Topic 15 Hydrocarbons

15 Hydrocarbons

15.1 Can understand and describe the alkanes

Candidates should be able to:

(a) write the general formula for alkanes;

(b) explain the construction of the alkane series (straight and branched), and IUPAC nomenclature of alkanes for C1 to C10;

(c) describe the structural isomerism in aliphatic alkanes and cis-trans isomerism in cycloalkanes;

(d) state the physical properties of alkanes;

(e) define alkanes as saturated aliphatic hydrocarbons;

(f) name alkyl groups derived from alkanes and identify primary, secondary, tertiary and quartenary carbons;

(g) explain the inertness of alkanes towards polar reagents;

(h) describe the mechanism of free radical substitution as exemplified by the chlorination of methane (with particular reference to the initiation, propagation and termination reactions);

(i) describe the oxidation of alkane with limited and excess oxygen, and the use of alkanes as fuels;

(j) explain the use of crude oil as a source of aliphatic hydrocarbons;

(k) explain how cracking reactions can be used to obtain alkanes and alkenes of lower Mr from larger hydrocarbon molecules;

(l) discuss the role of catalytic converters in minimising air pollution by oxidising CO to CO2 and reducing NOx to N2;

(m) explain how chemical pollutants from the combustion of hydrocarbon affect air quality and rainwater as exemplified by acid rain, photochemical smog and greenhouse effect.

15.2 Can understand and describe the alkenes

Candidates should be able to:

(a) write the general formula for alkenes;

(b) name alkenes according to the IUPAC nomenclature and their common names for C1 to C5;

(c) describe structural and cis-trans isomerism in alkenes;

(d) state the physical properties of alkenes;

(e) define alkenes as unsaturated aliphatic hydrocarbons with one or more double bonds;

(f) describe the chemical reactions of alkenes as exemplified by the following reactions of ethene:

(i) addition of hydrogen, steam, hydrogen halides, halogens, bromine water and concentrated sulphuric acid,

(ii) oxidation using KMnO4, O2/Ag,

(iii) ozonolysis,

(iv) polymerisation;

(g) describe the mechanism of electrophilic addition in alkenes with reference to Markovnikov‟s rule;

(h) explain the use of bromination reaction and decolourisation of MnO4 ions as simple tests for alkenes and unsaturated compounds;

(i) explain briefly the importance of ethene as a source for the preparation of chloroethane, epoxyethane, ethane-1,2-diol and poly(ethane).

15.3 Can understand and describe the arenes

Candidates should be able to:

(a) name aromatic compounds derived from benzene according to the IUPAC nomenclature, including the use of ortho, meta and para or the numbering of substituted groups to the benzene ring;

(b) describe structural isomerism in arenes;

(c) describe the chemical reactions of arenes as exemplified by substitution reactions of haloalkanes and acyl chloride (Friedel-Crafts reaction), halogen, conc. HNO3/conc. H2SO4 and SO3 with benzene and methylbenzene (toluene);

(d) describe the mechanism of electrophilic substitution in arenes as exemplified by the nitration of benzene;

(e) explain why benzene is more stable than aliphatic alkenes towards oxidation;

(f) describe the reaction between alkylbenzene and hot acidified KMnO4;

(g) determine the products of halogenation of methylbenzene (toluene) in the presence of

(i) Lewis acid catalysts,

(ii) light;

(h) explain the inductive effect and resonance effect of substituted groups (OH, Cl, CH3, NO2, COCH3, NH2) attached to the benzene ring towards further substitutions;

(i) predict the products in an electrophilic substitution reaction when the substituted group in benzene is electron accepting or electron donating;

(j) explain the uses of arenes as solvents;

(k) recognise arenes as carcinogen.

15 Hydrocarbons

15.1 Can understand and describe the alkanes

Candidates should be able to:

(a) write the general formula for alkanes;


(b) explain the construction of the alkane series (straight and branched), and IUPAC nomenclature of alkanes for C1 to C10;

branched / IUPAC nomenclature of alkane

 

 

 

straight / IUPAC nomenclature of alkane

cyclo / ring

 

(c) describe the structural isomerism in aliphatic alkanes and cis-trans isomerism in cycloalkanes;

structural isomerism in aliphatic alkanes kiv
cis-trans isomerism in cycloalkanes

 

(d) state the physical properties of alkanes; (Go to van der Waals forces)

 

(e) define alkanes as saturated aliphatic hydrocarbons;

