Organic - 3.5 Alcohols Flashcards
What are the physical properties of alcohol?
- Greater boiling point than alkanes with similar Mr due to presence of hydrogen bonding between alcohol molecules.
- VDW forces and hydrogen bonding present between alcohol molecules.
What are the three classifications of alcohols?
Primary (1R Group)
Secondary (2 R Groups)
Tertiary (3 R Groups)
This depends on the position of the -OH group in the carbon chain
What are primary alcohols oxidised to?
Aldehydes then carboxylic acids
What are secondary alcohols oxidised to?
Ketones
Why are tertiary alcohols not easily oxidised?
They do not have two hydrogen atoms directly attached to the carbon that is bonded to the -O-H group.
They can be oxidised using hot concentrated nitric acid because the breaking of the strong C-C bond is required.
What are the conditions for oxidising a primary alcohol?
- Oxidising agent in excess (acidified potassium or sodium dichromate)
- Refluxed gently
- Carboxylic acid can be removed from the mixture in the reaction vessel by distillation.
- To produce the aldehyde, the primary alcohol must be in excess and the product distilled off immediately.
What are the conditions for oxidising a secondary alcohol?
- Must be refluxed gently with an excess of the oxidising agent (acidified potassium or sodium dichromate) to produce a ketone.
What are the tests for aldehydes and ketones?
The silver mirror test (Tollens reagent)
When tollens reagent is warmed gently in the presence of an aldehyde the aldehyde is oxidised to a carboxylic acid and the silver ions in the tollens reagent are reduced to silver atoms.
Ketones will not react with tollens reagent and the mixture remains colourless and the silver mirror does not form.
What is the test for aldehydes and ketones?
When warmed gently with an aldehyde fehlings solution’s blue colour disappears and an orange red precipitate forms.
When reacting with a ketone, the solution remains blue
In what type of reaction is water removed from an alcohol?
In an elimination reaction
