This is a Newman projection of a substituted cyclohexane.

c. G...

Question

This is a Newman projection of a substituted cyclohexane.

c. Give the IUPAC name.

Accepted Answer

Hello, everyone. Let's do this problem. It says, refer to the Newman projection below, determine the Iupac name of the substituted Cyclohexane. So I know Newman projections can be a little bit intimidating, but I'm going to give you a secret on how to make this easier. We can convert the Newman projection to a flat ring drawing. And we will show those substituent groups on the ring with wedges and dashes. OK. And that will make it much easier to name. All right. So on the left hand Newman projection, we have a methyl group in the axial position pointing up and on the right hand Newman projection on the front carbon, the methyl group is on the front carbon on the left. And on the right hand Newman projection down in the equatorial position, we have a chlorine atom. So as the problem mentions, this is Cyclohexane. So let's draw a six membered ring flat. OK. And let's number our ring and we want to number it according to the Newman projection. So where do we number this compound? Do we start at the chlorine or at the methyl? Well, this brings me to our first rule of Iupac naming, we want to number the parent chain, giving the substituent the lowest numbers possible. And we want to start with the highest priority group, but halogens have the same priority as alco groups. So in this case, when we have the same priority, we want to go in alphabetical order because we list the substitutes in alphabetical order. But again, we only do this if they have the same priority. So we will start numbering one at the carbon with chlorine and we will go clockwise, which means the methyl is on carbon three. OK. So let's number our flat ring. All right. And now the second step is we want to list the substituent with their locus. And again, we said we'll do that in alphabetical order. So we have chlorine on carbon one. So that will be one Chloro and our methyl on carbon three. So three methyl, now let's add those to the ring properly, right? And by properly, I mean, showing their configuration. So on carbon one, that chlorine atom is down, right, pointing down. So it's going to be on the bottom face of the ring. So we will draw that with a dash and the methyl group we said is pointing up in the axial position. So that is going to be wedge. And the last step of our IU pack naming is to show or rather assign configuration. And that means either R or S configuration or E configuration. Does this apply for this compound. Yes, because we have two chiral centers, right at carbons, one in three where our substituent groups are, there are four different groups on those carbons. So let's review quickly how to assign RS configuration. We first assign priorities to the four different groups on that carbon. And we do this by atomic mass. And then when we are determining R or S configuration, it's going to depend on the orientation of the lowest priority group. So is group number four dashed or is it wedge? Now, once we have that figured out, we want to connect groups 12 and three in a circle in that circle, we either go counter clockwise or clockwise. And that is what will determine R or S configuration. So if group four is dashed, counterclockwise is going to be S configuration clockwise is R, if number four is wedge, counterclockwise is R and clockwise is S. So let's assign the configuration for these chiral centers. So we want to add the hydrogen that is on both of these carbons. So since carbon number one, that chlorine is dashed, the hydrogen will be wedge. And on carbon three, the methyl is wedged, so that hydrogen will be dashed. And we know that hydrogen is always the lowest priority group. So those are our group number fours for each carbon. Now let's assign the other priorities. So for carbon one, chlorine has the highest atomic mass. So that will be number one priority. Now, which carbon on either side is the 2nd and 3rd priority. Well, if we keep moving to the adjacent atoms, we get to carbons three and five and carbon five has two hydrogens and another carbon. But carbon three has that extra carbon in the methyl group. So going clockwise to carbon two is going to be the second highest priority. Carbon six, that group is going to be third priority. So looking at group number four, it is wedge here, if we connect groups 12 and three, they go clockwise. So wedge clockwise is going to be s configuration. OK. So we have one s and let's look at carbon three. Now, you might automatically assign that methyl highest priority, but that is actually incorrect, right? Because that carbon has three hydrogens, whereas the carbons in the ring are attached to another carbon. So carbons two and four are identical. But if we go to carbons five and one carbon one has that chlorine and we know that chlorine is high priority. So that's going to make carbon two, that group the first highest priority group. And then that will make carbon four that direction. The second highest priority in the methyl group is third priority. So on this side, our hydrogen is dashed connecting groups and three, they go counterclockwise. So dash and counterclockwise is S orientation as well. So we have three S configuration as well. So putting all of these components together. The correct name for this compound is going to be 1 S S one Chloro three methyl cyclohexane. That's it for this problem. I hope this video was helpful and thanks for watching.

This is a Newman projection of a substituted cyclohexane. c. Give the IUPAC name.

Key Concepts

Newman Projection

Cyclohexane Conformation

IUPAC Nomenclature

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