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Solutions to Problems 101 55. (a) H C H OH H HO H CH₂OH (b) No. An object can have only one mirror image. (c) There are several. Here's one: H C H OH HO H H OH CH₂OH (d) Yes. (e) + 105° (f) There is no way to predict the optical rotation of a diastereomer of a compound whose optical rotation you know. Diastereomeric compounds usually have very different physical properties. (g) No. Because the groups on the two end carbons are different, there is no way to have the plane of symmetry that would be required for a meso compound. 56. S-1,3-Dichloropentane is the compound's name. (a) A single achiral product is formed: (b) Two diastereomers are formed in unequal amounts: R S H CI CH₃ CI CH₃ H C C and C C H H CH₂CH₂Cl Cl CH₂CH₂Cl R R Notice that the designation for C3 has changed to R because the priority of the CHCICH₃ group is higher than that of the CH₂CH₂Cl group. (c) A single achiral product is formed: Notice that in (a) and (c) the chirality at C3 has been eliminated in two slightly different ways. In (a), a bond to C3 has been broken and a second Cl attached. In (c), no bond to C3 has been affected, but a remote change has made two groups on C3 identical.