NMR

Question 1

The intensity of a total ion chromatogram (TIC) is_____________

Answer 1

The sum of all intensities from the spectrum

Question 2

The intensity of a base peak chromatogram (BPC) is_____________

Answer 2

The highest intensity from the spectrum

Question 3

The intensity of an extracted ion chromatogram (EIC) is_____________

Answer 3

The intensity of a chosen mass from the spectrum

Question 4

Write the formula to calculate the mass to charged ratio (m/z) using ESI-MS

Answer 4

m/z = (M+n*X)/n

Question 5

Calculate the m/z value of a compound with the monoisotopic mass 625.3814 charged with 2 protons

Answer 5

Brug formel: (M+n*X)/n
og bestemmes til 313.699 ved indsætning af:
(625.3814+2 * 1.0078)/2=313.699

Question 6

When you want to predict a chemical formula from MS data, it is extremely important to have an accurate measurement. A precission at the third decimal or better is preferred. Why?

Answer 6

Many compounds share the same nominal mass, but differ slightly on the exact mass

Question 7

Which values can the nuclear spin quantum number of 24Mg adopt? Magnesium is element no. 12 in the periodic table of elements.

Muligheder:
a. I ∈ of…,-4,-3,-2,-1,0,1,2,3,4,…..
b. I ∈ of 1/2, 3/2, 5/2, 7/2, ….
c. I ∈ of1,2,3,4,…..
d. I=0
e. I ∈ of…,-7/2,-5/2,-3/2,-1/2, 1/2, 3/2, 5/2, 7/2,….
f. I=½

Answer 7

Svar: d. I=0

Spins with even mass and even charge always have I=0

Question 8

When a nucleus is scalar coupled to 1 nucleus of I=1 : how many signals will it be split into?

Answer 8

Svar: 3

m = 2 * I * n+1
2 * 1 * 1+1 = 3

Question 9

The phenomenon, that substituents on an aromatic ring can influence the chemical shift of hydrogen atoms in the ring, by delocalization of electrons into or out of the ring, is called….

Muligheder:
a. push-pull effect
b. substitution effect
c. mesomeric effect
d. inductive effect
e. electron-mediated coupling
f. chemical anisotropy
g. aromatic effect
h. magnetic anisotropy

Answer 9

Svar: c. mesomeric effect

Eller også kaldet M-effect

Question 10

Pulsed-field gradients are used to… (multiple answers possible)

Muligheder:
a. enhance resolution
b. calibrate the NMR spectrometer
c. suppress solvent signals
d. enhance field homogeneity
e. enhance sensitivity
f. charge the magnet
g. measure diffusion coefficients
h. remove unwanted signals

Answer 10

Svar: c, d, g og h

Question 11

Which of the following statements is/are correct? More than one correct answer is possible. Pick all correct answers.

(If you pick an incorrect answer, it will count negative. The total points for this question cannot become lower than zero, however.)

Muligheder:
a. The smaller the molecule, the slower T1 relaxation.
b. T2 relaxation is always faster than T1 relaxation
c. Small organic molecules have slow T2 relaxation.
d. Fast T2 relaxation yields broad lines in the NMR-spectrum.
e. The larger the molecule, the faster T2 relaxation.

Answer 11

Svar: b, c, d, e

Question 12

Insert the missing words:

The process where the frequency of the probe is adjusted to the desired resonance frequency, is called ___1___.

Adjusting the impedance of the probe to the desired level is called ___2___.

The process of making the magnetic field homogeneous throughout the sample, is called ___3___.

Muligheder:
1) Locking, tuning, aligning, frequency-aligning, matching, chimming
2) Locking, aligning, imoedance-fitting, tuning, shimming, matching
3) Homogenizing, matching, locking, tuning, shimming, aligning

Answer 12

Svar:
1) tuning
2) matching
3) shimming

Question 13

The z^0 coil is part of the …

Muligheder:
a. … console
b. … lock system
c. … mass analyzer
d. … probe
e. … chromatographic setup
f. … ion source
g. … shim system
h. tuning and matching

Answer 13

Svar: b

Question 14

All atomic nuclei with a spin ___1___ have angular momentum, P.
The magnetic moment, µ, is connected to the angular momentum P by the following relationship: ___2___, where γ is called the ___3___. The unit of γ is ___4___

Muligheder:
1) (I=½), (I=0), (I=½, 3/2, 5/2, 7/2,…), (I), (I>0), (I=1, 2, 3, 4, 5, 6,…)

2) (μ=γP), (μ=(P/γ)^½), (μ=γP^2), (μ=P/γ), (μ=(P/γ)^2)

3) nuclear magnetization coefficient, gromagnetic factor, gryromagnetic ratio, nuclear magnetic ratio

4) (rad(1/s^2)T), (T(1/rad)(1/s)), (rads(1/T)), (rad(1/s)(1/T)), (rad(1/s^2)(1/T^2)), (rad(1/s^2)*(1/T))

Answer 14

Svar:
1) I >0
2) μ = γP
3) gyromagnetic ratio
4) rad (1/s)(1/T)

Question 15

Excitation of nuclear magnetic moments in NMR is typically achieved by short ___1___. They are typically on the order of ___2___.
The recorded raw data is called ___3___. It is converted to an NMR spectrum by ___4___

Muligheder:
1) laser pulses, radiofrequency pulses, neutron bombardment, X-ray pulses, UV pulses

2) microseconds, seconds, milliseconds, picoseconds, minutes, nanoseconds

3) shift-intensity bell, niclar relaxation profile, free induction decay, time decay

4) Lorentz transformation, inverse Fourier tranformation, Laplace transformation, Fourier transformation, inverse Laplace transformation, Scalar transformation

Answer 15

Svar:
1) radiofrequency pulses
2) microseconds
3) free induction decay
4) Fourier transformation

Question 16

Under which circumstances are the two hydrogen atoms of a CH2 group NOT chemically equivalent?

