Consider the following reaction coordinate diagram where A reacts with achiral r
ID: 987436 • Letter: C
Question
Consider the following reaction coordinate diagram where A reacts with achiral reagent R and gets converted to C, and B reacts with the same reagent (R) under identical conditions and gets converted to D. Compounds A and B are stereoisomers of each other, and compounds C and D are stereoisomers of each other. Which statement about these compounds must be true?
a. A and B are diastereomers
b. C and D are meso compounds
c. C and D are constitutional isomers
d. A and B are E/Z isomers
A+ R Reaction coordinateExplanation / Answer
First to all, let's define the concept of stereoisomers. Stereoisomers are isomeric molecules that have the same molecular formula and sequence of bonded atoms (constitution), but differ in the three-dimensional orientations of their atoms in space. This contrasts with structural isomers, which share the same molecular formula, but the bond connections or their order differs. By definition, molecules that are stereoisomers of each other represent the same structural isomer.
Now basing on this, we can assume that A and B are stereoisomers, as C and D. Now both of their products ends with the same energy, meaninng that in spite of the fact that A is in higher energy than be, released more energy than B, but both of them ends with the same energy. If they have the same energy, then both compounds cannot be E/Z isomers because this kind of compounds are generated and ends with a different energy. Same thing with constitutional isomers, where the functional group may vary. So the answer would have to be either A or B. In this case, meso compounds are diastereoisomers, and meso compounds have all of the substituyent eclipsed one with another in the chiral centers. We don't have enough information to know if both A or B, even though they are stereoisomers (They have same molecular formula) to know if they are diastereoisomers, but if they are both meso compounds, it has logic that they ended with the same energy, so, option B is the correct option.
Hope this helps