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
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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
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3
Q

What two chemicals can be used to test for aldehydes and ketones?

A
  • Fehling’s solution

- Tollen’s reagent

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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
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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
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