Topic 14 Introductions to Organic Chemistry

14 Introductions to Organic Chemistry

14.1 Bonding of the carbon atoms: the shapes of ethane, ethene, ethyne and benzene molecules

Candidates should be able to:

(a) use the concept of sp3, sp2 and sp hybridisations in carbon atoms to describe the bonding and shapes of molecules as exemplified by CH4, C2H4, C2H2 and C6H6;

(b) explain the concept of delocalisation of electrons in benzene ring.

 

14.2 General, empirical, molecular and structural formulae of organic compounds

Candidates should be able to:

(a) state general, empirical, molecular and structural formula of organic compounds;

(b) determine empirical and molecular formulae of organic compounds.

14.3 Functional groups: classification and nomenclature

Candidates should be able to:

(a) describe the classification of organic compounds by functional groups and the nomenclature of classes of organic compounds according to the IUPAC rules of the following classes of compounds:

(i) alkanes, alkenes, alkynes and arenes,

(ii) haloalkanes/ alkyl halide,

(iii) alcohols (including primary, secondary and tertiary) and phenols,

(iv) aldehydes and ketones,

(v) carboxylic acids and their derivatives (acyl chlorides, amides and esters),

(vi) primary amines, amino acids and protein.

14.4 Isomerism: structural and stereoisomerism

Candidates should be able to:

(a) define structural and stereoisomerism (geometrical and optical);

(b) explain the meaning of a chiral centre in optical isomerism;

(c) classify isomers as structural, cis-trans and optical isomers;

(d) identify chiral centres and/or cis-trans isomerism in a molecule of given structural formula;

(e) deduce the possible isomers for an organic compound of known molecular formula.

14.5 Free radicals, nucleophiles and electrophiles

Candidates should be able to:

(a) describe homolytic and heterolytic fissions;

(b) define the terms free radical, nucleophile and electrophile;

(c) explain that nucleophiles such as OH, NH3, H2O, Br, I and carbanion are Lewis bases;

(d) explain that electrophiles such as H+, NO2+, Br2, AlCl3, ZnC12, FeBr3, BF3 and carbonium ion are Lewis acids.

14.6 Molecular structure and its effect on physical properties

Candidates should be able to:

(a) describe the relationship between the size of molecules in the homologous series and the melting and boiling points;

(b) explain the forces of attraction between molecules (van der Waals forces and hydrogen bonding).

14.7 Inductive and resonance effect

Candidates should be able to:

(a) explain inductive effect which can determine the properties and reactions of functional groups;

(b) use inductive effect to explain why functional groups such as NO2, CN, COOH, COOR, >C=O, SO3H, X (halogen), OH, OR, NH2, C6H5 are electron acceptors whereas R (alkyl) is an electron donor;

(c) explain how the concept of induction can account for the differences in acidity between CH3COOH, C1CH2COOH, C12CHCOOH and Cl3CCOOH; between C1CH2CH2CH2COOH and CH3CH2CHClCOOH;

(d) use the concept of resonance to explain the differences in acidity between ethanol & phenol, as well as the differences in basicity between methylamine & aniline.

By writing the equations and state reagents and the conditions, give one example for each of the following mechanism:
1. free radical substitution reaction (Topic 14 & Topic 15)
2. electrophilic addition reaction (Topic 15)
3. electrophilic substitution reaction (Topic 15 & Topic 17)
4. nucleophilic substitution reaction (Topic 16)
5. nucleophilic addition reaction (Topic 18)
6. friedel-craft reaction (Topic 15 & Topic 19)

Chemical Test:
1. for alkenes and unsaturated compounds (Topic 15)
2. for phenol (Topic 17)
3. to detect the presence of >C=O groups (Topic 18)
4. to differentiate between aldehyde and ketone(Topic 18)
5. iodoform test (Topic 18)

14 Introductions to Organic Chemistry (APPS)

14.1 Bonding of the carbon atoms: the shapes of ethane, ethene, ethyne and benzene molecules

 

 

Candidates should be able to:

(a) use the concept of sp3, sp2 and sp hybridisations in carbon atoms to describe the bonding and shapes of molecules as exemplified by

sp3
sp2
sp

CH4,

C2H4,

C2H2 and

C6H6;

QUIZ

sp3
sp2
sp

 

 

 

CH4

 

C2H4

 
 

C2H2 and

 

 
C6H6 ;

 

(b) explain the concept of delocalisation of electrons in benzene ring.

