CONFORMATIONS OF ALKANES AND CYCLOALKANES 57 however, in that it also shows the spatial arrangement of the substituents attached to the main 2, 2,5.5-Tetramethy lhexane (c) An isopropyl group is bulkier than a methyl group, and will have a greater preference for an equatorial orientation in the most stable conformation of cis-1-isopropyl-3-methylcyclohexane Draw a chair conformation of cyclohexane, and place an isopropyl group in an equatorial H Add a methyl group to C-3 so that it is also down H CH(CH3)2 Both substituents are equatorial in the most stable conformation of cis-l-isopropyl-3-methyl (d) One substituent is up and the other is down in the most stable conformation of trans-1 opropyl-3-methylcyclohexane. Begin as in part(c)by placing an isopropyl group in an equa orial orientation on a chair conformation of cyclohexane. CH(CH3)2 To be trans to the C-1 isopropyl group, the C-3 methyl group must be up CH(CH3)2 The bulkier isopropyl group is equatorial and the methyl group axial in the most stable conformation (e) To be cis to each other, one substituent must be axial and the other equatorial when they are located at positions I and 4 on a cyclohexane ring Back Forward Main Menu TOC Study Guide Toc Student OLC MHHE Websitehowever, in that it also shows the spatial arrangement of the substituents attached to the main chain. (c) An isopropyl group is bulkier than a methyl group, and will have a greater preference for an equatorial orientation in the most stable conformation of cis-1-isopropyl-3-methylcyclohexane. Draw a chair conformation of cyclohexane, and place an isopropyl group in an equatorial position. Notice that the equatorial isopropyl group is down on the carbon atom to which it is attached. Add a methyl group to C-3 so that it is also down. Both substituents are equatorial in the most stable conformation of cis-1-isopropyl-3-methyl￾cyclohexane. (d) One substituent is up and the other is down in the most stable conformation of trans-1- isopropyl-3-methylcyclohexane. Begin as in part (c) by placing an isopropyl group in an equa￾torial orientation on a chair conformation of cyclohexane. To be trans to the C-1 isopropyl group, the C-3 methyl group must be up. The bulkier isopropyl group is equatorial and the methyl group axial in the most stable conformation. (e) To be cis to each other, one substituent must be axial and the other equatorial when they are located at positions 1 and 4 on a cyclohexane ring. H H 1 4 H H CH(CH3)2 CH3 H CH(CH3)2 1 3 H H3C H CH(CH3)2 H CH(CH3)2 1 3 2,2,5,5-Tetramethylhexane CONFORMATIONS OF ALKANES AND CYCLOALKANES 57 Back Forward Main Menu TOC Study Guide TOC Student OLC MHHE Website