Chapter 26 Carbonyl Compounds

Question 1

what is the difference between an aldehyde and a ketone

Answer 1

aldehydes - position of C=O bond is on the end of a carbon chain
ketone - position of C=O bond is on an inner carbon

Question 2

oxidation of aldehydes and ketones?

Answer 2

aldehydes can be oxidised into carboxylic acids using an oxidising agent

ketones cannot be oxidised

Question 3

tollens’ reagent on aldehydes and ketones?

Answer 3

aldehydes - forms a silver mirror
ketones - no silver precipitate formed

Question 4

fehling’s solution on aldehydes and ketones?

Answer 4

aldehydes - goes from a blue solution to a brick red precipitate
ketones - remains a blue solution

Question 5

reduction of aldehyes and ketones

Answer 5

both can be reduced to form primary and secondary alcohols
-> mechanism for this is a nucleophilic addition

Question 6

what happens when potassium cyanide (KCN) reacts with a carbonyl compound?

Answer 6

produces hydroxynitriles
- this is done via a nucleophilic addition
CN- ion attacks carbonyl group and adds on to make a hydroxynitrile

Question 7

what are the risks of potassium cyanide?

Answer 7

is an irritant and very dangerous if ingested or inhaled

if it reacts with moisture it can form the toxic gas, hydrogen cyanide

Question 8

what is a carboxylic acid?

Answer 8

compound which has the -COOH functional group, this contains both a carbonyl group and hydroxyl group

Question 9

what type of acids are carboxylic acids?

Answer 9

weak acids and can also react with carbonates to form carbon dioxide
-> only partially dissociate
equilibrium lies to the left

Question 10

what is the equation for the reaction between ethanoic acid and sodium carbonate?

Answer 10

2 CH3COOH + Na2CO3 -> 2CH3COONa + H2O + CO2

Question 11

what happens when a carboxylic acid reacts with carbonates?

Answer 11

will form a salt, carbon dioxide gas and water

Question 12

how are esters formed? (esterfication)

Answer 12

when alcohols are reacted with carboxylic acids and acid anhydrides - forms a -COO- group

Question 13

how is an ester formed from a carboxylic acid and an alcohol?

Answer 13

• use of sulfuric acid catalyst

Question 14

how are esters named?

Answer 14

first - alkyl group
second - carboxylic acid group and replace ending with -oate

Question 15

what are esters used in

Answer 15

commercially and in industrial processes
1. perfumes and food flavourings - some have sweet smells making them ideal in fragrances and food products
2. solvents - polar so other polar compounds dissolve readily in esters. they also have low boiling points and evaporate easily
3. plasticisers - used to make plastics more flexible during polymerisation, but can leach out of the plastic over time

Question 16

how can ester hydrolysis be sped up

Answer 16

• esters can be hydrolysed
  can be sped up using an acid and a base