92 STRUCTURE AND PREPARATION OF ALKENES: ELIMINATION REACTIONS problem specifies that the pheromone has the cis configuration, the first 8 carbons and the last 13 must be on the same side of the c-9-C-10 double bond (CH,)12CH H H cis-9.Tricosene 5.6 (b) One of the carbons of the double bond bears a methyl group and a hydrogen; methyl is of higher rank than hydrogen. The other doubly bonded carbon bears the groups -CH,CH F and-CH,CH,CH CH3. At the first point of difference between these two, fluorine is of igher atomic number than carbon, and so-CH, CH, F is of higher precedence Higher CH CH,CH,F Higher CH,CH,CH,CH Higher ranked substituents are on the same side of the double bond the alkene has the Z con- guration (c) One of the carbons of the double bond bears a methyl group and a hydrogen; as we have seen methyl is of higher rank. The other doubly bonded carbon bears-CH,CH,OH and-C(CH Lets analyze these two groups to determine their order of precedence C(C, H, H C(CCC Lower priority Higher priority We examine the atoms one by one at the point of attachment before proceeding down the chain. Therefore, -C(CH;) outranks-CH,CH,OH Higher CH; CHCHOH Lower C(CH3)3 Higher Higher ranked groups are on opposite sides; the configuration of the alkene is E. (d) The cyclopropyl ring is attached to the double bond by a carbon that bears the atoms( C, C, h) and is therefore of higher precedence than an ethyl group-C(C, H, H) Lower Higher ranked groups are on opposite sides; the configuration of the alkene is E 5.7 A trisubstituted alkene has three carbons directly attached to the doubly bonded carbons. There are three trisubstituted CHi isomers, two of which are stereoisomers H3 CH,CH CH2CH3 2-Methyl-2-penter (E)3-Methyl-2-pentene (Z)-3-Methyl-2-pentene Back Forward Main Menu TOC Study Guide Toc Student OLC MHHE Website92 STRUCTURE AND PREPARATION OF ALKENES: ELIMINATION REACTIONS problem specifies that the pheromone has the cis configuration, the first 8 carbons and the last 13 must be on the same side of the C-9–C-10 double bond. 5.6 (b) One of the carbons of the double bond bears a methyl group and a hydrogen; methyl is of higher rank than hydrogen. The other doubly bonded carbon bears the groups @CH2CH2F and @CH2CH2CH2CH3. At the first point of difference between these two, fluorine is of higher atomic number than carbon, and so @CH2CH2F is of higher precedence. Higher ranked substituents are on the same side of the double bond; the alkene has the Z con- figuration. (c) One of the carbons of the double bond bears a methyl group and a hydrogen; as we have seen, methyl is of higher rank. The other doubly bonded carbon bears @CH2CH2OH and @C(CH3)3. Let’s analyze these two groups to determine their order of precedence. We examine the atoms one by one at the point of attachment before proceeding down the chain. Therefore, @C(CH3)3 outranks @CH2CH2OH. Higher ranked groups are on opposite sides; the configuration of the alkene is E. (d) The cyclopropyl ring is attached to the double bond by a carbon that bears the atoms (C, C, H) and is therefore of higher precedence than an ethyl group @C(C, H, H). Higher ranked groups are on opposite sides; the configuration of the alkene is E. 5.7 A trisubstituted alkene has three carbons directly attached to the doubly bonded carbons. There are three trisubstituted C6H12 isomers, two of which are stereoisomers. C C CH3 CH3 CH2CH3 H C C CH3 H CH3 CH2CH3 C C CH3 H CH2CH3 CH3 2-Methyl-2-pentene (E)-3-Methyl-2-pentene (Z)-3-Methyl-2-pentene C C CH3CH2 H CH3 Higher Lower Lower Higher C C H CH3 CH2CH2OH C(CH3)3 Higher Lower Higher Lower CH2CH2OH C(C,H,H) Lower priority C(CH3)3 C(C,C,C) Higher priority C C H CH3 CH2CH2F CH2CH2CH2CH3 Higher Lower Higher Lower C C H CH3(CH2)7 H (CH2)12CH3 cis-9-Tricosene Back Forward Main Menu TOC Study Guide TOC Student OLC MHHE Website