Answer 16

De to hydrogenatomer i en CH₂-gruppe er ikke kemisk ækvivalente, når de befinder sig i et asymmetrisk kemisk miljø, dvs. når de oplever forskellige elektroniske omgivelser og ikke kan udveksles ved en symmetrioperation.

Question 17

In an APT spectrum, you see:

Muligheder:
a) 13C nuclei bound to one or three 1H with positive sign and 13C nuclei bound to two 1H with negative sign

b) all 1H nuclei bound to 13C

c) only 1H nuclei in CH-groups

d) all 13C nuclei with a positive signal

e) all 1H nuclei in CH2 groups negative, all 1H nuclei in CH and CH3 groups positive

f) all 13C nuclei with an odd number of 1H attached will yield a positive signal, 13C nuclei with no or two 1H atoms attached will yield a negative signal

g) only 13C nuclei bound to 1H

h) only 13C nuclei bound to exactly one 1H

Answer 17

Svar: f

Question 18

How many different orientations can the nuclear magnetic moment of a spin with I = 9/2 adopt?

Answer 18

Svar: 10

Formel: 2I+1
2(9/2)+1

Question 19

Which values can the nuclear spin quantum number of Samarium-150 (150Sm) adopt? Samarium is element number 62 in the periodic system of elements.

Muligheder:
a) I ∈ of1/2, 3/2, 5/2, 7/2, ….
b) I ∈ of1,2,3,4,…..
c) I ∈ …, -4, -3, -2, -1, 0, 1, 2, 3, 4, …..
d) I=0
e) I=½
f) I ∈ of…,-7/2,-5/2,-3/2,-1/2, 1/2, 3/2, 5/2, 7/2,….

Answer 19

Svar: d) I=0

spins with an even mass and even charge always have I=0

Samarium har atomnummer 62 -> altså 62 protoner.
Isotopen er 150Sm, og har dermed: 150-62 = 88 neutroner
Protoner = 62 -> lige
Neutroner = 88 -> lige

Question 20

What are pulsed field gradients and what can they be used for?

Answer 20

En feltgradient er en midlertidig ændring i det magnetiske felt, der varierer over rummet (typisk langs én akse, f.eks. z-retningen). Det betyder, at forskellige dele af prøven oplever lidt forskellige magnetfelter under gradienten.

En pulsed field gradient betyder, at denne ændring kun er tændt i meget kort tid, typisk i millisekunder, som en “puls”.

Gradientpulser bruges til selektivt at dekoherere signaler fra f.eks. vandmolekyler.
Gør spektrum renere og mere tydeligt.

Question 21

When a molecule is brought into a magnetic field, all individual nuclei will experience ___1___ magnetic field. It is ___2___ the external magnetic field. This phenomenon is called ___3___ and it is caused by ___4___

Muligheder:
1) two types of - three types of - the exact same - a different - no - the inverse

2) slightly (less then 1%) weaker then - twice as strong as - slightly (less than 1%) stronger than - a third of the strength of - three times as strong as - equal to - half as strong as

3) Boltzman dissipation - relaxation - shielding - field amplification - nuclear overhauser effect - NMR

4) field inhomogeneity - different isotopes - the electrons - the solvent - relaxation - the radiofrequency pulse

Answer 21

Svar:
1) a different
2) slightly (less than 1%) weaker than
3) shielding
4) the electrons

Question 22

Below is a description of different types of spectra commonly used in metabolomics investigations.
Select the matching names of such a type of spectrum.
1D 1H-NMR, attenuating NMR signals from small molecules ___1___
1D 1H-NMR eliminating the influence of scalar coupling, showing only singlets ___2___
1D 1H-NMR, attenuating NMR signals from large molecules and aggregates ___3___
unfiltered 1D 1H-NMR with superior water suppression ___4___

Muligheder for alle:
a) Diffusion-filtered 1D
b) 1D-COSY
c) CPMG
d) 1D-TOCSY
e) projected J-res
f) 1D-NOESY

Answer 22

Svar:
1 = a) Diffusion-filtered 1D
2 = e) projected J-res
3 = c) CPMG
4 = f) 1D-NOESY

Question 23

Select the correct answers to the questions below. They all revolve around sensitivity and resolution in NMR spectra and how they are influenced by changes in the experiment.
Adding ethanol to the sample … ___1___
Cooling the probe … ___2___
Cooling the sample … ___3___
Increasing sample concentration … ___4___
Gaussian multiplication of the FID … ___5___
Recording a spectrum multiple times, adding up the results … ___6___
Purifying the sample … ___7___
Exponential multiplication of the FID … ___8___
Improved magnetic field homogeneity … ___9___
Increased magnetic field strength … ___10___

Muligheder for alle:
a) decreases resolution
d) decreases sensitivity and increases resolution
c) improves sensitivity
d) increases sensitivity and decreases resolution
e) improves both sensitivity and resolution
f) influences neither resolution nor sensitivity
g) improves resolution
h) decreases sensitivity

Answer 23

Svar:
1 = h) decreases sensitivity
2 = c) improves sensitivity
3 = a) decreases resolution
4 = c) improves sensitivity
5 = d) decreases sensitivity and increases resolution
6 = c) improves sensitivity
7 = f) influences neither resolution nor sensitivity
8 = d) increases sensitivity and decreases resolution
9 = g) improves resolution
10 = e) improves both sensitivity and resolution

Question 24

Which of below particle(s) can have spin? (more than one answer possible)

a) Atomic nuclei
b) Neutron
c) Atoms
d) Proton
e) Electron

Answer 24

Alle 5 svar er korrekte

Side note (all elementary particles (proton, neutron and electron) have a spin ½.
Nuclei CAN(!) have spin. Atoms CAN(!) have spin, but they are not elementary particles)

Question 25

All atomic nuclei with a spin _____ have angular momentum, P Choose what is missing: a) I = 0 b) I > 0 c) I d) I = 1/2 e) I =1, 2, 3, 4, 5, 6, ... f) I = 1/2, 3/2, 5/2, 7/2, ...

