Chapter 29 - Chromatography and Spectroscopy Flashcards
What is chromatography?
A technique used to separate compounds with similar physical properties from a mixture.
What are the types of phases for chromatography? What does affinity mean?
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
What is a TLC plate made of?
a Plastic/glass sheet coated with a thin layer of a solid adsorbent substance such as silica
Outline Thin-Layer Chromatography
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.
How is the retention factor calculated?
Rf= Distance moved by the component/distance moved by the solvent front
What is gas chromatography useful for?
Separating and identifying volatile organic compounds present in a mixture
What are the different phases for gas chromatography?
1) Stationary - high boiling point liquid adsorbed onto an inert solid support
2) Mobile - is an inert carrier gas such as helium
How does time taken to move through the column change as solubility in stationary phase increases?
The more soluble the component is in the liquid stationary phase, the slower it moves through the capillary column.
What is retention time?
Time taken for a component to travel through the column
How is retention time used for identification?
Compare to retention times in database
What can peak integrations for gas chromatograph be used to determine?
Concentrations of components in the sample
What’s the test for carboxylic acid?
What’s the test for a primary and secondary alcohol and aldehyde?
What’s the test for a carbonyl?
C=O
What’s the test for a haloalkane?
What’s the test for an Alkene?
What is resonance for NMR?
When the nucleus absorbs energy and rapidly flips between the two spin directions
What must the nucleus of an atom have to work with NMR?
It must have an ODD number of nucleons to work.
What is the standard reference chemical for NMR?
Tetramethylsilane (TMS) - Si(CH3)4
What is the purpose of D2O as a solvent in proton NMR spectroscopy?
O-H and N-H peaks no longer appear as D replaces H to form O-D/N-D.
What two pieces of information does analysis of carbon-13 NMR show?
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
What would the proponal spec look like?
Example of propanone, what would the spec look like?
What four pieces of info does the proton NMR spec tell you?
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
What are the names of the different peaks?
What are some common splitting patterns?
How does gas chromatography work?
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
How do you predict signal patterns of H NMR?
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
What are examples of commonly used solvents for NMR?
C6D6, CDCl3 and CCl4
How do you describe chemical shifts?
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)
What type of electromagnetic frequency does NMR use?
What are the other electromagnetic frequencies you need to know? What are they associated with?
NMR = Radio waves
- infrared radiation = contributes to greenhouse effect.
- UV radiation = contributes towards breakdown of ozone layer with CFCls and radicals.
