Determine the relationship between each of the pairs of the following compounds. Are they structural isomers (different molecules), conformational isomers (the same molecule), or not related?

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Video transcript

Welcome back everyone. For the pair of the compounds below determine whether they are structural isomers, which means different molecules, confirmational isomers, which means the same molecule stereo isomers, which means same connectivity but different spatial arrangement of atoms or unrelated. So we're going to see structures and as we can see, they are cyclic alk canes. And essentially, if we want to identify the relationship between those structures, we first of all want to determine their molecular formulas. And we can see that by counting the number of carbon atoms. So first of all, we notice that every structure contains a five member ring, 1234 and five. This gives us five carbon atoms. And then we have a side chain which gives us seven carbon atoms for each structure. So we can state C seven and C seven game. Now the question is, do we need to count the number of Hagens? The answer is no, we don't need to count the number of hydrogen atoms because we know that the general formula or a cyclic alkane would be CNH two N. So we essentially have the same number of hydros which is 14 for each structure, we can of course, verify that, but there is no necessity, right? We always want to save time. So if we have the same molecular formula, those structures cannot be unrelated. Now, they cannot be stereo isomers because we don't have any wedges or dashes shown. So we don't really know about specific spatial arrangement of atoms, right? We don't see any wedges or dashes, we only see solid bonds, they are not unrelated. Now, can they be conformational isomers the same molecule? Well, they cannot because they don't look the same right. Confirmational isomers essentially means that we can have specific bond rotation. In this case, let's say we had an ethyl group for the second structure and we could simply rotate that bond in through a zigzag in a different direction. And then yes, we could say those would be confirmational isomers, but this is not the case. So we're left with structural isomers, different molecules. And we have to recall that structural isomers or constitutional isomers, they have the same molecular formula but different connectivity of atoms. What we notice is that the first structure contains an ethyl substituent bonded to one of the carbon atoms. And the second structure simply has two methyl groups as side chains. So we can clearly see that the connectivity of carbon atoms differs, which is the definition of structural isomers. And that will be our final la sir. Thank you for watching