Answer 25

Svar: b

Question 26

The magnetic moment, µ, is connected to the angular momentum P by the following relationship ____1____, where γ is called the ____2____. The unit of γ is ____3____ 1: a) μ=(P/γ)^1/2 b) μ=(P/γ)^2 c) μ=γ*P^2 d) μ=γ*P e)μ=P/γ 2: a) gyromagnetic factor b) gyromagnetic ratio c) nuclear magnetization coefficient d) nuclear magnetic ratio 3: a) rad (1/s) (1/T) b) rad (1/s^2) T c) rad (1/s^2) (1/T^2) d) rad s (1/T) e) rad (1/s^2) (1/T)

Answer 26

Svar 1: d Svar 2: b Svar 3: a

Question 27

Which values can the nuclear spin quantum number of zirconium-91 adopt? a) I=½ b) I ∈ ..., -4, -3, -2, -1, 0, 1, 2, 3, 4, .... c) I=0 d) I ∈ ..., -7/2, -5/2, -3/2, -1/2, 1/2, 3/2, 5/2, 7/2, .... e) I ∈ 1, 2, 3, 4, ... f) I ∈ 1/2, 3/2, 5/2, 7/2, ....

Answer 27

Korrekt svar: f Bonus info: spins with an odd mass can adopt any half-integer value: 1/2, 3/2, 5/2, 7/2, ... (The actual value of Zr-91 is I=5/2.)

Question 28

Tin (element no. 50) has several naturally occurring isotopes. Line 1 = isotope Line 2 =natural abundance Line 3 = nuclear spin quantum number Line 1 Line 2 Line 3 112Sn 1% 0 114Sn 0.7% 0 115Sn 0.3% 1/2 116Sn 14.5% 0 117Sn 7.7% 1/2 118Sn 24.2% 0 119Sn 8.6% 1/2 120Sn 32.6% 0 122Sn 4.6% 0 124Sn 5.8% 0 Which of the isotopes would you choose for liquid-state-NMR (more than one answer allowed)? a) 112Sn b) 114Sn c) 115Sn d) 116Sn e) 117Sn f) 118Sn g) 119Sn h) 120Sn i) 122Sn j) 124Sn

Answer 28

Svar: c, e og g Bonus info: isotopes with I=0 do not possess a magnetic moment and are thus useless for NMR. The isotopes with I=½ can be used. You would preferably use the one with the higher natural abundance.

Question 29

How many different orientations can the nuclear magnetic moment of a spin with I = 3/2 adopt?

Answer 29

4 Can be calculated with 2I + 1

Question 30

What would the resonance frequency be of a nucleus with γ=181089658.3 rad T^(-1) s^(-1) at a magnetic field strength of B=13.0 T ? a) 374677085.40 MHz b) 374.68 MHz c) 0.00 MHz d) 749.35 MHz e) 1177.08 MHz f) 3697.91 MHz

Answer 30

svar: a The frequency is given by: ν [Hz] = γ*B/(2π)

Question 31

When a nucleus is scalar coupled to 3 nuclei of I=5/2 : how many signals will it be split into?

Answer 31

svar: 16 m=2*n*I+1 n = antal nuclei

Question 32

Which of the following statements is/are not correct? Question 8Select one or more: a) T2 relaxation is always faster than T1 relaxation. b) The smaller the molecule, the slower T1 relaxation. c) The larger the molecule, the faster T2 relaxation. d) Fast T2 relaxation yields narrow lines in the NMR-spectrum. e) Small organic molecules have slow T2 relaxation.

Answer 32

svar: d

Question 33

A spin echo is a pulse element consisting of a ___1___, followed by ___2___, followed by ___3___ 1: a) spin-lock b) decoupling c) delay d) 90 degree pulse e) 180 degree pulse f) 270 degree pulse 2: a) spin-lock b) decoupling c) delay d) 90 degree pulse e) 180 degree pulse f) 270 degree pulse 3: a) spin-lock b) decoupling c) delay d) 90 degree pulse e) 180 degree pulse f) 270 degree pulse

Answer 33

Svar 1: c Svar 2: e Svar 3: c

Question 34

The pupose of a spin echo is ___1___. It also ___2___ 1: a) Introduce chemical shift evolution b) Eliminate the NOE c) Refocus chemical shift evolution d) Eliminate longitudinal relaxation e) Refocus heteronuclear coupling f) Eliminate transverse relaxation g) Introduce homonuclear coupling h) Introduce heteronuclear coupling i) Refocus homonuclear coupling 2: a) Eliminates the NOE b) Eliminates longitudinal relaxation c) Refocus heteronuclear coupling d) Eliminate transverse relaxation e) Introduce homonuclear coupling f) Introduce heteronuclear coupling g) Refocus homonuclear coupling

Answer 34

Svar 1: c Svar 2: g

Question 35

Insert the missing word: A 2D-NMR spectrum where you can observe correlations between two nuclei of the same isotope, is called _____ a) Heteronuclear b) Homonuclear c) COSY d) interspin e) TOCSY f) Homospin g) mirrored

