of products would be obtained.

4.

Reaction with alkoxide

R X haloalkane + R' O-Na+ sodium alkoxide R O R' ether

5.

Reaction with carboxylate ion

R X haloalkane + sodium carboxylate R' C O O-Na+ R' C O O R ester

B. Elimination

reaction

1.

Reaction with alcoholic sodium hydroxide to form alkene

NaOH(alc.) _{R C C} R R R C C R R R R X H haloalkane alkene

2.

Reaction with alcoholic sodium hydroxide to form alkyne

C C R H H R X X boiling NaOH(alc.) R C C R 1,2-dihaloalkane alkyne

V. Hydroxy

compounds

A.

Reactions of alcohols

1.

Formation of halide

a)

by halogenating agent

R OH R Cl chloroalkane alcohol PCl5 / PCl3 / SOCl2

b)

by heating with halide salt in acidic medium

R OH R X haloalkane alcohol Na+_X-_{, conc. H} 2SO4(l) heat

2.

Formation of alkoxide

2 C2H5OH(l) + 2 Na(s) → 2 C2H5O-Na+(alc.) + H2(g C2H5OH(l) + NaOH(s) d C2H5O-Na+(alc.) + H2O(l)

3.

Oxidation of alcohols

aldehyde carboxylic acid 1° alcohol R C O O H [O] [O] R C O H R C O H H H ketone 2?alcohol [O] R C O R R C O H H R 3?alcohol [O] R C O H R R Resistant to oxidation

4.

Dehydration of alcohols

C C O H H H H H H C C H H H H conc. H2SO4 heat ethanol ethene

5. Esterification

R OH + R' C O OH R' C O O R ester H2O + conc. H2SO4(l) heat alcohol carboxylic acid

6. Triiodomethane

formation

C C H H H O H H R alcohol with 1-hydroxyethyl group NaOH(aq) + I2(aq) R C O O -C I I I H carboxylate ion iodoform (yellow ppt.) +

Note : 1. Test for the presence of 1-hydroxyethyl group. 2. Shorten the carbon chain by 1 C.

Details : oxidation methyl ketone 2 H2O 2 I -2 OH -I2 + + + + C C H H H R O C C H H H O H H R alcohol with 1-hydroxyethyl group methyl ketone C C O H H H R R C O O -C I I I H carboxylate

ion iodoform(yellow ppt.) NaOH(aq) + I2(aq)

+

7.

Distinction between primary, secondary and tertiary alcohols

a)

With potassium dichromate(VI)

aldehyde carboxylic acid 1° alcohol R C O O H [O] [O] R C O H R C O H H H ketone 2?alcohol [O] R C O R R C O H H R 3?alcohol [O] R C O H R R Resistant to oxidation

b) Lucas'

test

C R OH H H conc. HCl(aq) ZnCl2(aq) no reaction 1° alcohol C R OH H R conc. HCl(aq) ZnCl2(aq) R C Cl H R 2° alcohol slow reaction C R OH R R conc. HCl(aq) ZnCl2(aq) R C Cl R R 3° alcohol fast reaction

B.

Reactions of phenol

1.

Reaction with sodium

OH O-Na+

+ H2 Na

phenol sodium phenoxide_{/ sodium phenolate}

2.

Reaction with sodium hydroxide

OH O-Na+ + H2O NaOH(aq) sodium phenoxide / sodium phenolate phenol

Note : Phenol is soluble in sodium hydroxide solution.

3. Esterification

OH O_{C O R} phenol R C O Cl R C O O C O R or ester

4.

Reaction with bromine

OH Br Br Br Br2(aq) OH

phenol 2,4,6-tribromophenol _{(a white ppt.)} Note : A test for phenol.

VI. Carbonyl

compounds

A. Nucleophilic

addition

1.

Reaction with hydrogen cyanide

R C R O HCN + R C R O H C N

2.

Reaction with sodium hydrogensulphate(IV)

C O R CH3/H + Na+HSO3- C R CH3/H O H SO3-Na+ white precipitate

Note: 1. Sensitive to steric hinderance and reacts with aldehyde and methyl ketone only. 2. Can be used to purify aldehyde or methyl ketone.

B. Addition-elimination

(condensation)

1.

Reaction with hydroxylamine

R C R O +H N H OH hydroxylamine C R R N OH + H2O oxime (white ppt.) Note : 1. A test for aldehyde or ketone.

2. Identify the carbonyl compound by characterization.

2.

Reaction with 2,4-dinitrophenylhydrazine

+ 2,4-dinitrophenylhydrazine NO2 O2N N N H C R R 2,4-dinitrophenylhydrazone (orange ppt.) + H2O NO2 O2N N N H H H C R R O

Note : 1. Test for aldehyde or ketone but no reaction with carboxylic acid and its derivatives 2. Identify the carbonyl compound by characterization.

3. Triiodomethane

formation

methyl ketone C C O H H H R R C O O -C I I I H carboxylate

ion iodoform(yellow ppt.) NaOH(aq) + I2(aq)

+

Note : 1. Test for methyl ketone.

C.

Oxidation and reduction

1.

Oxidation of aldehyde with potassium dichromate(VI)

R C O

H R C

O OH aldehyde carboxylic acid

[O]

Note : Orange acidified potassium dichromate will turn to green chromium(III) ion.

2.

Oxidation of aldehyde with Tollens' reagent

aldehyde ammonium carboxylate R C O H R C O O-NH4+ + [Ag(NH3)2]OH(aq) Tollen's reagent Ag(s) silver mirror Note : Test for aldehyde

3.

Oxidaton of aldehyde with Fehling's reagent

aldehyde carboxylate ion R C O H R C O O- + Cu2O brick red ppt. Fehling's reagent

Note : Test for aldehyde

4.

Resistance of ketones to oxidation

R C O

R [O] no reaction

Note : Ketone is stable to general oxidation.

5.

Reduction with sodium tetrahydridoborate / lithium tetrahydrioaluminate

R C R/H O + R C R/H O H H NaBH4(aq) R C R/H O -H H3O+ aldehyde

or ketone alkoxide alcohol

R C R/H O + R C R/H O H H R C R/H O -H H3O+ aldehyde

or ketone alkoxide alcohol

LiAlH4(ether)

Note : LiAlH4 cannot be used in aqueous medium.

6. Haloform

reaction

methyl ketone C C O H H H R R C O O -C I I I H carboxylate

ion iodoform(yellow ppt.) NaOH(aq) + I2(aq)

+

Note : 1. Test for methyl ketone.

