STRUCTURE AND PREPARATION OF ALKENES: ELIMINATION REACTIONS (e) When a hydroxyl group is present in a compound containing a double bond, the hydroxyl takes precedence over the double bond in numbering the longest carbon chain H2=CHCH, CHCH3 4-Penten-2-ol 5.2 There are three sets of nonequivalent positions on a cyclopentene ring, identified as a, b, and c on the cyclopentene structure shown Thus, there are three different monochloro-substituted derivatives of cyclopentene. The carbons that bear the double bond are numbered C-I and C-2 in each isomer, and the other positions are num bered in sequence in the direction that gives the chlorine-bearing carbon its lower locant. I-Chlorocyclopentene 3-Chlorocyclopentene 4-Chlorocyclopentene 5.3(b) The alkene is a derivative of 3-hexene regardless of whether the chain is numbered from left to right or from right to left. Number it in the direction that gives the lower number to the substituent 3-Ethyl-3-hexene (c) There are only two sp-hybridized carbons, the two connected by the double bond. All other carbons(six) are sp-hybridized (d) There are three sp - o bonds and three sp-sp o bonds. 5.4 Consider first the c he alkenes that have an unbranched carbon chain I-Pent 2-Pentene trans-2-Pentene There are three additional isomers. These have a four-carbon chain with a methyl substituent 2-Methyl-1-butene 5.5 First, identify the constitution of 9-tricosene. Referring back to Table 2. 4 in Section 2.8 of the text, we see that tricosane is the unbranched alkane containing 23 carbon atoms. 9-Tricosene therefore contains an unbranched chain of 23 carbons with a double bond between C-9 and c-10. Since the Back Forward Main Menu TOC Study Guide Toc Student OLC MHHE Website(e) When a hydroxyl group is present in a compound containing a double bond, the hydroxyl takes precedence over the double bond in numbering the longest carbon chain. 5.2 There are three sets of nonequivalent positions on a cyclopentene ring, identified as a, b, and c on the cyclopentene structure shown: Thus, there are three different monochloro-substituted derivatives of cyclopentene. The carbons that bear the double bond are numbered C-1 and C-2 in each isomer, and the other positions are num￾bered in sequence in the direction that gives the chlorine-bearing carbon its lower locant. 5.3 (b) The alkene is a derivative of 3-hexene regardless of whether the chain is numbered from left to right or from right to left. Number it in the direction that gives the lower number to the substituent. (c) There are only two sp2 -hybridized carbons, the two connected by the double bond. All other carbons (six) are sp3 -hybridized. (d) There are three sp2 –sp3 bonds and three sp3 –sp3 bonds. 5.4 Consider first the C5H10 alkenes that have an unbranched carbon chain: There are three additional isomers. These have a four-carbon chain with a methyl substituent. 5.5 First, identify the constitution of 9-tricosene. Referring back to Table 2.4 in Section 2.8 of the text, we see that tricosane is the unbranched alkane containing 23 carbon atoms. 9-Tricosene, therefore, contains an unbranched chain of 23 carbons with a double bond between C-9 and C-10. Since the 2-Methyl-1-butene 2-Methyl-2-butene 3-Methyl-1-butene 1-Pentene cis-2-Pentene trans-2-Pentene 5 4 3 2 1 6 3-Ethyl-3-hexene Cl 1 2 3 4 5 Cl 2 1 5 4 3 Cl 1 2 3 4 5 1-Chlorocyclopentene 3-Chlorocyclopentene 4-Chlorocyclopentene a a b c b OH CH2 CHCH2CHCH3 5 4 3 2 1 4-Penten-2-ol STRUCTURE AND PREPARATION OF ALKENES: ELIMINATION REACTIONS 91 Back Forward Main Menu TOC Study Guide TOC Student OLC MHHE Website