Exam 1

Question 1

Describe NMR

Answer 1

NMR (Nuclear Magnetic Resonance) is a powerful tool that determines the structure of compounds using interactions of radio waves

Question 2

What are the 4 pieces of information we can get from NMR spectroscopy?

Answer 2

1. Origin of NMR signal
2. Chemical Shift
3. Multiplicity
4. Area

Question 3

Adding energy is an

Answer 3

Absorption

Question 4

What is nuclear spin?

Answer 4

A spinning charged nuclei that generates a magnetic field

Question 5

Releasing energy is an

Answer 5

Emission

Question 6

What are responsible for the NMR signal?

Answer 6

Alpha and Beta spin states

Question 7

The difference in energy between the spins states is the …

Answer 7

Frequency (radio wave)

Question 8

What causes an organic molecule to have a NMR active nuclei?

Answer 8

Mass numbers that are odd -> NMR Active Nuclei -> Alpha & Beta spin-states

Question 9

What does it mean for a proton to be deshielded?

Answer 9

The electron density around the proton is reduced (due to the presence of electronegative atoms, double bonds, or aromatic rings nearby).

Question 10

What is a vicinial hydrogen?

Answer 10

A hydrogen that is 3 bonds away from another hydrogen

Question 11

What is the universal standard for NMR?

Answer 11

TMS because its chemical shift is 0.0

Question 12

What are homotopic hydrogens?

Answer 12

Hydrogens that give rise to the same peak (NMR Signal)

Question 13

What is the result of a substitution test with identical compounds?

Answer 13

Homotopic hydrogens

Question 14

What are homotopic hydrogens?

Answer 14

Hydrogens that give rise to the same peak (NMR Signal)
Symmetric environments
Identical compounds (same molecular formula)

Question 15

What are heterotopic hydrogens?

Answer 15

Hydrogens that give rise to different peaks (NMR Signal)
Assymmetric environments]
Different compounds

Question 16

What is the result of a substitution test with different compounds?

Answer 16

Heterotopic hydrogens

Question 17

What are enantiotropic hydrogens?

Answer 17

Hydrogens that are in mirror image environments
They give rise to the same peak
Both chiral centers change

Question 18

What are diastereotopic hydrogens?

Answer 18

Hydrogens that are not in mirror image environments
They give rise to different peaks
Only one chiral center changes

Question 19

Chemical Shift

Answer 19

Electron density around a nuclei

Question 20

Deshielded Proton

Answer 20

(Downfield)
High Chemical Shift

Question 21

What causes a proton to become deshielded?

Answer 21

It loses electron density due to the presence of electronegative atoms, double bonds and triple bonds

Question 22

Shielded Proton

Answer 22

(Upfield)
Low Chemical Shift

Question 23

Chemical shift range for aldehyde protons?

Answer 23

9.5 - 10.5 ppm

Question 24

Chemical shift range for aromatic protons?

Answer 24

6.0 to 8.5 ppm

Question 25

Chemical shift range for alkenes protons?

Answer 25

4.5 to 6.5 ppm

Question 26

Chemical shift range for protons on carbons attached to electronegative atoms?

Answer 26

3.0–3.9 ppm

Question 27

Signal splitting?

Answer 27

n + 1 rule n = # of vicinal hydrogens 1 singlet 2 doublet 3 triplet 4 quartet 5 pentet 6 sextet

Question 28

Integration

Answer 28

number of hydrogens producing a given signal

Question 29

Coupling Constant

Answer 29

Distance between the individual peaks of a signal in a doublet or a triplet

Question 30

Broadband de-coupled 13C NMR

Answer 30

Hydrogens are decoupled (removed) -> Carbon atoms appears as one peak without splitting

Question 31

DEPT Spectra

Answer 31

Used to identify carbon atoms by # of hydrogens attached CH3 CH odd ↑↑ CH2 even ↓

Question 32

GC/MS stands for

Answer 32

Gas-Chromatography Mass Spectrometry

Question 33

Base Peak

Answer 33

Tallest peak 100% relative abundance

Question 34

Isotopic Ratio (1:1), What isotope is present?

Answer 34

Bromine

Question 35

Isotopic Ratio (3:1), What isotope is present?

Answer 35

Chlorine

Question 36

Mass Spectrometry Fragmentation

Answer 36

Alpha cleavage of alpha position (one carbon over form FG) carbons Product is daughter ions that can be analyzed based on mass-to-charge ratio (M/Z) to give information about a compounds structure and composition

Question 37

Electron Impact Ionization

Answer 37

Process of bombarding a molecule with electrons to produce a molecular ion (radical cation). That molecular ion can then undergo fragmentation.

Question 38

High Resolution Mass Spectrometry (HR MS)

Answer 38

Gives the molecular formula

Question 39

Which molecule can associate with each other through hydrogen bonding?

Answer 39

Alcohols

Question 40

Oxygen atom of the hydroxyl group is

Answer 40

Nucleophilic and basic

Question 41

Hydrogen atom of the hydroxyl group is

Answer 41

Acidic