OPTION H - Further Organic Chemistry (HL Only)

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H.2 Free radical

H.1 Steroisomerism (3hr)

H.1.1 Describe and explain geometrical isomerism in non-cyclic alkenes.

• The existence of geometric (cis-trans) isomers as the result of restricted rotation around the C=C bond in organic chemistry.

H.1.2 Explain the difference in physical and chemical properties of geometrical isomers.

• Different boiling points for, eg. cis-1,2-dichloroethene, and trans-1,2-dichloroethene, different reactions when heated of, eg. cis- and trans-but-2-ene- 1,4-dioic acid.

H.1.3 Describe and explain the reason for geometrical isomerism in (C3 and C4) cyclo-alkanes.

• Use dichloro-derivatives of cyclopropane and cyclobutane as examples. Restricted rotation because the C-C bond is now part of a cyclic system.

H.1.4 Define plane-polarized light and describe how it interacts with enantiomers.

• This should build upon 11.3.3. Include the use of a polimeter

H.1.5. Define the term 'racemic mixture'.

H.1.6 Describe the similarities and differences in the physical and chemical properties of enantiomers.

H.2 Free radical substitution reactions (3h)

H.2.1 Describe the gas phase reactions of alkanes and methylbenzene with halogens in terms of free radical reactions.

• Be able to recall the mechanism for the reaction of methane and methylbenzene with chlorine, and identify the initiation, propagation and termination steps.

H.2.2 Describe how the gas phase reactions of chloroalkanes and other molecules affect the level of ozone in the atmosphere.

• Explain how the free radical reactions in the atmosphere result in ozone depletion.

H.3 Electrophilic Addition Reactions (4h)

H.3.1 Describe and explain the electrophilic reactions of symmetrical alkenes.

• A stepwise mechanistic approach is required. Reacting species should include halogens, mixed halogens and hydrogen halides.

H.3.2 Apply Markovnikov rule to predict the outcome of the electrophilic addition reactions of symmetrical alkenes.

• A stepwise mechanistic approach is required. reacting species should include, mixed halogens and hydrogen halides.

H.3.3 State and explain the relative stabilities of carbocations.

• Consideration should be restricted to the stability of CH3+, (CH₃)₂CH+, (CH₃)₃C+ and Ph+ only.

H.4 Electrophilic Substitution Reactions (4h)

H.4.1 Describe and explain the mechanism for the nitration of benzene.

• A stepwise electrophilic aromatic substitution mechanism is required. Students should be able to recall the formation of NO₂⁺.

H.4.2Describe and explain the Friedel Crafts reactions of benzene and methylbenzene.

• Examples should include chlorination and alkylation with FeCl₃ or AlCl₃ as catalysts.

H.4.3 Describe and explain the directing effects and relative rates of different substituents on a benzene ring.

• Examples should be restricted to -CH₃, -OH, -Cl, -NO₂, -CO₂CH₃. The reaction of phenol with chlorine to form trichlorophenol (TCP) should be covered.

H.5 Nucleophilic Addition Reactions (1h)

H.5.1 Describe and explain the mechanism for the addition of hydrogen cyanide to alkanals and alkanones, followed by hydrolysis to give alkanoic acids.

H.6 Nucleophilic substitution reactions (12h)

H.6.1 Describe how the relative rate of nucleophilic substitution is affected by different nucleophiles.

• Eg. relative rate of reaction using hydroxide or water (polarity differences).

H.6.2 Describe and explain inductive and steric effects of substituents on substitution reaction.

H.6.3 Describe and explain the relative rates of hydrolysis of halogenated benzene compounds.

• Compare the inertness of halogenated benzene compounds towards substitution relative to halogenoalkanes. Relate to 21.3

H.7 Elimination reactions (2h)

H.7.1 Describe the mechanism for the elimination of water from alkanols.

H.7.2 Describe and explain the mechanism for the elimination of HBr from bromoalkanes.

• It should be pointed out that under different conditions the same reactants can undergo either nucleophilic substitution or elimination, eg. 1-bromobutane with OH-.

H.8 Addition - elimination reactions (1.h)

H.8.1 Describe and explain the reactions of 2,4-dinitro phenylhydrazine with alkanals and alkanones.

H.9 Acid-base reactions (2h)

H.9.1 Discuss and explain the acidic properties of phenol and substituted phenols in terms of bonding.

• Compare the acidity of phenol with other alkanols. Compare the acidity of 2,4,6 - trinitrophenol with phenol.

H.9.2 Discuss and explain the acidic properties of substituted alkanoic acids in terms of bonding.

• Relative accidities can be explained in terms of the ease of dissociation of the hydrogen ion or in tern=ms of the relative stability of the conjugate base.

H.9.3 Compare and explain the relative basicities of ammonia, amines and amides.

• Lone pair on nitrogen, effect of alkyl group (increased Kb).
• Formation of salts, liberation of the amine with NaOH. Cross reference to topic 18.

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