VII. Carboxylic acids and their derivatives

A.

Formation of carboxylic acid

1.

Hydrolysis of nitrile

R C N R C O OH dil. H2SO4(aq) reflux

nitrile carboxylic acid Note : Complete hydrolysis of nitrile

2.

Oxidation of alcohol

aldehyde carboxylic acid 1° alcohol R C O O H [O] [O] R C O H R C O H H H

Note : Aldehyde intermediate can be separated from the reacting mixture by distillation.

3.

Oxidation of aldehyde

R C O H R C O OH aldehyde carboxylic acid

[O]

4.

Oxidation of alkylbenzene

alkylbenzene R _{C OH} O 1) KMnO4, OH-, heat 2) H3O+ benzenecarboxylic acid

B.

Reactions of carboxylic acid

1.

Formation of salt

R C O OH NaOH(aq) carboxylic acid R C O O-Na+ sodium carboxylate

2.

Formation of acyl chloride

C OH O R C Cl O R chloroalkane alcohol PCl5 / PCl3 / SOCl2

3.

Formation of anhydride

O H H O O C C H H C C OH OH O O 140°C + H2O

cis-butenedioic acid butenedioic_anhydride Note : Intramolecular dehydration

ethanoic acid ethanoic acid ethanoic anhydride C O CH3 OH C O CH3 HO C O C O O CH3 CH3 + P2O5 (P4O10) Note : Intermolecular dehydration

C O CH3 O-Na+ C O CH3 Cl C O C O O CH3 CH3 + + NaCl

4.

Formation of ester

R X haloalkane + sodium carboxylate R' C O O-Na+ R' C O O R ester R C O Cl + R OH R C O O R acyl

chloride alcohol ester

R C O O C O R + R OH R C O O R acid

anhydride alcohol ester

R C O OH + R OH H3O+ heat R C O O R carboxylic

acid alcohol ester

5.

Formation of amide

R C O

NH2 amide R C N cold dil. H2SO4(aq)

or hot conc. H2SO4(l) nitrile

Note : Partial hydrolysis of nitrile.

6.

Reduction with lithium tetrahydridoaluminate

R C O OH carboxylic acid R C OH H H 1° alcohol (1) LiAlH4(ether) (2) H3O+

C.

Reactions of acyl chlorides and anhydrides

1.

Reaction with water

R C O Cl acyl chloride R C O OH + HCl H2O(l) carboxylic acid R C O O C O R' acid anhydride H2O(l) R C O OH + R' C O OH carboxylic acid

2.

Reaction with alcohol

R C O Cl acyl chloride R C O OR + HCl ROH ester R C O O C O R' acid anhydride ROH R C O OR + R' C O OH ester

3.

Reaction with ammonia

R C O Cl acyl chloride R C O NH2 conc. NH3(aq) amide R C O O C O R' acid anhydride R C O NH2 conc. NH3(aq) amide

4.

Reaction with amine

R C O Cl acyl chloride R C O NH R N-substituted amide RNH2 R C O O C O R' acid anhydride R C O NH R N-substituted amide RNH2

D.

Reactions of ester

1.

Acid and base-catalysed hydrolyses

R OH + H3O+ heat R C O O R alcohol ester R C O OH carboxylic acid R OH + R C O O R alcohol ester R C O O -carboxylate ion NaOH(aq) heat

Note : Rate of hydrolysis : alkaline medium > acidic medium > neutral medium

2.

Reduction with lithium tetrahydridoaluminate

R C O O R ester R C OH H H 1° alcohol (1) LiAlH4(ether) (2) H3O+

E.

Reactions of amide

1.

Hydrolysis of amide

R C O OH R C O NH2 H3O+ reflux

amide carboxylic acid R C O NH2 R C O O -OH- reflux

amide carboxylate ion

2.

Dehydration of amide

R C NH2

O P2O5 or (CH3CO)2O

or SOCl2 R C N

3.

Hofmann degradation of non-substituted amide

Br2 / NaOH(aq) N H H R 1?amine with 1 C less amide R C NH2 O

Note : Only applicable to non-substituted amide.

4.

Reduction with lithium tetrahydridoaluminate

1° amine amide 1) LiAlH4 / ether 2) H3O+ R C H H N H H R C NH2 O

VIII. Nitrogen compounds

A.

Formation of amine

1. From

nitrile

R C N R C N H H H H (1) LiAlH4(ether) (2) H3O+ nitrile 1° amine

Note : LiAlH4 could not be used in aqueous medium.

2. From

amide

1° amine amide 1) LiAlH4 / ether 2) H3O+ R C H H N H H R C NH2 O

Note : Amide is the only acid derivative which will not be reduced to alcohol.

3.

1º, 2º, 3º amines and quaternary ammonium compounds by alkylation

R X haloalkane N H H H ammonia + H N H R + HX 1° amine R X haloalkane N H R H 1° amine + R N H R + HX 2° amine R X haloalkane N R R H 2° amine + R N R R + HX 3° amine R X haloalkane N R R R 3° amine + R N R R R X -quaternary ammonium halide Note : A mixture of products would be obtained.

4.

Phenylamine from nitrobenzene

NO2 NH2

1) Sn, conc. HCl(aq) 2) OH-_(aq)

B.

Base properties of amine

1. Salt

formation

R N H H + HCl R N H H H Cl

-C.

Reactions of amine

1.

Reactions with ethanoyl chloride and benzoyl chloride

R N H H + CH3 C O Cl CH3 C O N R H amine ethanoyl

chloride N-substituted ethanamide

C O Cl R N H H + C O N H R N-subsituted benzenecarboxamide benzoyl chloride amine

2.

Reaction with nitric(III) acid

R N H H R+ + N2 carbocation nitrogen bubbles aliphatic primary amine HNO2 0-5°C NH2 HNO2 0-5°C N N+ aromatic primary amine benzenediazonium ion

Note : A test used to distinguish aliphatic primary amine from aromatic primary amine.

3.

Coupling reaction of benzenediazonium ion with naphthalen-2-ol and phenol

benzenediazonium ion N N HO OH N N+ red orange ppt. naphthalen-2-ol N N OH OH N N+ phenol orange ppt. benzenediazonium ion

IX. Other

reactions

Radical addtion of X2 to benzene

X X X X X X H H H H H H X2 uv

Reactions of benzenediazonium ion

CuCN

CN N N+

H3PO2 N N+

Preparation of vinyl chloride C C H H H H C C H H H H Cl Cl C C H H Cl H Cl2 Electrophilic addition alcoholic NaOH Anti-Markownikov's addition Cl H C C C H H H H H H propene + C C C H H H H H H H Cl 2-chloropropane C C C H H H H H H H Cl 1-chloropropane + R O O R alkyl peroxide minor product major product

Test for terminal alkyne R–C≡CHCu NH R–C≡C( 3 2)+→ -Cu+

(s) (red ppt.)

