236 CONJUGATION IN ALKADIENES AND ALLYLIC SYSTEMS 10.15 An electrophile is by definition an electron-seeker: When an electrophile attacks ethylene, it inter acts with the T orbital because this is the orbital that contains electrons. The Orbital of ethylene is unocal 10.16 Analyze the reaction of two butadiene molecules by the Woodward-Hoffmann rules by examining e symmetry properties of the highest occupied molecular orbital(HOMO)of one diene and the lowest unoccupied molecular orbital (LUMO)of the other. Soop Antibonding/ LUMO This reaction is forbidden by the Woodward-Hoffmann rules. Both interactions involving the ends of the dienes need to be bonding for concerted cycloaddition to take place. Here, one is bonding and the other is antibonding 10.17 Dienes and trienes are named according to the IUPAC convention by replacing the -ane ending of the alkane with -adiene or -atriene and locating the positions of the double bonds by number. The stereoisomers are identified as E or Z according to the rules established in Chapter 5 (a) 3, 4-0ctadiene: CH CH,CH=C=CHCH2,CH3 H3C H (b) (E, E)-3,5-Octadiene CHCH (c)(Z, 2)-1, 3-Cyclooctadiene (d) (Z, Z)-1, 4-Cyclooctadiene (e)(E, E)-1, 5-Cyclooctadiene H,C HH CH3 (f)(2E, 42, 6E)-2, 4, 6-0ctatriene (g) 5-Allyl-1, 3-cyclopentadiene CH,CH=CH H,C=CH (h) trans-1, 2-Divinylcycloprop CH=CH, H, C=CCH=CCH (i 2,4-Dimethy l-1, 3-pentadiene: CH Back Forward Main Menu TOC Study Guide Toc Student OLC MHHE Website10.15 An electrophile is by definition an electron-seeker. When an electrophile attacks ethylene, it inter￾acts with the orbital because this is the orbital that contains electrons. The * orbital of ethylene is unoccupied. 10.16 Analyze the reaction of two butadiene molecules by the Woodward–Hoffmann rules by examining the symmetry properties of the highest occupied molecular orbital (HOMO) of one diene and the lowest unoccupied molecular orbital (LUMO) of the other. This reaction is forbidden by the Woodward–Hoffmann rules. Both interactions involving the ends of the dienes need to be bonding for concerted cycloaddition to take place. Here, one is bonding and the other is antibonding. 10.17 Dienes and trienes are named according to the IUPAC convention by replacing the -ane ending of the alkane with -adiene or -atriene and locating the positions of the double bonds by number. The stereoisomers are identified as E or Z according to the rules established in Chapter 5. (a) 3,4-Octadiene: (b) (E,E)-3,5-Octadiene: (c) (Z,Z)-1,3-Cyclooctadiene: (d) (Z,Z)-1,4-Cyclooctadiene: (e) (E,E)-1,5-Cyclooctadiene: ( f ) (2E,4Z,6E)-2,4,6-Octatriene: (g) 5-Allyl-1,3-cyclopentadiene: (h) trans-1,2-Divinylcyclopropane: (i) 2,4-Dimethyl-1,3-pentadiene: H2C CCH3 CH3 CCH CH3 H H2C CH H CH CH2 H CH2CH CH2 H H H H H H3C CH3 H C C H CH3CH2 C H C H CH2CH3 H CH3CH2CH CHCH C 2CH2CH3 HOMO LUMO Antibonding Bonding 236 CONJUGATION IN ALKADIENES AND ALLYLIC SYSTEMS Back Forward Main Menu TOC Study Guide TOC Student OLC MHHE Website