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Unformatted text preview: Disubstituted Cycloalkanes: Cis-Trans Isomers When there are two substituents in a cycloalkane at different positions, cis and trans isomers, as found in alkenes, are possible. 1,2-Dimethylcyclopentanes H H CH 3 CH 3 H H CH 3 CH 3 (shown as planar structures to illustrate stereoisomerism) cis-1,2-dimethylcyclopentane trans-1,2-dimethylcyclopentane methyl groups are on the same side of ring methyl groups are on opposite sides of ring BP 99.5 o C BP 91.9 o C The cis and trans 1,2-dimethylcyclopentanes are stereoisomers , they differ in the arrangement of atoms in space but have the same basic bond connectivities. These stereoisomers cannot be interconverted by simple bond rotations--- they are not conformational isomers . These stereoisomers are called diastereomers and are separable by physical methods. Additional Examples of cis- and trans- Isomers These examples are all shown as planar structures to more easily illustrate the stereochemical relationships....
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