Draw the structure that corresponds to the compound names show...

Question

Draw the structure that corresponds to the compound names shown.

(a) (S)-3-bromo-3-ethylcyclohex-1-ene

Accepted Answer

Hello everyone. Let's do this problem. It says illustrate the Lin ale formula that corresponds to the following compound R three Chloro three Isopropyl Cyclo pen one in. So let's review the IU pack naming rules and we can slightly modify them or apply them to this situation where we are going from the name to the structure. So first, we usually identify and number the parent chain and in this case, we want to find the name of the parent chain and then convert it to the structure. So we look at the end of the name, right, we sort of read the name backwards from right to left to identify the parent chain. So in this case, Cyclo pen one E is going to be our parent chain and notice that the number of the double bond or the triple bond, which is called the Logan goes before the double bond or triple bond ending. And to recall that ending for a double bond is in and for a triple bond, it is. So if we see these endings, we know that we have a double bond or a triple bond, OK? And those double bonds and triple bonds also get numbering priority as well. All right, then we have our substituent and just like the double bond and triple bond, the locat is in front of the name and our substituent are listed in front of the parent chain name. So in this case, we have three chloro and three isopropyl as our substituent groups. And then lastly, we have to consider any configuration. So if we have an alkene, we would consider possibly E or Z configuration. If we have a chiro carbon, we would consider R or S configuration, which I do see an R listed out front here. So we do have to use our con led pre nomenclature rules in order to determine or apply that our configuration to our structure. So what are the con and gold pre log rules? Well, since we are dealing with a chiro carbon, there are four different groups on that carbon. And the first step is to assign the priorities of those four different groups. And that is by atomic mass. So highest atomic mask, its highest priority. If there's a tie between two atoms, we go to the adjacent atoms that are connected to those ones and compare those. And if we have a double bond or a triple bond, we count those multiple times double bond, we count as two atoms, triple bond, we count as three atoms. Then to decide R or S, we look at the orientation of group number four, the lowest priority group? Is it dash or is it, is it wedge? And if it is neither, then we would have to adjust our structure in order to make it one of these. I usually like to make it dash. And if we can't necessarily switch to groups, say because we have a ring hint hint like we will, in this case, I like to draw an eyeball on the side of the structure in order to make the group number four that we have be dashed. OK. And why are we doing all of this? Well, because we want to draw a circle between groups 12 and three and see if they connect in a counterclockwise or a clockwise direction. If group number four is dash, counterclockwise is s clockwise is R, if group number four is wedge, counterclockwise is R clockwise is S. So let's apply all of these rules to draw our structure or our line angle formula. So we said cyclo pen one in is our parent chain. So we have a ring that is five carbons long pent, right? So let's draw a five carbon ring and we have a double bond in on carbon number one. So we can draw our double bond in the number our ring one through five. So the double bond is between carbons one and two. And then we have our substituent chlorine on carbon three. I'll make that chlorine wedged, why not? And I'll make the isopropyl group that is on carbon three dashed. And since we are trying to figure out the structure, we just have to draw something first and then see if it is correct by using our rules. So it might not be right the first time. And that's OK, we can always change it. So we just have to make sure if this configuration is correct. So let's assign the priorities to our chiro carbon groups. And again, I know that we are talking about this carbon because it is the only Carro carbon, it has four different groups attached to it. So chlorine has the highest atomic mass that is going to be oops priority number one. Now let's see what is attached to these other carbons. They are all carbon atoms. So carbon number two, besides the carbon, number, carbon is attached to two carbons and a hydrogen. Carbon four is attached to one carbon and two hydrogens and carbon. The isopropyl group, the first carbon is attached to two carbons and a hydrogen. All right. So we see that carbon four has the most hydrogen. So that is automatically our lowest priority group. Now, in order to compare the other two groups, they both have the same atoms attached. So we have to go to the adjacent atoms again. So carbon number one has two carbons to the right, one carbon to the left and a hydrogen. So three carbons and a hydrogen. This time, I'm counting the carbons on the right hand side as well. And our isopropyl carbons both have three hydrogens and a carbon, right? If we count the carbon where it's coming from. So carbon number one has more carbons. So that will be higher priority and our iso purple group will be third priority. Ok. Let me erase this to make it cleaner. So before we can identify RRS configuration, we have to have group four, either wedge or dash. But notice that group four is in the ring. So we can't necessarily just switch places with our isopropyl group, right? So actually, we could actually, no, we wouldn't want to draw it like that. So I like to draw an eyeball on the side and I know to draw it on this side because if I'm looking from the top here, that will make the back of my ring or sorry, this side of my ring going towards the back. So let me redraw the ring. But from this perspective, I would have the double bond group in the front group number four would be dash in the back. I I should draw my eyeball right about there. So now Chlorine is going to be on the right hand side and the isopropyl group is going to be on the left hand side. Does that make sense? So now we have our group number four is in the back. Let's redraw our priorities. So now we can connect groups 12 and three and we see that they go clockwise, which would in fact be our configuration. OK. So drawing chlorine wedge and isopropyl dash would be the correct orientation for this drawing. So let me redraw the structure neatly with dashed or sorry wedge, chlorine and dash isopropyl. All right. So this is the correct line angle formula for R three chloro three Isopropyl cyclo pen one E. That's it for this one. I hope this was helpful and thanks for watching.

Draw the structure that corresponds to the compound names shown.
(a) (S)-3-bromo-3-ethylcyclohex-1-ene

Key Concepts

Stereochemistry

Cycloalkenes

Substituents and Nomenclature

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