Question
Which of the following alkyl halides undergoes the fastest SN2 reaction ?|CH;CI
Which of the following alkyl halides undergoes the fastest SN2 reaction ?| CH;CI
Answers
Which of the alkyl halides is more reactive in an E2 reaction?
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Of the two compounds? The second one. C. Three. Oh okay. C H ch two reacts more rapidly. Friends. Mhm. With H. P. R. Because we've got mhm compare here. Mhm. H. 30 plus. So if we've got this lone pair that's gonna come in here. Double bond football fear mm Bond we go here we have a resonance form that would give us C. H. 30 Double bond double bond double bond. Mhm. Ch two CH three in such resonating structures. Mhm. Yeah. The carbo cat eye in yeah. Get stabilized by the positive effects. Whoa. Yeah. Yeah. Yeah. Of the O. C. Three groups. Yeah but yeah in the case yeah. Of the first molecule. Yeah. Because of a cut iron carbon cat. I am yeah does not Okay. Get any resonance stabilization. Mhm. Mhm.
Okay. So for this problem you're given three different reactions. And you're told if you double the concentration of the nuclear file in which of these problems would the reaction go faster. So before we do that we need to figure out which of these reactions are going to be S. And one or S. N. Two. And the reason that we need to do that is we have to think back to our rate equations. So for SN one, if you remember the rate of the reaction is going to be equal to K. Times the concentration of your Hello out Kane. For S. N. Two reactions, the rate is a little bit different. So in this case the rate is going to be equal to K. Times the concentration of your hello al caine times the concentration of your nuclear file. So the question because it's asking which of the reactions if you increase the concentration of the nuclear file is also going to cause an increase in the rate you have to think about S. And two reactions. Because in this rate equation, your nuclear file is comparable to your rate. So whichever of these reactions SN two is going to be our answer to the question. Yeah. So let's look at this first example. So here we have a secondary alcohol. Hey lied, Call our X. And now, you know, secondary out kill highlights can either go SN one or S. N two reactions depending on the reaction conditions. So in this case, because this is a Cairo carbon kind of a hint that we can do to figure out if this is us in one or S. N two is look at the configuration of the stereo chemistry of our product. And if you look at the stereo chemistry of our product, we have there should be a hydrogen on this atom here. And actually I think I drew this. Oh yeah, this is sorry about that. Let's fix this up. Okay, so for this problem, we actually have an inversion of stereo chemistry stereo chemistry, whereas this initial carbon had a configuration of 123 S. This product now has a configuration of our So because we have an inversion of stereo chemistry, this tells us that our reaction is less than two. And so because we have an SN two reaction, then if we double the concentration of the nuclear file, then our rate is also going to increase as well. So A would be an answer. Okay, let's look at our second problem. So in the second problem, we have a primary Hello, al caine. And we know what we've seen in the chapter so far, is that primary Hello Wilkins are never going to be very rarely, but mostly never going to undergo as in one reactions. So this is going to be an SN two reaction because this is an snt reaction. Then if we double the concentration of our nuclear file, then our rate is also going to increase. And finally, let's look at this reaction. So this Hallowell came here is tertiary hala locking and in this case a tertiary Hallowell Kane is going to very rarely undergo SN one or sorry, is very rarely going to undergo SN two. Because if you have a concurrent reaction where your nuclear file attacks and kicks off the leaving group, this reaction center is very hysterically hindered. So instead your first step is going to be your leaving group leaving. And this is going to result in an SN. One reactions. So because it's S. N. One, the concentration of the nuclear file. To go back up here, the concentration of nuclear file has no bearing on the rate. So any change in the concentration of the nuclear file is not going to affect the rate. So the of these three problems, only the 1st and 2nd reactions can be classified as SN. Two, and only these two, not the third one, are going to have a changed rate when you change the concentration of the nuclear file.