Carbonyls and carboxyls

Shape around the carbonyl bond

Trigonal planar

What is the nature of the C-O double bond

It is polar with the oxygen being +ve, and it is a pi bond with p orbitals and a sigma bond

What is the reagant for reduction of aldehydes/ketones

NaBH₄ and water

What does the reaction of a ketone with HCN produce

a hydroxynitrile

What is the mechanism in reduction of aldehydes/ketones

Nucleophilic addition

What is the nucleophile reduction of ketones/aldehydes

Hydride

Mechanism for HCN added to propanal

Test for carbonyls

Add 2,4-DNP and a yellow precipitate will form if an aldehyde or ketone are present, you can then filter the solid precipitate and recrystallise it to purify. Then find the melting point and compare this to a table of melting points to find what the original compound is

Test for aldehydes

Add tollens reagant, in the presence of aldehyde, the solution becomes a silver mirror

How soluble are carboxylic acids

Very soluble because they can form H bonds with water with the carbonyl bond and the O-H bond

How to test for carboxylic acids

Add to sodium carbonate, as this is the only organic molecule acidic enough to react with that weak base

How to name an ester

The alkyl chain added is the first word, for the second word remove the “-oic acid” and replace with “-oate”

How to name an acyl chloride

Remove the “oic acid” and replace with “oyl chloride”

How to form acid anhydrides

Remove water from 2 carboxylic acids

Structure of ethanoic anhydride

Esterification reaction (including catalyst)

Carboxylic acid + alcohol → ester + water (reversible with sulfuric acid catalyst)

What are esters used for

Perfumes and fragrances and flavourings

Why is esterification not a good method for synthesising esters

It is reversible so the yield will be low and does not work with phenol

Acid hydrolysis of an ester conditions

Heated under reflux with sulfuric acid

Acid hydrolysis of an ester reaction

ester + water → Carboxylic acid + alcohol (reversible with sulfuric acid catalyst)

Alkaline hydrolysis reaction

ester + water → Carboxylic acid + alcohol, then, carboxylic acid + alkali → water + salt

overall reaction: ester + alkali → salt + alcohol

Conditions of alkaline hydrolysis

Heated under refux with sulfuric acid

Reaction to make acyl chloride (and where should it be made)

Carboxylic acid + SOCl₂ (thionyl chloride) → acyl chloride + sulfur dioxide + hydrogen chloride gas

Should be synthesised in a fume cupboard and in anhydrous conditions

Why would we use acyl chlorides to form esters instead of carboxylic acids

Reactions are not reversible and carboxylic acids could not react with phenol, also does not require a catalyst

Reaction of water and acyl chloride

acyl chloride + water → carboxylic acid + HCl. very vigorous and dangerous due to HCl fumes

Acyl chloride + ammonia → ?

Primary amide + ammonium chloride

Acyl chloride + primary amine

secondary amide + alkyl ammonium salt

Acid anhydride + alcohol → (catalyst?)

ester + carboxylic acid

(no catalyst)