NMR and HNMR

Question 1

what is nuclear magnetic resonance

Answer 1

the absorbance of radio-frequency radiation by nuclei in a magnetic field

Question 2

what is the frequency and wavelength range for nmr

Answer 2

v=4 to 900 MHz, Wavelength = 0.6 to 10 m

Question 3

what happens when a nuclei absorbs radiation

Answer 3

change in nuclear spin

Question 4

4 basic applications of nmr

Answer 4

structure, molecular dynamics, concentration, and diagnostics

Question 5

p is

Answer 5

angular momentum

Question 6

what creates the magnetic field

Answer 6

the circular movement of charge

Question 7

each nucleus is a what

Answer 7

magnetic body

Question 8

magnetic moment is proportional to what

Answer 8

angular momentum

Question 9

what is the magnetogyric ratio

Answer 9

how sensitive a magnetic unit will respond to a change in the magnetic field

Question 10

what are fermions

Answer 10

odd mass. nuclei with an odd number nucleons (fraction spins)

Question 11

what are bosons

Answer 11

even mass nuclei with odd number of protons and neutrons

Question 12

even mass nuclei with even p and n have what spin quantum number

Answer 12

0

Question 13

fermions have what spin quantum number

Answer 13

fractional

Question 14

bosons have what spin quantum number

Answer 14

integral

Question 15

if a needle is not spinning along its axis and it is bent 90 degrees then released what happens

Answer 15

oscillation of the needle until it returns to its normal frequency

Question 16

if a needle is spinning along its axis and it is bent and then released what happens

Answer 16

the needle precesses around the axis of the magnetic field.

Question 17

if a needle is spinning along its axis, bent, then released what is the restoring force perpendicular to

Answer 17

the original position causing a gyroscopic motion

Question 18

the angular frequency of precession of magnetic dipole around the applied magnetic field is proportional to what

Answer 18

the strength of the magnetic field

Question 19

the lamar frequency is

Answer 19

the frequency of precision, and the “resonance” frequency of the nucleus

Question 20

the nucleus can assume how many discrete states

Answer 20

2I+1

Question 21

what is the magnetic quantum number

Answer 21

+I to -I

Question 22

what 4 nuclei are of greatest interest for NMR

Answer 22

1H, 13C, 19F, and 31P

Question 23

in the absence of a magnetic field, the energies of m= +1/2, and -1/2 are equal, meaning

Answer 23

equal number of atoms in each state

Question 24

what is the zeeman effect

Answer 24

in the presence of a magnetic field the energy levels split, causing atoms with their magnetic moments aligned more with the field are lower in energy than those aligned more against it.

Question 25

what can be used to calculate the relative number of nuclei in each state

Answer 25

boltzmann distribution

Question 26

what can be provided to cause nuclei to transition from one state to another

Answer 26

thermal energy

Question 27

what are two types of nmr

Answer 27

continuous wave, and fourier transform

Question 28

frequency of the continuous wave instrument

Answer 28

60, 90, 120 MHz

Question 29

frequency of the fourier transform nmr

Answer 29

200-1000 MHz

Question 30

magnet of the continuous wave instrument

Answer 30

permanent

Question 31

magnet of the fourier transform instrument

Answer 31

superconducting magnet of liquid nitrogen

Question 32

three things required to get a nmr spectrum

Answer 32

1. nuclear spins in zero field 2. magnetic field 2. RF source

Question 33

in zero field, how are the nuclear spins of 1H and 13C oriented

Answer 33

randomly

Question 34

in zero field does the number of allowed nuclear spin states change

Answer 34

no

Question 35

in the presence of an external magnetic field, what orientation of nuclear magnetic moments are allowed

Answer 35

only certain orientations

Question 36

what is resonance

Answer 36

the absorbance of EMR by a nucleus which causes the nuclear spin to flip from a low energy state to a high energy state

Question 37

what is the source, detector, monochromate of a nmr

Answer 37

coil, coil, none

Question 38

what is the uncertainty principle of the continuous wave nmr

Answer 38

1 sec/Hz of the sweep width to measure the frequency with a precision of 1 Hz

Question 39

how long does it take for the CW nmr to make one scan at 300 MHz with a poor resolution of 1 Hz

Answer 39

4500seconds per scan at

Question 40

how long does it take for the FT NMR to make one scan at 300 MHz for a poor resolution of 1 Hz

Answer 40

1 second/ scan

Question 41

In FT NMR how is a strong magnetic field applied

Answer 41

brief pulses of intense RF (100-1000 MHz) to nuclei for 1 to 10 microseconds

Question 42

what is the free induction decay signal (FID)

Answer 42

RF signal emitted over time

Question 43

Source, detector, monochromate of FT nmr

Answer 43

coil, same coil, none

Question 44

FT NMR is in what domain

Answer 44

frequency

Question 45

what are the 4 types of available nmr spectra

Answer 45

chemical shift, multiplicities for 1H spectra (proton NMR), peak areas, and coupling constants

Question 46

what is chemical shift

Answer 46

the small difference in absorbance frequency from normal value

Question 47

what causes chemical shift

Answer 47

reduced shielding of nuclei from the applied magnetic field

Question 48

what are electron withdrawing groups that cause chemical shifts

Answer 48

nearby groups within the molecule that decrease the electron density around the nucleus causing a greater chemical shift

Question 49

typical range of chemical shifts for 1H, and 13C

Answer 49

0-13 ppm, and 0-220 ppm

Question 50

what standard is the chemical shift measured relative to

Answer 50

TMS

Question 51

high field is high or low frequency

Answer 51

low

Question 52

what is the effect of hetero atoms on chemical shifts

Answer 52

electronegativity deshields 1H nuclei and increases the chemical shift

Question 53

is chemical shift dependent or independent of magnetic field strength

Answer 53

independent

Question 54

what does resolution do with field strength and why

Answer 54

increases because lower peak widths

Question 55

does lamar frequency increase or decrease with field strength

Answer 55

increase

Question 56

what is the relationship between frequency and field strength

Answer 56

proportional

Question 57

nuclear spin on what 1H nuclei gives rise to multiplied peaks

Answer 57

adjacent

Question 58

the spin of neighboring 1H nuclei adds to or subtracts from what, causing what?

Answer 58

the applied magnetic field causing the effective field to be greater than the applied field

Question 59

whether the effective field is greater or less than the applied field is dependent on what

Answer 59

whether the adjacent nucleus' spin is aligned with or against the applied field

Question 60

in the peak integral spectra, what is the area under the peak proportional to

Answer 60

the number of protons of a particular type that are absorbing EMR

Question 61

JAB is what

Answer 61

the coupling constant

Question 62

splitting almost always results from what

Answer 62

1H on adjacent C

Question 63

what is the minimum sample size for 1H analysis

Answer 63

0.01 to 1 mg

Question 64

what is the minimum sample size for 13C analysis

Answer 64

1 to 5 mg

Question 65

solutions must be soluble in what

Answer 65

a denatured solvent such as CDCl3 or D2O

Question 66

what can be done is a denatured solvent cannot be used

Answer 66

use a solvent that does not interfere the chemical shift of the analyte

Question 67

why do the samples have to have a low concentration

Answer 67

so viscosity does not become significant

Question 68

what do particulates in the samples do

Answer 68

lowers the resolutions

Question 69

all samples must contain what

Answer 69

tms