S3.2.12 Determine the structure of an unknown compound (HL)

[@mohkadro4547]

Hey, i just wanna say that I got a high 7 in HL Chemistry. Without your videos, i wouldnt have been able to do that. Thank you so much for the effort you put in these videos and also thanks alot for replying to comments when we have questions. You replied to all of my questions. THANK YOU SIR

[@MSJChem]

Glad I could help and congratulations for getting that 7!

[@zipporahappiah4474]

I learnt way more in 3 mins than in any of my lessons. Thank you so much for the video it was short but now I get spectroscopy!!

[@MSJChem]

It is a difficult topic but I’m glad I could help.

[@blazebear42]

I've been struggling with this for days and I finally got it!!!!! You make it so intuitive somehow, tysm Mr Mike!

[@MSJChem]

Glad I could help.

[@ishikasoni3809]

Aren't 2 hydrogen atoms attached to the carbon atom adjacent to COOH at 3:16? So shouldn't there be 3 peaks, rather than one (for R-COOH) on the HNMR spectrum?

[@MSJChem]

The hydrogen in the carboxyl group is bonded to an oxygen atom which is bonded to a carbon atom which is not bonded to any hydrogen atoms, therefore, this produces a singlet.

[@notyash9567]

there's a tiny peak at 75 as well, what is that for, if not the molecular mass?

[@MSJChem]

That’s the M+1 peak

[@notyash9567]

@@MSJChem is that because of C-13 isotope?

[@MSJChem]

@notyash9567 yes

[@notyash9567]

@@MSJChem alright, thanks a lot!

[@notyash9567]

@@MSJChem alright, thanks a lot!

[@dhvaniagrawal2319]

At 0:57, isn't there a possibility of Peak A corresponding to a C-H bond as well which is for alkanes, alkenes and arenes? How do we decide which one to choose?

[@MSJChem]

It’s possible but remember that a C-H bond is present in all organic compounds and does not really help much when trying identify an organic compound. It’s more useful to identify an O-H or a COOH or a C=O bond.

[@dhvaniagrawal2319]

@@MSJChem Oh okay. Thanks for clearing this up.

[@YKang-pi5rt]

At 2:01, how do we know whether to choose the peak at m/z 29 or m/z 28? Isn't the peak at m/z 38 greater?

[@MSJChem]

74-45=29. The 45 is the loss of a COOH group.

[@advaithbala]

The intensity of the peak in the mass spectrum does not matter.

[@anikamittal6721]

At 1:52s how do you know the compound at m/z=74?

[@MSJChem]

m/z 74 is the mass of the molecular ion.

[@dhvaniagrawal2319]

Also, at 2:20, there is a peak at 57, why do we choose to ignore that?

[@MSJChem]

Dhvani Agrawal The peak at m/z 57 is for the loss of an OH group (17) leaving the C2H5CO+ fragment.

[@SirSheldon]

At 3:06 you have CH2 as a type of proton with the chemical shift 2.0-2.9. Was this in the old data booklet? It isn't in the current one. At least not with 2.0-2.9.

[@MSJChem]

It is caused by deshielding. This is not covered in the IB syllabus. www.chem.ucla.edu/~harding/ec_tutorials/tutorial51.pdf

[@coolkid9206]

Why only peak A and Peak B for the IR spec?

[@ultrasuperplus]

How much of the compound should be present in the solvent test tube for HNMR, IR and mass spectrum to pick up on it? I mean minimum amount. Thanks.

[@sarabohra2201]

What do you mean when you talk about splitting techniques?

[@MSJChem]

Check out my video on high resolution 1H NMR. www.msjchem.com/topic-21-measurement-and-data-processing.html

[@bossman-ci2md]

Is there no X-ray crystallography video?

[@MSJChem]

No - all you need to know is that it is used to measure bond lengths and bond angles.

[@agnesskanuty1463]

Thanks you