R–C≡CHAg NH R–C≡C( 3 2)+→ -Ag+

(s) (white ppt.) Test for phenol

[Fe(H2O)6]3+(aq) + 2C6H5O-(aq) → [Fe(H2O)4(C6H5O)2]+(aq) + 2H2O(l)

from neutral from phenol purple complex iron(III) chloride

Nomenclature of Organic compounds

I.

Nomenclature of organic compounds

A.

Labelling of carbon

1.

Methyl, primary, secondary and tertiary carbon

2.

α carbon, β carbon and γ carbon

B.

Skeletal formula / Stick formula

II.

Nomenclature of hydrocarbon

A.

Alkyl and aryl group

III.

Other functional group

A. Halogeno-compounds

B.

Alkanols and phenol

C.

Aldehydes and ketones

D. Carboxylic

acids

1.

Carboxylic acid derivatives – esters, acid chlorides, anhydrides and amides

E. Nitriles

F. Amines

G. Amino-acids

H. Ethers

IV. Priority of functional groups

V. Examples

Acid-Base Theory

I.

Definition of acid-base

A. Arrhenius

definition

B. Bronsted-Lowry

definition

C. Lewis

definition

II.

Strength of acid and base

A. Leveling

effect

III.

Factors determining the strength of a Bronsted-Lowry acid

A.

Relative stability of the conjugate base comparing with the acid

1. Inductive

effect

(1) Amine vs Amide

2. Resonance

effect

a)

Resonance effect on a benzene ring

(1) Phenol

(2) Aromatic amine

3.

Intramolecular hydrogen bond

4.

Solvation / hinderance to solvation

a)

Steric hinderance to solvation

b)

Effect of solvent

5.

Strength of the bond between the proton and the conjugate base

6.

Electronegativity of the atom

Isomerism

I. Structural

isomerism

A. Chain

isomerism

B. Position

isomerism

C.

Functional group isomerism

D.

Tautomerism / Tautomerization

II. Stereoisomerism

A.

Diastereomerism / Geometrical isomerism

1.

Physical properties of cis-/trans-geometrical isomers of 1,2-dichloroethene

2.

Physical and chemical properties of cis-/trans-geometric isomers of butenedioic

acid

a) Physical

properties

b) Chemical

properties

B.

Optical isomerism / Enantiomerism

1. Physical

properties

2. Optical

activity

a)

Plane polarized light

b)

Measurement of optical activity by polarimeter

c) Specific

rotation

3. Chiral

centre

Reaction Mechanism

I. Bond

breaking

A.

Bond breaking of a bond to carbon

II.

Types of reactive species

A.

Free radical (electron deficiency)

B.

Electrophile (electron deficiency)

C.

Nucleophile (electron rich)

III.

Classification of reaction

A.

Types of reaction

1. Substitution

2. Addition

3. Elimination

IV. Nucleophilic

substitution

A. Nucleophilic

substitution

1. Nucleophile

2. Leaving

group

B. S

N

2 reaction (1 step reaction)

C. S

N

1 reaction (2 steps reaction)

D.

Competition between S

N

1 and S

N

2 reactions

E.

Alkanol from haloalkane (RX

→

ROH)

1.

Alkaline hydrolysis of haloalkane

2.

Hydrolysis of haloalkane

F.

Rate of hydrolysis of haloalkane, haloalkene and halobenzene

G.

Other relevant reactions

1.

Reactions of haloalkane

a)

Nitrile from haloalkane (RX

→

RCN)

b)

Alkylation of ammonia and amine (NH

3

→

RNH

2

)

c)

Use of S

N

2 reaction in organic synthesis

2.

Reactions of alkanol

a)

Haloalkane from alkanol (ROH

→

RX)

(1) Use of chlorinating and brominating reagent

b)

Luca's test to distinguish 1º, 2º and 3º alkanol

3.

Reactions of amine

a)

Action of nitric(III) acid on 1º amine

(1) 1º aliphatic amine (2) 1º aromatic amine

b)

Laboratory preparation of phenol from benzenamine

V. Elimination

reaction

A. Elimination

reaction

1.

Stability of elimination product

2.

E2 reaction (not required in A-Level)

3.

E1 reaction (not required in A-Level)

B.

Competition between substitution and elimination reaction

1.

Effect of temperature

2.

Effect of bulkiness of the substrate and base

3.

Effect of bascity of the nucleophile

C.

Conditions favouring substitution and elimination reaction

D.

Other relevant reactions

1.

Reaction of haloalkanes with alcoholic sodium hydroxide to alkene, diene and

alkyne

2.

Preparation of vinyl chloride

3.

Dehydration of alkanol

VI. Nucleophilic addition (Nucleophilic addition-elimination)

A. Ad

N

reaction

1.

Addition of HCN to carbonyl compound

2.

Rate of nucleophilic addition

a) Electronic

effect

(1) Inductive effect

(a) Effect of protonation (2) Resonance effect

b) Steric

effect

3.

Other relevant reactions

a)

Reactions of carbonyl group

(1) Reduction of carbonyl compound by LiAlH4 and NaBH4

(2) Addition of NaHSO3 to carbonyl compound

(3) Condensation reaction with hydroxylamine

(4) Condensation reaction with 2,4-dinitrophenylhydrazine (5) Haloform reaction / Iodoform reaction

b)

Reactions of carboxylic acid and its derivatives

(1) Carboxylic acid and its derivatives

(a) Difference between carbonyl compound and carboxylic acid and its derivatives

(b) Reactivities of carboxylic acid and its derivatives (2) Formation of different acid derivatives

(a) Use of chlorinating agent to prepare acyl chloride

(b) Formation of ester (Esterification with alkanol and phenol) (c) Formation of acid anhydride

(i) Through intramolecular dehydration by heating (ii) Through intermolecular dehydration by a very strong

dehydrating agent (iii) From acyl chloride

(d) Formation of amide (Acylation and benzoylation of amine) (3) Reaction of ester

(a) Hydrolysis of ester (4) Reaction of amide

(a) Reduction of amide and other acid derivatives (b) Hofmann degradation of amide

c)

Reactions of nitrile

(1) Hydrolysis of nitrile and amide (a) Dehydration of amide (2) Reduction of nitrile

VII. Electrophilic

addition

A.