Answer 35

Svar: b

Question 36

Excitation of nuclear magnetic moments in NMR is typically achieved by short ___1___. They are typically on the order of ___2___. The recorded raw data is called ___3___. It is converted to an NMR spectrum by ___4___. 1: a) UV pulses b) neutron bombardment c) laser pulses d) radiofrequency pulses e) X-ray pulses 2: a) minutes b) picoseconds c) nanoseconds d) milliseconds e) seconds f) microseconds 3: a) free induction decay b) time decay c) nuclear relaxation profile d) shift-intensity bell 4: a) Laplace transformation b) Inverse fourier transformation c) scalar transformation d) Lorens transformation e) Fourier transformation f) inverse Laplace transformation

Answer 36

HUUUUSSSSKKK Svar 1: d Svar 2: Svar 3: Svar 4: e

Question 37

The distribution of spins over possible spin-states in a magnetic field is follows a .... a) Normal distribution b) Bernoulli distribution c) Boltzmann distribution d) Even distribution e) Gaussian distribution f) Poisson distribution g) χ2 distribution h) Log-normal distribution i) Hypergeometric distribution j) Pareto distribution k) Statistical distribution

Answer 37

Svar: c

Question 38

Which values can the nuclear spin quantum number of 53Cr adopt? Chromium is element no. 24 in the periodic table of elements. a) I=½ b) I ∈ 1, 2, 3, 4, ..... c) I ∈ ..., -7/2, -5/2, -3/2, -1/2, 1/2, 3/2, 5/2, 7/2, .... d) I=0 e) I ∈ 1/2, 3/2, 5/2, 7/2, .... f) I ∈ ..., -4, -3, -2, -1, 0, 1, 2, 3, 4, .....

Answer 38

e)

Question 39

Which values can the nuclear spin quantum number of 53Cr adopt? Chromium is element no. 24 in the periodic table of elements. a) I=½ b) I ∈ 1,2,3,4,..... c) I ∈...,-7/2,-5/2,-3/2,-1/2, 1/2, 3/2, 5/2, 7/2, .... d) I=0 e) I ∈ 1/2, 3/2, 5/2, 7/2, .... f) I ∈ ..., -4, -3, -2, -1, 0, 1, 2, 3, 4, ...

Answer 39

Svar: e Bonus info; spins with an odd mass can adopt any half-integer value: 1/2, 3/2, 5/2, 7/2, ... (The actual value of 53Cr is I=3/2.)

Question 40

Tin (element no. 50) has several naturally occurring isotopes. Isotopes of Sn Line 1 = isotope Line 2 = natural abundance Line 3 = nuclear spin quantum number Line 1 Line 2 Line 3 112Sn 1% 0 114Sn 0.7% 0 115Sn 0.3% 1/2 116Sn 14.5% 0 117Sn 7.7% 1/2 118Sn 24.2% 0 119Sn 8.6% 1/2 120Sn 32.6% 0 122Sn 4.6% 0 124Sn 5.8% 0 Which of the isotopes would you choose for liquid-state-NMR (more than one answer allowed)? a)112Sn b)114Sn c)115Sn d)116Sn e)117Sn f)118Sn g)119Sn h)120Sn i)122Sn j) 124Sn

Answer 40

Svar: e og g Bonus info: isotopes with I=0 do not possess a magnetic moment and are thus useless for NMR. The isotopes with I=½ can be used. You would preferably use the one with the higher natural abundance.

Question 41

How many different orientations can the nuclear magnetic moment of a spin with I = 1/2 adopt?

Answer 41

2 Brug formlen: 2I+1

Question 42

What would the resonance frequency be of a nucleus with γ=260232873.1 rad T-1 s-1 at a magnetic field strength of B=14.1 T ? a) 5763.70 MHz b) 583984608.34 MHz c) 1834.64 MHz d) 1167.97 MHz e) 583.98 MHz f) 0.00 MHz

Answer 42

Svar: e Regnes med formlen: v(Hz)=γ*B/(2*π) Bonus: Vigtigt at se det man regner med formlen giver Hz og man skal give svaret i MHz.

Question 42

When a nucleus is scalar coupled to 3 nuclei of I=1 : how many signals will it be split into?

Answer 42

Svar: 7 Brug formlen: 2n*I+1 n er antallet af nuclei

Question 43

Which chemical shift would you (approximately) expect for C1 of lactobionic acid? Just give one number, NOT a range. (Any number within the correct range will be accepted.)

Answer 43

The chemical shift is around 178 ppm - any answer between 168-188 is acceptable.

Question 44

An INEPT is a pulse sequence designed to ____

Answer 44

An INEPT is a pulse sequence designed to transfer magnetisation between nuclei through heteronuclear scalar coupling.

