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Chem
Analysis
| Question | Answer |
|---|---|
| Thin Layer Chromatography | Stationary phase - adsorbent surface (e.g silica) Mobile phase - Solvent Solute spotted with capillary tube, solvent rises up TLC plate, solute adsorbs at different distances, spots often visualised with UV, Rf calculated (solute/solvent) |
| Gas Chromatography | Stationary phase - High boiling liquid adsorbed to inert solid Mobile phase - Inert gas carrier Components carried in gas, more soluble in liquid = longer the time to reach detector, Rt recorded, conc found by comparing area with calibration curve |
| Test for alkenes | Add bromine water Decolourises - Orange to colourless |
| Test for haloalkanes | Add silver nitrate and ethanol in a 50C water bath Chloroalkane = white precipitate Bromoalkane = cream precipitate Iodoalkane = yellow precipitate |
| Test for phenols | Ph indicates an acid but no reactivity with carbonates |
| Test for carbonyls | Add 2,4 - DNP Orange precipitate |
| Test for aldehydes | Add Tollen's reagent and warm Silver mirror |
| Test for primary and secondary alcohols and aldehydes | Add acidified Potassium dichromate in a warm water bath Colour change from orange to green as it is oxidised |
| Test for carboxylic acids | Add an aqueous carbonate (e.g sodium carbonate) Effervesence |
| Nuclear Magnetic Resonance | Observe frequency of resonance of nuclei spin when in presence of a magnetic field (chemical shift/ppm) More shielded a nucleus, the less effect magnetic field has, the closer to 0ppm Deshielded includes double bonds and strong electronegativity |
| Carbon-13 NMR | Number of peaks = number of carbon environments Chemical shift/ppm of peaks = type of carbon environment 13C used due to odd number of nucleons |
| Proton NMR | Number of peaks = number of proton environments Chemical shift/ppm = type of proton environment Integration trace = relative number of protons in environment Splitting pattern = number of adjacent protons (n+1 rule) |
| n+1 rule | Number of peaks in a splitting pattern is equal to 1 less the number of protons in the adjacent environment(s) |
| Use of TMS (Tetramethylsilane) | Used as the standard reference given a chemical shift of 0 ppm due to being highly shielded, producing 1 peak, and being chemically inert/non-toxic |
| Use of deuterated solvents (e.g CDCl3) | 2H atoms (deuterium) produce no NMR signal CDCL3 will still produce a peak in Carbon-13 NMR |
| Identification of NH and OH | OH and NH are hard peaks to identify due to large ppm range D2O is added to replace the H atom with D in OH and NH removing it from the spectrum making it identifiable |
Created by:
silver54331