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Give the stereochemical relationships between each pair of
Chapter 6, Problem 30SP(choose chapter or problem)
Give the stereochemical relationships between each pair of structures. Examples are same compound, structural isomers, enantiomers, diastereomers. Which pairs could you (theoretically) separate by distillation or recrystallization?
Questions & Answers
QUESTION:
Give the stereochemical relationships between each pair of structures. Examples are same compound, structural isomers, enantiomers, diastereomers. Which pairs could you (theoretically) separate by distillation or recrystallization?
ANSWER:
Solution 30SP
(a)
The first two compounds are both glycols.
These two compounds both have a mirror plane of symmetry running horizontally through the center of the compound. Rotation of either compound by 180o leads to a structure that can be superimposed with its partner. This indicates that these two structures are actually identical compounds. By definition, recrystallization or distillation cannot be used to separate the same compound from itself.
(b)
The second pair of compounds is both triols.
Because the configuration of both asymmetric carbon atoms is reversed, these two compounds are enantiomers. Enantiomers have identical chemical and physical properties (except for their behavior towards plane-polarized light), and so they could not be separated by distillation or recrystallization.
(c)
The third pair of compounds is both glycols.
Because the configuration of both asymmetric carbon atoms is reversed, these two compounds are enantiomers. Enantiomers have identical chemical and physical properties (except for their