Organic Analysis Flashcards
What can you use as a notation to represent an oxidising agent?
[O]
What is potassium dichromate?
An oxidising agent.
What can potassium dichromate oxidise and what does it form?
Primary and Secondary alcohols to form aldehydes and ketones.
What are the steps to use the colour change to test for the prescence of primary, secondary and tertiary alcohols?
- Add ten drops of the alcohol to two cm cubed of acidified potassium dichromate solution in a test tube.
- Warm the mixture gently in a hot water bath.
- Watch for a colour change, primary and secondary alcohols go from an orange solution to a green solution. There is no colour change in tertiary alcohols.
What does it mean if you oxidise an alcohol under reflux and it tests positive for being a carboxylic acid?
It is a primary alcohol.
What does it mean if you oxidise an alcohol under distillation conditions and it tests positive for being an aldehyde?
It is a primary alcohol.
What does it mean if you oxidise an alcohol under reflux or distillation and it tests positive for being a ketone?
It is a secondary alcohol.
What is Fehling’s solution?
A blue solution of complexed copper (II) ions dissolved in sodium hydroxide.
How do you test an aldehyde or ketone using benedict or fehling’s solution?
- Add two cm cubed of fehling or benedict’s solution to a test tube.
- Add five drops of the aldehyde or ketone to the test tube.
- Put the test tube in a hot water bath and warm it for a few minutes.
- Both produce a brick red colour if it is an aldehyde.
- Both will stay the same colour if it is an aldehyde.
What does Tollens’ Reagent contain?
A [Ag(NH3)2]+ complex.
How do you make Tollens’ Reagent?
- Put 2 cm cubed of 0.1 mol dm to negative cubed of silver nitrate solution in a test tube.
- Add a few drops of dilute sodium hydroxide solution and a brown precipitate should form.
- Add drops of dilute ammonia solution until the brown precipitate dissolves completely.
