Two dimensional NMR L9 Flashcards
How is a typical 2D nmr experiment carried out
A complex pulse is used which contains a delay (t2) which is varied systematically over a series of experiment. This gives a series of FIDs linked by t2. Double Fourier transformations gives 2D spectra.
What are 2D spectra typically plots of
Signal intensity (represented as contours) vs chemical shift
What does COSY stand for
Correlation spectroscopy
What does the COSY experiment show
This experiment shows for a single nuclide which nuclei are coupled to which. Eg which protons are couples to which protons
What do off diagonal cross peaks in COSY indicate
Scalar coupling
What does HSQC stand for
Heteronuclear single quantum, correlation
What does HSQC show
Typically used to show correlation between 13C nuclei and directly bonded 1H nuclei. Ie which 1H is scalar coupled to which 13C
What is edited HSQC
Combination of HSQC and DEPT-135 experiments
What does HMBC stand for
Heteronuclear multiple bond correlation
What is HMBC used for
Like HSQC but optimised for coupling between 13C and 1H across 2 or 3 bonds
What is HMBC useful for
Useful for assigning quaternary 13C and nuclei separated by nmr inactive nuclei eg C-O-C
What does NOESY stand for
Nuclear overhauser effect spectroscopy
What is NOESY used for
Correlation mediated by dipole coupling. I.e nOe. Shows which nuclei are close in space to which (not bonded)
What is NOESY useful for
aids determination of 3D structure of a molecule e.g. cis/trans isomers, diastereomers, conformers
