Organic Analysis

• What is the reagent when testing for alcohols?

  Acidified potassium dichromate
• What is the observation when testing for alcohols with acidified potassium dichromate?

  Colour change from orange to green
• What is the reagent when testing for the presence of alkenes?

  Bromine water
• What is the observation when testing for the presence of alkenes?

  Colour change from orange to colourless
• Why is there a colour change when testing for the presence of alkenes?

  The carbon-carbon double bond breaks to form a halogenoalkane with the bromine in the water
• What are the two reagents for testing the presence of aldehydes?

  1. Tollens’ reagent
  2. Fehling’s solution
• What is the observation when testing for the presence of an aldehyde with Tollens’ reagent?

  Colour change from a colourless solution to a silver mirror
• What is the observation observed when testing for the presence of an aldehyde with Fehling’s solution?

  Colour change from a blue solution to a brick-red precipitate
• What’s a molecular ion?

  An ion formed by the addition or removal of one or more electrons from a neutral molecule.
• What can high resolution mass spectrometry be used to find?

  Molecular formulae of a compound from the accurate mass of the molecular ion
• What is the reagent for testing the presence of carboxylic acids?

  sodium carbonate
• what is observed when testing for the presence of carboxylic acids?

  effervescence as CO2 is formed
• What is another alternative reaction of alcohols?

  Alcohols react with metallic sodium
• What is the observation when using the alternative method for testing the presence of alcohols?

  Effervescence as hydrogen gas is liberated
• What is the reagent when testing for the presence of hlogenoalkanes?

  sodium hydroxide and warm nitric acid and silver nitrate
• What is the observation for the silver halide precipitates?

  • AgCl- white
  • AgBr- cream
  • AgI- yellow
• Why do you react the halogenoalkanes with sodium hydroxide first?

  Nucleophilic substitution to liberate halide ions from a halogenoalkane
• Why would you use nitric acid when testing for the presence of halogenoalkanes?

  The nitric acid would react with OH- ions and any carbonate ions which would both form precipitates with silver ions