Addition of HBr to alkene

1. Markownikoff's

rule.

2.

Reactivity of alkene towards electrophilic addition

B.

Other relevant reaction

1.

Addition of Br

2

to alkene

2.

Addition of H

2

SO

4

to alkene

a)

Preparation of alkanol from alkene

3.

Hydration of alkene

4.

Ozonolysis of alkene

5.

Preparation of ethane-1,2-diol

a)

Oxidative Cleavage of double bond

b)

Comparision of ozonolysis and oxidative cleavage

VIII. Electrophilic substitution

A.

Representation of arenium ion

B.

Other relevant reaction

1.

Sulphonation of benzene

a)

Preparation of phenol

2.

Nitration of benzene

a)

Reduction of nitrobenzene

3.

Halogenation of benzene

4.

Alkylation of benzene (Friedel-Crafts alkylation)

5.

Diazocoupling of diazonium ion

a)

Colour of a substance

6.

Bromination of phenol

IX. Free radical Reaction

A.

Formation of free radical

B.

Free radical Substitution

1.

Chain reaction e.g. chlorination of methane

a)

Chain initiation (chain initiating step)

b)

Chain propagation (chain propagating step)

c)

Chain termination (chain terminating step)

2.

Reaction between H

2(g)

and Cl

2(g)

C.

Free radical Addition

1.

Chain reaction e.g. Polymerization of alkene

2. Anti-Markownikoff

orientation

Amino acids

I. Amino

acids

A. Zwitterion

B. Polypeptides

Oxidation and Reduction

I. Oxidation

A.

Combustion of alkane

B.

Oxidation of alkanol and aldehyde

C.

Oxidation of aromatic side chain

II. Reduction

A.

Reduction of nitrobenzene

Uses of Different Compounds

I.

Uses of halogeno-compounds

A.

Use as solvent

B.

Manufacture of polymer

1.

Preparation of vinyl chloride

2.

Physical properties of PVC and Teflon

II.

Uses of alcohols

A.

Use as solvent

B. Alcoholic

drink

C. Blending

agent

D. Ethan-1,2-diol

III.

Uses of carbonyl compounds

A.

Preparation of urea-methanal

B.

Use of propanone

IV. Uses of carboxylic acids and their derivatives

A. Food

preservatives

B.

Manufacture of nylon and terylene

C.

Use of ester

V.

Uses of amines and their derivatives

A.

Azo compounds as dyes in dyeing industries

B.

Amine derivatives as drugs

Determination of Structure

I.

Determination of empirical formula and molecular formula

A.

Different kinds of formula

B.

Determination of empirical formula

C.

Determination of molecular formula

II.

Degree of unsaturation

A.

Determination of degree of unsaturation

B.

Meaning of degree of unsaturation

III.

Sodium fusion test

IV. Test for different functional groups by wet chemistry

V.

Introduction to IR and NMR spectroscopy

A.

Use of infra-red (IR) spectrum in the identification of functional groups

Organic synthesis

I. Retrosynthetic

analysis

II. Structural

analysis

A. Chain

length

1. Carbon

chain

2.

Nitrogen and Oxygen containing chain

B.

Degree of unsaturation

C.

Oxidation or Reduction

D.

Position of functional group

III.

Systematic approach to organic synthesis

IV. Examples

Organic Laboratory Technique

I.

Purification of organic compound

A. Solvent

extraction

B. Steam

distillation

C. Chromatography

D. Recrystallization

E.

Filtration and Suction filtration

II.

Use of quickfit apparatus

A.

Handling of quickfit apparatus

B.

Different setup of quickfit apparatus

1. Reflux

setup

2. Distillation

setup

III.

Testing for purity

A.

Determination of melting point

B.

Determination of boiling point

Nomenclature of Organic compounds

I.

Nomenclature of organic compounds

A.

Labelling of carbon

1.

Methyl, primary, secondary and tertiary carbon

2.

α carbon, β carbon and γ carbon

B.

Skeletal formula / Stick formula

II.

Nomenclature of hydrocarbon

A.

Alkyl and aryl group

III.

Other functional group

A. Halogeno-compounds

B.

Alkanols and phenol

C.

Aldehydes and ketones

D. Carboxylic

acids

1.

Carboxylic acid derivatives – esters, acid chlorides, anhydrides and amides

E. Nitriles

F. Amines

G. Amino-acids

H. Ethers

IV. Priority of functional groups

V. Examples

Topic

Nomenclature of organic compounds

Unit 1

Reference

Reading

13

Organic Chemistry, Fillans, 3rd _{Edition pg. 50–65}

Guidelines for systematic chemical nomenclature, HK Exam. Authority pg. 7–17 Chemical nomenclature, symbols and terminology for use in school science. pg. 58–65

Assignment

Reading

Chemistry in Context, 5th Edition, Thomas Nelson and Sons Ltd., pg. 380–381, 400–401, 414, 428, 432, 438, 439, 446, 453, 467, 484, 498, 516–517

Organic Chemistry, 6th Edition, Solomons, pg. 41-47, 65-75, 128-137, 284-286, 288-289, 415-417, 615-617, 705-706, 792-793, 797-800, 899-900

Syllabus

Nomenclature of organic compounds Classification of hydrocarbons

Priority of functional group in IUPAC naming

Notes

I. Nomenclature of organic compounds

The basic idea of the IUPAC (International Union of Pure and Applied Chemistry) system of naming is that by following some rules, a name can be assigned to a molecule. And from the assigned name, the original molecule can be reconstructed unambiguously.

A given structure may have several different names but a name will only give 1 structure.

For example, the structure is called C C C C H H H O H H H H H H

H is called butan-1-ol or 1-butanol but no matter

butan-1-ol or 1-butanol refer to the same structure.

IUPAC system of naming is a kind of substitutive nomenclature. In substitutive nomenclature, hydrogen atoms in a named 'parent' hydrocarbons are considered to be substituted by other groups.

Actually, the IUPAC system of naming is not very strict. It is possible to have more than 1 name for a given molecule. But no matter which name is assigned, only 1 structure can be rebuilt.

A. Labelling of carbon

To facilitate discussion, carbon atoms on a carbon chain can be labelled by 2 different methods.