Question 45

The process where the frequency of the probe is adjusted to the desired resonance frequency, is called ____. a) matching b) locking c) frequency-aligning d) tuning e) shimming f) aligning

Answer 45

Svar: d

Question 46

The process of making the magnetic field homogeneous throughout the sample, is called ______ a) matching b) locking c) frequency-aligning d) tuning e) shimming f) aligning

Answer 46

Svar: e

Question 47

Adjusting the impedance of the probe to the desired level is called ___. a) matching b) locking c) frequency-aligning d) tuning e) shimming f) aligning

Answer 47

Svar: a

Question 48

After a couple of beers, your friend boasts with his NMR spectrometer, featuring a resonance frequence of 74 MHz for 13C. You look up the gyromagnetic ratio for 13C, it is 6.72828*10^7 rad s^-1 T^-1. What is the magnetic field strength of his NMR magnet? a) 5.53 T b) 49.79 T c) 0.69 T d) 69.10 T e) 6.91 T f.) 69104691.36 T

Answer 48

Svar: e Brug formlen: B=(2*π*v)/γ B = magnetic field strength v = resonance frequency i Hz γ = gyromagnetic ratio in rad*s^-1*T^-1 Bonus: husk at omregne MHz til Hz, gøres ved at gange med 10^6

Question 49

What would the resonance frequency be of a nucleus with γ=399846959.6 rad T-1 s-1 at a magnetic field strength of B=6.2 T ? a) 789.11 MHz b) 1239.53 MHz c) 394.55 MHz d) 0.00 MHz e) 394553244.63 MHz f) 3894.08 MHz

Answer 49

Svar: c Brug formlen: ν [Hz] = γ*B/(2*π) for at få det til MHz fra Hz skal der ganges med 10^-6

Question 50

Which values can the nuclear spin quantum number of boron-10 adopt? Boron is element no. 5 in the periodic table. Question 3Select one: a) I ϵ 1,2,3,4,..... b)I ϵ ..., -4, -3, -2, -1, 0, 1, 2, 3, 4, ... c) I ϵ ...,-7/2,-5/2,-3/2,-1/2, 1/2, 3/2, 5/2, 7/2, .... d) I ϵ 1/2, 3/2, 5/2, 7/2, .... e) I=½ f) I=0

Answer 50

Svar: A Bonus: nuclei with an even mass and odd charge can adopt any whole-integer value (except for 0): 1, 2, 3, ... (The actual value for 10B is I=3.)

Question 51

Excitation of nuclear magnetic moments in NMR is typically achieved by short ___1___. They are typically on the order of ___2___. The recorded raw data is called ___3___. It is converted to an NMR spectrum by ___4___. 1: a) laser pulses b) UV pulses c) X-ray pulses d) radiofrequency pulses e) neutron bombardment 2: a) microseconds b) seconds c) picoseconds d) minutes e) milliseconds f) nanoseconds 3: a) free induction decay b) shift-intensity delay c) nuclear relasxation profile d) time decay 4: a) Inverse Laplace transformation b) laplace transformation c) lorentz transformation d) scalar transformation e) Fourier transformation f) inverse fourier transformation

Answer 51

Svar1: d Svar2: a Svar3: a Svar4: e

Question 52

How many different orientations can the nuclear magnetic moment of a spin with I = 3/2 adopt?

Answer 52

4 Brug formlen: 2*I+1

Question 53

Ytterbium (element no. 70) has several naturally occurring isotopes. Line 1= isotope Line 2= natural Line 3= abundance nuclear spin quantum number line 1: line 2: line:3 168Yb 0.1% 0 170Yb 3.0% 0 171Yb 14.0% 1/2 172Yb 21.7% 0 173Yb 52.1% 1/2 174Yb 5.8% 0 176Yb 3.3% 0 Which of the isotopes would you choose for liquid-state-NMR (more than one answer allowed)? a)n168Yb b) 170Yb c)171Yb d)172Yb e)173Yb f) 174Yb g) 176Yb

Answer 53

Svar: c og e Bonus: isotopes with I=0 do not possess a magnetic moment and are thus useless for NMR. The two isotopes with I=½ can both be used. You would preferably use the one with the higher natural abundance.

Question 54

Tellurium (element no. 52) has several naturally occurring isotopes. Line 1=isotope Line 2=natural abundance line 3=nuclear spin quantum number' line 1: line 2: line 3: 120Te 0.1% 0 122Te 2.6% 0 123Te 0.9% 1/2 124Te 4.7% 0 125Te 7.1% 1/2 126Te 18.8% 0 128Te 31.7% 0 130Te 34.1% 0 Which of the isotopes would you choose for NMR? (Only one correct answer) a) 120Te b) 122Te c) 123Te d) 124Te e) 125Te f) 126Te g) 128Te h) 130Te

Answer 54

Svar: e Bonus: Isotopes with I=0 do not possess a magnetic moment and are thus useless for NMR. The two isotopes with I=½ can both be used. You would preferably use the one with the higher natural abundance

Question 55

Which of below particle(s) can have spin? (more than one answer possible) a) Electron b) atoms c) Proton d) Neutron e) atomic nuclei

Answer 55

Alle svar er korrekte Bonus: all elementary particles (proton, neutron and electron) have a spin ½. Nuclei CAN(!) have spin. Atoms CAN(!) have spin, but they are not elementary particles.

Question 56

The distribution of spins over possible spin-states in a magnetic field follows a .... a) Normal distribution b) Even distribution c) Pareto distribution d) Poisson distribution e) Hypergeometric distribution f) Boltzmann distribution g) Statistical distribution h) Log-normal distribution i) Gaussian distribution j) Bernoulli distribution k) χ2 distribution

Answer 56

Svar: f

Question 57

Which values can the nuclear spin quantum number of zirconium-91 adopt? a) I ∈ 1,2,3,4,..... b) I ∈ 1/2, 3/2, 5/2, 7/2, .... c) I ∈ ..., -4, -3, -2, -1, 0, 1, 2, 3, 4, ... d) I=0 e) I ∈ ...,-7/2,-5/2,-3/2,-1/2, 1/2, 3/2, 5/2, 7/2, .... f) I=½

Answer 57

Svar: b bonus: spins with an odd mass can adopt any half-integer value: 1/2, 3/2, 5/2, 7/2, ... (The actual value of Zr-91 is I=5/2.)

