CONFORMATIONS OF ALKANES AND CYCLOALKANES All methyl groups are equatorial in cis-1, 3,5-trimethylcyclohexane. It is more stable than trans 1, 3, 5-trimethylcyclohexane(shown in the following), which has one axial methyl group in its most H3C CH H CH H,C H CH 3.10 In each of these problems, a tert-butyl group is the larger substituent and will be equatorial in the most stable conformation. Draw a chair conformation of cyclohexane, add an equatorial tert-butyl group, and then add the remaining substituent so as to give the required cis or trans relationship to the tert-butyl group (b) Begin by drawing a chair cyclohexane with an equatorial tert-butyl group. In cis-l-tert-butyl 3-methylcyclohexane the C-3 methyl group is equatorial (c) In trans-l-tert-butyl-4-methylcyclohexane both the tert-butyl and the C-4 methyl group are equatorial H3C H (d) Again the tert-butyl group is equatorial; however, in cis-l-tert-butyl-4-methylcyclohexane the methyl group on C-4 is axial. H 3.11 Isomers are different compounds that have the same molecular formula. Compare the molecular formulas of the compounds given to the molecular formula of spiropentane H=CH, CH Spiropentane(CsHg) CsHs CHIO CsH& Only the two compounds that have the molecular formula Cs Hg are isomers of spiropentane 3. 12 Two bond cleavages convert bicyclobutane to a noncyclic species; therefore, bicyclobutane is bicycl A一一不个 Back Forward Main Menu TOC Study Guide Toc Student OLC MHHE WebsiteAll methyl groups are equatorial in cis-1,3,5-trimethylcyclohexane. It is more stable than trans- 1,3,5-trimethylcyclohexane (shown in the following), which has one axial methyl group in its most stable conformation. 3.10 In each of these problems, a tert-butyl group is the larger substituent and will be equatorial in the most stable conformation. Draw a chair conformation of cyclohexane, add an equatorial tert-butyl group, and then add the remaining substituent so as to give the required cis or trans relationship to the tert-butyl group. (b) Begin by drawing a chair cyclohexane with an equatorial tert-butyl group. In cis-1-tert-butyl- 3-methylcyclohexane the C-3 methyl group is equatorial. (c) In trans-1-tert-butyl-4-methylcyclohexane both the tert-butyl and the C-4 methyl group are equatorial. (d) Again the tert-butyl group is equatorial; however, in cis-1-tert-butyl-4-methylcyclohexane the methyl group on C-4 is axial. 3.11 Isomers are different compounds that have the same molecular formula. Compare the molecular formulas of the compounds given to the molecular formula of spiropentane. Only the two compounds that have the molecular formula C5H8 are isomers of spiropentane. 3.12 Two bond cleavages convert bicyclobutane to a noncyclic species; therefore, bicyclobutane is bicyclic. Spiropentane (C5H8) CH CH2 C5H8 C6H10 C5H8 C5H10 CH2 CH3 H C(CH3)3 H H3C H C(CH3)3 H H H3C H C(CH3)3 H H H H3C CH3 H3C trans-1,3,5-Trimethylcyclohexane CH3 CH3 H H CH3 H CONFORMATIONS OF ALKANES AND CYCLOALKANES 49 Back Forward Main Menu TOC Study Guide TOC Student OLC MHHE Website