4.2.3 Organic synthesis

Question 1

what does a basic set of quickfit apparatus include

Answer 1

• round-bottom / pear-shaped flask
• receiver
• screw-tap adaptor
• condenser
• still head

Question 2

how do you set up apparatus for reflux

Answer 2

• reaction mixture + anti-bumping granules added to flask
• apply grease (vaseline) to joint of condenser + put into flask
  > condenser in upright poistion
  > water out at top + water in at bottom
• condenser clamped loosely to clamp stand
• flask heated

Question 3

why are anti-bumping granules used for reflux

Answer 3

• so contents boil smoothly

Question 4

what are benefits of reflux heating

Answer 4

• prevents volatile components from escaping + flask from boiling dry

Question 5

how does reflux heating work

Answer 5

• vapour from mixture rises up inner tube of condenser until it meets outer jacket containing cold water
• vapour condenses + drips back into flask

Question 6

why must there be no stopper on top of condenser under reflux

Answer 6

• you make a close system + pressure will build up ad heated air expands
  > can lead to apparatus exploding

Question 7

what is distillation used for

Answer 7

• separating a pure liquid from its impurities

Question 8

how do you set up the apparatus for distillation

Answer 8

• flask clamped by neck
  > still head attached to flask (T shaped + has 2 ground-glass joints)
  > condenser attached to still head adaptor + screw cap adaptor (with thermometer)
• second clamp around receiver adaptor which attached to condenser
• water enters at lower end + leavs at top
• flask used to collect distillate
• flask heated

Question 9

how does heating under distillation work

Answer 9

• diff liquids in mixture have diff bp
  > liquid with lowest bp is most volatile + boils first
• vapour moves out flask + reaches cold condenser, condenses + becomes liquid
  > liquid drips into collecting flask

Question 10

what are the different ways you can heat up compounds when using reflux or distil apparatus

Answer 10

• bunsen burner
• water bath (less than 100)
• heating mantle for flammable liquids

Question 11

how can you purify organic products using separating funnel

Answer 11

• pour mixture of liquids into separating funnel
• tap is closed + invert to mix contents
• allow layers to settle
• place conical flask under separating tunnel, remove stopper, open tap, until whole of lower layer has left funnel

Question 12

how can you remove any acid impurities from your impure product

Answer 12

• add aqueous sodium carbonate + shake mixture in separating funnel
  > any acid present will react with sodium carbonate releasing CO2 gas

Question 13

what to do if there is any water left in an organic product

Answer 13

• add drying agent
  > anhydrous inorganic salt that readily takes up water to become hydrated

Question 14

name some drying agents

Answer 14

• anhydrous magnesium sulfate (Mg SO4): general drying
• anhydrous calcium chloride (CaCl2): drying hydrocarbons

Question 15

give the procedure for drying an organic liquid

Answer 15

• add drying agent to liquid + swirl to mix contents
• add stopper to prevent evaporation of products + leave for 10 mins
• if solid stuck together in lump, there is still water present
  > add more drying agent until some solid is dispersed in the solution as fine powder
• pour liquid from solid in another flask + if liquid dry it should be clear

Question 16

what is a sign that the organic product is dry

Answer 16

• the liquid should be clear

Question 17

what is redistillation

Answer 17

• if organic liquids have similiar bp then prepared sample may have impurities
  > distillation clean + dry + set up again so 2nd distillation is carried out
  > this time only collect product with bp of compound you are trying to make

Question 18

what is organic synthesis

Answer 18

• preparation of complex molecules from simple starting molecules

Question 19

what are target molecules

Answer 19

• compound that chemist is trying to prepare by organic synthesis

Question 20

to convert a starting molecule into target molecules you need to carry out the 2 stage synthesis which includes:

Answer 20

• identifying functional groups in your starting + target molecules
• identifying the intermediate that links the starting + target molecules
• state the reagents + conditions for each step

Question 21

state the reagents + conditions needed to convert from an alkane to a haloalkane

Answer 21

• halogen
• UV light
• free radical substitution

Question 22

state the reagents + conditions needed to convert from an alkene to a haloalkane

Answer 22

• hydrogen halide
• room temp
• electrophilic addition

Question 23

state the reagents + conditions needed to convert from an alkene to an alkane

Answer 23

• H2
• nickel catalyst
• 150C
• 5 atom
• addition

Question 24

state the reagents + conditions needed to convert from a haloalkane to an alcohol

Answer 24

• aqueous alkali (NaOH)
• reflux
• nucleophilic substitution

Question 25

state the reagents + conditions needed to convert from an alkene to an alcohol

Answer 25

- H3PO4 catalyst - H2O - reflux

Question 26

state the reagents + conditions needed to convert from an alcohol to an alkene

Answer 26

- conc H2SO4 - elimination

Question 27

state the reagents + conditions needed to convert from an alcohol to a haloalkane

Answer 27

- sodium halide - H2SO4 - reflux - substitution

Question 28

state the reagents + conditions needed to convert from an to an

Question 29

state the reagents + conditions needed to convert from an alcohol to an aldehyde

Answer 29

- primary alcohol - distil - partial oxidation - acidified potassium dichromate

Question 30

state the reagents + conditions needed to convert from an alcohol to a ketone

Answer 30

- secondary alcohol - reflux - acidified potassium dichromate

Question 31

state the reagents + conditions needed to convert from an aldehyde to a carboxylic acid

Answer 31

- oxidation