Carbonyl Group

Question 2

Boiling points of aldehyde and ketones

Answer 2

Higher than alkanes
Van der waals and permanent dipole forces between molecules
Less than alcohols due to hydrogen bonding
Ketone higher than aldehyde due to position of carbonyl group

Question 4

Solubility of aldehyde and ketone in water

Answer 4

All short chain are soluble due to polarity

Question 5

Reduction of aldehyde and ketone

Answer 5

NaBH4
Heated under reflux, aqueous ethanol, acidification with dilute sulfuric acid
Nucleophilic addition

Question 6

Aldehyde and ketone reaction with cyanide

Answer 6

Nucleophilic addition
Hydroxynitrile produced
KCN used not HCN as extremely toxic flammable gas
However KCN is still toxic if ingested
Forms racemic mixture

Question 7

Solubility of carboxylic acids

Answer 7

Very soluble short chain
Solubility decreases as chain length increases

Question 8

Boiling points of carboxylic acids

Answer 8

Higher than alcohols
Form dimers, hydrogen bonding between two molecules
Doubles their size so increased van der waals

Question 9

Test for carboxylic acid

Answer 9

Add sodium carbonate
Efferevesnce
Collect gas and bubble through lim3 water
Cloudy is a positive result

Question 10

Estsers

Answer 10

Produced when alcohol and carboxylic acids react
Alkyl carboxylate

Question 11

Uses of esters

Answer 11

plasticizer mixed into polymers to improve flexibility
Solvents for organic compounds, volatile so easily seperated from solute
Perfumes- pleasant smells
Food flavourings- pleasant taste

Question 12

Acid hydrolysis

Answer 12

Not completely hydrolysed forming equilibrium mixture
Heat under reflux with dilute sulfuric acid
Saponification

Question 13

Alkaline hydrolysis

Answer 13

Complete hydrolysis and quicker reaction
Heat under reflux with aqueous NaOH
Dilute acid added to get acid from its salt
Saponifcation

Question 14

Hydrolysis of vegetable oils and fats (saponification)

Answer 14

Using hot alkali
Heat under reflux with aqueous NaOH
Sodium/potassium salts are soaps

Question 15

Biodiesel (trans esterification)

Answer 15

Renewable fuel from vegetable oils
Heat vegetable oils with methanol with acid catalyst
Ester and alcohol to form at different ester and alcohol (glycerol)

Question 16

Carboxylic acid derivatives

Answer 16

Acyl chloride
Acid anhydride

Question 17

Acylation

Answer 17

Replacing a H atom with acyl group RCO-

Question 18

Acyl chloride reactions

Answer 18

Water: carboxylic acid and HCl
Alcohol: ester and HCl
Ammonia: amide and HCl ( or ammonium chloride NH4Cl)
Primary amine: N-substituted amide and HCl
Nucleophilic addition elimination

Question 19

Acid anhydride reactions

Answer 19

Water: carboxylic acid
Alcohol: ester and carboxylic acid
Ammonia: amide and carboxylic acid
Primary amine: N substituted amide and carboxylic acid
Nucleophilic addition elimination

Question 20

Why are anhydrides preferred over acyl chlorides

Answer 20

Less corrosive
Less vulnerable to hydrolysis
Less violent reaction
Cheaper
No corrosive fumes of HCl

Question 21

Recrystalisation

Answer 21

Dissolve impure crystals in minimum volume of hot solvent
Filter hot solution With vacuum filtration removing insoluble impurities (concentrated solution)
Let solution cool to crystallise
Filter off crystals with vacuum filtration to remove soluble impurities
Dry between two sheets of paper

Question 22

Checking purity of organic solid

Answer 22

Pure: fixed m3lting point
Impure: melts over wide range, begins melting at lower temperature
Range of <2°C is fairly pure

Question 23

Determining melting point

Answer 23

Place some solid in thiole tube
Place in melting point apparatus and heat slowly
Record temperature it starts to melt and finishes melting
Repeat and average temperatures
Compare with known values in data book