30c: Determining molecular structure from H-NMR spectra

[@PunmasterSTP]

More really great examples, and I was glad to see a healthy discussion in the comments. It was also cool to see an example with a carbon-carbon double bond locking in two hydrogens on the same carbon and forcing them to split each other!

[@shahiii596]

What a lovely explanation! thanks and please keep sharing with us more...❤

[@taylorereilman7855]

thank you so much, I have watched so many video and this is the video that made it click for me

[@RoxiHulet]

I'm so glad!

[@dishanthakur8570]

The C3H4Br2 is weird even the structure that you came up with will only give 2 peaks both singlets, I think the NMR used is wrong it may be that it has 3 peaks ( Quartet, Doublet, Singlet)

[@RoxiHulet]

The hydrogen atoms attached to the end of the double bond are not equivalent to each other, so they each generate their own signal and they each have their own splitting.

[@sindilesira1117]

Thank you Prof, love you for this

[@timta9611]

Thanks for the help! Really useful vid

[@cris5285]

For C3H4Br2, I understand that the 2 hydrogens are not chemically equivalent due to being locked by the double bond, but if they are on the same side, how can you ensure that they are 3 bonds apart?

[@RoxiHulet]

I may not totally understand your question, so please comment back if I misunderstood. The "3 bond" rule doesn't take spatial orientation into consideration, so it doesn't matter if the hydrogens are cis, trans, or on the same carbon atom. So if the 2 H atoms were cis to each other, they would still be 3 bonds apart - H to its C, C to C, and C to the 2nd H.

[@cris5285]

Ah, apologies, what I meant was both of the hydrogens being on the same carbon. It makes sense that they would still "talk" to each other, it just didn't occur to me that they didn't have to be 3 bonds apart.

[@RoxiHulet]

@@cris5285 oh, I think I understand. The 3 bond rule is a minimum of 3 bonds. So in this case, 2 bonds apart means they are going to split each other. Is that what you were asking?

[@cris5285]

@@RoxiHulet Yes! That was exactly what I wanted to ask

[@PunmasterSTP]

@@RoxiHuletMan, hydrogens being locked by double bonds has definitely tripped me up. Thanks for providing all of these really nice examples, and taking the time to explain things in the comments!

[@afrashahed989]

you slayed with this thank you

[@RoxiHulet]

You’re welcome!

[@anissamsudin8697]

what if the question does not provide integrals?

[@RoxiHulet]

That's tough.. If you have no hints about the number of H atoms, I'm not sure how you could solve this type of problem.

[@asuramunikavishadesilva371]

Many thanks!❤

[@sakura-rc3ed]

hi, how would you do this problem if you were just given the relative area, absorption, and ppm values along with the IR absorption of the formula?

[@PunmasterSTP]

Which problem specifically? Overall, I think you just have to try to fit the puzzle pieces together as best as possible, and if the question seems ambiguous, check in with your professor.

[@smalliver365]

Thank u shawty

[@RoxiHulet]

Anything for you, boo

[@smalliver365]

@@RoxiHulet Damn bae u da best!!!