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Mechanism of addition of HBr to an Alkene. Step 1: Formation of a carbocation Step 2: Nucleophillic addition of bromide. Addition Rx Mechanism (electron density diagram). Alkene Polymerization. Polymerization of alkenes is an industrially important reaction
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Mechanism of addition of HBr to an Alkene Step 1: Formation of a carbocation Step 2: Nucleophillic addition of bromide
Alkene Polymerization • Polymerization of alkenes is an industrially important reaction • Plastics such as polypropylene and polyethylene are products of alkene polymerization • Alkene polymerization takes place in presence of catalysts • Refer to Table 13.1 of textbook for some important alkene monomers and their polymers
Addition of Halogens: Halogenation Halogens add to alkenes to form 1,2-dihaloalkanes Fundamentals of General, Organic and Biological Chemistry, Prentice-Hall, McMurry et.al, 5ed
Alkenes & their Polymers Fundamentals of General, Organic and Biological Chemistry, Prentice-Hall, McMurry et.al, 5ed
Aromatic Compounds • The term ‘aromatic’ originated from compunds that had a fragrant smell and were isolated from nature • Aromatic compounds have an arrangement of alternating double and single bonds, i.e C6H6, , a delocalized, conjugated p system • Coplanar structure • Following shows resonance stabilized Benzene structure
Benzene • Benzene lacks reactivity due to its resonance stabilization • Benzene does not undergo any addition reactions Fundamentals of General, Organic and Biological Chemistry, Prentice-Hall, McMurry et.al, 5ed
Naming Aromatic Compounds Fundamentals of General, Organic and Biological Chemistry, Prentice-Hall, McMurry et.al, 5ed
Nomenclature of Aromatics • The cyclic aromatic ring is treated as the parent chain compound • The parent compound has accepted names such as indole, furan, phenol being accepted in the IUPAC nomenclature
Substitution reaction of Aromatics • Nitration – A ring hydrogen gets substituted with an -NO2 group • Sulfonation- A ring hydrogen is substituted with a –SO3H group • Halogenation – A ring hydrogen is substituted with a halogen (Cl, Br, I)