NMR Spectroscopy And Chromatography

Question 1

NMR

Answer 1

Examines 1H and 13C nuclei within organic molecules
Half spin nuclei act as mini magnetic
If strong magnetic field applied the spin of nuclei will line with or against external magnetic field
When aligned against, higher energy state

Question 2

Chemical shift

Answer 2

Measure of energy to flip the spin of nuclei

Question 3

Proton spectroscopy

Answer 3

Peak integration- ratio of peaks indicates ration of H atoms
Splitting patterns- n+1 rule, shows number of protons on adjacent molecule

Question 4

Carbon spectrosocpy

Answer 4

Number of peaks- number on different environments

Question 5

Standard solvents

Answer 5

TMS: Easily identified and removed (volatile), Peak at 0 for TMS, all same environment
CDCl3- polar compounds, one/no peak
CCl4- non polar compounds, one/no peak

Question 6

Chromatography

Answer 6

Time in stationary phase depends on
Size of molecules
Solubility in mobile phase vs stationary phase
Binding to solid stationary phase (adsorption)

Question 7

TLC

Answer 7

Prepare silica gel tlc plate
Mark fine line in pencil 0.5cm from bottom
Use capillary tube to place samples
Place tlc in solvent
Allow to run for 20-30 mins
Draw pencil line to top of solvent front
Calculate Rf values of spots

Question 8

Column chromatography

Answer 8

Silica gel placed in gas column with glass wool at btoom to prevent silica gel escaping
Glass wool is non absorbant
Silica gel is solid stationary phase
Solvent runs through
Sample dissolved in hexane (non polar)
Fluent samples taken for further analysis
Amount of time in column is retention time

Question 9

Gas chromatography

Answer 9

Coiled tube contained in ov3n
More soluble the substance is in stationary phase the longer time they spend in
Sample heated and mixed with inert carrier gas nitrogen or helium to enter column
Computer detects substances eluting and calculates retention time