Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

instrumental exam 2 > NMR and HNMR > Flashcards

NMR and HNMR Flashcards

1
Q

what is nuclear magnetic resonance

A

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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what is the frequency and wavelength range for nmr

A

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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what happens when a nuclei absorbs radiation

A

change in nuclear spin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

4 basic applications of nmr

A

structure, molecular dynamics, concentration, and diagnostics

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

p is

A

angular momentum

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what creates the magnetic field

A

the circular movement of charge

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

each nucleus is a what

A

magnetic body

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

magnetic moment is proportional to what

A

angular momentum

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what is the magnetogyric ratio

A

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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what are fermions

A

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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what are bosons

A

even mass nuclei with odd number of protons and neutrons

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

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

A

0

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

fermions have what spin quantum number

A

fractional

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

bosons have what spin quantum number

A

integral

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

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

A

oscillation of the needle until it returns to its normal frequency

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

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

A

the needle precesses around the axis of the magnetic field.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

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

A

the original position causing a gyroscopic motion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

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

A

the strength of the magnetic field

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

the lamar frequency is

A

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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

the nucleus can assume how many discrete states

A

2I+1

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

what is the magnetic quantum number

A

+I to -I

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

what 4 nuclei are of greatest interest for NMR

A

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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

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

A

equal number of atoms in each state

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

what is the zeeman effect

A

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.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

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

A

boltzmann distribution

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

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

A

thermal energy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

what are two types of nmr

A

continuous wave, and fourier transform

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

frequency of the continuous wave instrument

A

60, 90, 120 MHz

29
Q

frequency of the fourier transform nmr

A

200-1000 MHz

30
Q

magnet of the continuous wave instrument

A

permanent

31
Q

magnet of the fourier transform instrument

A

superconducting magnet of liquid nitrogen

32
Q

three things required to get a nmr spectrum

A
  1. nuclear spins in zero field 2. magnetic field 2. RF source
33
Q

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

A

randomly

34
Q

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

A

no

35
Q

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

A

only certain orientations

36
Q

what is resonance

A

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

37
Q

what is the source, detector, monochromate of a nmr

A

coil, coil, none

38
Q

what is the uncertainty principle of the continuous wave nmr

A

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

39
Q

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

A

4500seconds per scan at

40
Q

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

A

1 second/ scan

41
Q

In FT NMR how is a strong magnetic field applied

A

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

42
Q

what is the free induction decay signal (FID)

A

RF signal emitted over time

43
Q

Source, detector, monochromate of FT nmr

A

coil, same coil, none

44
Q

FT NMR is in what domain

A

frequency

45
Q

what are the 4 types of available nmr spectra

A

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

46
Q

what is chemical shift

A

the small difference in absorbance frequency from normal value

47
Q

what causes chemical shift

A

reduced shielding of nuclei from the applied magnetic field

48
Q

what are electron withdrawing groups that cause chemical shifts

A

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

49
Q

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

A

0-13 ppm, and 0-220 ppm

50
Q

what standard is the chemical shift measured relative to

A

TMS

51
Q

high field is high or low frequency

A

low

52
Q

what is the effect of hetero atoms on chemical shifts

A

electronegativity deshields 1H nuclei and increases the chemical shift

53
Q

is chemical shift dependent or independent of magnetic field strength

A

independent

54
Q

what does resolution do with field strength and why

A

increases because lower peak widths

55
Q

does lamar frequency increase or decrease with field strength

A

increase

56
Q

what is the relationship between frequency and field strength

A

proportional

57
Q

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

A

adjacent

58
Q

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

A

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

59
Q

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

A

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

60
Q

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

A

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

61
Q

JAB is what

A

the coupling constant

62
Q

splitting almost always results from what

A

1H on adjacent C

63
Q

what is the minimum sample size for 1H analysis

A

0.01 to 1 mg

64
Q

what is the minimum sample size for 13C analysis

A

1 to 5 mg

65
Q

solutions must be soluble in what

A

a denatured solvent such as CDCl3 or D2O

66
Q

what can be done is a denatured solvent cannot be used

A

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

67
Q

why do the samples have to have a low concentration

A

so viscosity does not become significant

68
Q

what do particulates in the samples do

A

lowers the resolutions

69
Q

all samples must contain what

A

tms

instrumental exam 2 (6 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions