These are detailed Revision Notes for Topic 3.15 of AQA A-Level Chemistry (Nuclear Magnetic Resonance). They were written by me using a combination of the textbook and class notes. I will also be uploading the other topics and creating bundles.
Topics Included:
- Nuclear Magnetic resonance spect...
Structure Determination
32.1 Nuclear Magnetic Resonance (NMR)
32.1 nuclear magnetic resonance (NMR) spectroscopy
Spectroscopy:
- NMR is used to help determine the structure of 32.2 proton NMR
organic molecules. 32.3 interpreting proton, 1H NMR, spectra
- 13C gives a simpler spectrum than 1H.
- The larger the shielding around the nucleus, the smaller the magnetic field felt by the nucleus and the
lower frequency that it resonates at.
- The chemical shift is measured in parts per million, tetramethylsilane (TMS) is used as zero as a
standard.
- TMS is used as it is inert, non-toxic, and easy to remove from the sample
32.2 Proton NMR:
- The greater the electron density around a hydrogen the smaller the chemical shift.
- Shifts in proton NMR are much smaller than 13C.
- The further away a hydrogen atom is from an electronegative atom the smaller its chemical shift.
- In proton NMR the area under the peak is proportional to the number of hydrogen atoms in each
environment. This is shown by an integration trace.
32.3 Interpreting Proton, 1H, NMR Spectra:
- Spin-spin coupling is why the peaks can split into smaller peaks
- The amount of splitting depends on the number of hydrogen atoms on the neighbouring carbon atoms.
- The number of peaks is found by the n + 1 rule:
- N hydrogens on an adjacent carbon atom will split a peak into n + 1 smaller peaks
- If there are 2 peaks, they will split in a 1:1 ratio. This is called a duplet
- If there are 3 peaks, they will split in a 1:2:1 ratio. This is called a triplet
- If there are 4 peaks, they will split in a 1:3:3:1 ratio. This is called a quartet.
- The solvents used cannot contain any hydrogen as that would swamp the signals from the sample.
- A commonly used solvent is tetrachloromethane CCl4.
- Some solvents contain deuterium (2H) but this is expensive such as CDCl3, D2O, C6D6
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller emilysarahjudge. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for £2.99. You're not tied to anything after your purchase.