What you’ll learn5 learning objectivesChoose one objective for a focused lesson, or study the complete topic.14.2.1Preparation of alkenes• Recall preparation of alkenes: (a) elimination of HX from a halogenoalkane by ethanolic NaOH and heat; (b) dehydration of an alcohol, by using a heated catalyst (e.g. Al2O3) or a conc. acid (e.g. conc. H2SO4); (c) cracking of a longer chain alkaneSyllabus objective14.2.2Reactions of alkenes• Describe reactions of alkenes:- (a) the electrophilic addition of- (i) hydrogen in a hydrogenation reaction, H2(g) and Pt/Ni catalyst and heat- (ii) steam, H2O(g) and H3PO4 catalyst- (iii) a hydrogen halide, HX(g), at room temp.- (iv) a halogen, X2- (b) the oxidation by cold dil. acidified KMnO4 to form the diol- (c) the oxidation by hot conc. acidified KMnO4 leading to the cleavage of the carbon–carbon double bond and the identities of the subsequent products to determine the position of alkene linkages in larger molecules- (d) addition polymerisation exemplified by the reactions of ethene and propeneSyllabus objective14.2.3Of aq. bromine to show the presence of a C=C• Describe the use of aq. bromine to show the presence of a C=C bondSyllabus objective14.2.4Mechanism: electrophilic addition in alkenes,• Describe the mechanism of electrophilic addition in alkenes, using bromine/ethene and hydrogen bromide/propene as examplesSyllabus objective14.2.5Inductive effects of alkyl groups• Describe/explain: the inductive effects of alkyl groups on the stability of primary, secondary and tertiary cations formed during electrophilic addition (this should be used to explain Markovnikov addition)Syllabus objective