(f) name alkyl groups derived from alkanes and identify primary, secondary, tertiary and quartenary carbons;

name alkyl groups (common names)

primary, secondary, tertiary and quartenary

(g) explain the inertness of alkanes towards polar reagents;

(h) describe the mechanism of free radical substitution as exemplified by the chlorination of methane (with particular reference to the initiation, propagation and termination reactions);

mechanism of free radical substitution (chlorination of methane)

 

 

chlorination vs bromination

(i) describe the oxidation of alkane with limited and excess oxygen,

and the use of alkanes as fuels;

(j) explain the use of crude oil as a source of aliphatic hydrocarbons;

kiv

(k) explain how cracking reactions can be used to obtain alkanes and alkenes of lower Mr from larger hydrocarbon molecules;

 

 

 

(l) discuss the role of catalytic converters in minimizing air pollution by oxidizing CO to CO2 and reducing NOx to N2;

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

(m) explain how chemical pollutants from the combustion of hydrocarbon affect air quality and rainwater as exemplified by acid rain, photochemical smog and greenhouse effect.

chemical pollutants

 

 

 


combustion of hydrocarbon (do fire contains plasma?)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

air quality and

 

 

 

 

 


rainwater (harvesting)

 

 

 

 

 

 

 


acid rain


photochemical smog

 

 

 

 

 

 

 

 

 

 

 


greenhouse effect.

 

15.2 Can understand and describe the alkenes

 

 

 

Candidates should be able to:

(a) write the general formula for alkenes;

(b) name alkenes according to the IUPAC nomenclature and their common names for C1 to C5;

 

 

(c) describe structural and cis-trans isomerism in alkenes;

(d) state the physical properties of alkenes;

(e) define alkenes as unsaturated aliphatic hydrocarbons with one or more double bonds;

 

(f) describe the chemical reactions of alkenes as exemplified by the following reactions of ethene:

(i) addition of hydrogen, steam,


hydrogen halides,

 

 

 

halogens,

 


bromine water and

 

 

 

concentrated sulphuric acid,

 

(ii) oxidation using KMnO4,

if hot acidified first will produce diol (intermediate) then ckeavage into carbonyl (ketone and carboxylic acid)

 

O2/Ag,



(iii) ozonolysis,

 


(iv) polymerisation;

 

 

(g) describe the mechanism of electrophilic addition in alkenes with reference to Markovnikov’s rule;

 

 

 

(h) explain the use of bromination reaction and decolourisation of MnO4 ions as simple tests for alkenes and unsaturated compounds;

 

 

 

 

 


(i) explain briefly the importance of ethene as a source for the preparation of chloroethane, epoxyethane, ethane-1,2-diol and poly(ethane).

 

 

 

15.3 Can understand and describe the arenes

 

 

 

 

 

 

Candidates should be able to:

(a) name aromatic compounds derived from benzene according to the IUPAC nomenclature, including the use of ortho, meta and para or the numbering of substituted groups to the benzene ring;

 

 

 

 

(b) describe structural isomerism in arenes;


(c) describe the chemical reactions of arenes as exemplified by substitution reactions of haloalkanes and acyl chloride (Friedel-Crafts reaction), halogen, conc. HNO3/conc. H2SO4 and SO3 with benzene and methylbenzene (toluene);

 

 

 

 

 

 

 

 

 

 

(d) describe the mechanism of electrophilic substitution in arenes as exemplified by the nitration of benzene;

 

 

 

(e) explain why benzene is more stable than aliphatic alkenes towards oxidation;

 

 

 

(f) describe the reaction between alkylbenzene and hot acidified KMnO4;

 

(h) describe the mechanism of free radical substitution as exemplified by the

 

 

 

(g) determine the products of halogenation of methylbenzene (toluene) in the presence of

(i) Lewis acid catalysts,

 

 

 

 


Akylation of Benzene by using Friedel Craft reagent:


(ii) light;

 

(h) explain the inductive effect and resonance effect of substituted groups (OH, Cl, CH3, NO2, COCH3, NH2) attached to the benzene ring towards further substitutions;

OH, Cl, CH3, NO2, COCH3, NH2

OH

Cl

CH3
NO2,
COCH3
NH2

 

 

 

 

 

 

 

(i) predict the products in an electrophilic substitution reaction when the substituted group in benzene is electron accepting or electron donating;


(j) explain the uses of arenes as solvents;

 

(k) recognise arenes as carcinogen.

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