Draw a structure for a compound that meets each of the following descriptions:
b. An 8-carbon ketone with six carbons as its longest chain

Question

Draw a structure for a compound that meets each of the following descriptions:

b. An 8-carbon ketone with six carbons as its longest chain

Accepted Answer

I'll come back. Our next problem says, sketch the line structure of the molecule that satisfies the condition ketone with six carbons total and four carbons as its longest chain. So sometimes these can feel a little bit challenging. But the best way to start is focus in on the longest chain. And while line structures are often really useful for going from structure to name. In this case, I think doing a condensed structural formula is a little bit easier. So we'll start that way and then work our way to the line structure. So I have four carbons as the longest chain. So let's go ahead and put four carbons with lines of bonds between them. Oops one weirdly long there, I've put spaces there to add the hydrogens. Although since I'm not looking for like an instruct formula, as my answer, I don't really need to go all the way through this if I don't need to. So I have four carbons and then I know this must be a ketone. But let's recall that the structure of a ketone is we have an R group. So an alkyl group attached to a carbon which is double bondage in oxygen and then has a second r group on the other side. So are molecules drawn here, the ketone must be on carbons, two or three. It cannot be so no ketone on either carbons, one or four, because this wouldn't be a ketone. It would be an aldehyde. If you put a double bond to an oxygen here, you'd have a hydrogen on that carbon. And that would be an aldehyde because an aldehyde just has one alkyl group attached to that carbonyl group and then a hydrogen on the other side. So a ketone cannot be on a terminal carbon in the chain. So our ketone group must be on carbon two or three. When we have a four carbon chain that will be identical, it doesn't matter two or three. It's the same molecule. So let's just put it on carbon two for instance. So we'll put our double bond to an oxygen on carbon two. And now we have our ketone and then what's the other part of the condition? It must have six total carbons. So my first instinct must might be again, I cannot put, I'll add in red where I've put no ketone, I cannot add no extra carbons on my terminal carbons because that just lengthens the chain, it won't give me extra carbons without lengthening the chain. So my next instinct might be let's add an ethyl group to carbon three. I cannot add anything. So no more carbons to my carbon carbon. It already has four bonds, it's bonded to two neighboring carbons and it has a double bond with the oxygen. So it's full for lack of a better word. So my extra carbons must go on carbon three. So let's try adding an ethyl group ch two ch three, two carbon three. However, if I do that, I'm going to highlight in blue for a minute here, I will make my chain longer and end up with a five carbon chain because remember that the chain can go in any direction. So if I add an ethyl branch, I just switch where the longest chain is. So I cannot add both carbons in a row like that. Or my chain is suddenly too long. I need the longest chain to be four carbons. So what's the other possibility here? Well, add one methyl group ch 32 carbon three, carbon three can still form one more bond. So put a second methyl group on there. Now, I have six total carbons and my longest chain is four carbons. So I've got four carbons and the two middle carbons have a ketone on one and two methyl groups on the other. So let's draw that line structure. I have 1234 carbons and that sort of zigzag arrangement, I put a double bond to an oxygen on carbon two and then on carbon three, I add two more methyl groups give that sort of trident shape there. And I have my line structure for this molecule with a ketone group and six total carbons. But my longest chain being four carbons long. See you in the next video.

Draw a structure for a compound that meets each of the following descriptions:
b. An 8-carbon ketone with six carbons as its longest chain

Verified video answer for a similar problem:

Key Concepts

Ketone Structure

Carbon Chain Length

Molecular Formula and Isomerism

Draw a structure for a compound that meets each of the following descriptions:b. An 8-carbon ketone with six carbons as its longest chain

Verified video answer for a similar problem:

Key Concepts

Ketone Structure

Carbon Chain Length

Molecular Formula and Isomerism

Draw a structure for a compound that meets each of the following descriptions:
b. An 8-carbon ketone with six carbons as its longest chain