Draw the condensed structural formula, or line-angle formula, ...

Question

Draw the condensed structural formula, or line-angle formula, if cyclic, for each of the following:

b. 1-bromo-3-hexyne

Accepted Answer

Hi, everybody. Our next problem says give the condensed structural formula of the molecule with the name five Chloro three oct time. And we have four answer choices, lad A through D, each of which is a different possible formula. And we'll describe these more in detail as we go through them, comparing them to the name. So first we determine are these all condensed structural formulas? Well, yes, they are, they have lines to show the how the atoms are attached. So lines four bonds, but then the hydrocarbon groups are listed. So ch groups are depicted as letter groups. So we don't have each bond to every single hydrogen shown they're depicted as ch three ch two things like that. So indeed all four of our structures are the correct condensed structural formula. I'll put a big check mark by that description. Now let's look at our name. So we have five Chloro three octane. The yne means we have a triple bond and the number three means our triple bond goes from carbon three. So that's triple bonded, two carbon four. And we have this prefix oct. So we have an eight carbon chain. Then we have five chloro. So we have a chlorine atom on carbon five. So we can take a quick overall view of all of our structures. Each of the four structures does have a triple bond in it. And each of the four structures has a chlorine atom. So we can't rule out any of them on that basis. So now we'll go through and start counting carbons looking for a total of eight carbons with that triple bond from C three to C four. So let's start with structure A. So starting from the first CH three group, counting that as carbon one, we count 123, there's our triple bond to carbon 4567. So we know choice. A can't be the correct answer because there are only seven carbons in this chain. So let's rule out choice a. Now one note, if we have the carbon, the triple bond on the wrong carbon, we have a chain, an A carbon chain, it can be counted from either end. So if we encounter one where the triple bond is too far down, we want to double check that it isn't counted from the opposite direction. But again, it should be the third carbon from the end, whichever way you count it. Now let's move on to structure number B. So starting with the first CH three, I'm just counting left to right. But again, I'll double check to make sure it doesn't work the other direction. So I have the CH three. So that's carbon one and then I count 12 and then I have a triple bond from 2 to 3. So my triple bond is on the wrong carbons. It's carbon two to carbon three and it doesn't matter which way we order it because this triple bond is only one carbon away from the end, which is incorrect. So choice B is not our answer. Choice. Now, we move on to choice C starting with the first CH three, we have 12 and again, the triple bond is on carbon two from carbon two to carbon three. So this is also in the incorrect place. So choice three C cannot be our answer. Now, why do we have two options with this car, double triple bond going from 2 to 3? Why is it thought that might mix us up? Because don't forget in our name, it only says three oc time. So we know that one of the carbons in the triple bond is carbon three. So just in case you get confused and think it might go from 3 to 2, that's why they present that. But we always give the number being the first carbon in the double bond. So we assume it goes 3 to 4 going down in order. So we've just got choice D left by elimination. Let's double check that this is correct. So starting with the first CH three, we have carbon one carbon two. So ch three, ch two, then carbon three is C triple bonded two C four. Then another ch that's carbon five with the chlorine attached. So our chlorine is in the right place. Our triple bond is in the right place. We just need to make sure we have eight carbons. So we keep going ch two, that's carbon six CH two, that's carbon seven and CH three, that's carbon eight. So we have eight carbons triple bond from carbon 3 to 4 chlorine group on carbon five. So choice D is indeed our correct condensed structural formula of five chloro three oct time. See you in the next video.

Draw the condensed structural formula, or line-angle formula, if cyclic, for each of the following:
b. 1-bromo-3-hexyne

Key Concepts

Condensed Structural Formula

Line-Angle Formula

Alkynes

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