8.2 NMR spectroscopy

Question 1

lower energy released when

Answer 1

nuclei is aligned with external magnetic field

Question 2

higher energy released when

Answer 2

nuclei is aligned AGAINST external magnetic field

Question 3

nuclei has nuclear spin IF

Answer 3

odd mass number

Question 4

NMR instrumentation

Answer 4

1) sample dissolved in solvent put in glass tube
2) tube placed and spun in centre of powerful magnet
3) radio transmitter produces short pulses of radio waves absorbed by nuclei, which turns it into high-energy spin states
4) radio receiver detects radio freq. energy emitted as nuclei returns to lower energy spin state
5) computer interprets into NMR spectrum

Question 5

what is a chemical environment

Answer 5

section of unique central chain atom and surrounding atoms and electrons

Question 6

what is TMS

Answer 6

ref. compound tetramethylsilane used to compare relative chemical shift

Question 7

what is a chemical shift

Answer 7

energy required to change spin states (ppm)

Question 8

the no. of NMR peaks means

Answer 8

no. of different carbon chemical environments

Question 9

the higher the value of chemical shift,

Answer 9

the more electronegative (left of graph)

Question 10

proton-NMR aka H-NMR usage:

Answer 10

number of hydrogen nuclei and arrangement

Question 11

n+1 rule

Answer 11

number of neighbouring H atoms of an environment + 1

Question 12

number of small grouped peaks in H-NMR

Answer 12

number of hydrogen atoms in and surrounding a hydrogen environment

Question 13

relative peak area of each signal

Answer 13

the number of hydrogen atoms in a particular environment

Question 14

splitting pattern means…

Answer 14

triplet, quartet, etc… how many small peaks there are

Question 15

signals =

Answer 15

big groups of small peaks