Illustrated Guide to Home Chemistry Experiments

Chapter 21 Laboratory: Synthesis of Useful Compounds 375

SBSTITUTIU oNS ANd modIfICATIoNS

• The reaction requires that the contents of the flask
  be kept at about 60°C for 60 to 90 minutes by
  partially immersing the reaction flask in a hot water
  bath. You can make a hot water bath by placing a
  large beaker half-filled with water on a hotplate,
  adding water as necessary, and keeping an eye on the
  temperature. Alternatively, you can simply partially
  fill a large beaker with water at about 60°C and add
  small amounts of boiling water periodically to keep
  the temperature near 60°C. Pure methanol boils at
  64.7°C, and the boiling point of the aspirin solution
  in methanol is slightly higher. Our goal is to keep
  the methanol solution near the boiling point without
  actually bringing it to a boil.


• You can make an ice bath by filling a medium or large
  beaker about half full of chipped ice, adding a layer
  about 1 cm thick of rock salt or table salt to the top of
  the ice, and then stirring to mix.


• If you do not have a separatory funnel, you may use
  the separation procedure described in Chapter 5.


• You may substitute any container of similar size for
  the 50 mL beaker, which is used as a weighing boat
  when determining the density of the product.


• Use ordinary (unbuffered) aspirin tablets. Generic
  aspirin is fine. You may assume that the aspirin content
  of aspirin tablets is accurately labeled. For the 13.0 g
  aspirin sample, you may use 40 standard (325 mg)
  tablets or 26 extra-strength (500 mg) tablets.


• This reaction is acid-catalyzed, which means that
  you may substitute another strong acid, such as
  concentrated hydrochloric acid, for the sulfuric acid.
  The presence of any water in the reaction mixture
  reduces yield. Concentrated sulfuric acid contains
  almost no water, and concentrated hydrochloric acid
  contains a significant amount of water.

RIREEqU d EqUIpmENT ANd SUppLIES

£ goggles, gloves, and protective clothing

£ balance

£ hot water bath (see Substitutions and modifications)

£ ice bath (see Substitutions and modifications)

£ test tube

£ beaker, 50 mL

£ beaker, 250 mL

£ beaker, 600 mL

£ separatory funnel (optional)

£ Erlenmeyer flask, 125 mL

£ graduated cylinder, 10 mL

£ graduated cylinder, 100 mL

£ pipette, mohr or serological, 10.00 mL

£ ring stand

£ utility clamp (for flask)

£ stirring rod

£ eye dropper or Beral pipette

£ thermometer

£ aspirin (13.0 g)

£ methanol (~100 mL)

£ sulfuric acid, concentrated (~10 mL)

£ saturated sodium bicarbonate solution

(50 mL; 3.9 g/50 mL)

CUTIOA nS

Methanol is toxic (particularly to the optic nerve; eye protection is essential), extremely

flammable, and has a flash point of only 11°C. (The flash point is the lowest temperature

at which a flammable liquid can form an ignitable mixture in air.) Have a fire extinguisher

handy and avoid all open flames. Concentrated sulfuric acid is extremely corrosive. Methyl

salicylate is toxic, irritating, and penetrates the skin. Do not taste the methyl salicylate

produced in this lab, and be cautious when you test its odor. Wear splash goggles, gloves,

and protective clothing.

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