Propose structures that are consistent with the following spec...

Question

Propose structures that are consistent with the following spectra. (Integral ratios are given from left to right across the spectrum.)

b. The ¹H NMR spectrum of a compound with molecular formula C₆H₁₀O₂ has two singlets with integral ratios of 2 : 3.

Accepted Answer

Hello everyone. Let's do this problem together. It says determine the structure of the compound with the molecular formula C H 22 02 which produces the following spectrum. A proton N M R spectrum containing two singlets with integral ratios of 229. Note the integral ratios are given across the spectrum from left to right. All right. Before we look at the integral ratios, we can use the molecular formula to calculate the index of hydrogen deficiency. And that will give us some guidelines about what our structure will look like. Right? If we have any characteristics of uns saturation like a double bond, a ring, a triple bond. So to calculate the index of hydrogen deficiency, we use the formula two multiplied by the number of carbons plus two plus the number of nitrogens minus the number of hydrogens minus the number of halogens all divided by two plugging in the values that we are given that will be two multiplied by 14, right, the number of carbons plus two, we have no nitrogens or halogens. So then simply minus 22 hydrogens all divided by two. And that gives us a value of four for the index of hydrogen deficiency. So recall that a value of one is given for a ring or a double bond in a value of two is given for a triple bond. So there are several different combinations of rings, double bonds or triple bonds that we could have to get four. So we'll just leave this here for now and keep moving on and we'll come back to this. So now let's look at the integral ratio of 2 to 9. So if we have 2 to protons, if we add these two numbers nine plus two, we get a value of 11, right? Do we have 11 protons? No, we have 22 right? So this is a simplified ratio. So let's multiply 11 by two to get 22. And that tells us that in order to determine the integration of our signals, we should multiply our ratio by two. So let's multiply the ratio 2 to by two in order to get a ratio of 4 to 18. All right. So that tells us that we have one signal that has an integration of four hydrogens and one signal that is an integration of 18 hydrogens. And our problem tells us that these are both singlets. So we have a four hydrogen singlet and an hydrogen singlet. And we said that these are from left to right. So the 4h singlet is going to be more downfield and the 18 hydrogen signal is going to be more upfield. All right. Well, one thing I noticed about these numbers is we have a lot of carbons, right, 14 carbons and 22 hydrogens, but there are only two signals. So when there are very few signals compared to the number of carbons or hydrogens, and that tells me that we are going to have symmetry in our structure. OK. So we know our structure is going to be symmetrical and we have a four hydrogen singlet, an index of hydrogen deficiency of four. So all of these oops index of hydrogen deficiency of four. So all of these characteristics tell me that we are going to have a per substituted benzene ring. And let's see why that makes sense. If we have a benzene ring, we have a ring which counts as one value for the index of hydrogen deficiency. And a benzene ring has three double bonds. So that is 1234 that checks out for our index of hydrogen deficiency. If our benzene ring is para substituted with the same group, right, then we are left with four hydrogens that are all chemically equivalent. So they will be represented by one signal. And that confirms that these hydrogens are represented by the 4h singlet. OK. And they have no neighboring protons because of the group that is paras substituted. So that takes care of one signal. Let's look at the other signal that is left over. So in our structure that we have drawn here, we have used 123456 of our carbons, right? Six carbons used. And our molecular formula tells us that our structure has 14 carbons. So that means we have eight carbons left over, all right. And it is a singlet. So that means we must have two tt beutel groups, right? Because in a trt bey group, we have three methyl groups coming off of a carbon so that carbon is not going to have a proton. So the that makes the singlet for those methyl protons. Let me draw out what I'm talking about and we also have two oxygen atoms in our molecular formula. So these trt buttal groups can be on the other side of these oxygen atoms. So we attach the oxygen atoms to the benzene ring and then draw our trt beutel groups. OK. So we have C H three C H three C H three C H three C H three C H three. So that is 369, 12, 15, 18 hydrogens, which makes sense because we found out in our ratio that the second signal is represented by 18 hydrogens. And like I was saying that hydrogen or sorry, that carbon, that is the center of the turtle group has no hydrogen. So it makes sense why all of these hydrogens have a singlet as their signal. So let me draw, let me redraw the final structure with no hydrogens on it. So we have a benzene ring and a 14 die substitution with an oxygen atom and then a trt buttal group attached to each oxygen atom. So that is the final structure for this compound. I hope this video is helpful and thanks for watching.

Propose structures that are consistent with the following spectra. (Integral ratios are given from left to right across the spectrum.)
b. The ¹H NMR spectrum of a compound with molecular formula C₆H₁₀O₂ has two singlets with integral ratios of 2 : 3.

Key Concepts

1H NMR Spectroscopy

Integral Ratios

Molecular Formula and Degree of Unsaturation

Propose structures that are consistent with the following spectra. (Integral ratios are given from left to right across the spectrum.) b. The 1H NMR spectrum of a compound with molecular formula C6H10O2 has two singlets with integral ratios of 2 : 3.

Key Concepts

1H NMR Spectroscopy

Integral Ratios

Molecular Formula and Degree of Unsaturation

Propose structures that are consistent with the following spectra. (Integral ratios are given from left to right across the spectrum.)
b. The ¹H NMR spectrum of a compound with molecular formula C₆H₁₀O₂ has two singlets with integral ratios of 2 : 3.