14-friedel crafts acylation ferrocene

7/25/2019 14-Friedel Crafts Acylation Ferrocene

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Organic Chemistry with Vernier Vernier Software & Technology 1

Friedel-Crafts Acylation of Ferrocene

Friedel-Crafts reactions are examples of electrophilic aromatic substitution reactions. Thereaction involves the substitution of hydrogen on the aromatic ring system by an electrophilic

carbon species forming a new carbon-carbon bond. Friedel-Crafts reactions may be used tointroduce either an alkyl or acyl group.

Ferrocene does not undergo addition reactions typical of cyclopentadiene, but undergoeselectrophilic aromatic substitution. The Friedel-Crafts acylation reaction of ferrocene involves theaddition of the acylium cation to one of the carbon atoms on the ring, followed by loss of a proton(to solvent. The acylium cation is produced from acetic anhydride, which also serves as a solventfor this reaction. !f only one ring reacts, then the product is the orange acetylferrocene. !f bothrings react, then the product is the red ","-diacetylferrocene. The reaction time of this experimentis reduced to limit the formation of ","-diacetylferrocene.

#our ob$ectives in this experiment will be to synthesi%e, isolate, and characteri%e acetylferrocene.

The reaction e&uation is shown below. !n this experiment you will also become familiar with atechni&ue called column chromatography, which can be used to separate the desired product fromunreacted starting material and side products. The compounds are colored which will make it easyto see the separation. 'elting temperature analysis will be used to characteri%e the synthesi%edproduct.

CH3 O CH3

O O

CH3 OH

O

Fe + Fe

O

CH3

+H 3 P O 4 ( a q )

Ferrocene Acetic anhydride Acetylferrocene Acetic acid

OBJECTIVES

!n this experiment, you will

ynthesi%e acetylferrocene.

!solate and purify the product using column chromatography.

'easure the melting temperature range of your product.


2/102 Organic Chemistry with Vernier

MATERIALS

Part I Synthesis Materials

)* m+ round bottom flask ferrocenestir bar ) phosphoric acid solutiondrying tube li&uid acetic anhydride

ring stand with utility clamp distilled water /chner funnel icefiltering flask sodium bicarbonate, 0a1C23, solidfilter paper grease"* m+ graduated cylinder balancespatula weighing paper cotton plug watch glass4rierite5 magnetic stirrer6hot platecork ring Temperature 7robe or thermometer "** m+ beaker compressed air two 8)* m+ beakers p1 paper (optionaldisposable 7asteur pipets and bulb

Part II Col!n Chro!ato"ra#hy

"* m+ disposable serological pipet, glass hexanecotton plug acetonesand diethyl ether silica gel 9:" hexane6acetone mixtureweighing paper two 8*")* mm test tubesdisposable 7asteur pipets and bulb test tube rack four 8)* m+ ;rlenmeyer flasks hot platepp or +oggerPro samples from 7art !!?ernier 'elt tation mortar and pestleglass capillary tubes, one end closed

PROCE$%RE

Part I Synthesis

". 2btain and wear goggles. 7rotect your arms and hands by wearing a long-sleeve lab coat and

gloves. Conduct this reaction in a fume hood.

8. 7repare the reaction mixture. CAUTION:Handle the phosphoric acid and acetic anhydridewith care. Both substances can cause painful burns if they come in contact with the skin.

a. @eigh out ".* g of acetic anhydride in the )* m+ round bottom flask and record to thenearest *.*" g.

b. @eigh out about *.8) g of ferrocene and transfer to the round bottom flask. Aecord themass to the nearest *.*" g.


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Organic Chemistry with Vernier 3


c. >dd a stir bar to the flask.

d. Clamp the round bottom flask securely to the ring stand, lower onto the stir plate, andbegin stirring.

e. lowly add drops of ) phosphoric acid to the mixture over 8 minutes. This reaction isexothermic.

3. >fter the addition of the phosphoric acid, e&uip the flask with a drying tube containing4rierite5. Brease the $oints to prevent the glass from sticking.



