Organic Chemistry / Drawing Isomers with Functional Groups
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Solution: Photochemical chlorination of 2,2,4-trimethylpentane gives f...

Question

Photochemical chlorination of 2,2,4-trimethylpentane gives four isomeric monochlorides.

(a) Write structural formulas for these four isomers. 

Video Transcript

Alright guys. So, in this question we have 2,2,4 trimethyl pentane, which I've drawn in free bond line, and this is that we get 4 different isomeric mono chloride products, just what that means is you get four products that are isomers of each other all of them are just where we add on one chlorine, okay? So they're mono chlorinated. Now, wants us to draw the 4 different isomers and their structural formula and that's basically a formula that looks like this where you have all your atoms drawn in. Now, we could do this different ways but I drew it out for you, so we can actually compare that to the original but first what I want to do is, let's take a look at our bond line. So, where are the 4 different positions before and nonequivalent hydrogen that we can add a chlorine to, there's four of them, okay? Well, the easiest one is going to be right here, there's a hydrogen there, this is not a symmetrical molecule, so this is going to be one as well, can you think of anywhere else? Well, it's going to be right here, we're going to say that this methyl group is going to be equivalent to that one, so this would be the last position, okay? So what we're going to do and again these would be equivalent as well to ones over there, same thing with these, okay? So, all we need to do is draw on the structural formulas adding chlorines to all those positions, just replacing one of the hydrogens. So, here this is the structural formula of our original, so let's go ahead and draw the monochloride products in their structural formulas, okay? Now, what I'm going to do is take my copy in one. Now, here is example of one of them, okay? Where let's take a look, it looks like the hydrogen that we replaced is, do you know which one it is? one of these, okay? So that is where we replace one chlorine. Now, go ahead and try to replace one right here, one of those, try to replace one right here, okay? One of these and then of course try to replace this last one. Alright, which would be right here, let's see what we would get, all we need to do is just let's copy this and now let's paste it in we have 1, 2 and 3, let's erase the hydrogens, erase the highlighted part and let's see if you were able to fill them all in, so what do you guys think? Well, for the first one what we can do is we're going to write CH2 and then all we need to do is just write in a chlorine like that, okay? And that would represent the split one. Now, for the next one we're going to represent that as the propyl and just replace one of these, so it becomes CH2 and then we added that Cl, this would be the purple and go ahead, did you come up with the last one, the one that's green? that one we're going to replace this, we have to simply take this CH3, move it over and then add in our chlorine, alright? so the chlorine that were ending in would be right there, okay guys? and that would be that green one, so these are going to be the 4 different monochlorides that we can draw as our products, okay? And they're all isomers of each other. So, recognize that this was just bond line, what we can do is simply just take our pentane with our 2-methyl, 3-methyl groups and then just go ahead and add on the chlorines, okay? It's going to be equivalent to that but it asked specifically for our structural formulas, alright guys? So, I hope this made sense and let me know if you have any questions.