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Solution: (a) Menthol, used to flavor various foods and tobacco, is th...


(a) Menthol, used to flavor various foods and tobacco, is the most stable stereoisomer of 2-isopropyl-5-methylcyclohexanol. Draw its most stable conformation. Is the hydroxyl group cis or trans to the isopropyl group? To the methyl group? 

Video Transcript

Hey everyone. In this question we're going to be drawing the most stable conformation of our 2-isopropyl 5-methyl cyclohexanol, so the more stable conformation of a cyclohexane ring, right? Would be the one that a ring and adopt chair conformation, so if we want to start out by drawing the ring, right? That looks like this, of our structure, we can actually do that. So, methyl cyclohexanol means that at position one we're going to have an OH. Now, position 2 we're going to have an isopropyl and at position five we're going to have a methyl, so this would be position 2, 3, 4 and 5. So, 5, we have methyl and 2 we have an isopropyl group, so what does an isopropyl look like? remember, it's going to look like this, it's going to have a regular chain with two methyls coming off, so now we can actually take this structure and adopt it into the chair conformation, which would be more stable.

Now, it turns out the most stable chair conformation would be where all of our groups are substituents or equatorial. So, just remember equatorial means we're going to be at an angle where axial means we're are straight up and down, so we can start off by calling this R1, this 2, this would be 3, 4, and 5, okay? So we're going to draw all of our groups equatorial. Now, equatorial here, would be OH, right? We have an OH there that's the down position at two equatorial will be facing this direction and that's maybe an isopropyl. Now, we can turn that into a structure that is CH, CH3 to the second and then finally for our methyl group at position 5 equatorial would be in this direction, let's take a look relative to our alcohol where are both of our groups, we're going to say about our isopropyl group is cis or trans to the OH, what do you think? Well, they're facing opposite directions, what I mean by that is our OH is facing down and our isopropyl is facing up. So, we're going to say they're trans to each other and what about our methyl relative to our alcohol? What, you guys think there? this is our methyl and our isopropyl? Well, to our alcohol we're going to say that they're facing the same direction because they're both facing down that would mean that they have a cis relationship, okay? So this is going to be our chair conformation and the two are two substituents other than our alcohol, we looked at their relationship, okay? So I hope this made sense, let me know if you have any questions.