Question 58

In a DEPT-135 spectrum, you see: a) all 13C nuclei b) all 1H nuclei bound to 13C c) all 13C nuclei bound to 1H d) only 1H nuclei in CH-groups e) 13C nuclei bound to one or three 1H with positive sign and 13C nuclei bound to two 1H with negative sign f) all 1H nuclei in CH2 groups negative, all 1H nuclei in CH and CH3 groups positive g) only 13C nuclei bound to exactly one 1H

Answer 58

Svar: e Bonus: (Note: the phase is arbitrary, the signs can be switched, but DEPT-135 spectra are always presented with CH2 peaks negative.) Så CH og CH3 vil være positive og CH2 vil være negativt

Question 58

In a DEPT-45 spectrum, you see: a) only 13C nuclei bound to exactly one 1H b) all 13C nuclei bound to 1H c) 13C nuclei bound to one or three 1H with positive sign and 13C nuclei bound to two 1H with negative sign d) all 13C nuclei e) all 1H nuclei in CH2 groups negative, all 1H nuclei in CH and CH3 groups positive f) all 1H nuclei bound to 13C g) only 1H nuclei in CH-groups

Answer 58

Svar: b

Question 59

In a DEPT-90 spectrum, you see: a) only 1H nuclei in CH-groups b) only 13C nuclei bound to exactly one 1H c) all 1H nuclei bound to 13C d) all 13C nuclei bound to 1H e) all 13C nuclei f) all 1H nuclei in CH2 groups negative, all 1H nuclei in CH and CH3 groups positive g) 13C nuclei bound to one or three 1H with positive sign and 13C nuclei bound to two 1H with negative sign

Answer 59

Svar: b

Question 60

Which effect has scalar coupling to 12C on a 1H-NMR spectrum: a) it changes the sign of the 1H-NMR spectrum b) it leads to dublets c) it leads to dublets of dublets d) There is no scalar coupling between 1H and 12C e) It leads to quartets f) It leads to triplets g) It is always visible h) It is sometimes visible i) It is never visible

Answer 60

Svar: d 12C has an even number of protons and an even number of neutrons in the nucleus. Thus, it has a spin of I=0, i.e. no spin at all. It therefore does not give rise to scalar coupling at all.

Question 61

A 2D-NMR spectrum showing correlations through a single scalar coupling step between two nuclei of the same isotope is called ___1___ . If correlations through multiple scalar coupling steps are involved, the spectrum is called ___2___ Valgmuligheder: a) COSY b) HMQC c) TOCSY d) DEPT e) NOESY f) INEPT

Answer 61

Svar 1: a Svar 2: c

Question 62

A 2D-NMR spectrum where you can observe correlations between two different nuclei, is called ____ a) homonuclear b) heteronuclear c) COSY d) interspin e) TOCSY f) Homospin g) mirrored

Answer 62

Svar: b

Question 63

A NOESY spectrum is a ___1___ D-NMR spectrum showing correlations between nuclei ___2___. The intensity of its peaks depends on ___3___ 1: a) 1 b) 2 c) 3 2: a) Through dipolar coupling b) through one scalar coupling step c) through multiple consecutive scalar coupling steps 3: a) distance between the two atoms b) dihedral angle between the two atoms c) number of oxygen atoms in the molecule

Answer 63

Svar 1: b Svar 2: a Svar 3: a

Question 64

A 2D-NMR spectrum where you can observe correlations between two nuclei of the same isotope, is called ___ a) homonuclear b) heteronuclear c) COSY d) interspin e) TOCSY f) Homospin g) mirrored

Answer 64

Svar: a

Question 65

The ___1___ is the part of the spectrometer that creates the radiofrequency waves and processes the signal from the sample. The radiofrequency-pulses are sent by the ___2___, and the signals are detected by the ___3___. Valgmuligheder: a) console b) probe c) magnet d) lock system e) shim system

Answer 65

Svar 1: a Svar 2: b Svar 3: b

Question 66

The process where the frequency of the probe is adjusted to the desired resonance frequency, is called ___ a) shimming b) locking c) frequency-aligning d) tuning e) matching f) aligning

Answer 66

Svar: d

Question 67

Adjusting the impedance of the probe to the desired level is called ___ a) matching b) shimming c) tuning d) aligning e) impedance-fitting f) locking

Answer 67

Svar: a

Question 68

The process of making the magnetic field homogeneous throughout the sample, is called ___ a) homogenizing b) matching c) locking d) aligning e) shimming f) tuning

Answer 68

Svar: e

Question 69

Solvents used in NMR are special in that... a) ... they must not be poisonous. b) ... they must not be magnetic. c) ... they are very pure. d) ... they are labelled with 2H. e) ... they are labelled with 13C. f) ... they glow in the dark. g) ... they must not contain water. h) ... they must not emit radiation.

Answer 69

Svar: d

Question 70

Increased magnetic field strength ... a) Improves resolution b) decreases resolution c) increases sensitivity and decreases resolution d) influences neither resolution nor sensitivity e) decreases sensitivity and increses resolution f) decreases sensitivity g) improves sensitivity h) improves both sensitivity and resolution

Answer 70

Svar: h

Question 71

Improved magnetic field homogeneity ... a) Improves resolution b) decreases resolution c) increases sensitivity and decreases resolution d) influences neither resolution nor sensitivity e) decreases sensitivity and increses resolution f) decreases sensitivity g) improves sensitivity h) improves both sensitivity and resolution

Answer 71

Svar: a

Question 72

Cooling the sample ... a) Improves resolution b) decreases resolution c) increases sensitivity and decreases resolution d) influences neither resolution nor sensitivity e) decreases sensitivity and increses resolution f) decreases sensitivity g) improves sensitivity h)improves both sensitivity and resolution