1. Methyl, primary, secondary and tertiary carbon

The first way is based on the no. of carbon atoms attached to the carbon to be concerned. If no other carbon is attached to the carbon, the carbon atom is called a methyl carbon.

If 1 carbon atom is attached to the carbon, the carbon atom is called a primary carbon, 1º carbon If 2 carbon atoms are attached to the carbon, the carbon atom is called a secondary carbon, 2º carbon If 3 carbon atoms are attached to the carbon, the carbon atom is called a tertiary carbon, 3º carbon

C H H H X methyl carbon C CH3 H H X 1° carbon C CH3 CH3 H X 2° carbon C CH3 CH3 CH3 X 3° carbon

2. α carbon, β carbon and γ carbon

Another way is according to the position of the carbon relative to a substituent (functional group). If the carbon is immediately next to the substituent, it is called a α carbon.

The carbon attached to the α carbon is called a β carbon. The carbon attached to the β carbon is called a γ carbon.

α C β C γ C C C C C O carbonyl carbon C C C X γ C β C α C

B. Skeletal formula / Stick formula / Bond line formula

In order to make the presentation simple, sometimes skeletal formula is used instead of the full structural formula or condensed structural formula. In the skeletal formula, all atomic symbols of carbon and hydrogen are omitted.

Full structural

formula structural formula Condensed

Skeletal formula / Stick formula / Bond line formula

Full structural

formula structural formula Condensed

Skeletal formula / Stick formula / Bond line formula

C C

H

H

H

H

H

H

CH

3

CH

3

CH

3

CH

3

H

3

C CH

3

C

C C

C

H

H

H

H

H

H

CH

2

CH

2

CH

CH

C C H H H H H C H H H

CH

₃

CH

₂

CH

₃

C

C

C

C

C

C

H

H

H

H

H

H

C C H H H H C H H H C H H H CH3CHCH3 CH3 CH3CH(CH3)CH3

C

C

C

C

C

C

H H

H

H

H

H

H

H

H

H

H

H

C

C

C

C

H

H

H

H

H

H

H

H

CH

₂

CH

₂

CH

₂

CH

₂ H C C C C H H H H H H H H O H CH3CH2CH(OH)CH3

OH

H C C C H H H H H

CH

3

CHCH

2

CH

3

CH CH

2 C O O C C H H H H H C H H H CH3COOCH2CH3

O

O

H C C C C H H H H H H H

CH

₃

C(CH

₂

)CH

₃

II. Nomenclature of Hydrocarbon Some examples C C C C H H H O H H H H H H

H is called butan-1-ol (or 1-butanol). (a primary alcohol)

C CH3 H3C

H

CH2 CH3 is called 2-methylbutane (or isopentane). iso- means 1 C is attached to the next-to-end C.

C CH3 H3C CH2 CH3

CH3

is called 2,2-dimethylbutane (or tert-butylethane).

C CH3

H3C

CH3

is called the tert-butyl group.

CH2 CH2 CH CH CH2 CH2 CH3 CH3 CH3 H3C

is called 4-(1-methylethyl)heptane (or 4-isopropylheptane).

CH3 NH2is called methanamine (or methylamine).

C H O

benzenecarbaldehyde (or benzaldehyde)

C O

The basis of IUPAC substitutive nomenclature is that every name consists of a root, one suffix and as many prefixes as necessary.

prefix - root - suffix

Root represents the longest carbon chain containing the principal functional group as indicated by the suffix and also it should contain the largest no. of substituent.

Suffix represents the functional group with the highest priority among all the functional groups present. Prefix represents other functional group and arranged in alphabetical order.

e.g. CH3 CH CH2 CH2 OH NH2 Cl 3-amino-2-chlorobutan-1-ol 3-amino is a prefix 2-chloro is a prefix butan- is a root -ol is a suffix

The numbers are called locants used to indicate the position of the functional group. The numbers are arranged to give

(a) the lowest possible number to the group cited by a suffix (principal functional group), then (b) the lowest possible individual numbers (not sum) to those cited as prefixes.

CH3 CH2 CH CH CH2 CH2 CH2 CH2 CH CH3 CH3 CH3 CH3

2,7,8-trimethyldecane (not 3,4,9-trimethyldecane)

N.B. hyphen (-) is used to separate number from letter. comma (,) is used to separate number from number. Name of the first 10 straight chain hydrocarbons

1. methane (meth-) 2. ethane (eth-) 3. propane (prop-) 4. butane (but-) 5. pentane (penta-) 6. hexane (hex-/hexa-) 7. heptane (hept-/hepta-) 8. octane (oct-/octa-) 9. nonane (nona-) 10. decane (dec-/deca-)

For the parent chain containing double bond or triple bond, suffixes -ene and -yne are used respectively. C C ethene C C ethyne C C Cpropyne C C C Cbut-1-ene C C C C but-2-yne C C C C C C C hepta-1,3-diene

If the chain contains both double bond and triple bond, the name will be ended with -yne. C C C C C pent-3-en-1-yne C C C C C _{pent-1-en-3-yne}

C C C C C C _{hex-3-ene-1,5-diyne}

N.B. -e- is omitted if it is followed by a vowel e.g. y, a, o.

If both double bond and triple bond has the same lowest possible number, double bond will be given a higher priority.

C C C C C pent-1-en-4-yne C C C C C C _{hexa-1,3-dien-5-yne}

Classification of hydrocarbons

cyclohexane Alicyclic (Cyclic)

Aliphatic (Acyclic) _Aromatic

benzene Alkyne CH CH ethyne Alkene CH2 CH2 ethene Alkane CH3 CH3 ethane Hydrocarbons (Arene)

Aliphatic (Acyclic) : Hydrocarbon with no ring structure. It can be further classified into straight chain and branched hydrocarbon.

Alicyclic (Cyclic) : Hydrocarbon with ring structure.

Aromatic : A special kind of ring compound with extra stability due to delocalization of electrons.

Benzene and naphthalene are aromatic. Originally, 'aromatic' means having a sweet smell since the firstly discovered aromatic compounds possess special smell.

A. Alkyl, vinyl, allyl and aryl group

When a hydrogen is removed from an alkane, the structure is called an alkyl group R–. It is cited by adding -yl. C

H H

H

methyl group

When a hydrogen is removed from an alkene, the structure is called a vinyl group. It is cited by adding -enyl. C H H C H C H H prop-2-enyl group

When a hydrogen is removed from an alkyne, the structure is called an allyl group. It is cited by adding -ynyl. C

H

H C C

H

prop-1-ynyl group

N.B. The carbons are counted from the point joining to the main chain.

