U1 Drug Analysis

Question 1

What is NMR?

What is the function of the magnet controller in NMR?

Answer 1

nuclear magnetic resonance

stimulate the resonance of specific nuclei; nuclei with odd numbers

Question 2

What are the common nuclei used in NMR?

What is special about them?

Answer 2

H1, C13 etc

spin and charge of nuclei means they act like magnets

Question 3

What is the nuclei resonance detected as?

Answer 3

radio wave signals

Question 4

What determines the position where a nucleus resonates?

Answer 4

• exact magnetic environment
• somewhat determined by electronic environment nearby ie. nearby atoms

Question 5

What is electronegativity?

Answer 5

ability of an atom to attract electrons

Question 6

How does electronegativity of an atom affect its chemical shift on an NMR?

Answer 6

the more electronegative, the higher the shift e.g. Fluorine most electroneg halide; shifts to 4

e.g. CH2Cl2 shifts to 5.30
CHCl3 shifts to 7.27

Question 7

chemical shift units on NMR

Answer 7

delta ppm

Question 8

electron withdrawing groups are described as what on NMR?

What effect do they have?

Answer 8

deshielding

movement to a higher delta - DOWNFIELD (towards 12)

Question 9

What happens if electron density is increased? ie presence of electron donating group

Answer 9

nuclei is ‘shielded’

move delta upfield (towards zero)

Question 10

What functional groups can you expect to see from zero to three?

Answer 10

alkyl
alkyne

Question 11

What functional groups would you expect to see in 5/6?

Answer 11

alkenes

Question 12

Where would you expect to see aromatics?

Answer 12

7/8

Question 13

Where would you expect to see carbonyls?

Answer 13

9-12

e.g. aldehyde 9/10
COOH 10/12

Question 14

Where would you expect to see hydroxyls (-OH) and amines (-NH2)?

Why is the variation in chemical shift so big?

Answer 14

1-6

presence of H bonding

Question 15

What is the proton NMR scale?

Answer 15

0-12

Question 16

What is the 13C NMR scale?

Answer 16

0-250

Question 17

What is integration in regards to proton NMR?

Answer 17

used to quantify the relative number of protons contributing to each system in the spectrum

Question 18

What is the area under a proton NMR peak proportional to?

Answer 18

the number of hydrogen atoms represented by the peak

Question 19

the size of the jumps ie the difference between peaks on proton NMR spec is proportional to what?

Answer 19

number of Hs

Question 20

What are splitting patterns on proton NMR determined by?

What is the rule?

Answer 20

number of adjacent protons

n+1
where n = number of adjacent protons

Question 21

What will the splitting pattern be if there are no adjacent protons?

Answer 21

1, singlet

Question 22

What will the splitting pattern be if there is 1 adjacent proton?

What will the relative intensities be?

Answer 22

2 peaks, doublet

1:1

Question 23

What will the splitting pattern be if there are 2 adjacent protons?

What will the relative intensities be?

Answer 23

3, triplet

1:2:1

Question 24

What will the splitting pattern be if there are 3 adjacent protons?

What will the relative intensities be?

Answer 24

4, quartet

1:3:3:1

Question 25

What is meant by ‘coupling’ ?

Answer 25

refers to the interaction between neighboring nuclear spins, which results in the splitting of NMR signals into multiple peaks

Question 25

What splitting pattern can be seen in monosubstituted arenes?

Answer 25

1. usually split into 2 groups
   - those closest to monosubstitution
   - those further away
2. peaks in ratio 2:3 or 3:2

Question 26

With aromatics, what factor is arguably more influential on the delta value than electronegativity?

Answer 26

the substituent on the ring

Question 27

What is the effect on NMR spec of adding an electron donating group as the substituent on the ring?

Answer 27

• adds to conjugated system, shields aromatic proteins
• shift upfield

Question 28

What sorts of groups are electron donating?

Answer 28

amine, OH, amides, OR, aryl, alkyl (strongest to weakest)

Question 29

What groups are considered electron withdrawing?

Answer 29

all carbonyls (electron deficient carbon), nitriles, nitro