RPA - Carbonyls Flashcards
What causes reactivity of carbonyls, therefore how do they react?
Polar C=O bond causes nucleophilic addition by breaking double bond
What type of compounds are classed as carbonyls?
Aldehydes and Ketones
On oxidation of a primary alcohol, which two possible products are possible? Give conditions and reagents for each.
Immediate distillation - aldehyde. H+/Cr2O72-
Reflux - carboxylic acid. H+/Cr2O72-
Give the equation for the oxidation of ethanol to form ethanal
CH3CH2OH + [O] -> CH3CHO + H2O
Give the equation for the oxidation of ethanol to form ethanoic acid
CH3CH2OH + 2[O] -> CH3COOH + H2O
Give the equation for the oxidation of ethanal to form ethanoic acid
CH3CHO + [O] -> CH3COOH
Give the equation for the oxidation of propan-2-ol to form propanone
CH3CHOHCH3 + [O] -> CH3C=OCH3 + H2O
What type of reactant is NaBH4?
Reducing agent. It produces H-
By which mechanism does NaBH4 react with aldehydes and ketones?
nucleophilic addition
Talk through the steps involved in the reaction of propanone and NaBH4
.
What is the product when aldehydes and ketones react with NaBH4?
Aldehydes - primary alcohols
Ketones - secondary alcohols
Give the equation for the reduction of a ethanal to ethanol
CH3CHO + 2[H] – > CH3CH2OH
Give the equation for the reduction of propanone to propan-2-ol.
CH3C=OCH3 + 2[H] – > CH2CHOHCH3
What is Tollens reagent made from?
AgNO3 + excess NH3 in NaOH solution
What type of reagent is Tollens
Mild oxidising agent
What type of compounds can tollens react with?
Aldehydes
What is observed when Tollens reacts with aldehydes, ketones and alcohols.
It forms a silver mirror/dark precipitate when it is reduced to Ag(s)
It is only a mild oxidising agent, so will not react with alcohols or ketones.
What is Brady’s Reagent?
2,4-dinitrophenylhydrazine
What does Brady’s reagent do when reacted with aldehydes and ketones? What is observed?
It forms orange precipitates whos melting points can be observed.
What is the reason for using Brady’s reagent?
Boiling points of volatile aldehydes/ketones can be hard to find experimentally as many are low.
Reaction with 2,4-DNPH causes the melting point to be above room temperature, hence it can be measured using thiele tube.
