Topic 1: NMR Spectroscopy

Question 1

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

Answer 1

Higher

Question 2

As the nuclear charge spins, it generates a….

Answer 2

Localized magnetic moment (𝜇)

Question 3

When is the formula 2I + 1 used?

Answer 3

Finding potential orientations in an applied magnetic field

Question 4

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

Answer 4

F, it will have a larger energy difference

Question 5

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

Answer 5

Yes

Question 6

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

Answer 6

Equals

Question 7

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

Answer 7

Magnetization

Question 8

What is detected on NMR spectrums?

Answer 8

Proton shifts

Question 9

What is integration on an NMR spectrum?

Answer 9

Number of equivalent/ non-equivalent protons in a molecule

Question 10

What is chemical shift in NMR spectrum?

Answer 10

Tells us the chemical environment of the various protons

Question 11

What is shown by spin-spin coupling in NMR?

Answer 11

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

Question 12

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

Answer 12

Chemical equivalence

Question 13

Will chemically equivalent protons show more than one resonance signal?

Answer 13

No, they only show one resonance signal

Question 14

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

Answer 14

The number of protons it represents

Question 15

Can integrals be imperfect?

Answer 15

Yes, there are impurities possible in real life

Question 16

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

Answer 16

Magnetic moment

Question 17

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

Answer 17

1. Opposes
2. Shields

Question 18

What is shielding?

Answer 18

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

Question 19

What is deshielding?

Answer 19

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

Question 20

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

Answer 20

Resonance frequency

Question 21

NMR is a good tool to obtain…

Answer 21

Structural information

Question 22

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

Answer 22

TMS

Question 23

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

Answer 23

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

Question 24

Nuclei are _________ from the applied magnetic field

Answer 24

Protected

Question 25

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

Answer 25

1. Magnetic field 2. Sum

Question 26

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

Answer 26

Deshield

Question 27

Higher electronegativity equals a greater _______ effect (downfield shift)

Answer 27

Deshielding

Question 28

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

Answer 28

Smaller

Question 29

Electro_______ atoms shield neighbouring atoms

Answer 29

Positive

Question 30

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

Answer 30

Added

Question 31

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

Answer 31

Deshielded, produces a downfield shift

Question 32

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

Answer 32

Alkene, aromatic, aldehyde, carboxylic acid

Question 33

What is conjugation essentially?

Answer 33

How electron density is shared

Question 34

Identify being shielded and deshielded with charges

Answer 34

Shielded = negative charge Deshielded = positive charge

Question 35

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

Answer 35

Shielding

Question 36

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

Answer 36

Deshielding

Question 37

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

Answer 37

Increase

Question 38

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

Answer 38

Heights

Question 39

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

Answer 39

False, it is the strongest but it has big separations

Question 40

Doublets of doublets are a result of ______ coupling

Answer 40

Unequal