Demonstration of pentyl acetate

Chemicals needs

acetic acid C     R 10-35    S (1/2)-23-26-45

1-pentanol Xn    R 10-20    S (2)-24/25

sulphuric acid 96 %  C    R 35   S (1/2)-26-30-45

The acetic acid should be as concentrated as possible (glacial acetic acid).

Dangerous substance information

pentyl acetate    R 10-66    S (2)-23-25

Equipment needed

2 test tubes
rubber plugs with hole and discharge tube
stand with double sleeve and clamp
beaker or the like
burner (preferably alcohol)

Test procedure

• Safety goggles!
• Add to a test tube 1 ml pentanol and 1 ml acetic acid, then add about 1 ml concentrated sulphuric acid.
• Carefully sway the mixture back and forth so that a good mixing results. If this is not done the mixture will boil in the beginning with eructation and carbonize strongly.
• Clamp the test tube steeply or vertically to the stand, apply the plug with discharge tube, such that the discharge tube leads into a test tube, which is in a beaker with cold water. In order to avoid recoil the discharge tube should discharge a goodly distance from the bottom.
• Sufficiently warm the mixture, which after a while becomes an ester, with the burner so that the boiling remains constant. End the warming after about one-third of the mixture has been distilled off. A clear distillate has been transferred. Before opening the apparatus extinguish the flame.
• The product is, as can easily be verified, scarely soluble and lighter than water. It has a characteristic odor, which reminds one of fruit or 'Gletscher-Eis' candies. Due to its odor the ester was previously called "pear ether".

Disposal

• After cooling water is added to the reaction mixture (warming!) and then disposed of as halogene-free organic waste.
• The product itself can also be disposed of as halogen-free organic waste.

Elucidation

Esterification is a balance reaction. Due to the dehydrating effect of concentrated sulphuric acid and the distilling off of the product the balance is shifted in the desired direction. Compared with the Demonstration of ethyl acetate the product is less volatile, therefore the increased admixture of sulphuric acid. Esterification with distillation has herewith reached its limit of practical applicability, for a demontration of a low-volatility ester see Demonstration of ethyl benzoate.

Photos

Apparatus before begin of destillation.

Literature

reduced version of experiment 1713 S,"Essigsäureamylester", p. 305, [2]