Organic Chemistry MCQ
Organic Chemistry MCQ: Which of the following compounds exhibit cis–trans isomerism?
Analysis: The question is straightforward. Which compounds exhibit cis-trans isomerism? In the Chemistry H2 syllabus, we learnt about the two criteria for cis-trans isomerism.
- Presence of C=C bond
- Different atoms/group of atoms bonded to each of the carbon atoms
Although in the H2 Chemistry syllabus, it is required that C=C bond cannot be in a cyclic structure.
Looking at the three options, looks like none of them can exhibit cis-trans isomerism! But this cannot be the case, let us examine the options carefully.
The three options examined
Option 1: Although there’s no C=C, there is a four-carbon ring structure which restricts rotation. Moreover, the two central carbon atoms each have different atoms bonded to it. So it is able to display cis-trans forms!
Option 2: This is outright wrong as it violates the rule that C=C bond cannot be in a cyclic structure. (But we shall see that the cyclic structure is only limited to 7 carbon ring and below)
Option 3: This is not in the H2 syllabus as cis-trans isomerism can be exhibited by C=C bond in a cyclic structure having more than 7 carbon atoms. Click here to find out more
This Organic Chemistry MCQ isn’t the run-of-the-mill type. Two of the options involves knowledge outside of the H2 syllabus. Most likely, this question is meant to challenge the stronger ability students to read beyond their syllabus requirements. Also, it expose students to a novel context that is slightly outside of their comfort zone.
In our weekly classes, we let students have a chance to try out these challenging questions to stretch them. If you liked doing this question, come join us and broaden your horizon!