Answer 72

Svar: b

Question 73

Adding ethanol to the sample ... a) Improves resolution b) decreases resolution c) increases sensitivity and decreases resolution d) influences neither resolution nor sensitivity e) decreases sensitivity and increses resolution f) decreases sensitivity g) improves sensitivity h)improves both sensitivity and resolution

Answer 73

Svar: e

Question 74

Recording a spectrum multiple times, adding up the results ... a) Improves resolution b) decreases resolution c) increases sensitivity and decreases resolution d) influences neither resolution nor sensitivity e) decreases sensitivity and increses resolution f) decreases sensitivity g) improves sensitivity h)improves both sensitivity and resolution

Answer 74

Svar: g

Question 75

Exponential multiplication of the FID ... a) Improves resolution b) decreases resolution c) increases sensitivity and decreases resolution d) influences neither resolution nor sensitivity e) decreases sensitivity and increses resolution f) decreases sensitivity g) improves sensitivity h)improves both sensitivity and resolution

Answer 75

Svar: c

Question 76

Increasing sample concentration ... a) Improves resolution b) decreases resolution c) increases sensitivity and decreases resolution d) influences neither resolution nor sensitivity e) decreases sensitivity and increses resolution f) decreases sensitivity g) improves sensitivity h)improves both sensitivity and resolution

Answer 76

Svar: g

Question 77

Purifying the sample ... a) Improves resolution b) decreases resolution c) increases sensitivity and decreases resolution d) influences neither resolution nor sensitivity e) decreases sensitivity and increses resolution f) decreases sensitivity g) improves sensitivity h)improves both sensitivity and resolution

Answer 77

Svar: d

Question 78

Cooling the probe ... a) Improves resolution b) decreases resolution c) increases sensitivity and decreases resolution d) influences neither resolution nor sensitivity e) decreases sensitivity and increses resolution f) decreases sensitivity g) improves sensitivity h)improves both sensitivity and resolution

Answer 78

Svar: g

Question 79

Gaussian multiplication of the FID ... a) Improves resolution b) decreases resolution c) increases sensitivity and decreases resolution d) influences neither resolution nor sensitivity e) decreases sensitivity and increses resolution f) decreases sensitivity g) improves sensitivity h)improves both sensitivity and resolution

Answer 79

Svar: e

Question 80

What would the resonance frequency be of a nucleus with γ=180415658.3 rad T^(-1) s^(-1) at a magnetic field strength of B=20.3 T ? a) 1831.22 MHz b) 582895089.75 MHz c) 582.90 MHz d) 1165.79 MHz e) 0.00 MHz f) 5752.94 MHz

Answer 80

Svar: c

Question 81

When a nucleus is scalar coupled to 1 nucleus of I=3/2 : how many signals will it be split into?

Answer 81

Svar: 4 m=2*I*n+1 m=signals n=number of nuclei

Question 82

What sort of information do you obtain from a TOCSY spectrum?

Answer 82

A TOCSY spectrum helps you identify which protons in a molecule are part of the same spin system. In simpler terms, it shows you groups of hydrogen atoms that are connected through a chain of covalent bonds and can pass magnetization to each other via scalar (J) coupling. Unlike a COSY spectrum, which only shows direct coupling between neighboring protons (e.g., H–C–H), TOCSY shows all the protons in a connected network — even if they're not directly bonded. It works by relaying the magnetization through the spin system. For example, if you look at a sugar like glucose, each proton on the ring (H-1, H-2, H-3, etc.) is connected to the next via bonds. In a TOCSY spectrum, if you pick out the signal for H-1, you'll see cross-peaks to H-2, H-3, H-4, and so on — showing that they're all part of the same spin system. This is especially helpful in molecules with repeating units or overlapping signals, like sugars, peptides, and amino acids, because it lets you track entire sections of the molecule. So in summary: A TOCSY spectrum tells you which protons are connected through a chain of bonds — it shows the full set of coupled protons in a spin system, not just the ones directly next to each other.

Question 83

What sort of information do you obtain from a DOSY spectrum?

Answer 83

A DOSY spectrum gives you information about how fast different molecules move, or diffuse, through a solution. In other words, it tells you about the size and shape of molecules based on how quickly they spread out in the solvent. In a regular ¹H NMR spectrum, you only see where the hydrogen atoms are (chemical shift). But in a DOSY spectrum, you also see how fast each group of signals diffuses. Small molecules move quickly, while larger ones move more slowly because they experience more resistance in the solvent. This means that if you have a mixture of compounds, a DOSY spectrum can help you figure out: Which signals belong to the same molecule (they will have the same diffusion rate) Whether a molecule is interacting with something else (for example, if it forms a larger complex or aggregate, it will diffuse more slowly) How many different species are in your solution — even if their normal NMR signals overlap So in short: A DOSY spectrum separates signals by how fast the molecules move in solution, helping you distinguish between different molecules based on their size or how they interact.

Question 84

What is T2-relaxation? What does it depend on? How does it manifest itself in NMR spectra?

Answer 84

T₂-relaxation, also known as transverse relaxation, is the process by which the NMR signal decays after the excitation pulse due to a loss of phase coherence among spinning nuclei. When nuclei are placed in a magnetic field and excited, they begin to precess together in the transverse plane (perpendicular to the main magnetic field). Over time, small differences in their local magnetic environments cause them to drift out of sync. As a result, the combined signal fades — this decay is what we call T₂-relaxation. The speed of T₂-relaxation depends on how quickly and irregularly the local magnetic environment changes. Factors like molecular size, motion, and interactions with nearby spins all play a role. In general, small, rapidly tumbling molecules have long T₂ times and produce sharp peaks, while large or rigid molecules relax faster (short T₂), leading to broad peaks in the spectrum. So, in an NMR spectrum, T₂-relaxation is directly related to line width: a shorter T₂ causes broader peaks, and a longer T₂ gives sharper ones. This makes T₂ a valuable indicator of molecular dynamics and interactions in solution.

Question 85

Why are NMR magnets immersed in liquid helium?

Answer 85

NMR magnets use superconducting coils that must be cooled below their critical temperature to function properly. Liquid helium boils at 4.2 K, which is cold enough to maintain superconductivity in materials like niobium-titanium. Superconductivity allows the magnet to produce a strong, stable magnetic field with zero electrical resistance, essential for high-resolution NMR. Without liquid helium, the coils would not stay cold enough, leading to power loss, heat generation, and unstable magnetic fields. Often, liquid nitrogen is also used to reduce helium boil-off by blocking external heat.

Question 86

Scalar coupling between two spins separated by four bonds is called ___ a) allylic coupling b) vicinal coupling c) geminal coupling

Answer 86

Svar: a

Question 87

Scalar coupling between two spins separated by two bonds is called ___ a) allylic coupling b) vicinal coupling c) geminal coupling

Answer 87

Svar: c

Question 88

Scalar coupling between two spins separated by three bonds is called. a) allylic coupling b) vicinal coupling c) geminal coupling

Answer 88

Svar: b

Question 89

What is "sensitivity" in NMR? What does it depend on and how can it be improved?

Answer 89

Sensitivity in NMR is the ability to detect weak signals, measured as signal-to-noise ratio (SNR). It can be improved by; - using stronger magnets - Recording more scans, adding up the results - cooling the probe - optimized pulse sequences - Increasing sample concentration - Increased magnetic field strength this improves both sensitivity and resolution

Question 90

Which of the following abbreviations is NOT covering a known NMR-experiment? (multiple answers allowed) Question 15Select one or more: a. TOCSY b. DEPT c. INEPT d. ROESY e. APT f. COSY g. BARP h. Jres i. NOESY j. HSQC k. DOSY l. HMBC

Answer 90

Svar: g (BARP)

Question 91

What is JRES in NMR, and what is it used for?

Answer 91

JRES (J-Resolved Spectroscopy) is a 2D NMR technique that separates chemical shift and J-coupling information. The F2 axis shows chemical shifts, and the F1 axis shows J-couplings. It simplifies complex spectra and helps interpret overlapping signals by resolving multiplets into singlets in the 1D projection.

Question 92

What is the Nuclear Overhauser Effect (NOE) in NMR?

Answer 92

NOE is a change in the NMR signal intensity of one nucleus due to dipole–dipole interactions with a nearby nucleus. It reveals spatial proximity (typically < 5 Å) between atoms and is widely used in structure determination via 1D NOE or 2D NOESY experiments.

Question 93

What does the magnitude of the Nuclear Overhauser Effect (NOE) depend on?

Answer 93

The NOE magnitude depends primarily on the distance between nuclei (∝ 1/r⁶), molecular size and tumbling rate (correlation time), magnetic field strength, the gyromagnetic ratios of the interacting nuclei, and their relaxation properties. It is strongest for nearby protons in small, fast-tumbling molecules.

Question 94

Which information does a ROESY spectrum contain?

Answer 94

A ROESY (Rotating-frame Overhauser Effect SpectroscopY) spectrum shows through-space interactions between nuclei, typically protons that are within ~5 Å of each other. It reveals spatial proximity, not bond connectivity, and is used to deduce 3D structure and conformation.

Question 95

Which experiment can give you the same information as ROESY (most of the time)?

Answer 95

NOESY (Nuclear Overhauser Effect Spectroscopy) usually provides the same type of spatial proximity information as ROESY. Both are 2D NMR techniques that show cross-peaks between nearby protons.

Question 96

When do you have to use the ROESY experiment?

Answer 96

Use ROESY when studying intermediate-size molecules (typically 500–2000 Da), where the NOE is weak or cancels out due to correlation time effects. In this regime, NOESY may fail (cross-peaks disappear or become negative), while ROESY still gives clear, positive cross-peaks.

Question 97

What is T₁ relaxation in NMR?

Answer 97

T₁ relaxation (also called longitudinal or spin-lattice relaxation) is the process by which nuclear spins return to their equilibrium population distribution along the external magnetic field (z-axis) after being disturbed by a pulse.

Question 98

When does T₁ relaxation occur, and what happens during the process?

Answer 98

T₁ relaxation occurs after an RF pulse tips the net magnetization away from the z-axis. Energy is transferred from the spin system to the surrounding lattice (environment), allowing the longitudinal magnetization (Mz) to gradually recover to its equilibrium value.

Question 99

What does the speed of T₁ relaxation depend on?

Answer 99

Nucleus type (e.g., ¹H relaxes faster than ¹³C) Size of molecule

Question 100

When do you have to consider T₁ relaxation in experimental planning?

Answer 100

T₁ must be considered when choosing repetition times between scans. If you don’t wait long enough for full T₁ recovery, signals can be underestimated (saturation). This is critical in quantitative NMR and in experiments like inversion-recovery (used to measure T₁).

Question 101

What are pulsed field gradients and what can they be used for?

Answer 101

Pulsed Field Gradients (PFGs) are short variations in the magnetic field used in NMR to control and select signals by affecting the phase of the spins. They can be used to suppress unwanted signals (e.g., from solvents). Signals are suppressed because pulsed field gradients cause the spins to dephase spatially, so that their signals cancel out and are no longer detected.