Organic Chemistry - Organic Structure Determination

Front 1

How do chemical bonds move according to IR spectroscopy? And how are they detected?

Back 1

Only vibrations producing a change in dipole moment are observed i.e. 'large' electronegativity differences.

Front 2

How can frequency of an IR spectrum be calculated?

Back 2

Hint 2

Front 3

What are the two main regions on an IR spectrum and what are they called?

Back 3

Front 4

How does 'OH' stretch and 'NH' appear in an IR spectrum?

Back 4

They have a very large due to hydrogen bonding. The peaks for both normally occur at 3500 cm^-1 because of hydrogen bonding. A monomeric hydroxyl has a sharper peak at 3600 cm^-1 and NH2 can give two separate peaks.

Front 5

What are the general rules of IR?

Back 5

Front 6

What happens at the 3300-2700 region in an IR spectrum?

Back 6

Front 7

What happens at the 2500-1900 region in an IR spectrum?

Back 7

Front 8

What happens at the 1900-1500 region in an IR spectrum?

Back 8

Hint 8

Front 9

What are the different types of C=O and what properties do they have in an IR spectrum?

Back 9

Hint 9

Front 10

How does ring strain relate to IR?

Back 10

Front 11

What is the basic schematic of mass spectrometers?

Back 11

Front 12

What are the two types of mass analysers?

Back 12

Hint 12

Front 13

How does ion detection work for MS?

Back 13

It amplifies signals and only detects charged species.

Front 14

What are the different ionisation methods for MS?

Back 14

Front 15

How does 'electron impact (EI)' work?

Back 15

EI causes fragmentation to stable cationic daughter peaks.

Front 16

How does 'chemical ionisation (CI)' work?

Back 16

Front 17

How does 'electrospray ionisation (ESI)' work?

Back 17

Front 18

How does 'MALDI ionisation' work?

Back 18

Front 19

How are the methods of organic structure determination used to ID unknown compounds?

Back 19

Hint 19

Front 20

How can isotopic data be identified from MS?

Back 20

Hint 20

Front 21

What is the theory behind NMR?

Back 21

Hint 21

Front 22

How can resonance frequency be observed?

Back 22

Front 23

How would an NMR experiment be carried out?

Back 23

Front 24

How is the resonance frequency calculated?

Back 24

Front 25

How can we identify which nuclei are NMR active?

Back 25

Front 26

How does the fourier transform NMR experiment work?

Back 26

Front 27

What does a NMR spectrum look like?

Back 27

Front 28

What are the practical considerations of NMR?

Back 28

Front 29

How does chemical shift work in NMR?

Back 29

Hint 29

Front 30

How are the integrals calculated in a NMR spectrum?

Back 30

Front 31

What are the general trends for chemical shift in NMR?

Back 31

Front 32

Apply knowledge of NMR to carbonyl groups.

Back 32

Front 33

How do anisotropic effects work in NMR?

Back 33

Hint 33

Front 34

How do anisotropic effects occur in aromatic compounds?

Back 34

Front 35

What are the effects of proton change?

Back 35

Hint 35

Front 36

Back 36

Hint 36

Front 37

Give some coupling terminology.

Back 37

Front 38

What are the sizes of coupling dependent on?

Back 38

• Number of bonds

• Angles between the bonds

• Substituents on the coupling path

Front 39

What do 2 bond coupling and 3 bond coupling look like?

Back 39

Front 40

How much distance is allowed for coupling to occur?

Back 40

Anything 20 H2 or under

Front 41

How is angular dependence on coupling calculated?

Back 41

Front 42

How can the configuration of cyclohexanes be determined using coupling rules?

Back 42

Front 43

Explain how 3 bond coupling can be used to differentiate between alkenyls.

Back 43

Front 44

How are the number of lines for couplings determined?

Back 44

Front 45

How do coupling patterns look like?

Back 45

Hint 45

Front 46

What are the typical patterns for 2 couplings?

Back 46

Front 47

What are the typical patterns for 3 couplings?

Back 47

Hint 47

Front 48

What are the two criteria that prevent H from coupling?

Back 48

Front 49

How would the proton nmr spectra look liked for these?

Back 49

Front 50

Back 50

Front 51

Back 51

Hint 51

Front 52

How can first and second order spectra be determined?

Back 52

Hint 52

Front 53

How can chemical equivalence state the relation between two molecules with regards to chiral centres?

Back 53

Front 54

Back 54

Front 55

What issues are associated with 13C NMR and what could be done to resolve these issues?

Back 55

Front 56

The schematic in this diagram is similiar to proton NMR, what makes carbon NMR different?

Back 56

Hint 56

Front 57

What happens to carbon NMR when H-C coupling occurs?

Back 57

Front 58

How can coupling be removed in carbon NMR?

Back 58

Front 59

What are the general features of carbon NMR?

Back 59

Front 60

What structures are anomalies in carbon NMR?

Back 60

Front 61

How are the numbers of spins determined in carbon NMR?

Back 61

2 x I + 1 where I is spin quantum number

Front 62

What is the DEPT experiment in 1D carbon NMR?

Back 62

Front 63

How should organic structure determination occur?

Back 63

Front 64

Explain the difference between the 1D experiment and the 2D experiment?

Back 64

Hint 64

Front 65

Back 65

.

Front 66

What are the different 2D experiments?

Back 66

• 1H-1H COSY

• HMQC

• HMBC

Front 67

Explain how 1H-1H COSY works.

Back 67

Front 68

Explain how HMQC works.

Back 68

Front 69

Explain how HMBC works.

Back 69