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The Medicine (Y2) > NMR > Flashcards

NMR Flashcards

1
Q

In medicinal chemistry, NMR is used to confirm the identity and purity of drugs. True or false?

A

True

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2
Q

How is NMR used in formulation science?

A

For determining aggregation properties of drugs, rates of drug degradation and rates of release of drugs from controlled release systems

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3
Q

How is NMR used in pharmacokinetics?

A

determination of metabolic products of drugs in urine and plasma

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4
Q

How is NMR used in medical diagnosis?

A

Imaging of tumours and other abnormalities

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5
Q

All atoms are magnetically active. True or false?

A

False - to be magnetically active, the atom must have an ODD number of protons and or odd number of neutrons

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6
Q

Nuclei that have a magnetic spin of 0 can be magnetically active. True or false?

A

False

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7
Q

How many states can a nucleus with a magnetic spin of 0.5 adopt?

A

Two (aligned against or with magnetic field)

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8
Q

Do the majority of spins align with or against the field and why?

A

Align with the field, as this requires less energy

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9
Q

The number of nuclei in the high energy state and the number in the low energy state will differ by an amount determined by Boltzmann distribution. True or false?

A

True

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10
Q

Does NMR have high or low sensitivity?

A

low

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11
Q

The sensitivity of NMR is reversibly proportional to the difference in population of high level and low energy. True or false?

A

False - it is proportional

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12
Q

How is the sensitivity of NMR increased?

A

Using a bigger magnetic strength (external magnet) or by increasing the amount of sample in the NMR tube

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13
Q

Doubling the magnetic strength reduced the radio frequency by half. True or false?

A

False - it also doubles the radio frequency

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14
Q

In an NMR experiment, you detect the relaxation back to equilibrium of excited nuclei. True or false?

A

True

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15
Q

In a Fourier transformation experiment, simultaneous excitation of all nuclei in the sample takes place. What is this due to?

A

The sample is irradiated with a short pulse of a broad range radiofrequency radiation

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16
Q

Free indcution decay is a plot of signal intensity against time. True or false?

A

True

17
Q

Fourier transformation converts the spectrum from units of time to units of frequency. True or false?

A

True

18
Q

In NMR, the number of peaks corresponds to the number of equivalent protons. True or false?

A

False, corresponds to the number of non-equivalent protons

19
Q

What does the area underneath each signal correspond to?

A

The number of protons responsible for this signal

20
Q

What does the shape of the signal depend on?

A

Whether the proton is exchangeable or non-exchangeable

21
Q

Can electrons generate their own magnetic field?

A

Yes - because they have their own charge so circulate around the magnet and can produce their own magnetic field

22
Q

The magnetic field experienced by the nucleus is increased by local magnetic field induced by electrons. True or false?

A

False - it is decreased

23
Q

What is usually used as the reference signal?

A

Tetramethyl silane (TMS)

24
Q

Nuclei less shielded than the reference has a negative chemical shift. True or false?

A

False - have a positive chemical shift

25
Q

What effect on shielding does an electron donating group attached to the atom have?

A

Increases shielding and lower resonance frequency

26
Q

Electronegative groups are “deshielding” and move proton NMR signals from neighbouring protons further “downfield” (higher ppm). True or false?

A

True

27
Q

In proton NMR, protons on oxygen and nitrogen have highly variable chemical shifts which are sensitive to temperature, concentration etc. True or false?

A

True

28
Q

In proton NMR, the pi system of alkenes, carbonyls and aromatics deshield attached protons and move them to lower ppm. True or false?

A

False - higher ppm

29
Q

The same concepts for proton NMR chemical shifts apply to C13 NMR. True or false?

A

True

30
Q

Natural abundance of C13 is higher than H1. True or false?

A

False - H1 is much higher

31
Q

C13 is more sensitive than H1. True or false?

A

False - less sensitive

32
Q

How does a multiplet structure arise?

A

interaction between neighbouring nuclei (i.e. spin-spin coupling)

33
Q

What is the unit for magnitude of coupling interactions?

A

Hertz

34
Q

The coupling constant, J is independent of the magnetic field strength. True or false?

A

True

35
Q

Chemically and magnetically equivalent protons couple to one another. True or false?

A

False

The Medicine (Y2) (34 decks)

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