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6.29 :0 a) b) OH H H H H H H H O H H H H H H H H H H OH H anti gauche anti gauche Besides steric and torsional strain, the stabilities of the conformations are influenced by dipole-dipole interactions (a and b) and hydrogen bonding (b). 6.30 Because its two methyl groups are eclipsed, cís-1,2-dimethylcyclopropane has more steric strain than trans-1,2-dimethylcyclopropane. Therefore trans-1,2-dimethylcyclopropane is more stable. 6.31 Linoleic acid has two double bonds, so there are four cis-trans isomers. acid has three double bonds, so there are eight stereoisomers. O HO linoleic acid O HO α-linolenic acid 6.32 Angle and torsional strain in its four-membered ring causes penicillin G to be relative unstable. One of the bonds in the four-membered ring will break relatively easily. 93