Estabilidade e Conformações Moleculares

Prévia do material em texto

6.33 This compound has a conformationally locked boat cyclohexane ring in which carbons 1 and 4 are connected by a CH₂ group (C-7). This compound has both angle strain and torsional strain. 7 7 4 5 4 1 3 3 2 6 1 2 5 6 6.34 a) Z b) Z 6.35 a) This is the most stable conformation of pentane because it is anti about all of the C-C bonds. b) This is a less stable conformation of pentane because it is eclipsed about one of the bonds. c) This is a less stable conformation of 2-methylbutane because the methyl group on one carbon is gauche to both of the methyl groups on the other carbon. 6.36 a) The stereoisomer on the right (trans-1,2-dimethylcyclopropane) is more stable because the cis-isomer has more steric strain due to its eclipsed methyl groups. b) The isomer on the left (the E-stereoisomer) is more stable because the larger groups ( ethyl and isopropyl) are trans on the double bond. c) The isomer on the right (the cis-stereoisomer) is more stable because it has the conformation with both groups equatorial. 6.37 Both methyl groups are axial in both compounds. However, in the isomer on the right (cis-1,3-dimethylcyclohexane), the two methyl groups are on the same side of the ring. The extra steric strain due to the 1,3-diaxial interaction of these two methyl groups is much larger than the 1,3-diaxial interactions between the methyl groups and the hydrogens in the other isomer, so the conformation on the right has more strain energy. 94