Lecture Six - NMR spectroscopy Flashcards
Where on the CNMR spectra do the different functional groups occur?
What is the relationship between molecular symmetry and the NMR spectra?
If a molecule has symmetry, it will simplify the NMR spectrum.
The two halves are identicle and we conly need to examine one half to determine the NMR spectrum.
What are the three key features of HNMR spectroscopy that give information about a molecule?
1) Chemical shift (d) - provides information about neighbouring functional groups (same rule for CNMR).
2) Integration - the relative areas of a signal is proportional to the number of hydrogens.
3) Splitting - (or multiplicity) measued in hertz (Hz), the coupling constant (J) can be used to determine the connectivity of a molecule.
Where on the HNMR spectrum do the different functional groups appear?
How does nuclear spin-spin coupling work?
When two or more hydrogen nuclei are close enough, their magnetic fields result in splitting.
Chemically equivalent protons show no splitting.
A proton with n equivilent neighbours will split into n+1 lines with coupling constant J.
Two groups of protons coupled with each other will have identical coupling constants J.
