spectroscopy and chromatography

Question 1

what is mass spectrometry used for

Answer 1

To calculate the molecular mass of an organic compound and gives further information about its structure

Question 2

what happens when a molecular ion splits up in mass spec

Answer 2

It forms a positive ion ie CH4+ and a radical ie CH2.

Question 3

What happens when a molecule first splits up in mass spec

Answer 3

A positive ion is formed and an electron ie CH4+ + e-

Question 4

What is the M+ peak

Answer 4

The peak with the highest m/z value, there may be a peak one unit after, this is the m+1 peak and is for isotopes. Its length with reflect its relative intensity

Question 5

How are the other peaks in mass spec formed

Answer 5

The molecular ions break down into smaller peaks known as fragments, this is called fragmentation.

Question 6

What is detected in the mass spec

Answer 6

The positive ion

Question 7

How does infrared spectroscopy work

Answer 7

Certain bonds in a molecule absorb infra-red radiation at characteristic frequencies causing the covalent bond to shake.

Question 8

Rf value

Answer 8

Distance moved by a component divided by distance moved by solvent.

Question 9

Retention time

Answer 9

The time between injection and detection of a component

Question 10

How is the mixture separated during gas chromatography

Answer 10

Solubility

Question 11

What is the role of gas in gas chromatography

Answer 11

Mobile phase

Question 12

What is the role of liquid in gas chromatography

Answer 12

Stationary phase

Question 13

How can gas chromatogram be used to determine the percentage composition of each component in the mixture

Answer 13

Measure the area under each peak, find total area

%=(area of one peak/total area) x100

Question 14

What is used as a solvent in proton NMR

Answer 14

A deuterated solvent because it would not give a peak as it does not contain H. Example, (CD3)SO

Question 15

What is TMS used for?

Answer 15

A reference

Question 16

What is D2O used for

Answer 16

In a process called proton exchange the OH peak will disappear. This helps differentiate between OH and NH peaks.

Question 17

What is the fingerprint area

Answer 17

Below 1500 cm-1. This part of the spectrum is unique for each compound and can be compared to a computer database of the fingerprint area of known compounds to identify the compound.

Question 18

What can infrared be used to detect

Answer 18

Functional groups

Question 19

What are the uses of infrared in the real world

Answer 19

Breathalysers test for ethanol by using analysing an infrared spectroscopy

Question 20

How is infrared associated with global warming

Answer 20

Water vapour, methane and carbon dioxide absorb longer wavelength IR radiation because it has the same frequency of the natural frequency of their bonds, C=O, O-H and C-H. Eventually the vibrating bonds re-emit this energy as radiation which increases the temperature of the atmosphere which leads to global warming.

Question 21

What does carbon NMR tell us

Answer 21

The number of different carbon environments from the peaks and the types of carbon environments from the shift.

Question 22

What will carbon NMR not tell us

Answer 22

If a compound is symmetrical and has the same atoms attached it will not tell us about the environments which are alike.

Question 23

What does proton NMR tell us

Answer 23

Provides the number of different proton environments from the number of peaks. The type of proton environments from the chemical shift. The relative number of each type of proton from the integration number. The number of protons adjacent to the given proton from the splitting pattern.

Question 24

What does a proton NMR not tell us

Answer 24

Two or more proton peaks will not show up if they are symmetrical and have the same groups attached

Question 25

What does integration tell us

Answer 25

We work out the ratio of the integration b simplifying the measured area to get whole numbers, This number is the number of hydrogen showing us that peak. So the number of hydrogen atoms attached to the carbon atom with that functional group.

Question 26

Splitting pattern

Answer 26

This is the number of peaks at a certain value. You take away one from this and this is the number of hydrogens on the adjacent carbon.

Question 27

Singlet

Answer 27

One peak, shows that there is no hydrogens on the adjacent carbon

Question 28

Doublet

Answer 28

Two peaks, shows that there is one hydrogen on the adjacent carbon.

Question 29

Triplet

Answer 29

Three peaks, shows that there is 2 hydrogens on the adjacent carbon

Question 30

Quartet

Answer 30

Four peaks, shows that there is three hydrogens on the adjacent carbon.

Question 31

Multiplet

Answer 31

More then four peals, shows that there is four or more hydrogens on the adjacent carbon.

Question 32

What is chromatography used for

Answer 32

Is used to separate individual components from a mixture of substances. They all have a stationary phase and a mobile phase

Question 33

The stationary phase

Answer 33

Does not move and is normally a solid or a liquid supported on a solid support.

Question 34

Mobile phase

Answer 34

Does move and is normally a liquid or gas.

Question 35

What does TLC test for

Answer 35

Adsorption to the stationary phase. The different components in the mixture have different affinities for the adsorbent and bind with differing strengths tp its surface.