Organic analysis 0.0 / 5 ? ChemistryFunctional GroupsA2/A-levelAQA Created by: HindleycCreated on: 30-06-18 17:18 What happens when organic molecules are passed through a mass spectrometer It detects both the whole molecule and fragments of the molecule 1 of 27 What will the peak with the highest mass/charge ratio be normally due to? Original molecule that hasn't been fragmented (called molecular ion) 2 of 27 As the charge of the ion is +1 what is the mass/charge ratio equal to Mr 3 of 27 Molecular ion formation eqn? M= [M]+ +e- 4 of 27 What Is the molecular ion Molecule with one electron knocked off (both an ion and a free radical) 5 of 27 What can high resolution mass spectrometry be used to determine? Molecular formula of a compound from the accurate mass of molecular ion 6 of 27 What can it measure mass to? 5 d.p 7 of 27 What can this help differentiate between Compound that appear to have similar Mr (to nearest whole number eg C=12 8 of 27 What happens if a compound contains a Chlorine or Bromine atom Then 2 molecular ion peaks will occur- a M and a M+2 peak due to the 2 naturally occurring isotopes of Chlorine and Bromine 9 of 27 What do certain groups in a molecule absorb? Infrared radiation at characteristic frequencies 10 of 27 What can be obtained that provide information about the types of bonds present in a molecule Complicated spectra 11 of 27 Above 1500 cm^-1 Fg identification 12 of 27 Below 1500 cm^-1 Finger printing- complicated and contains many signals - picking out fg signals is difficult 13 of 27 What is this part of the spectrum? Unique for every compound so used as 'finger print' 14 of 27 What will computer do Compare IR spectra against data base of known pure compounds to identify the compound 15 of 27 What else can you use to detect presence/absence of bonds/fg? IR absorption table 16 of 27 What do you use Spectra to identify particular fg and impurities 17 of 27 What should you do where the absorption/trough is? Quote wave number range from data sheet 18 of 27 What bonds absorption tends to be more broad? O-H 19 of 27 What can occur and what are they an indicator of? Rouge absorptions- impurities 20 of 27 What Is the absorption of IR radiation by bonds in this type of spectroscopy the same absorption as? Bonds in CO2, Methane and water vapour in atmosphere do that maybe causing global warming 21 of 27 How IR emitted by earth absorbed therefore warming earth 22 of 27 Test for Alkenes and results Shake with Bromine water, Orange colour decolourises 23 of 27 Test for aldehyde? Fehlings solution warm with=Blue solution turns to red precipitate, Tollens reagent warm with= Silver mirror formed 24 of 27 Test for primary and secondary alcohol Warm with acidified potassium dichromate (sulphuric acid) and orange solution turns to green 25 of 27 Test for Haloalkane? Warm with silver nitrate solution in ethanol. White precipitate=Cl, Cream=Br and Yellow=I 26 of 27 Carboxylic acid? Add sodium carbonate or sodium hydrogen carbonate= CO2 given off- effervescence- lime water cloudy. Add Mg= H gas produced squeaky pop with lit splint 27 of 27
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