When a hydrogen is removed from a benzene, the structure is called a phenyl group Ph– or . phenyl group

However if a phenyl group is attached to a –CH2–, it is called the benzyl group. CH2 benzyl group

Phenyl group and other substituted phenyl group (e.g. chlorophenyl group) are collectively called aryl group Ar–. NH2 phenylamine (or more accurate benzenamine).

III. Other functional group A. Halogeno-compounds

The presence of halogen (–X) is always cited by the prefixes (fluoro-), (chloro-), (bromo-) and (iodo-). C Cl H H H chloromethane C C Br Br H H H H 1,2-dibromoethane

B. Alkanols and phenol

The presence of hydroxyl group (–OH) is cited by suffix (-ol) or prefix (hydroxy-) C C OH H H H H H _ethanol C C H H H H OH OH ethane-1,2-diol C C O OH HO H H hydroxyethanoic acid

N.B. (-e-) of the root is omitted if it is followed by an vowel e.g. -o- or -y-.

When a hydrogen on the benzene is substituted by a hydroxyl group, the compound is called phenol. OH _phenol O2N OH4-nitrophenol

C. Aldehydes (Alkanals) and ketones (alkanones) Aldehyde (Alkanal) contains a terminal carbonyl group C

O

. It has the general formula R C O

H.

It is cited by suffix (-al) or prefix (oxo-). CH3 C O H _ethanal C C O H O OH oxoethanoic acid Ketone contains a non-terminal carbonyl group C

O

. It has the general formula R C R O

It is cited by suffix (-one) or prefix (oxo-) if the C is counted in the root or prefix (carbonyl-) if the C is not counted in the root.

CH3 C O CH2 CH2 CH3pentan-2-one CH3 C O CH2 C O OH_{3-oxobutanoic acid}

D. Carboxylic acids (Alkanoic acid) Carboxylic acid contains a carboxyl group C

O

OH. It is cited by suffix (-oic acid) or (-carboxylic acid) or by

prefix (carboxy-). C O OH CH3 ethanoic acid C O OH CH2 C O HO _{propanedioic acid.} C O

OH _{benzenecarboxylic acid (common name : benzoic acid)}

HO C O C H H N+ H H H Cl-_{(carboxymethyl)ammonium chloride}

N.B. 1. locant is not necessary for dioic acid since the carboxyl groups must occupy the ends of the C chain. 2. When suffix (-carboxylic acid) or prefix (carboxy-) is used, the C in the carboxyl group is not

1. Carboxylic acid derivatives – esters, acid chlorides, anhydrides and amides Esters, acid chlorides, anhydrides and amides are all derivatives of carboxylic acid. The derivative is formed by replacing –OH hydroxyl group with other functional groups.

–OH replaced by General formula Example Carboxylic acid C O R OH C O OH CH3 ethanoic acid Ester –OR C O R O R' C O O CH3 CH2CH2CH3 propyl ethanoate Acid chloride (acyl chloride) –Cl C O R Cl C O Cl CH3 ethanoyl chloride Anhydride (formed by dehydration of alkanoic acid) –OOCR C O R O C O R' C O O C O CH3 CH3 ethanoic anhydride C O O C O CH3 CH2CH2CH3

butanoic ethanoic anhydride

Amide –NH2 C O R NH2 C O NH2 CH3 ethanamide R C O

is called the acyl group. e.g. C O

CH3 ethanoyl group.

E. Nitriles

Nitrile contains cyano group –C≡N. It is cited by suffix (-nitrile) or (-carbonitrile) for cyclic nitrile or by prefix (cyano-) C N CH3 ethanenitrile C N benzenecarbonitrile C N _{cyclohexanecarbonitrile} C C C OH O H H N _{cyanoethanoic acid}

N.B. When suffix (-carbonitrile) or prefix (cyano-) is used, the C in the cyano group is not counted as a part of the parent chain.

F. Amines

Amine contains amino group –NH2. Amine is alkyl or aryl derivative of ammonia, with the hydrogen replaced by

alkyl group or aryl group. It is cited by suffix (-amine) or prefix (amino-).

CH3 NH2methanamine (methylamine) CH3 CH CH2 NH2 CH3 2-methylpropan-1-amine CH3 N CH2CH3 H N-methylethanamine (ethylmethylamine) CH3 N CH2CH3 CH2CH2CH3 N-ethyl-N-methylpropan-1-amine (ethylmethylpropylamine) NH2 benzenamine (phenylamine). N H N-phenylbenzenamine (diphenylamine). CH2 CH2 OH H2N 2-aminoethanol

N.B. The locant N- is used to indicate the alkyl or aryl group is attached to the N, not the parent C chain.

G. Amino-acids

Amino-acid contains both amino group –NH2 and carboxyl group –COOH. CH2 CH2 C OH

O

H2N 3-aminopropanoic acid H. Ethers

Ether contains –O–R group. It is cited by prefix (R-oxy-) e.g. methoxy-. CH3 O CH2 CH3 methoxyethane (ethyl methyl ether)

CH2CH3 O

CH3CH2 ethoxyethane (diethyl ether) CH2CH2

O O CH3

H3C 1,2-dimethoxyethane

N.B. In some circumstances, -oxy- is used alone to indicate the presence of oxygen.

IV. Priority of functional groups

If a compound has more than 1 functional group. The functional group with the highest priority would be named as the suffix and all others would be named as prefixes.

e.g. C O O OH C CH3 O C C O HO O O CH2 CH3 N C O CH2CH3 HO 2-ethanoyloxybenzenecarboxylic

V. Examples

Steps in writing

IUPAC name

C CH2 CH CH3 CH3 CH3 _{OH OH} CHCH2CH2CHCH2CHO C CH3 CH3 CH3

1. Identify the principal functional group hydroxyl group (–OH) alkanal group (–CHO) 2. Identify the parent chain containing the

principal functional group C C C C C_{OH OH C C C C C C C C}O _H

3. Number the parent chain so that the principal functional group is on the lowest numbered carbon.

pentane-2,4-diol oct-6-enal

4. Label other substituents as prefixes. 2-methyl 3-methyl, 7-methyl 5. Group the prefixes, arrange them in

alphabetic order and join with the root.

