Aldehydes and Ketones Flashcards
(34 cards)
What has the highest boiling points (aldehydes and ketones or alkanes or alcohols)?
Alcohols have the highest boiling point as they have H bonds.
Then, ketones and aldehydes as they have a permanent dipole dipole forces.
What is the solubility of aldehydes and ketones?
Short chains mix completely with water as H bonds form.
What is the reactivity of carbonyls?
Reactive due to the difference in electronegativity between the C and the O, so it is very polar.
What is a racemic mixture?
Equal amounts of each enantiomer as the C=O can be attacked from either side by equal amounts.
Give an oxidising agent.
Acidified potassium dichromate.
How can you distinguish between aldehydes and ketones using the Fehling’s test?
Aldehydes= Brick red ppt formed of Copper (I) Oxide.
Ketones= No reaction
What is Fehlings reagent?
Made up of Fehlings A and Fehlings B. Fehlings A contains Cu2+ ions and is coloured blue. Fehlings B contains an alkali and a complexing agent.
How is the silver mirror test used?
Aldehyde= Ag+ is reduced to metallic silver.
Ketones= No reaction
What is in Tollen’s reagent?
Contains the complex ion [Ag(NH3)2]+ which is formed when aq ammonia is added to aq solution of silver nitrate.
Why is Benedicts solution more convenient than Fehlings?
Does not have to be prepared by mixing.
Give an example of a reducing agent that will reduce aldehydes and ketones.
NaBH4
Why are carboxylic acids up to four carbon atoms soluble in water?
Can form H bonds with water.
Why do carboxylic acids have higher melting points than alkanes of similar molecular mass?
Can form H bonds with each other.
How can you identify carboxylic acids?
Measure melting point and compare with tables of known melting points. A Thiele tube may be used.
What is characteristic of carboxylic acids?
Smells
What makes the carboxylate ion stable?
Delocalisation
What happens when a carboxylic acid looses a proton?
It forms a carboxylate ion.
How are esters formed?
When alcohols react with carboxylic acids in the presence of a strong acid catalyst.
How are esters hydrolysed? (with an acid catalyst)
Does not go to completion, it produces an equilibrium mixture containing the ester, water, acid (catalyst) and alcohol.
How are esters hydrolysed? (with a base catalyst)
Salt of the acid is produced, equilibrium is not established and it goes straight to equilibrium.
What is an alternate name of glycerol?
Propane-1,2,3-triol
What are the industrial uses of glycerol?
- Cosmetic prep
- Food colourings
- Plasticise materials
- Solvent in medicines
How can triglycerides be hydrolysed?
Boiled with NaOH. To get glycerol and sodium salts. These salts are soaps.
What are sodium salts?
Ionic and dissociate into Na+ and RCOO-. RCOO- has two distinct ends- a long hydrocarbon chin which is non-polar and the COO- which is polar and ionic. The hydrocarbon mixes with the grease, the COO- mixes with the water.
