Complete the table of ¹H NMR data you'd generate for each of t...

Question

Complete the table of ¹H NMR data you'd generate for each of the following molecules.

(d) Structural formula of 1-chloropentane, showing a five-carbon chain with a chlorine atom attached to the terminal carbon.

Accepted Answer

All right. Hi, everyone. So for this question, let's go ahead and fill out the following proton and Mr table for the indicated hydrogens in the molecule given below with the molecule in question being two promo prop. So based off the information that's being specified in the table, right, there are a few different parameters we have to keep in mind here, the first of which is the chemical shift expressed in parts per million. Now recall that the chemical shift of any given signal in a proton in a more spectrum reflects the location of that signal in the spectrum itself. Right. Now, depending on what type of proton it happens to be, then we can more or less predict the chemical shift to a certain extent by taking into consideration what factors might shield or de shield that specific proton. Right. Now, when we talk about shielding, recall that electrons are which surround the protons inside of a nucleus and therefore protect it from NMR effects. So when something is shielded, then those specific protons are less exposed to NMR effects, which means that they tend to appear more upfield or to the right side of the spectrum itself with relatively low values of the chemical shift. And if we can discuss a proton being up field, we can also discuss the possibility of it being downfield, right, because protons that are connected to or are in close proximity to electron atoms, such as for example, oxygen, that oxygen and that electron atom in general can remove electron density away from a given proton, which will therefore expose it more to NMR effects. So when that happens, the specific signal is found to be relatively downfield or more. So to the left side of the spectrum. Now, with that said about the chemical shift, right, the next column over deals with the integration and the integration is simply the number of equivalent protons that will correspond to any given signal. Whereas the number of neighbors, the number of neighbors refer to the number of non equivalent protons that are a maximum of three sigma bonds away from the proton that you're looking at right from the hydrogen in question, whereas the multiplicity and the very last column deals with the splitting pattern of that particular signal and it is dependent on the number of neighbors. So let's go ahead and start by looking at proton A or rather the hydrogen label date. So starting off with proton A, right, the protons labeled A are oop protons and specifically they are methyl protons. So recall that oop protons in general tend to be the most shielded. So they're the ones that are going to appear the farthest to the right of the spectrum itself generally in between 1 to 2 parts per million. Now, granted, right, in addition to signal a here being a methyl proton are methyl protons plural, they are also in relatively close proximity to a bromine here, which is of course, electron. So because of this, these methyl protons are going to be relatively down field in the range that they typically occupy. So if they typically occupy a range of approximately 1 to 2 parts per million, then this proximity to an electron withdrawing bromine is going to bring it closer to two parts per million, slightly more downfield, right? So we can say that its chemical shift is going to be approximately 1.7 parts per million. Now, when it comes to the integration, let's go ahead and discuss something about the structure of T Brummel propane, right? Because notice how two promo propane has an element of symmetry to it, right? Because I can draw this imaginary line going down carbon two in the parent chain. And when I do that, what I'll notice is that carbons one and three of the parent chain are equivalent, right? Because notice how they're connecting to the same carbon. So because of the symmetry, right, carbons one and three, specifically the protons on carbons, one and three, all of them would correspond to signal a. So all of them would make up signal A and if we've got three methyl protons on our two different carbons here, that makes for an integration of six. So now with the number of neighbors, if we consider the number of neighbors for a second too, right, both carbons one and three are connected to carbon two and the parent chain that only has one hydrogen by itself. So the number of non equivalent neighbors is going to be just one, right? Because its referring to the single proton on the adjacent carbon, which in this case is carbon too. And lastly, we can talk about the multiplicity. Now recall that the multiplicity of a given signal is going to follow the N plus one rule. So if we consider our calculation here for proton for the protons labeled A N is equal to your number of neighbors. So if I do, if I plug in rather one for my end here, and I add one to that, then that gives me a total of two. So what that means right is because my sum happens to be two, my signal is going to appear as a doublet in my proton more spectrum. So that's what I'll be writing here. So now we can do the same thing for the proton label beat starting with the chemical shift. Now immediately, right, the proton labeled B is going to be more downfield than the protons labeled A because B is a lot closer to the Bromy. In fact, it's directly connected to the Bromy. So the bromine is going to have more of a de shielding effect. So therefore, the chemical shift of proton B is going to be approximately 4.5 parts per million because of how close it happens to be to our Bromy. Now, in terms of integration, right, there's only one proton on carbon two in the parent chain, which means that there's only going to be one proton labeled B here, which means that my integration should be one. Now as for my neighbors, bye. Carbon two of the parent chain is connected to carbons one and three, both of which provide the protons labeled A. So because of this, there are a total of six neighbors if I consider the two different methyl groups that are surrounded by or surrounding carbon two, each with three different protons. So that's a total of six. And lastly the multiplicity. So if I apply the N plus one rule for proton B, that's going to be six plus one for a sum total of seven. Now, because my sum happens to be seven, the signal for proton B is going to appear as a septet in the proton and the mar spectrum and there you have it. So here is how the chart should be filled overall. So if you stuck around to the end, thank you so very much for watching. And I hope you found this helpful

Complete the table of ¹H NMR data you'd generate for each of the following molecules.
(d)

Key Concepts

¹H NMR Spectroscopy

Chemical Shift

Spin-Spin Coupling

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