Flash Evaporation to Flash Evaporation to remove methylene chloride remove methylene chloride

andand

The recovery of the The recovery of the Aniline from Extraction.Aniline from Extraction.

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

If you have all three of these, you are ready for Flash If you have all three of these, you are ready for Flash Evaporation; p. 135 ZubrickEvaporation; p. 135 Zubrick.

(Note: IF the methylene chloride had evaporated, (Note: IF the methylene chloride had evaporated, you will need to add more.)you will need to add more.)

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

• Then, from this point, be sure Then, from this point, be sure that that ALLALL of the of the glasswareglassware you use is you use is ABSOLUTELYABSOLUTELY DRYDRY..

Start Start setting setting up with up with a good a good sturdy sturdy

ring ring stand.stand.

If the rod is If the rod is loose, loose,

tighten ittighten it before you before you begin so begin so

your set-up your set-up won’t won’t

WOBBLEWOBBLE

Place the Place the burnerburneron the on the

stand. stand. The The hotplate is hotplate is

NOTNOT a a good good

option for option for this this

procedure.procedure.

Be sure your Be sure your burner has a burner has a needle valveneedle valve to adjust gas to adjust gas flow, and a flow, and a

rotating rotating barrelbarrel to to

control air-control air-flow.flow.

Now, Now, add the add the

iron iron ringring

Leave 2 Leave 2 to 3 to 3

inches inches for the for the flameflame..

The The wire wire

gauzegauzeis is

next.next.

The wire The wire gauze gauze should should have a have a

ceramic ceramic center. center. Don’t Don’t

worry if worry if there is there is

hole in it.hole in it.

A A beaker beaker serves serves

as a as a hot hot

water water bath.bath.

Select a Select a LARGELARGEbeakerbeaker

with with sufficient sufficient capacity capacity

for your for your

50 mL RB 50 mL RB flask.flask.

Clamp Clamp your your 50 50 mL RB mL RB flaskflask(NO (NO

LARGER)LARGER) in the in the water water bathbath

Place Place the flask the flask

as far as far into the into the water as water as possiblepossible

.

Attach Attach thethe

three-three-way way

adapteradapter atop atop the the

flaskflask.

(The (The adapter is adapter is commonly commonly called the called the

“still “still head”.)head”.)

CLAMPCLAMP the the

condenser condenser to anotherto another

ring ring stand.stand.Rubber Rubber

bands are bands are available to available to snug up the snug up the

condensercondenser..

But do But do NOT trust NOT trust a rubber a rubber

band band alone, to alone, to hold that hold that $50.00$50.00 piece of piece of

glasswareglassware!!

Arrange Arrange an an Erlen-Erlen-

meyermeyer flask in flask in an ice an ice

slurry for slurry for your your

receiver.receiver.

You may You may want to want to clamp clamp

the the receiver receiver

onto onto another another

ring ring stand.stand.

Attach Attach water water

hoses to hoses to the water the water jacket of jacket of

the the condensercondenser

Water Water alwaysalways

enters enters at the at the

LOWERLOWER end of end of

the the water water jacket.jacket.

Place Place the the sep sep

funnel funnel on top on top of the of the still still

head.head.

No need No need for a for a

stopper; stopper; but be but be

sure the sure the stopcock stopcock

isis CLOSEDCLOSED

!!

Remove the Remove the spent spent

magnesium magnesium sulfate sulfate (GRAVITY (GRAVITY FILTER)FILTER)

from the from the aniline – in - aniline – in - methylenemethylene chloridechloride solution.solution.

Wash with Wash with small small

portions of portions of methylene methylene chloride; chloride;

collecting all collecting all of the filtrate.of the filtrate.

Make Make sure the sure the

stopcock stopcock is is

CLOSEDCLOSED..(Don’t be (Don’t be

one of one of those those

who will who will forget!)forget!)

THEN,THEN, transfer transfer

the the filtrate filtrate

into the into the sep sep

funnel.funnel.

Light Light the the

burner burner and and

adjust adjust to a to a

good good hot hot

flame.flame.

Bring Bring the the

water in water in the the

beaker beaker to near to near boiling.boiling.

Adjust Adjust the the

burner burner to a to a

smallsmall flame.flame.

