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Dolbier HW Solutions 262 - will be 12 p molecular orbitals...

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11.9 The dihydronaphthalene in which the double bond is conjugated with the aromatic ring is more sta- ble; thus 1,2-dihydronaphthalene has a lower heat of hydrogenation than 1,4-dihydronaphthalene. 11.10 ( b ) The regioselectivity of alcohol formation by hydroboration oxidation is opposite that pre- dicted by Markovnikov s rule. ( c ) Bromine adds to alkenes in aqueous solution to give bromohydrins. A water molecule acts as a nucleophile, attacking the bromonium ion at the carbon that can bear most of the positive charge, which in this case is the benzylic carbon. ( d ) Peroxy acids convert alkenes to epoxides. 11.11 Styrene contains a benzene ring and will be appreciably stabilized by resonance, which makes it lower in energy than cyclooctatetraene. 11.12 The dimerization of cyclobutadiene is a Diels Alder reaction in which one molecule of cyclobuta- diene acts as a diene and the other as a dienophile. 11.13 ( b ) Since twelve 2 p orbitals contribute to the cyclic conjugated system of [12]-annulene, there
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Unformatted text preview: will be 12 p molecular orbitals. These MOs are arranged so that one is of highest energy, one is of lowest energy, and the remaining ten are found in pairs between the highest and lowest Diene Dienophile Diels – Alder adduct CH CH 2 Structure contains an aromatic ring. Styrene: heat of combustion 4393 kJ/mol (1050 kcal/mol) Cyclooctatetraene (not aromatic): heat of combustion 4543 kJ/mol (1086 kcal/mol) 1 Styrene CH CH 2 Epoxystyrene (69 – 75%) CH CH 2 O Peroxybenzoic acid COOH C O 1 Benzoic acid COH C O CH Styrene 2-Bromo-1-phenylethanol (82%) Br 2 H 2 O CHCH 2 Br OH CH 2 2-Phenylpropene C CH 2 CH 3 CH 3 2-Phenyl-1-propanol (92%) 1. B 2 H 6 2. H 2 O 2 , HO 2 CHCH 2 OH 1,2-Dihydronaphthalene Heat of hydrogenation 101 kJ/mol (24.1 kcal/mol) 1,4-Dihydronaphthalene Heat of hydrogenation 113 kJ/mol (27.1 kcal/mol) 256 ARENES AND AROMATICITY...
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