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.

(b) Chemical structure of ethyl isopropyl ether, showing an oxygen atom bonded to an ethyl and isopropyl group.

Accepted Answer

All right. Hi, everyone. So for this question, let's fill out the values in the proton and Mr table given below for the indicated hydrogens in the following compound. And here we have two meth oxy propane. So here, right, there are four pieces of information that we have to understand about each proton indicated in the structure of two meth oxy propane. The first is the chemical shift in parts per million, which if you recall represents the location of that signal in the actual spectrum right in the actual NMR spectrum. Now the integration, the integration of any given signal is going to correspond to the number of equivalent protons that correspond to that specific signal. So for example, right, if there's only one proton of a certain type right, in a certain chemical environment, then the integration of the corresponding signal should only be one. And in addition, right, we have the number of neighbors or the number of protons that are adjacent to the indicated proton. And finally, we have the multiplicity or the splitting pattern. So let's go ahead and start off by figuring out the chemical shift or approximate chemical shift of protons. A B and C starting off with protons. A. Now recall, it all kill protons tend to be the most shielded, right. And because they tend to be the most shielded, what that means is that the electrons surrounding the nucleus are protecting that nucleus from NMR effects more effectively. Right. So when a given signal, when a given proton is shielded, it's going to appear more upfield, meaning that it's going to appear more on the right side of the spectrum generally between 1 to 2 parts per million. Now, because protons a of both of my metal groups here because they're both oop protons and they're relatively far away from the oxygen which is electron, then they're going to fall in between that 1 to 2 parts per million range, right. So we can say that the signal corresponding to protons A are going to show up at around 1.1 parts per million. But the same cannot be said for protons B and C, right, because protons B and C are connecting or connected to two carbons that are directly connecting to the oxygen of two meth oxy propane. And because oxygen is electron, it's going to draw electron density away from itself, which therefore means right, that the signals for B and C are going to be more d shielded because electron density is being drawn away from these hydrogens. However, proton C is a methyl proton, whereas carbon or excuse me, proton B is present on carbon two of our propal group here, right? Or, or propane. So because of this right, proton C is going to appear slightly more upfield than proton B because proton B is surrounded by other carbons in addition to oxygen, which has more of a de shielding effect than the single oxygen and hydrogens of our methyl proton C. So proton B is going to appear at around 3.8 parts per million, whereas proton C is going to appear at around 3.6 parts per million. So now we can get into the integration or the number of equivalent protons that corresponds to that one signal. Now proton A or protons, a protons A actually correspond to the two methyl groups of this left side of the structure. Right? Because notice how if we look at the three carbon parent chain into meth oxy propane carbons, one and three of the parent chain are of course connected to carbon too, right? Both of them. So therefore, right, theyre actually going to correspond to the same chemical environment and therefore the same signal. So if we have two methyl groups here corresponding to signal A, right, then that means that we have a total of six equivalent protons, which means that the integration of signal A should be six. Now signal B, signal B only corresponds to just one proton, which means that my integration is going to be one and signal C is just one methyl group on the right side of this molecule right in my metox group. So that means that my integration is only going to be three for those three protons in the methyl group. Now, we can go ahead and talk about the number of neighbors. Now, when we talk about neighbors, right, we're talking about non equivalent protons that are a maximum of three sigma bonds away from the proton that you're currently looking at. Right. So protons that are a maximum of three sigma bonds away and can couple together are therefore considered neighboring protons. Now, if we look at protons, A right, both carbons that contain protons A are connecting to just one other carbon that has one proton, which means that protons A have only one neighbor. So that's just one. But proton B. Well, proton B is connecting to both carbons that contain protons. A. So because it's connecting to these two metal groups here, proton B actually has six neighbors and carbon sea. Well, proton see, excuse me, proton C is connecting to a carbon that's connected to an oxygen and that oxygen has zero protons. So that's zero neighbors for signal seat. Now, we can talk about our multiplicity, right? Because the multiplicity of a given signal is going to obey the N plus one rule where N is the number of neighboring protons that we solved in the previous column, right. So if we go ahead and reconsider proton, A for instance, proton A has only one neighbor, right? So according to, to the N plus one rule, right, one plus one equals two, which means that the signal for proton A is going to appear as a doublet. So this is for A and we can do the same thing for B and C, right B has a total of six neighbors, which means that six plus one is equal to seven which makes that accepted and last but not least, right. Proton C has zero neighbors. So zero plus one equals just one, which means that signal C or proton C is going to appear as a singlet and there you have it here is how your proton and Mr table should be filled out. 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.
(b)

Key Concepts

¹H NMR Spectroscopy

Chemical Shift

Spin-Spin Coupling

Watch next