Flash Evaporation to remove methylene chloride and

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Flash Evaporation to remove methylene chloride and
Chemistry 227 Laboratory

• The recovery of the Aniline from Extraction.

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But first, a few words about your notebooks

• Give credit to the inventors Buchner, Bunsen,
  Erlenmeyer, etc.
• TWO as in Separate -- NONE in Soluble
• Literature values -- NOT literary values
• Subject Verb must agree in number
• Five grams of benzoic acid were . . .
• Then, 15 mLs of sodium hydroxide were . .
• No need to detail a previous procedure . . .

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At this point, you should be able to account for
the following items.

• If you have all three of these, you are ready for
  Flash Evaporation p. 135 Zubrick.
• (Note IF the methylene chloride had evaporated,
  you will need to add more.)

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You have gone to a great deal of effort to DRY
everything.

• Then, from this point, be sure that ALL of the
  glassware you use is ABSOLUTELY DRY.

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Start setting up with a good sturdy ring stand.

• If the rod is loose, tighten it before you begin
  so your set-up wont WOBBLE

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Place the burneron the stand. The hotplate is
NOT a good option for this procedure.

• Be sure your burner has a needle valve to adjust
  gas flow, and a rotating barrel to control
  air-flow.

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Now, add the iron ring

• Leave 2 to 3 inches for the flame.

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The wire gauzeis next.

• The wire gauze should have a ceramic center.
  Dont worry if there is hole in it.

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A beaker serves as a hot water bath.

• Select a LARGE
• beaker with sufficient capacity
• for your
• 50 mL RB flask.

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Clamp your 50 mL RB flask(NO LARGER) in the
water bath

• Place the flask as far into the water as possible.

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Attach the three-way adapter atop the flask.

• (The adapter is commonly called the still head.)

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CLAMP the condenser to anotherring stand.Rubber
bands are available to snug up the condenser.

• But do NOT trust a rubber band alone, to hold
  that 50.00 piece of glassware!

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Arrange an Erlen-meyer flask in an ice slurry
for your receiver.

• You may want to clamp the receiver onto another
  ring stand.

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Attach water hoses to the water jacket of the
condenser

• Water always
• enters from the LOWER end of the water jacket.

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Place the sep funnel on top of the still head.

• No need for a stopper but be sure the stopcock
  is CLOSED!

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Remove the spent magnesium sulfate (GRAVITY
FILTER) from the aniline in - methylene
chloride solution.

• Wash with small portions of methylene chloride
  collecting all of the filtrate.

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Make sure the stopcock is CLOSED.(Dont be one
of those who will forget!)

• THEN, transfer the filtrate into the sep funnel.

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Light the burner and adjust to a good hot flame.

• Bring the water in the beaker to near boiling.

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Adjust the burner to a small flame.

• The object is to keep the water bath hot.

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Open the stopcock SLIGHTLY and allow slow steady
drops to fall onto the hot flask.

• Methylene chloride boils over in an instant
• (in a flash?) as the high boiling aniline remains
  behind.

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While the Flash Evaporation is going on, filter
the magnesium sulfate from your
p-dichlorobenzene. Place the filtrate on your
hot plate UNDER YOUR SNORKEL, and and evaporate
off the methylene chloride.

• When the volume reached only a few mLs, you may
  begin to see white vapors rising from the beaker.
  STOP the evaporating, and COOL the contents.
  The residual
• p-dichlorobenzene should solidify.

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Finally, only aniline remains in the RB flask.

• Discard the methylene chloride in the waste
  receptacle provided for it -- and prepare to
  collect the aniline.

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Collecting the Aniline
Recovering the Aniline from Extraction.

• by distillation through an AIR-COOLED condenser.

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Turn off the burner flame.

• Remove the ice bath and receiver. Discard the
  methylene chloride in the receptacle provided.

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Drain the water from the water jacket.

• Remove the hoses from the condenser

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Remove the sep funnel from the still head.

• Loosen the blue retainng nut and return the sep
  funnel to the box from which you got it.

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You no longer need the water bath.

• Remove it and return the large beaker to the
  cabinet from which you got it.

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Lower the RB flask to sit firmly on the wire
gauze.LEAVE NO AIR SPACE!

• Lower the condenser assembly and re-attach it
  firmly to the still head.
• NO WATER HOSES!

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Place the thermo-meter assembly into the still
head.

• The thermo-meter bulb should be just below the
  side- arm of the still head.

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Pre-weigh and label two DRY 50-mL Erlen-meyer
flasks.

• The first is to catch the forerun the second
  is to catch the final product (aniline).

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With a good, hot flame, distill the contents in
the RB flask.

• Switch receivers as the temper-ature climbs
  rapidly toward 180 degrees.

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Collect the aniline that boils at 180- 185
degrees.

• Never distill to a dry flask. When dark droplets
  spatter in the RB flask, you may have difficulty
  cleaning it!

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Part F- recovering the neutral compound

• Remove the spent MgSO4 by gravity filtration.
• (You may have done this while working with the
  aniline.)

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UNDER YOUR SNORKEL, evaporate to near-dryness on
a hotplate.(You may have already done this too.)
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Transfer the residue into a larger RB flask, and
steam distill the mixture as before.

• Collect the distillate in an ice-cooled receiver.
• Recover the product on Buchner with suction.

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THIS CONCLUDES THE EXPERIMENT ON EXTRACTIONS

• Complete your laboratory report form, and prepare
  to turn in some of your products.