Isomerism + carbonyl compounds

Question 1

Define chiral carbon

Answer 1

Carbon that has 4 diff. groups attached to it

Question 2

Define enantiomer

Answer 2

Non-superimposable mirror image

Question 3

How do you test for optical isomerism?

Answer 3

• Shine plane polarised light
• 1 will rotate it clockwise
• 1 will rotate it anticlockwise

Question 4

Define racemate

Answer 4

Contains equal quantities of each enantiomer

Question 5

How do racemate mixtures form?

Answer 5

• C=O is planar
• Equal chances of nucleophile attacking either directions
• Equal amounts of each enantiomer will form

Question 6

Outline the properties of esters

Answer 6

• Sweet smell - used for flavouring
• Polar so polar organic compounds dissolve in them
• Low BP so good solvent for ink + glue
• Plasticisers

Question 7

What type of hydrocarbons do animal fats mainly have?

Answer 7

Saturated - long straight so strong VDW, high MP so solid

Question 8

What type of hydrocarbons do vegetable oils mainly have?

Answer 8

Unsaturated - chain bent so weaker VDW, lower BP so liquid

Question 9

What is needed to hydrolyse veg oil + animal fat to make glycerol, soap + FA?

Answer 9

3 Sodium hydroxide

Question 10

What is biodiesel made up of?

Answer 10

Mixture of methyl esters

Question 11

Acyl chloride names

Question 12

What happens when an acid anhydride reacts w/ water, ammonia, alcohol + amine?

Answer 12

Same w/ acyl chloride but forms carboxylic acid instead of HCl

Question 13

Why is acid anhydride used in industry instead of acyl chloride?

Answer 13

• Cheaper
• Safer - reacts slowly + doesn’t produce hydrogen chloride fumes

Question 14

How do you remove water soluble impurities from a product?

Answer 14

• Seperation: pour mixture into seperation funnel, add water, organic layer + aqueous layer are immiscible so seperate into 2 layers
• Organic layer will end up w/ water so dry w/ MgSO4/CaCl2 (binds to water to become hydrated) - keep adding salt until it disperses then filter

Question 15

How do you remove other impurities from a mixture?

Answer 15

• Washing
• E. add sodium hydrogen carbonate to mixture to remove acid, will give off CO2

Question 16

What do you do when both the product + impurities are soluble in water?

Answer 16

• Solvent extraction
• Add organic solvent which product is more soluble in than water to mixture
• Product will dissolve in solvent leaving impurities dissolved in water
• Use seperating funnel

Question 17

How do you purify volatile liquids?

Answer 17

• Distillation
• Connect condensor to round bottomed flask
• Place thermometer at neck of flask
• Heat
• Place flask at end of condensor to collect pure product

Question 18

How do you purify organic solids?

Answer 18

• Recrystallisation
• Add hot solvent to impure solid until it dissolves - saturated solution of impure product
• Filter through heated funnel to remove insoluble impurities
• Leave sol to cool, crystals will form
• Remove liquid containing impurities from crystals by filtering mixture under reduced pressure - filter paper lined buchner funnel sitting in side arm flask attached to vacuum line
• Wash crystals w/ ice cold solvents to remove soluble impurities

Question 19

Outline how impurities affect MP

Answer 19

Lowers MP + inc melting range