Write structural formulas for the following compounds.
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Question

Write structural formulas for the following compounds.

(g) cis-2,3-epoxyhexane

(h) (2R,3S)-2-methoxypentan-3-ol

(i) trans-2,3-dimethyloxirane

Accepted Answer

Hey everyone, let's do this problem and says draw the structures consistent with the names given below, we have to S three R two meth oxy Penton three all trans 34 epoxy hexane insists to three di chlor oh, oxy rain. So these highlighted parts tell me that these are going to be ethers which have our formula R O R and oxy rains or ip oxides Which are that ring with an oxygen atom and two carbons. So let's review a quick few things about naming these for ethers. We actually use the common name more than the APAC name. And to do that, we would list both alcohol groups in alphabetical order and then the ending ether. So those two are groups are the two alcohol groups. So we'll name them in alphabetical order and just say ether. Okay, if there is a ether substitue in group then we would use the alcohol group prefix, let's say meth or F or probe and then we'll use the suffix oxy and that will be what we call an alc oxy group. So instead of an alcohol group it's an alc oxy group. Okay, for oxy reigns or ip oxides, If we have a substitute wint, we'll write our typical al caine chain root name and then we'll write epoxy as a dye located. Substitue in. Right? So those two carbons will be a part of the parent chain. And since it is technically coming off of those two carbons, we would have to put the location of both of those carbons as a substitution group location. Di located substitution. Okay. If it is a route, we'll use the name oxy rain as the route ending. And in this case you count the oxygen as number one. Okay, so you know how we number our carbon chains, we would count the oxygen as number one. We also have R and S. Configuration. So using our con angled pre log, Will quickly mention that when our 4th priority group is dashed. If you go counterclockwise, that is S configuration. If you go clockwise for groups 12 and three connecting them, that will be our configuration. When number four is wedge, it's the opposite. So counterclockwise for groups 12 and three is our clockwise is S. Okay, so let's get into it. We have to S. Three R to meth oxy pen tan three All. That's a mouthful. Alright, so we have all is our alcohol ending. And that goes on carbon # three. We have Penton, which is our route and that is five carbons. Okay, now we have meth oxy so that means it's going to be a substitution group. And since we have the meth on one side and then our route on the other side, that means we'll connect to our chain at the oxygen and then we'll have the methyl group sticking off the other side. Alright, And that will be on carbon number two. And then we'll have to figure out these configurations. Once we draw out for carbons two and three. Alright, so let's draw this out, We have Penton. Let's do our five carbons 1, 2, 3, 4, 5. All right, now we have Meth oxy on carbon 12. So we'll draw Let's try wedge with our methyl group on the other side, in our alcohol on carbon number three. So we can see that these are Cairo centers. Right? Obviously, there are an S configuration. So we have to make sure that these are their correct orientation. So, let's start with carbon number two. So, we're gonna have our hydrogen group. Let me do the same color. Our hydrogen group is group number four. Always. And that's going to be dashed. Here are meth oxy group is going to be highest priority. And then this carbon with the alcohol will have next highest priority. And the methyl group will be third priority. So connecting 12 and three, that is going counterclockwise. And since our group, our lowest priority group is dashed, that will be as configuration. Okay, checking our alcohol group, we have our wedge hydrogen. So hydrogen is four alcohol group is one. The carbon with the meth oxy group will be next highest priority. And then our ethyl group on this side will be third priority. So connecting 12 and three is also counterclockwise. But this time our lowest priority group is wedged. So that is our Which confirms that this is the correct structure and orientation. Let me just redraw it without all this junk on it. one, oh missile in alcohol group. Okay, so that is it for part a let's move on to be Which shouldn't be as bad without the con angle pre log so be we have trans epoxy hex scene poxy hexi. Okay so let's start with our root name Heck seen six carbon chain. So we have and we have epoxy which is going to be our ring and it's di substituted right three and four. So that means on carbons three and 41234. We're going to have our epoxy ring which is going to change the structure and it also says trans. So that means one side is going to be wedge and one is dash. So let's actually draw it from the epoxy. So we'll draw one side wedge. So 1234 five Six carbons. Okay, so that is trans 34 epoxy hexane. And lastly we have sis 23 dyke loro, oxy rain. Okay so we see are a pock side as the root name this time. Die chlor Oh so two chlorine atoms on adam's two and three and they are sis. Okay, so those chlorine atoms are going to be on the same side. And when it says two and three we're talking about the numbers of our route. Right? Well since our route is oxy rain. Like we said we number our oxygen as number one. So two and three will be the two corner carbons of our ring and we'll attach those chlorine atoms on the same side so we can make them either both wedge or both dashed. We'll do them both dashed. Okay, so that is 6 to 3. Di claro oxy rain, which makes a the correct answer to this problem. That's it for this one. I hope this video is helpful and thanks for watching.

Write structural formulas for the following compounds.
(g) cis-2,3-epoxyhexane
(h) (2R,3S)-2-methoxypentan-3-ol
(i) trans-2,3-dimethyloxirane

Key Concepts

Stereochemistry

Epoxides

Chirality and R/S Nomenclature

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