RQP 5: Distillation of a product from a reaction Flashcards
What is the most common practical reaction that involves the distillation of a production that you will be asked about
The partial oxidation of a primary alcohol- the aldheyde is distilled off
What is the reaction, reagant and condition for the partial oxidation of a primary alcohol
Reaction: Primary alcohol –> aldehyde
Reagent: Acidified potassium dichromate
Conditions: warm gently and distil off the aldehyde as it forms
What colour change will be observed during the oxidaiton of a primary alcohlol using acidified potassium dichromate
The orange dichromate ion (Cr2O7 2-) reduces to the green Cr 3+ ion.
What safety precautions must be taken during the partial oxidation of a primary alcohol and the distillation of the aldehyde product
-Wear gloves when handling the solid potassium dichromate (VI) since it is highly toxic and an irritant
- Avoid inhaling any dust- do near a window
- Sulfuric acid is also corrosive
What end of the condenser for distillation does water go in
The bottom end- the water goes against gravity which ensures that the entire condenser is filled with water and there is no backflow
Where should the bulb of the thermometer be when drawing the distillation apparatus
At the T junction connecting the flaks to the condenser
What can be done to the collection flask to increase the yeild of distillate
It can be cooled in ice
What is used to heat the organic chemicals when distilling a product
Electric heater/water bath as organic chemicals are very flammable
Describe the practical method for the partial oxidation of propan-1-ol
-Place 10cm^3 of dilute sulfuric acid in a flask and add about 3g of potassium dichromate (VI) and 2 or 3 anti-bumping granules. Shake the contents of the flask until solution is complete
- Add 1.5 cm^3 of propan-1-ol in drops from a dropping pippete, shaking the flask so as to mix the contents and then assemble the distillation apparatus
- Heat to the boiling point of propanal and distil off the product
What is the key reaction for heating a product under reflux you may be asked about
The full oxidation of primary alcohols
What is the reaction, reagant and condition for the full oxidation of a primary alcohol
Reaction: Primary alchohol–> carboxylic acid
Reagent: Acidified potassium dichromate (VI)
Conditions: Excess potassium dichromate, heat under reflux, distil off the product after the reaction has finished
Why should you never seal the top of the condenser when heating a compound under reflux
The builup of gas pressure would cause the apparatus to explode.
What is the purpose of anti-bumping granules
To prevent vigorous uneven boiling by providing a surface for the reaction to take place on