2-methylpentane-2,4-diol 3,7-dimethyloct-6-enal

Steps in writing

IUPAC name

C2H5C(CH3)=CHCH2CH2CO2H C C C C C C C O OH C C C C OH

1. Identify the principal functional group carboxyl group (–COOH) hydroxyl group (–OH) 2. Identify the parent chain containing the

principal functional group _{C C C C C C} O_{C OH} OH_{C C C} 3. Number the parent chain so that the

principal functional group is on the lowest numbered carbon.

hept-4-enoic acid propan-1-ol

4. Label other substituents as prefixes. 5-methyl 1-phenyl 5. Group the prefixes, arrange them in

alphabetic order and join with the root. 5-methylhept-4-enoic acid 1-phenylpropan-1-ol

Steps in writing

IUPAC name

C C C C C C C C C C C C O C C 1. Identify the principal functional group double bond (C=C) Nil

2. Identify the parent chain containing the

principal functional group C C C C C C C C

3. Number the parent chain so that the principal functional group is on the lowest numbered carbon.

but-1-ene butane

4. Label other substituents as prefix. 3-methyl, 3-methyl 1-ethoxy, 3-methyl, 3-methyl 5. Group the prefixes, arrange them in

alphabetic order and join with the root.

VI. Other common abbreviations

Abbreviation Functional group Structure Example

R– Alkyl group

Me– Methyl group

C

H

H

H

C H

H

H

H

Me–H

Et– Ethyl group

C C

H

H

H

H

H

C C

H

H

H

H

H

H

Et–H Ph– Phenyl group H Ph–H

Ar– Alkyl group

H

H Ar–H

X– Halogeno group Cl–, Br–, I–

Glossary

nomenclature IUPAC parent chain prefix root suffix locant

functional group aliphatic (acyclic) alicyclic (cyclic) alkane alkene alkyne alkyl group vinyl group allyl group aryl group phenyl group alkanol phenol hydroxyl group aldehyde (alkanal) ketone (alkanone) carbonyl group

carboxylic acid (alkanoic acid) carboxyl group ester acid chloride (acyl chloride) anhydride amide acyl group nitrile amine amino group ether

Past Paper

Question

94 2C 8 c i ii iii 96 2C 9 c i ii 97 2B 5 d i ii iii 98 2B 7 c i ii 94 2C 8 c i ii iii

8c Give a systematic name to each of the following compounds. i CH3CH CH CH3 CH3 CH2CH CH2 1 4,5-dimethylhex-1-ene 1 mark ii CH3CH2CH2 O C CH2CH2CH3 O 1

propyl butanoate 1 mark

iii CH3CH2 C O CHCH2CH3 OH 1 4-hydroxyhexan-3-one 1 mark

9c Give a systematic name to each of the following compounds : (Deduct ½ marks for each minor mistake. Max. Deduction = 2 marks) i

CH3 CH CH2 CH CH3

CH3 OH 1

4-methylpentan-2-ol / 4-methyl-2-pentanol 1 mark

ii O CH3 CH3 CH3 1 2,5,5-trimethylcyclohex-2-enone 1 mark

C Disappointing answers for (i). Some candidates did not know the basic rules of nomenclature. Very few gave the correct name for (ii).

97 2B 5 d i ii iii

5d Give a systematic name to each of the following compounds: 3

i N CH3 CH3 ii C CH(CH3)CH2CH3 CH3CH2 O iii C C H H CH3 HO2C 98 2B 7 c i ii

7c Give a systematic name to each of the following compounds : 2

i CH3

CH2CH3

Acid-Base Theory

I.

Definition of acid-base

A. Arrhenius

definition

B. Bronsted-Lowry

definition

C. Lewis

definition

II.

Strength of acid and base

A. Leveling

effect

III.

Factors determining the strength of a Bronsted-Lowry acid

A.

Relative stability of the conjugate base comparing with the acid

1. Inductive

effect

(1) Amine vs Amide

2. Resonance

effect

a)

Resonance effect on a benzene ring

(1) Phenol

(2) Aromatic amine

3.

Intramolecular hydrogen bond

4.

Solvation / hinderance to solvation

a)

Steric hinderance to solvation

b)

Effect of solvent

5.

Strength of the bond between the proton and the conjugate base

6.

Electronegativity of the atom

Topic

Acid-base Theory

Unit 1

Reference

Reading

14.1

Principles of Organic Chemistry, Peter R.S. Murray, 2nd Edition pg. 41–43, 138–140, 185–186, 252–254 Organic Chemistry, Solomons, 5th Edition pg. 86–109, 830–834, 942–943

Organic Chemistry, Fillans, 3rd Edition pg. 218–220, 301–313

Organic Chemistry, Morrison Boyd, 6th _{Edition pg. 33–35, 729–736, 849–852, 903–905}

Organic Chemistry, 6th Edition, Solomons, pg. 90-93, 96-101

Syllabus

Acid-base Theory Expression of Ka and pKa

Relative strength of acids and bases

Notes

A. Acid-base Theory

At the early stage of development of acid-base theory, acid was only

described as a sour substance. And base is only a substance which neutralizes the sour taste of an acid.

Nevertheless, scientists find that acids and bases bear some other properties. According to these properties, they developed a series of definitions to describe acid and base. They are called Arrhenius definition, Brønsted Lowry definition and Lewis definition. The coverage of the latter definition is boarder than the former one.

Common

Sense

A

rr

he

nius

defin

itio

n

B

rφ

ns

ted

Lowry defin

itio

n

Le

wis definition

I. Definition of acid-base A. Arrhenius definition

In 1884, Swedish chemist Svante Arrhenius proposed that

Acid – a hydrogen-containing compound that, when dissolved in water, produces hydroxonium ions, H3O+(aq).

Base – a substance that, when dissolved in water, produces hydroxide ions, OH-_.

Examples of Arrhenius acid

e.g. H2SO4(l) + H2O(l) → H3O+(aq) + HSO4-(aq)

HSO4-(aq) + H2O(l) → H3O+(aq) + SO42-(aq)

Examples of Arrhenius base

e.g. NaOH(s) + aq → Na+(aq) + OH-(aq)

KOH(s) + aq → K+(aq) + OH-(aq)

B. Brønsted-Lowry definition Arrhenius theory is criticized that

1. Acid is restricted to hydrogen-containing species and base is restricted to hydroxide-containing species. 2. The theory is only applicable to aqueous medium where a lot of acid-base reaction takes place in the absence

of water.

