Organic Synthesis

Question 1

Drying agents that can be used to remove water from an organic product

Answer 1

-Anhydrous CaCl2 (drying hydrocarbons)
-Anhydrous CaSO4
-Anhydrous MgSO4

Question 2

Heating Under Reflux Apparatus

Answer 2

-Round bottom or Pear shaped flask
- Condenser ( lid = explosion bc pressure)
- Rubber tubing
- Stand and Clamp
- Heat source

Question 3

Why are anti bumping granules used?

Answer 3

Prevents liquid from jumping out of glassware or vibrating violently.

Question 4

Why is heating under reflux important?

Answer 4

Prevents volatile compounds from escaping

Question 5

Distillation

Answer 5

Liquid is boiled to a vapour that is then condensed into a liquid, liquid with the lowest boiling point is the most volatile and will boil first.

Question 6

Why is petroleum jelly used in these apparatus?

Answer 6

To stop things from getting stuck

Question 7

Purifying organic liquids

Answer 7

-Add mixture to separating funnel then add sodium carbonate to neutralise excess acids
-Add water and layer that gets bigger is the aqueous layer
-Organic layer is at the top
- Allow aqueous layer to run out and collect organic layer
-Add drying agent e.g anhydrous CaSO4/CaCl2
-Can redistill if you have multiple organic products at 44•C

Question 8

Alkane to Haloalkane

Answer 8

Halogen, UV light

Question 9

Alkene to Haloalkane

Answer 9

Hydrogen Halide (HX)

Question 10

Alcohol to Haloalkane

Answer 10

Sodium halide (NaX) and H2SO4 under reflux

Question 11

Haloalkane to Alcohol

Answer 11

NaOH (aq) under reflux

Question 12

Alkene to Alkane

Answer 12

H2, Ni catalyst

Question 13

Alkene to Alcohol

Answer 13

h2O(g), H3PO4 catalyst

Question 14

Alcohol to alkene

Answer 14

Conc H2SO4 under reflux

Question 15

Primary alcohol to Carboxylic acid

Answer 15

K2Cr2O7, H2SO4 under reflux

Question 16

Secondary alcohol to ketone

Answer 16

K2Cr2O7, H2SO4 under reflux

Question 17

Primary alcohol to aldehyde

Answer 17

K2Cr2O7, H2SO4 under distillation

Question 18

Why should water enter at the bottom of the condenser?

Answer 18

So that the condenser fills with water and promotes efficient cooling

Question 19

Purification of organic solids

Answer 19

• Recrystallise the impure solid by dissolving in the minimum amount of hot solvent (e.g water)
• Cool to allow crystallisation to occur then filter under reduced pressure using Buchner apparatus
• Wash the purified aspirin using cold water and dry

Question 20

Ways of checking purity

Answer 20

Melting point and TLC

Question 21

Checking purity using melting point

Answer 21

-Measure melting of sample using melting point apparatus
- Compare to data value
- Impurities lower melting points and widen the melting range
- The purer the sample, melting occurs closer to the true value and over a narrow range (2.C)

Question 22

Checking purity using TLC

Answer 22

-Run chromatogram of impure sample
- Calculate Rf value
- Compare to a known data base
- Or compare to a known pure chromatogram