Instruments and pharmaceuticals
Round bottom flask (100mL), thorn-shaped
fractionating column, a condenser straight wetted tube, cylinder (10mL),
thermometer (200 ℃), beaker (250mL), suction flask, Buchner funnel, small pumps, heat
funnel , electric sets
Aniline, glacial acetic acid, zinc powder,
activated carbon
Experimental Procedure
1. Acylation: In 100ml round bottom flask,
add 5 ml of freshly distilled aniline, 8.5ml glacial acetic acid and 0.1g of
zinc powder.
Now fitted fractionating column, a
thermometer was installed at the top of the column, with a small cylinder
collect the distilled water and acetic acid. Experimental setup Refer to Figure
16-9. With electric sets slowly heated to boiling reactants. Regulated voltage,
when the temperature rose to about 105 ℃ distillation begins.
Maintaining the temperature at about 105 ℃ about 30min, then
the reaction between the basic distilled water. When the thermometer readings
declining, then the reaction to reach the end, you can stop heating.
2. Crystallization filtration: add 100ml
water in a beaker, and the reaction solution was poured into hot water to thin
stream, while keep stirring, this time with fine particulate solid
precipitated. After cooling, filtration, and the solid was washed with a small
amount of cold water to give the white or yellow crude N-Acetylaniline.
3. Recrystallization: The crude
N-Acetylaniline was transferred to a beaker, add 100ml of water, heated to
boiling under stirring. Observe whether there is undissolved oil, if the
additional water until fully dissolved oil droplets. Coolish, add 0.5g of
activated carbon, and boiled 10min. In the heat activated carbon was removed by
hot filtration funnel. The filtrate was poured into a beaker of heat. Then cool
to room temperature with ice water, waiting to be completely precipitated
crystals for filtration. Cake was washed twice with a small amount of cold
water, pressed dry. The crystals were transferred to the surface of the dish,
dry naturally after weighing, and calculating yield.
Considerations
⑴ reaction glassware must be dry.
⑵ zinc's role is to prevent the oxidation of aniline, just a small
amount can be. Add too much, there will be a water-insoluble zinc hydroxide.
⑶ fractionating the reaction temperature is not so high that a large
number of distilling off the acetic acid and reduce the yield.
⑷ recrystallization, the crystal may not precipitated, the beaker
wall friction can be a glass rod or seed crystals are added to precipitate
crystals.
⑸ glacial acetic acid with a strong irritant to be drawn in a fume
hood.
⑹ must not in a boiling solution of activated carbon was added, in
order to avoid bumping.
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