Report

NMR - The Coupling Constant 4-1 ASSIGNMENT OF SPIN SYSTEMS For each compound: Describe all spin systems Determine the number of protons that are: • Chemical shift equivalent • Magnetic equivalent • Enantiotopic • Diastereotopic CHEM 430 – NMR Spectroscopy 1 NMR - The Coupling Constant 4-1 SPLITTING OF SIGNALS – STRUCTURE DETERMINATION MW 114 MW 116 CHEM 430 – NMR Spectroscopy 2 NMR - The Coupling Constant 4-1 SPLITTING OF SIGNALS – STRUCTURE DETERMINATION MW 169 has -Br MW 150 CHEM 430 – NMR Spectroscopy 3 NMR - The Coupling Constant 4-1 SPLITTING OF SIGNALS – STRUCTURE DETERMINATION MW 100 MW 74 CHEM 430 – NMR Spectroscopy 4 NMR - The Coupling Constant 4-1 SPLITTING OF SIGNALS – STRUCTURE DETERMINATION MW 73 MW 56 CHEM 430 – NMR Spectroscopy 5 NMR - The Coupling Constant 4-1 SPLITTING OF SIGNALS – STRUCTURE DETERMINATION MW 89 MW 138 CHEM 430 – NMR Spectroscopy 6 NMR - The Coupling Constant 4-1 SPLITTING OF SIGNALS – STRUCTURE DETERMINATION MW 122 MW 102 CHEM 430 – NMR Spectroscopy 7 NMR - The Coupling Constant 4-1 SPLITTING OF SIGNALS – STRUCTURE DETERMINATION MW 113 MW 94 CHEM 430 – NMR Spectroscopy 8 NMR - The Coupling Constant 4-1 SPLITTING OF SIGNALS – STRUCTURE DETERMINATION MW 152 MW 157 has -Cl CHEM 430 – NMR Spectroscopy 9 NMR - The Coupling Constant 4-1 SPLITTING OF SIGNALS – STRUCTURE DETERMINATION MW 208 MW 98 CHEM 430 – NMR Spectroscopy 10 NMR - The Coupling Constant 4-1 SPLITTING OF SIGNALS – STRUCTURE DETERMINATION MW 126 MW 116 CHEM 430 – NMR Spectroscopy 11 NMR - The Coupling Constant 4-1 SPLITTING OF SIGNALS – STRUCTURE DETERMINATION MW 162 2 -Cl MW 122 CHEM 430 – NMR Spectroscopy 12 NMR - The Coupling Constant 4-1 SPLITTING OF SIGNALS – STRUCTURE DETERMINATION MW 96 CHEM 430 – NMR Spectroscopy 13 NMR - The Coupling Constant 4-1 PRACTICE WITH POPLE NOTATION On graph paper, draw a schematic (line) representation of the pure firstorder spectrum AMX3 corresponding to the following parameters: n (Hz from TMS): nA = 80; nM = 220; nX = 320 J (Hz): JAM = 10; JAX = 12; JMX = 0 • Assume spectrum is a pure 1st order spectrum and ignore small distortions in relative intensities that would occur in a ‘real’ spectrum. • Sketch in “splitting diagrams” above the schematic spectrum to indicate which splittings correspond to which coupling constants. • Give the shifts on the d scale corresponding to the above spectrum on a 60 MHz NMR (1H). CHEM 430 – NMR Spectroscopy 14 NMR - The Coupling Constant 4-1 PRACTICE WITH POPLE NOTATION AMX3 n (Hz from TMS): nA = 80; nM = 220; nX = 320 J (Hz): JAM = 10; JAX = 12; JMX = 0 CHEM 430 – NMR Spectroscopy 15 NMR - The Coupling Constant 4-1 STRUCTURE DETERMINATION WITH POPLE NOTATION The 400 MHz 1H NMR spectrum of one of the following isomeric hydroxycinnamic acids is given below. Which one is it? Justify your answer based on chemical shift and coupling constants. CHEM 430 – NMR Spectroscopy 16 NMR - The Coupling Constant 4-1 STRUCTURE DETERMINATION WITH POPLE NOTATION CHEM 430 – NMR Spectroscopy 17