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Chem 263 > Topic 1: NMR Spectroscopy > Flashcards

Topic 1: NMR Spectroscopy Flashcards

1
Q

In absorb an r spectroscopy we are exciting electrons to a ——— energy level

A

Higher

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2
Q

As the nuclear charge spins, it generates a….

A

Localized magnetic moment (𝜇)

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3
Q

When is the formula 2I + 1 used?

A

Finding potential orientations in an applied magnetic field

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4
Q

T or F: The bigger the magnet in NMR, the smaller the energy difference

A

F, it will have a larger energy difference

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5
Q

Is there an even distribution of electrons between the alpha and beta half spin states?

A

Yes

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6
Q

Spin flip occurs when radio frequency has an energy that ____ change in energy

A

Equals

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7
Q

Excitation and relaxation results in change in the overall ______ of the sample

A

Magnetization

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8
Q

What is detected on NMR spectrums?

A

Proton shifts

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9
Q

What is integration on an NMR spectrum?

A

Number of equivalent/ non-equivalent protons in a molecule

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10
Q

What is chemical shift in NMR spectrum?

A

Tells us the chemical environment of the various protons

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11
Q

What is shown by spin-spin coupling in NMR?

A

The number of neighbouring protons, can piece together the structural backbone of the molecule

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12
Q

Atoms that are in chemically/ structurally identical environments, interchangeable through symmetry or bond rotation. This is the definition of:

A

Chemical equivalence

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13
Q

Will chemically equivalent protons show more than one resonance signal?

A

No, they only show one resonance signal

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14
Q

What does the area underneath a H NMR resonance peak directly reflect?

A

The number of protons it represents

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15
Q

Can integrals be imperfect?

A

Yes, there are impurities possible in real life

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16
Q

A localized magnetic field is the circulation of electrons around a nucleus, generating a _____________

A

Magnetic moment

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17
Q

This localized magnetic field always ______ the applied magnetic field, which _____ the nucleus from the full effect of the applied magnetic field

A
  1. Opposes
  2. Shields
18
Q

What is shielding?

A

More electron density at nucleus (chemical shift will be upfield, low values)

19
Q

What is deshielding?

A

Less electron density at nucleus (chemical shift is downfield, higher values)

20
Q

The frequency at which a nucleus undergoes spin flip is called…

A

Resonance frequency

21
Q

NMR is a good tool to obtain…

A

Structural information

22
Q

What is the standard frame of reference used in H NMR?

A

TMS

23
Q

Do integrals add together to provide a partial number of H atoms in the molecule?

A

No, they add together to provide the TOTAL number of H atoms in the molecule

24
Q

Nuclei are _________ from the applied magnetic field

A

Protected

25
Q

The basis of chemical shift is; the net __________ ______ that is experienced by a nucleus is the ____ of the applied magnetic field

A
  1. Magnetic field
  2. Sum
26
Q

Will electronegative atoms like fluorine and chlorine will deshield or shield neighbouring atoms?

A

Deshield

27
Q

Higher electronegativity equals a greater _______ effect (downfield shift)

A

Deshielding

28
Q

If an atom is farther away from an electron withdrawing group will the deshielding effect be smaller or greater?

A

Smaller

29
Q

Electro_______ atoms shield neighbouring atoms

A

Positive

30
Q

There’s an upfield shift/ increase in shielding when electron donating groups are…

A

Added

31
Q

When electron withdrawing groups are added neighbouring atoms will be increasingly….

A

Deshielded, produces a downfield shift

32
Q

List the following functional groups in increasing chemical shift/ deshielding/ downfield: Alkenes, carboxylic acid, aromatic, aldehyde

A

Alkene, aromatic, aldehyde, carboxylic acid

33
Q

What is conjugation essentially?

A

How electron density is shared

34
Q

Identify being shielded and deshielded with charges

A

Shielded = negative charge
Deshielded = positive charge

35
Q

When a magnetic field is opposing the applied magnetic field does a shielding or deshielding effect occur?

A

Shielding

36
Q

When a magnetic field is aligned with the applied magnetic field does a shielding or deshielding effect occur?

A

Deshielding

37
Q

More carbon double bonds results in a(n) _____ in electron density

A

Increase

38
Q

Pascal’s triangle gives the _______ of lines in a given multiplet

A

Heights

39
Q

T or F: Geminal coupling is the strongest and has small separations.

A

False, it is the strongest but it has big separations

40
Q

Doublets of doublets are a result of ______ coupling

A

Unequal

Chem 263 (2 decks)

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