The The object object is to is to keep keep the the

water water bath bath hothot..

Open the Open the stopcock stopcock SLIGHTLYSLIGHTLY and allow and allow

slow slow steady steady

dropsdrops to to fall onto fall onto the the hot hot flask.flask.

Methylene Methylene chloride chloride

boils over boils over in an in an

instant instant

(in a (in a

flash?)flash?) as the as the high high

boiling boiling aniline aniline

remains remains behind.behind.

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

and and evaporate off the methylene and and evaporate off the methylene chloride.chloride.

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

p-dichlorobenzene “should” solidify.p-dichlorobenzene “should” solidify.

Finally, Finally, only only

aniline aniline remains remains

in the in the RB RB

flask.flask.

Discard Discard the the

methylene methylene chloride in chloride in the waste the waste receptacle receptacle provided provided for it; -- for it; --

andand prepare to prepare to collect the collect the

aniline.aniline.

Collecting the AnilineCollecting the Aniline

by distillation through by distillation through anan AIR-COOLEDAIR-COOLED

condenser.condenser.

Turn Turn off the off the burner burner flame.flame.

Remove Remove the ice the ice

bath and bath and receiver. receiver. Discard Discard

the the methylene methylene chloride in chloride in

the the receptacle receptacle providedprovided.

Drain Drain the the

water water from from the the

water water jacketjacket..

Remove Remove the hosesthe hoses from the from the condensercondenser

Remove Remove the sep the sep funnelfunnel from from the the

“still “still head”.head”.

Loosen Loosen the blue the blue retainng retainng nut and nut and

return the return the sep funnel sep funnel to the box to the box

from from which you which you

got it.got it.

You You no no

longer longer need need the the

water water bath.bath.

Remove Remove it and it and return return

the large the large beaker to beaker to

the the cabinet cabinet

from from which which

you got you got itit.

Lower the Lower the RB flask RB flask

to sit to sit firmly on firmly on the wire the wire gauze.gauze.

LEAVE LEAVE NO AIR NO AIR SPACE!SPACE!

Lower the Lower the condenser condenser assembly assembly and re-and re-attach it attach it firmly to firmly to the still the still head.head.

NO NO WATER WATER HOSES!HOSES!

Place the Place the thermo-thermo-meter meter

assembly assembly into the into the

still still head.head.

The The thermo-thermo-meter meter bulb bulb

should should be just be just below below

the the side- side-

arm of arm of the still the still head.head.

Pre-Pre-weigh weigh

and label and label twotwo

DRYDRY 50- 50-mL mL

Erlen-Erlen-meyer meyer flasks.flasks.

The first The first is to catch is to catch

the the “forerun”“forerun”

; the ; the second is second is to catch to catch the final the final product product (aniline).(aniline).

With a With a good, hot good, hot

flame,flame, distill the distill the contents contents

in the in the RB flask.RB flask.

Switch Switch receivers receivers

as the as the temper-temper-

ature ature climbs climbs rapidly rapidly toward toward

180 180 degreesdegrees.

Collect Collect the the

aniline aniline that that

boils at boils at 180- 180- 185185

degrees.degrees.

Never Never distill to a distill to a dry flask.dry flask.

When dark When dark droplets droplets

spatter in spatter in the RB the RB

flask, you flask, you may have may have difficulty difficulty

cleaning it!cleaning it!

Part FPart F-- recovering the neutral compoundneutral compound

Remove the spent MgSORemove the spent MgSO44 by gravity filtration. by gravity filtration.

(You may have done this while working with the aniline.)(You may have done this while working with the aniline.)

UNDER YOUR SNORKEL,UNDER YOUR SNORKEL, evaporate evaporate to near-dryness on a hotplate.to near-dryness on a hotplate.(You may have already done this too.)(You may have already done this too.)

Transfer the residue into a larger RB flask, and steam distillsteam distill the mixture as before.

Collect the distillate in an ice-cooled receiver.Collect the distillate in an ice-cooled receiver.

Recover the product on Buchner with suction.Recover the product on Buchner with suction.

THIS CONCLUDES THE THIS CONCLUDES THE EXPERIMENT ON EXTRACTIONSEXPERIMENT ON EXTRACTIONS

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