 

 

14.2 General, empirical, molecular and structural formulae of organic compounds

Candidates should be able to:

(a) state general, empirical formulae, molecular formulae and structural formulae of organic compounds;


state general,

empirical formulae,

 

3.3 molecular formulae and

 

structural formula of organic compounds;

 

(b) determine empirical and molecular formulae of organic compounds.

empirical formulae

molecular formulae

 

 

14.3 Functional groups: classification and nomenclature

Candidates should be able to:

(a) describe the classification of organic compounds by functional groups and the nomenclature of classes of organic compounds according to the IUPAC rules of the following classes of compounds:

(i) alkanes, alkenes, alkynes and arenes,

(ii) haloalkanes/ alkyl halide,

(iii) alcohols (including primary, secondary and tertiary) and phenols,

(iv) aldehydes and ketones,

(v) carboxylic acids and their derivatives (acyl chlorides, amides and esters),

(vi) primary amines, amino acids and protein.

(i) alkanes, alkenes, alkynes and arenes ,

(ii) haloalkanes / alkyl halide,

(iii) alcohols (including primary, secondary and tertiary) and phenols,

(iv) aldehydes and ketones,

(v) carboxylic acids and their derivatives (acyl chlorides, amides and esters),

(vi) primary amines, amino acids and protein.

 

14.4 Isomerism: structural and stereoisomerism

Candidates should be able to:

(a) define structural and stereoisomerism (geometrical and optical (enantiomer)); chirality, optically inactive active

 

structural
stereoisomerism (geometrical and optical (enantiomer));
chiralitychiral centre,
optically inactive activeoptical isomers

 

(b) explain the meaning of a chiral centre in optical isomerism; chirality

(c) classify isomers as structural, cis-trans and optical isomers;

structural,

cis-trans and

optical isomers;


(d) identify chiral centres and/ or cis-trans isomerism in a molecule of given structural formula;

(e) deduce the possible isomers for an organic compound of known molecular formula.

 

14.5 Free radicals, nucleophiles and electrophiles

Candidates should be able to:

(a) describe homolytic and heterolytic fissions;

 


(b) define the terms free radical, nucleophile and electrophile;

free radical,

 

 

 


Free radicals are atoms or groups of atoms with an odd (unpaired) number of electrons and can be formed when oxygen interacts with certain molecules. Once formed these highly reactive radicals can start a chain reaction, like dominoes.

nucleophile

A nucleophile is a chemical species that donates an electron pair to an electrophile to form a chemical bond in relation to a reaction. All molecules or ions with a free pair of electrons or at least one pi bond can act as nucleophiles. Because nucleophiles donate electrons, they are by definition Lewis bases.

 

electrophile;

in organic chemistry, an electrophile is a reagent attracted to electrons. Electrophiles are positively charged or neutral species having vacant orbitals that are attracted to an electron rich centre. It participates in a chemical reaction by accepting an electron pair in order to bond to a nucleophile.

SO3 is the electrophile in the reaction with benzene ring

 

 


(d) explain that electrophiles such as H+, NO2+, Br2, AlCl3, ZnC12, FeBr3, BF3 and carbonium ion are Lewis acids.

H+,

NO2+,

Br2,

AlCl3,

ZnC12,

FeBr3,

BF3

carbonium ion

14.6 Molecular structure and its effect on physical properties

Candidates should be able to:

(a) describe the relationship between the size of molecules in the homologous series and the melting and boiling points;

 

 

(b) explain the forces of attraction between molecules (van der Waals forces and hydrogen bonding).

van der Waals forces

hydrogen bonding

14.7 Inductive and resonance effect

 

 

 

Candidates should be able to:

(a) explain inductive effect which can determine the properties and reactions of functional groups;


(b) use inductive effect to explain why functional groups such as NO2, CN, COOH, COOR, >C=O, SO3H, X (halogen), OH, OR, NH2, C6H5 are electron acceptors whereas R(alkyl) is an electron donor;

NO2,

 


CN,


COOH,

COOR,
>C=O,
SO3H,
X (halogen),
OH,
OR,
NH2,

 

C6H5

 

are electron acceptors whereas R (alkyl) is an electron donor

(c) explain how the concept of induction can account for the differences in acidity between CH3COOH, C1CH2COOH, C12CHCOOH and Cl3CCOOH; between C1CH2CH2CH2COOH and CH3CH2CHClCOOH;

acidity

Cl3CH2COOH > Cl2CHCOOH > ClCH2COOH > CH3COOH

CH3CH2CHClCOOH > ClCH2CH2CH2COOH

 

 

 

(d) use the concept of resonance to explain the differences in acidity between CH3CH2OH (ethanol) and C6H5OH (phenol), as well as the differences in basicity between CH3NH2 (methylamine) and C6H5NH2 (aniline).

acidity between ethanol & phenol

 

basicity methylamine & aniline



 

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