Alcohols: Testing for Oxidation of Alcohols Products Flashcards
1
Q
How do you test for primary, secondary and tertiary alcohols?
A
• Chemical used
- Acidified potassium dichromate(VI)
- Acidified with sulfuric acid
- K2Cr2O7
- Can use [O] to represent potassium dichromate, the oxidising agent
• Observation
- Orange solution turns green as aldehyde or ketone forms with primary and secondary alcohols
- No colour change seen with tertiary alcohols
2
Q
How do you distinguish between primary and secondary alcohols?
A
• Carboxylic acid
- If you oxidise an alcohol under reflux
- And it tests positive for being a carboxylic acid
- It’s a primary alcohol
• Aldehyde
- If you oxidise an alcohol under distillation conditions
- And it tests positive for being an aldehyde
- It’s a primary alcohol
• Ketone
- If you oxidise an alcohol under reflux (or distillation)
- And it tests positive for being a ketone
- It’s a secondary alcohol
3
Q
What two chemicals can be used to test for aldehydes and ketones?
A
- Fehling’s solution
- Tollen’s reagent
4
Q
Describe the Fehling’s solution way of testing for aldehydes and ketones
A
• Chemical used
- Fehling’s solution
- Contains copper(II) ions
• Observation
- Turns from blue to a brick red precipitate with aldehydes
- No reaction with ketone, solution stays blue
5
Q
Describe the Tollen’s reagent way of testing for aldehydes and ketones
A
• Chemical used
- Tollen’s reagent
- Uses [Ag(NH3)2]+ complex
• Observation
- Forms silver mirror with aldehydes
- No reaction with ketone, solution stays colourless