Chapter 29

• The stationary phase is silica or alumina (this is then on a glass/ plastic plate) • The mobile phase is the solvent • Separation occurs due to relative adsorption to the stationary phase, as the components in the mixture would each adsorb differently to the stationary phase

• Draw a base line near the bottom in pencil​ • Using a capillary tube, spot a small sample of the solution to be tested onto the baseline of the plate​ • Pour some solvent into the chromatography tank, ensuring the depth is lower than the pencil line • Place the TLC plate into the solvent, ensuring the solvent does not touch the spot, and that the edges of the TLC plate do not touch the sides of the tank • Place a lid on the solvent tank • Allow the solvent to rise until it is about 1 cm below the top of the plate​ • Remove the plate, and mark the solvent level immediately with pencil​ • Allow the plate to dry​, and use a dye if necessary to show the position of the spots

• The Rf (retention factor) is calculated for each component • Rf values are compared to a database to identify components

• Distance moved by the component / distance moved by the solvent front

• If the substance is impure, it will have a spot where the pure substance has a spot • It would also have a (smaller) spot where the starting material (or other contaminant) was

• Take samples from the reaction mixture at regular intervals • Run on a TLC plate, comparing against a control of the starting material to monitor the progress of the reaction, and to see when the reaction is complete

• To analyse compounds with low boiling points

• The stationary phase is a high boiling liquid adsorbed onto an inert solid support • The mobile phase is an inert carrier gas (e.g. nitrogen) • Separation is by relative solubility with the stationary phase

• The retention time (the time taken for each component to travel through the column) is compared to a database and is used to identify the component • The peak integration (area under the peak) tells you the relative concentrations of the components

• You prepare standard solutions of the component and run gas chromatograms for each • Plot a calibration curve of peak area against concentration • Run a gas chromatogram for your sample, and find the peak integration of the component • Use your calibration curve to find the concentration of the component

• Decolourise bromine water

• Heat with aqueous silver nitrate in ethanol • Chloroalkanes will form a white precipitate • Bromoalkanes will form a cream precipitate • Iodoalkanes will form a yellow precipitate

• Add 2,4-DNP • Orange precipitate formed

• Add Tollens’ reagent • Silver mirror formed

• Primary alcohols • Secondary alcohols • Aldehydes • Warmed with acidified potassium dichromate, colour change from orange to green

• As weak acids, they can react with strong bases (e.g. NaOH) but not weak bases, such as Na2CO3 • You therefore react it with sodium carbonate and see no reaction, AND use indicator paper to show the pH is less than 7

• They can react with weak bases like Na2CO3 • Effervescence would be given off

• NMR spectrometers measure what frequency of radio waves interact with samples with an odd number of nucleons

• TMS • A deuterated solvent

• Si(CH3)4 • It is used as the standard reference chemical that all chemical shifts are measured against (it has a chemical shift of 0ppm)

• Most solvents contain carbon and hydrogen atoms, so would produce a peak in both 13C and 1H NMR spectra • A deuterated solvent is used instead as all of the 1H atoms are replaced with 2H atoms, so any hydrogen atoms would not produce a peak • CDCl3

• The number of carbon environments from the number of peaks • The types of carbon environments present from their chemical shift

• They would absorb radiation of the same frequency

• Line of symmetry • Rotation • If there is only one substituent, counting on from it