Organic Chemistry Spectroscopy: No idea how to read these graphs. Part 2

[MonkeySage]

I'm furious. Spectroscopy (IR, CNMR, HNMR, etc) graphs in general make absolutely no sense to me. I get by purely on guess work, and in the end I can't put together any molecules based on them. They are like a different language to me, only not even google translate can help me.

And my prof just keeps including more and more spectroscopy questions on our material. I have told him in the past that I don't know how to read them, and he's been completely and utterly unhelpful with teaching me how to read them in general. He'll help me with individual problems, but not with actually coming up with a method for reading them consistently.

Knowing the answer to one or two questions isn't helpful to me.

[Peelee]

A couple questions.

Have you told the professor in those exact terms your problem? Does your university offer free tutoring? Have you asked any classmates if they can help? These I'm asking because no matter how helpful this forum can be, actually having in-person help where you can look at graphs and they can point out things in real time would is immeasurably helpful. Your professor also may not understand the difficulty you're having (or may just be a crap professor. If you're at a big research college, for instance, teaching may effectively be a chore for them).

[ArjenC]

Did you miss a prerequisite course or something? It sounds strange they would throw spectroscopy problems at you when you haven't learned the basics yet. Normally you would first get a class in which all the common techniques and their theoretical background. Then you usually get to apply them in a couple lab courses, comparing your data to literature references and explaining any differences. Then you will graduate to question of the type ' Chemist A mixed reagents from unlabeled bottles and megically got a well-defined product instead of the likely brown tar. Here are the NMR and mass spectra, figure out what he made and what was in the bottles'. It sounds like you're in one of the later stages, without knowing the basics.
We can try to help you out if you have specific questions, but otherwise I'm afraid the topic is just too big to communicate through a forum post. Like, even ignoring the nitty gritty physics/maths behind it, 1H NMR and chemical shifts is already an hour's lecture, then there splitting patterns/J-coupling, 13C NMR, maybe 2-D NMR, maybe other nuclei. Then for mass spectrometry you have different ionization techniques, fragmentation/rearrangements, etc etc. It really is a full course.

[Knaight]

I'm furious. Spectroscopy (IR, CNMR, HNMR, etc) graphs in general make absolutely no sense to me. I get by purely on guess work, and in the end I can't put together any molecules based on them. They are like a different language to me, only not even google translate can help me.

And my prof just keeps including more and more spectroscopy questions on our material. I have told him in the past that I don't know how to read them, and he's been completely and utterly unhelpful with teaching me how to read them in general. He'll help me with individual problems, but not with actually coming up with a method for reading them consistently.

Knowing the answer to one or two questions isn't helpful to me.

The same theory behind the example questions works for the rest of them, at least in the context of artificial problems used for undergraduate teaching. All of this fundamentally comes down to memorization.

IR? Specific functional groups absorb specific wavelengths. This looks like 2d "hills" in specific places with some particular shapes (wide, narrow, 2 points). Memorize the key ones (alcohols, amides, amines, carboxylic acids, ketones, esters, ethers), look for them.

HNMR? The electrons around the hydrogens are shielded. The amount of shielding depends on the polarity of the bonds the electrons are in and the a lesser context on atoms further away that still affect the molecular orbitals overall. Learn the numbers associated with particular functional group, and take advantage of how the size of the peaks indicate how many bonds there are.

CNMR? Basically the same deal, albeit less convenient.

I assume you at least have mass spec down though, which is something.