17- Carbonyl Compounds Flashcards
What are the characteristic type of reaction for Carbonyls?
(Nucleophilic) addition.
Colour change for Chromate ions? Dichromate (6+) to Chromate (3+)
Orange to Green.
Conditions and reactant required for the reduction of Carbonyls?
LiAlH4 in dry ether, followed by the addition of a dilute acid.
How is HCN formed?
In reaction with KCN and dil. H2SO4
Why do the reactions of carbonyls produce racemic mixtures?
The products are chiral. This is as the atoms around the carbonyl group are trigonal planar, and the attacking nucleophile has equal chance to bond from either side.
Test for carbonyl using 2,4-dinitrophenylhydrazine?
Reacts with carbonyl and form orange/yellow solid at room temp to form dinitophenylhydraZONE. Filter this off and recrystalize. Melting point is determined and compared to data value, along with the boiling temp of the original carbonyl.
What is Fehling’s solution made from?
Copper (II) Sulphate in water and 2,3-dihydroxybutanedioate.
Colour change for solution of aldehyde and either Fehling’s or Benedict’s solution?
Blue to orange.
What is Tollens’ reagent’s chemical name? What is the sign of a positive test?
Ammonical silver nitrate. A silver precipitate forms, shiny layer of silver like a mirror.
What are the reagents and conditions for an iodoform reaction? What is made, what does it test for, and what is the sign of a positive result .
Iodine and NaOH. Testing for a carbonyl group directly next to a methyl group. Positive test forms a yellow precipitate. Also oxidises secondary alcohols (and ethanol) to ketones.
Products when R-COOH reacts with HCO3- (Sodium carbonate or sodium hydrogen carbonate) ?
R-COO- + H20 + CO2
How to convert a Carboxylic acid into a primary alcohol? State equation and reagents.
Reduce with LiAlH4 in dry ether and add dilute acid.
What’s formed when a carboxylic acid reacts with PCl5?
Acyl chloride (R-COCl), POCl3 and HCl(g).
Conditions for esterification of Carboxylic acids and alcohols?
Small amount of strong acid (H+) catalyst and heat.
How is the yield of of esterification increased?
Distilling off ester or water formed, encouraging the reaction to go to completion. Alternatively, use excess of either one of the reactants. Using excess conc. sulfuric acid catalyst can help as it reacts with the water formed, driving the reaction to completion (limited use as the amount of acid added is so small).
What is acylation?
The substitution of an acyl group for a hydrogen atom.
What is formed when an acyl chloride reacts with water?
A carboxylic acid and gaseous HCl.
Ethanoyl chloride reacts violently with water.
Whats formed when acyl chloride reacts with an alcohol?
An ester and HCl
Whats formed when an acyl chloride reacts with aqueous concentrated ammonia?
An amide and gaseous HCl.
Reacts rapidly with
Whats formed when acyl chlorides react with amines?
N substituted amides and gaseous HCl.
What is a polyester?
A polymer in which the monomers are joined together by ester groups.
What sort of reaction forms polyesters?
Condensation reactions.
What is a condensation reaction?
A reaction in which molecules join together by splitting of a molecule such as water.
State the two combinations of molecules possible to form a polyseter?
A diol and a dicarboxylic acid.
or
Two molecules with an OH group and a COOH group ( HO-R-COOH ).
