Chapter 29 - Chromatography and Spectroscopy

Question 1

What is chromatography?

Answer 1

A technique used to separate compounds with similar physical properties from a mixture.

Question 2

What are the types of phases for chromatography? What does affinity mean?

Answer 2

Stationary phase and Mobile phase

Solid stationary phase: separated by adsorbtion as molecules bind to the surface. Stronger adsorbtion = slower.

Liquid stationary phase: separate by relative solubility as molecules dissolve into the phase. Greater solubility = slower

Affinity = attraction towards

Question 3

What is a TLC plate made of?

Answer 3

a Plastic/glass sheet coated with a thin layer of a solid adsorbent substance such as silica

Question 4

Outline Thin-Layer Chromatography

Answer 4

Sample added to a starting point on the plate which is then placed in a liquid solvent (mobile phase) which will get drawn up.

Solvent front and height of solvent is marked.

Question 5

How is the retention factor calculated?

Answer 5

Rf= Distance moved by the component/distance moved by the solvent front

Question 6

What is gas chromatography useful for?

Answer 6

Separating and identifying volatile organic compounds present in a mixture

Question 7

What are the different phases for gas chromatography?

Answer 7

1) Stationary - high boiling point liquid adsorbed onto an inert solid support
2) Mobile - is an inert carrier gas such as helium

Question 8

How does time taken to move through the column change as solubility in stationary phase increases?

Answer 8

The more soluble the component is in the liquid stationary phase, the slower it moves through the capillary column.

Question 9

What is retention time?

Answer 9

Time taken for a component to travel through the column

Question 10

How is retention time used for identification?

Answer 10

Compare to retention times in database

Question 11

What can peak integrations for gas chromatograph be used to determine?

Answer 11

Concentrations of components in the sample

Question 12

What’s the test for carboxylic acid?

Answer 12

Question 13

What’s the test for a primary and secondary alcohol and aldehyde?

Answer 13

Question 14

What’s the test for a carbonyl?

Answer 14

C=O

Question 15

What’s the test for a haloalkane?

Answer 15

Question 16

What’s the test for an Alkene?

Answer 16

Question 17

What is resonance for NMR?

Answer 17

When the nucleus absorbs energy and rapidly flips between the two spin directions

Question 18

What must the nucleus of an atom have to work with NMR?

Answer 18

It must have an ODD number of nucleons to work.

Question 19

What is the standard reference chemical for NMR?

Answer 19

Tetramethylsilane (TMS) - Si(CH3)4

Question 20

What is the purpose of D2O as a solvent in proton NMR spectroscopy?

Answer 20

O-H and N-H peaks no longer appear as D replaces H to form O-D/N-D.

Question 21

What two pieces of information does analysis of carbon-13 NMR show?

Answer 21

The two pieces of information analysis of carbon-13 NMR shows is:

1) The number of different carbon environments from the number of carbon peaks
2) The types of carbon environments present from the chemical shift

Question 22

What would the proponal spec look like?

Answer 22

Question 23

Example of propanone, what would the spec look like?

Answer 23

Question 24

Answer 24

Question 25

Answer 25

Question 26

What four pieces of info does the proton NMR spec tell you?

Answer 26

the proton nmr tells you 4 pieces of info:

1) number of proton environments
2) Types of proton environments
3) The relative numbers of protons
4) The number of non-equivalent protons adjacent to a given proton

Question 27

What are the names of the different peaks?

Answer 27

Question 28

What are some common splitting patterns?

Answer 28

Question 29

Answer 29

Question 30

How does gas chromatography work?

Answer 30

1) Stationary - high boiling point liquid adsorbed onto an inert solid support
2) Mobile - is an inert carrier gas such as helium
3) small amount of volatile mixture is injected into the gas chromatograph
4) The mobile carrier gas carries the component in the sample through the capillary column containing the stationary phase
5) the more soluble the component is in the liquid stationary phase, the slower it moves through the capillary column

Question 31

How do you predict signal patterns of H NMR?

Answer 31

Identify number of signals (enviornments)
Identify relative intensity of signals (ratio of Hs)
Identiy splitting patterns (e.g. t,m,s)
Identify position of signals

Question 32

What are examples of commonly used solvents for NMR?

Answer 32

C6D6, CDCl3 and CCl4

Question 33

How do you describe chemical shifts?

Answer 33

e.g. proton environment 1 is next to one C=O, while proton environment 2 is next to C=O AND aldehyde so greater chemical shift.

+ give examples of numbers (ppm)

Question 34

What type of electromagnetic frequency does NMR use?

What are the other electromagnetic frequencies you need to know? What are they associated with?

Answer 34

NMR = Radio waves

• infrared radiation = contributes to greenhouse effect.
• UV radiation = contributes towards breakdown of ozone layer with CFCls and radicals.