Exam 3

Question 1

H-H COSY

Answer 1

• Correlation Spectroscopy
• important experimental factor but has no bearing on interpretation
• protons on carbons directly attached to each other

Question 2

DQF- COSY

Answer 2

• Double Quantum Filtered H-H COSY
• remove or filter single quantum transitions so that only double-quantum or higher transitions remain
• reduce the number of methyl singlets by selecting only systems with at least two spins
• Deconvolutes the spectrum

Question 3

H-C HETCOR

Answer 3

• Heteronuclear Correlation
• Carbon detected
• Low sensitivity
• Not common

Question 4

H-C HMQC

Answer 4

• Heteronuclear Multiple Quantum Coherence
• Proton Detected
• More sensitive than HETCOR
• Eliminates long range coupling
• preserves directly attached coupling
• interprets protons directly attached to carbon

Question 5

H-C HMBC

Answer 5

• Heteronuclear Multiple Bond Coherence
• Proton detected
• Can correlate quaternary carbons back to a proton signal
• Don’t always see 2-3 bond correlations, sometimes see 4
• Interpret two to three bonds from carbon

Question 6

C-C INADEQUATE

Answer 6

• Incredible Natural Abundance Double Quantum Transfer Experiment
• Similar to COSY but for Carbon
• Allows for sketching carbon skeleton unambiguously
• low sensitivity and long experimental times
• Interprets Carbon directly attached to one another

Question 7

TOCSY

Answer 7

• Total Correlation Spectroscopy
• Allow us to see correlations among nuclei that are not directly coupled to each other but within same spin system
• Longer mixing times, all spins within spin system appear coupled
• Interpreted by following spin system proton signal to proton signal
• stringing together COSY correlations

Question 8

HMQC-TOCSY

Answer 8

• 2D Hybrid experiment
• Correlates one bond proton and carbon coupling but shows these correlations throughout an entire spin system
• used for complex carbohydrates and peptide systems

Question 9

ROESY

Answer 9

• Rotating-frame Overhauser Effect Spectroscopy
• Useful for molecules of all sizes
• correlate protons that are close to each other in space
• useful for stereochemical assignment and 3D structure

Question 10

NOESY

Answer 10

• Similar to ROESY

- useful only for large moelcules

Question 11

Pulsed Field Gradient NMR

Answer 11

• Phase cycling takes times
• can greatly reduce the need for phase cycling thus shortening experiment time
• experiments can be run more efficiently and quickly

Question 12

N NMR

Answer 12

• most useful of multinuclear scpectroscopy
• important for organic chemists, natural product chemists, pharmacology, and biochemistry
• order of magnitude less sensitive than carbon
• long t1 times (relaxes slowly)
• similar chemical shift to carbon
• protonation important to consider
• run decoupled to proton like carbon

Question 13

F NMR

Answer 13

• ideal nucleus for NMR
• important for polymer chemistry, metabolism, biopharmaceuticals, magnetic resonance imaging, and fluorine labeled proteins
• interest involved for replacement of hydrogen in synthetic compounds
• couples like hydrgoen –> causes coupling in proton and carbon

Question 14

Si NMR

Answer 14

• Used by organic and polymer chemists

- couples protons

Question 15

P NMR

Answer 15

• Interest to organic and biochemists because of phosphorous containing functional groups and nucleic acids, ADP, and ATP
• chemical shifts do not vary much while oxidation states, attached groups, and others do
• couples protons and carbons
• important applications for metal-phosphine complexes and related compounds