Carbonyls and Carboxylic Acids
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Where is the functional group located in a carbonyl?
The end of the carbon chain
What can aldehydes be oxidised to?
Carboxylic acids when refluxed with acidified potassium dichromate
What can ketones be oxidised to?
Cannot be oxidised
What is the double bond made of in a ketone and an aldehyde?
A sigma bond and a pi bond
Is the C=O bond in carbonyl compounds polar or non-polar? Why?
Polar Electron density in the double bond lies closer to the double bond
Why is a nucleophile attracted to a carbonyl?
Nucleophile is attracted to the slightly carbon atom
What chemical reduces an aldehyde and what is it reduced to?
Primary alcohols by NaBH4
What chemical reduces a ketone and what is it reduced to?
Secondary alcohols by NaBH4
Why is a carbonyl reacted with HCN?
Increase the length of the carbon chain
How is HCN formed for the reaction of carbonyls with HCN?
Sodium cyanide and sulfuric acid
What are the two steps usually associated with the addition to a carbonyl group?
Nucleophilic attack on the carbonyl group to form a negatively charged intermediate Protonation of the intermediate to form an alcohol
What chemicals are present in the Brady’s reagent?
2,4- DNP Methanol Sulfuric Acid
What is formed when a carbonyl group is present in Brady’s reagent?
Yellow or orange precipitate
How can you identify between aldehyde or a ketone?
Tollens’ reagent
What is Tollens’ reagent made from?
A solution of silver nitrate in aqueous ammonia
How can you distinguish an aldehyde group?
A silver mirror
Explain the chemistry of the Tollens’ test
Silver ions act as an oxidising agent in presence of ammonia Silver ions are reduced to silver as aldehyde is oxidised to carboxylic acid
Explain the solubility of carboxylic acids
Carboxylic acids with up to four carbons are soluble Number of carbons increases the solubility decreases
What type of acids are carboxylic acids?
Carboxylic acids are weak acids which means they partially dissociate in water
How can you tell a redox reaction of carboxylic acid and metal is occurring?
Hydrogen gas Carboxylate salt Effervescence