Flashcards
NMR
Cards in this deck (9)
- 1What is NMR?It stands for nuclear magnetic resonance. it is a technique used to examine molecular structure in detail, especially using isotopes.
- 2What is a chemical shift?it is a scale that compares with frequency of an NMR adsorption with the frequency of the reference peak of TMS at 0 ppm.
- 3What is the use in TMS in NMR spectroscopy?The chemical shift is measured relative to TMS. TMS are chemically unreacttive and volatile so easily can be removed.
- 4What is the use of CDCl3?This is used for solvents, the H isoptopes will give no signal in the NMR spectrum. Organic solvents contain carbon and hydrogen and these both produce a signal.
- 5What does a Carbon- 13 NMR shows?- Type of C environment (chemical shifts)
- Number of C environment (number of peaks) - 6What does a Proton NMR shows?- No. of different proton environments (no. of peaks)
-Type of proton environment (chemical shifts)
- No. of protons in environment ( peak area)
- No. of neighbouring protons (splitting pattern) - 7Calculating the splitting pattern?n+1 rule
- when n is the number of neighbouring protons on the directly adjacent C atoms - 8Why are -OH and -NH protons so difficult to identify in proton NMR spectra?- Chemical shifts can change depending on solvent and conc. of sample
-Signals are often broad
-Often no splitting patterns (do not split other peaks) - 9How can -OH and -NH be identified?- It uses D2O. The D exchanges with -OH or -NH protons.
-D gives no proton NMR signal and therefore peak due to -OH or -NH disappears in 2nd NMR spectrum.
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- A-Level A2 chemistry (Module 3 - Analysis) Flashcards on NMR, created by Mary Doria on 12/12/2015.
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- Mary Doria
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