Give the IUPAC name (including cis or trans, if needed) for ea...

Question

Give the IUPAC name (including cis or trans, if needed) for each of the following:

a. Structural formula of an alkene showing carbon double bond and attached hydrogen and methyl groups.

Accepted Answer

Hi, everyone. Our next question says, what is the correct Iupac name use cis or trans if necessary for the structure given below. And we have a condensed structural formula here. So we have AC C double bond and the first carbon in the double bond has a methyl group and a hydrogen attached to it. The second carbon has a hydrogen and ach two ch, two ch three branch attached to it. So three carmens, the hydrogens are on opposite sides of the double bond, one hydrogen on top and one on bottom. And then the methyl substituent and the branch chain are also one on top and one on bottom. Our name choices are a cis three hexen, B trans three hexen, csis two hexen or D trans, two hexen. So the first step, whenever we're naming something is find the longest carbon chain, we have a double bond here. So we want the double bond to be in that chain. So I'm going to highlight in blue our chain here and how many carbons or I'll just highlight the carbons and we can count them. So we're looking straight at our cc double bond right in the middle. But let's remember that, that methyl group can be the start of a chain, the methyl group off of the first carbon in the double bond. So if I start up on the methyl group as carbon one, and then number two in the double bond, number three in the double bond, and now just go on into that three carbon chain. So 456, so I can form a chain of six carbons. Now, I have a double bond, so I know what's going to be that ene ending for my double bond. So I'm going to have for six carbons. I'm going to have a hex in and now I just need to number where this double bond is. So when I number a chain with a double bond, I number it so that the double bond will have the lowest possible number. So we can see that the way it's written, there's just one carbon on the left side. So I want to start with that. So I'm calling that number one and then number two will be where the first carbon in the double bond is. So my double bond will be going from C two and then a double bond to C three. I don't have any other substituents. So I'm not really going to worry about numbering it further. I just have this six carbon chain with a double banda carbon two. So that will give it the name two hyphen hexen So I've located my double bond. The last thing is, do I need to clarify whether this is cis or trans? And remember the rule about knowing if cis trans isomers are possible. And I've posted up the little diagram, if I have a double bond and the groups attached to it are labeled R one and R two on the top on two different carbons, R three and R four on the bottom on the two different carbons. And if R one is not the same, so it does not equal R three and R two does not equal R four, then cis trans isomers exist. So there's two clarifications on the same carbon, the two substituents must not be the same. And that's the case for both carbons. So it's important to note that this does not mean the R groups on the two different carbons. If R one is the same as R two, that's perfectly fine. So in our case, that is what's happening, we have a hydrogen on both carbon two and carbon three. What matters is, does each carbon have two different substituents? So let's look at that carbon two has hydrogen and a methyl group. So those two are different carbon three has a hydrogen and a propal group. So they are both different. So in this case, we do have cyran isomer isomers. So which do we have here? Well, our hydrogen atoms it's easiest to start with that. They're very simple. We know they're identical, they are on opposite sides. So H Adams or on the opposite sides of the bond. So it is a trans arrangement. So I do need to put that in my knee. So in front of the two hexen, I should have trans and that corresponds with choice D trans to hexen. We'll just look briefly at our other answer. Choices to be thorough choice. A says three S sis three hexen. So that has the double bond in the wrong place. We label it by the first carbon, not the second. So carbon three is in the double bond, but we start with the first one. So or we use the first number to identify it. So choice A is incorrect. Choice B says trans three hexen. So again, double bond in the wrong place. And then choice C is cis two hexen double bond in the right place, but incorrectly labeled as the cis isomer. So choice C is incorrect. So once again, our answer here for the correct Iupac name of our structure. Choice D trans to hexen. See you in the next video.

Give the IUPAC name (including cis or trans, if needed) for each of the following:
a.

Key Concepts

IUPAC Nomenclature

Stereochemistry

Functional Groups

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