Aldehydes, Ketones, Carboxylic Flashcards
Why must the formation of aldehydes from alcohols be a controlled process?
This is so because Aldehydes will quickly oxidise to carboxylic acids , hence the aldehydes must be removed . This can be done easily because they have a much lower bp than alcohol.
What stops further reduction in Rosamund’s reduction?
The use of BaSO4 and S poisons the Pd catalyst and prevents further rxn.
Why can’t formaldehyde be prepared from Rosamund’s rxn?
This is because Formyl chloride is unstable at room temperature.
Aldehydes and ketones have the same functional group. What is it?
The carbonyl group.
Why are aldehydes more reactive than ketones?
This is because they have a hydrogen attached to the carbonyl group rather than an alkyl group like ketones.
Why do aldehydes and ketones readily undergo nucleophilic substitution?
This is because the carbon atom has a partial positive charge.
Where are the rxns of weak nucleophiles and strong nucleophiles carried out?
Weak = weak acidic medium Strong= basic medium
How does an acid catalyst catalyse a rxn?
It does so by increasing the nucleophilic character of the carbon of the carbonyl group.
How does the base catalyst catalyse a rxn?
It does so by increasing the nucleophilic character of the nucleophilic group.
Which is the most reactive aldehyde. Why.
Formaldehyde. Because of the +I effect.
Why does trichloro acetaldehyde undergo nucleophilic rxns more readily than acetaldehyde?
This is because of the -I effect.
What is the steric effect w.r.t. aldehydes and ketones?
Larger the size of the alkyl groups attached to the carbonyl group, more difficult is the approach of the nucleophile , and consequently lesser the reactivity.
Why are aromatic ald. and ket. less reactive than aliphatic ones?
This is because of the resonance effect.
What kind of resonating effect does benzene show?
It shows e- donating resonance effect.
What is Brady’s reagent?
2,4 Dinitrophenylhydrazine
