Draw the following three isomers of C₅H₁₂ as condensed structures:
b.

Question

Draw the following three isomers of C₅H₁₂ as condensed structures:

b.

Accepted Answer

Hi, everyone. Welcome back. Here's our next problem. It says, consider the isomers of HEPT shown below. And we have three molecules drawn as structures here. The first being three methyl hexane, then three apple painting then 33 dimethyl pentane. Then our problem says, give their condensed structures and we have options A through D each with different condensed structures offered. So we'll work our way through them one by one. So these being seven carbon molecules, these are going to be long and then structures. So let's look at just the very first part up to the methyl branch. Our first molecule has a methyl branch on the third carbon. So let's see if we can eliminate anything by just looking at that first part of the molecule. So we know that the first carbon has three hydrogens, the second two, the third, just one hydrogen. And then the methyl group that methyl group will need to be indicated in parentheses to show that it's a branch. So looking at choice A for three methyl hexane, we see the beginning of it here is correctly CH three CH two CH and then in parentheses, ch three, we'll come back to the rest of the molecule. But for now, I'm going to check each of the answer choices to see if that beginning of our three methyl hexane is correct. So choice B that is indeed correct. Choice C correct up to the methyl branch. But in choice D while it shows the branch correctly on the third carbon, it has the subscript too after the methyl group indicating two methyl branches. But this is incorrect since our molecule just has one. So we can go ahead and eliminate choice D altogether. Now let's look at the rest of the molecule. This is hexane. So there should be three more carbons after our branch. So it should be CH two, ch, two ch three. So looking at choice A, that is correct. Choice B that is correct. But in choice C, we have an extra carbon. It has four carbons after the branch and therefore, we can eliminate choice C. Well, that's as much as we can do with our first structure. So let's look on to our second structure. Three ayl pentane. So now we have a five carbon main chain because two of our carbons are in the branch. The branch occurs on our third carbon again, but it has two carbons in it. So our branch in parentheses should say ch two, ch three for the ethel group. So let's look at choice. A. Well, in choice A, we indeed show a branch on our third carbon, but it's showing two branches. However, when you look back at the name of the molecule, our answer choices list 33 dimethyl pentane first, which is the third structure in our structures. So that's kind of a little tricky. So go back and look at the name. It's actually listing the structure for our third, the condensed structure for our third expanded structure. So we need to go all the way to the end to look for the structure corresponding to three ethyl pentane. So let's look at that last canon structure which indeed shows on the third carbon A branch. However, instead of it being the proper format of C two C three, it's showing two CH two molecules, which is not the correct notation. In addition, an AYL group would have CH two CH three as its notation. So choice A is incorrect. And by process of elimination, we have our answer of choice B but to be thorough here, let's look and make sure this name is correct for three ethyl pentane again listed as the third structure here, even though it's the middle one drawn. So we have our three carbons CH three CH two ch, then our branch correctly written as an ethyl group in parentheses, ch two CH three and then the remaining two carbons CH two CH three since this is a Penta chain. So only five carbons in the main chain. Now let's move to our third structure. 33 dimethyl pentane, which is written as the second condensed structure. So the two branches aren't our third carbon. So correctly, we have C three C two C, there are no hydrogen since we have two branches. And that is correctly written as CH three in parentheses with a two subscript because there are two branches that is correct. And then there's two remaining carbons, ch two CH three. So the correct condensed structures for these isomers of HEP are written in choice B indicating the correct branches and locations and how many hydrogens are present? See you in the next video.

Draw the following three isomers of C₅H₁₂ as condensed structures:
b.

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Draw the following three isomers of C₅H₁₂ as condensed structures:
b.