In 1923, Danish chemist Johannes Brønsted and British chemist Thomas Lowry proposed, a boarder definition, that Acid – a proton donor

Base – a proton acceptor

e.g. HCl(aq) + CuO(s) → Cu2+Cl-2(aq) + H2O(l)

proton proton

donor acceptor

e.g. NH3(aq) + H2O(l) d NH4+(aq) + OH-(l)

proton proton proton proton

acceptor donor donor acceptor

(base) (acid) (conjugate (conjugate acid of NH3(aq)) base of H2O(l))

e.g. HCl(aq) + H2O(l) d H3O+(aq) + Cl-(aq)

proton proton proton proton

donor acceptor donor acceptor

(acid) (base) (conjugate (conjugate acid of H2O(l)) base of HCl(aq))

e.g. H2O(l) + H2O(l) d H3O+(aq) + OH-(aq)

proton proton proton proton

acceptor donor donor acceptor

(base) (acid) (conjugate (conjugate acid of H2O(l)) base of H2O(l))

When a Brønsted-Lowry acid, a proton donor, donates a proton, it becomes a potential proton acceptor and is called the conjugate base of the acid. Stronger a proton donor, weaker will be the conjugate base.

Conversely, when a Brønsted-Lowry base, a proton acceptor, accepts a proton, it becomes a potential proton donor and is called the conjugate acid of the base. Stronger a proton acceptor, weaker will be the conjugate acid. All Arrhenius acids and bases can be classified into Brønsted-Lowry acid and base accordingly.

C. Lewis definition

The American chemist Gilbert N. Lewis (1923) proposed an even broader definition for acid and base. He proposed that

Acid – an electron acceptor Base – an electron donor

This definition offers many advantages, including

i. The acids are not limited to compounds containing hydrogen. ii. It works with solvents other than water.

iii. It does not require formation of a salt or of acid-conjugate pairs.

Since all chemical species are potential electron acceptor or electron donor, virtually, all chemical species are either Lewis acid or Lewis base.

e.g. H3N:(g) + BF3(g) → H3N→BF3(s)

electron electron donor acceptor

(Lewis base) (Lewis acid)

Most of the chemical reaction is caused by redistribution of electrons which leads to rearrangement of atoms and formation of a new substance. Therefore, all kind of reactions may be considered as Lewis acid-base reaction. Concept of Lewis acid-base is very useful in describing reaction mechanisms.

II. Strength of acid and base

In measuring the strength of acid, Brønsted-Lowry definition is usually used.

Strength of an acid can be measured by an equilibrium constant called acidity constant or acid dissociation constant, Ka.

For an acid, HA in water

HA(aq) + H2O(l) d H3O+(aq) + A-(aq) Equilibrium constant, Keq = [H3O +

(aq)][A-(aq)]

[HA(aq)][H2O(l)]

Acidity constant, Ka is defined as

Ka = [H3O +

(aq)][A-(aq)]

[HA(aq)] = Keq[H2O(l)] where [H2O(l)] is a constant since water is the solvent in large excess.

For a stronger acid, more HA(aq) molecules will dissociate into H3O+(aq) ion and A-(aq) ion and give a larger value for

Ka.

Similar to concentration of H+

(aq) ion, Ka can also be expressed in a negative log scale.

pH = - log [H+_{] A low pH means a high concentration of H}+ (aq) ion.

Relative strength of selected acids and their conjugate bases

Stronger an acid, weaker will be its conjugate base.

Stronger a base, weaker will be its conjugate acid.

N.B.

Redox reaction can be considered as a competition for electron.

oxidizing agent + e- _{d reducing agent}

In redox reaction, only strong oxidizing agent reacts with reducing agent.

Similarly, acid base reaction can be considered as a compeition for proton.

cojugate base + H+ _{d conjugate acid}

In acid base reaction, only strong acid react with strong base.

The strength of an acid or a base is also an indicator of their stability. A strong acid or base is less stable than a weak acid or base. A strong acid tends to react with a strong base to form a weak conjugate base and weak conjugate acid.

A. Leveling effect

An acid stronger than hydroxonium ion H3O+(aq), does not show difference in acidity in water. The water will

convert all those acid molecules into H3O+(aq) ions.

HCl(aq) + H2O(aq) → H3O+(aq) + Cl-(aq)

strong strong weak weak

acid base acid base

HBr(aq) + H2O(aq) → H3O+(aq) + Br-(aq)

strong strong weak weak

acid base acid base

A base stronger than hydroxide ion, e.g. NH2- amide ion, also does not exist in aqueous medium. Water will

convert all those base molecules into OH

-(aq) ions.

NH2- + H2O(l) → NH3(aq) + OH-(aq)

This is known as leveling effect of solvent.

Glossary

Arrhenius acid-base Brønsted-Lowry acid-base Lewis acid-base

Past Paper

Question

Topic

Acid-base Theory

Unit 2

Reference

Reading

14.0 14.2–14.4

Principles of Organic Chemistry, Peter R.S. Murray, 2nd Edition pg. 41–43, 138–140, 185–186, 252–254 Organic Chemistry, Solomons, 5th Edition pg. 86–109, 830–834, 942–943

Organic Chemistry, Fillans, 3rd Edition pg. 218–220, 301–313

Organic Chemistry, Morrison Boyd, 6th _{Edition pg. 33–35, 729–736, 849–852, 903–905}

Assignment

Reading

Chemistry in Context, 5th Edition, Thomas Nelson and Sons Ltd., pg. 471, 499–501, 519–520 Organic Chemistry, 6th Edition, Solomons, pg. 102-118, 320, 433-434, 795-796, 903-905, 970-972

Syllabus

Factors determining the strength of an acid

Notes

III. Factors determining the strength of a Bronsted-Lowry acid A. Relative stability of the conjugate base comparing with the acid 1. Inductive effect

2. Resonance effect

3. Intramolecular hydrogen bond 4. Solvation / hinderance to solvation 5. Size of the conjugate base

6. Electronegativity of the atom

A. Relative stability of the conjugate base comparing with the acid

The strength of an acid is mainly determined by the relative stability of the conjugate base comparing with the acid.

The equilibrium constant is related to the standard free energy change (∆Go) equation ∆Go = -2.303 RT log Keq = -RT ln Keq = -RT ln _[HKa

2O(l)] where ∆Go = ∆Ho - T∆So

∆Go is an indicator of the relative stability of the product comparing with the reactant. A very negative value means the product is more stable than the reactant. For a reaction with small change in entropy, i.e. reaction without change in physical state, the ∆Go is roughly the same as ∆Ho.

Since Ka = Keq [H2O(l)], a very negative value of ∆Go means a very strong acid. The acidity of the acid increase as