synthesis

Question 1

fingerprint region

Answer 1

below 1500

Question 2

rough area of C-H peak

Answer 2

3000

Question 3

molecular ion peak

Answer 3

highest peak, on right hand side of mass spectrum = molecular mass of compound/substance

Question 4

amount of bond bend/strectch depends on: (2)

Answer 4

• mass of atoms (heavier = vibrate more)

- strength of bonds (stronger = vibrate more/faster)

Question 5

SHC eq.

Answer 5

q (heat energy given out) = mcΔT

Question 6

enthalpy change (per mole) eq.

Answer 6

= -q / number of moles reacting

Question 7

what do you need for heating under reflux? (5)

Answer 7

• pear shaped flask
• condenser
• rubber tubing
• stand and clamp
• heat source

Question 8

what do you need for distillation? (9)

Answer 8

• pear shaped flask
• condenser
• rubber tubing
• heat source
• stand and clamp
• screw cap adaptor
• receiver adapter
• still heat
• thermometer

Question 9

how do you separate an organic product (liquid)

Answer 9

• pour mix into funnel
• place stopper on and invert
• add water to see which layer increases in volume = aq layer
• place conical flask under and open tap, until lower layer is gone
• add Na2CO3, add stopper and invert, open tap and allow gas to escape - removes acid impurities

Question 10

how do you purify a (separated) organic product (liquid) – [drying]
- agent typically used

Answer 10

• add drying agent using spatula (CaSO4) and swirl
• place stopper to prevent evaporation and leave for 10
• if solid is stuck together there is still liquid - add more drying agent and repeat
• continue adding until solid is dispersed like a fine powder
• decant liquid into another flask

Question 11

how do you separate a solid from liquid mixture?

Answer 11

• connect pressure tubing to vacuum outlet and attach other end to Buchner flask
• fit funnel to flask, ensuring tight fit by using a bung
• switch vacuum on
• check for suction by placing hand over funnel
• put filter paper in funnel - wet with solvent used in mixture
• slowly add mixture into centre of funnel
• rinse beaker with solvent so that all crystals collect in funnel
• rinse crystals in funnel with more solvent and leave for a few mins to start to dry

Question 12

what do you need for filtration under reduced pressure?

Answer 12

• Buchner flask
• Buchner funnel
• pressure tubing
• filter paper
• access to vacuum pump to filter

Question 13

method for recrystallisation

Answer 13

• pour solvent into conical flask
• if flammable heat with water bath, if not use bunsen
• add sample to second beaker
• slowly add hot solvent to sample until sample just dissolves
• once dissolved, allow to cool - crystals should form
• when no more forms filter under reduced pressure to get solid

Question 14

melting range

Answer 14

difference between temperatures at which sample starts to melt and melting is complete

Question 15

if sample contains impurities…

….

Answer 15

range is wider

melting point is lower

Question 16

preparation for melting point determination

Answer 16

• ensure sample completely dry
• take capillary tube and heat end in bunsen until is sealed
• allow to cool and then add sample until about 3mm deep

Question 17

2 methods of melting point determination

Answer 17

1) electrically heated melting point apparatus

2) oil bath/Theile tube method

Question 18

how does electrically heated melting point apparatus method work?

Answer 18

• place capillary tube w sample in sample hole
• place thermometer in thermometer hole
• use rapid heat setting - observe through magifying window
• once solid has started to melt, stop and record temp
• repeat on low setting and observe = more accurate

Question 19

how does Theile tube/oil bath method work?

Answer 19

• set up T. tube or oil bath
• attach capillary tube to thermometer using elastic band
• insert thermometer through hole in cork (/clamp it if using oil bath)
• use micrometer to slowly heat - record temp when starts to heat
• repeat for accuracy

Question 20

further purification after distillation

Answer 20

• pour solution into separating funnel and shake
• separate layers by tapping off
• add small amount of CaSO4 to organic layer in dry conical flask
• redistill organic layer
• collect fraction distilling at 150-156C