Organic Analysis

Question 1

What are the stages in mass spectrometry?

Answer 1

Vaporisation
Ionisation
Acceleration
Deflection
Detection

Question 2

What is the molecular ion peak?

Answer 2

The peak with the highest M/Z ratio in he spectrum

Question 3

How can you determine the relative molecular mass using a mass spectrum?

Answer 3

Use the molecular ion peak to determine he relative molecular mass

But watch out for the (M+1) peak caused by carbon 13 isotope

Question 4

How can we use mass spectrometry to identify different individual isomers?

Answer 4

2 isomers will have the same molecular formulas and therefore the same molecular ion peak however they produce different fragmentation patterns.

Different fragment ions will produce different peaks

Question 5

Why can we use infrared spectroscopy (IR) to identify molecules?

Answer 5

IR radiation can be absorbed by molecules

Question 6

How can we make an IR spectrum?

Answer 6

1. Bean of IR radiation is passed through the sample.
2. Molecule of our sample will absorb some of these frequencies
3. The bean that passes through is analysed
4. Plot a graph of transmittance against frequency ( this is the IR spectrum)
5. Analyse the spectra that are formed

Question 7

What is the fingerprint region of an IR spectrum?

Answer 7

Region between 500 - 1500 cm^-1

Absorption’s always e caused mainly be bending and are therefore specific to each molecule (hence fingerprint)
Tris region can be used to identify the molecule.

Question 8

What are the applications of IR spectroscopy?

Answer 8

Breathalyser
Air quality monitor
Forensics

Question 9

What is chromatography?

Answer 9

A separation technique for identifying chemicals in a mixture.

Question 10

What is the stationary phase in thin layer chromatography?

Answer 10

A thin piece of unreactive material and cover it in an absorbent chemical (eg aluminium oxide)

Question 11

What is the mobile phase in thin layer chromatography?

Answer 11

Usually and organic solvent that will move in 1 direction up the thin. Layer

Question 12

How do you calculate the Rf value?

Answer 12

Distance moved by the compound / distance moved by the solvent.

Rf values are always between 0-1

Question 13

What is column chromatography?

Answer 13

A Column is packed with a solid and a solvent moves down the column

Question 14

What is gas chromatography?

Answer 14

A column is packed with a solid or with a solid coated by a liquid and a gas is passed through the column under pressure at high temperatures