"8. >ssemble the chromatography column. CAUTION:Silica powder is harmful if inhaled.se only in the fume hood.

a. 7lace a small piece of cotton into the bottom of the "* m+ serological pipet followed by*.) cm of sand and enough silica to fill the pipet about 863 full. Note:@eighing paper maybe used to help fill the pipet with silica.

b. Bently tap the tip of the pipet on the table top for "E8 minutes to pack the silica.c. >dd another *.) cm of sand to the top of the pipet.

"3. 2btain two test tubes to collect the column fractions and a 8)* m+ ;rlenmeyer flask forwaste. Important:2nce you start the elution process, it cannot be stopped. #ou must go tocompletion. Aead teps "dd " m+ of hexane down the sides of the column and drain until the solvent level is belowthe top of the sand. Aepeat this procedure until your compound is a tight band bound onthe silica.

"). Carefully fill the pipet column with 9:" hexane6acetone. >dd solvent as needed during theprocedure.

". Collect the fractions during the elution process.Note:To slow down the flow rate,remove the air pressure.

a. Collect the clear portion in the waste flask.

b. Collect the ferrocene in a clean test tube.

c. >fter all the ferrocene has passed through the pipet column, continue adding9:" hexane6acetone.

d. Collect the acetylferrocene fraction in a clean test tube.

e. 2nce the acetylferrocene fraction has been collected, collect the remaining solvent in thewaste flask.

". 7repare a *DC hot water bath in a


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Part III Test the Meltin" Te!#eratre of Ferrocene and Acetylferrocene&

8*. 2btain a small amount of ferrocene from 7art !!. The solid should be in a powdered form.!f it is not, use a mortar and pestle to carefully grind the solid to a powder.

8". 7repare a sample for melting.

a. 7ack a capillary tube 3E< mm (H"6 inch deep with your sample by inserting the open endinto a small pile of the solid. > small amount of the solid will be pushed up into the tube.

b. Tap the closed end of the capillary tube on the table top to compress the sample into theclosed end.

c. Check the control knob on the 'elt tation to confirm that it is in the 2ff position.

d. Carefully insert the capillary tube of solid into one of the sample holders of the 'elttation.

88. Connect the 'elt tation power supply to a powered electrical outlet.

83. Connect the 'elt tation sensor cable to +ab=uest or to a computer interface.

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c. Carefully observe the temperature !s. time graph. @hen the temperature is withinapproximately "*JC of the lowest possible melting temperature of your sample, turn thecontrol knob to a temperature setting corresponding to your expected melting temperature.

d. Carefully observe your sample. @hen the solid begins to melt, click 'ark to mark thetemperature on your graph. @hen the entire solid has completely melted, click 'ark again.The two values marked on your graph describe the estimated melting temperature range of

your substance. @hen you are finished with this step, stop data collection.e. tore the run.

f. 4iscard the capillary tube and sample as directed by your instructor.

g. 2n the 'elt tation, turn the control knob to the Fan6Cooling setting to get ready for thenext trial.

8. Aepeat tep 8 until you have determined the melting temperature range of the solid.Aecord the range in the data table.

8. 7repare an acetylferrocene sample for analysis according to teps 8*E8".

89. Aepeat tep 8)E8 for the acetylferrocene sample.

3*. >t the end of the experiment, turn the control knob on the 'elt tation to 2ff.

$ATA TABLE

Part I Synthesis of Acetylferrocene

Mass of ferrocene (g)

Mass of acetic anhydride (g)

Mass of filter paper (g)

Mass of filter paper and product (g)

Mass of product (g)

Part III Meltin" Te!#eratre

Measure melting temperature

range (C)

!solated ferrocene

!solated acetylferrocene

$ATA A'AL(SIS

". @hat is the theoretical yield of acetylferrocene in your synthesis if the reaction went tocompletionL @hat is the actual yieldL


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I'STR%CTOR I'FORMATIO'

". This experiment can be divided into two days. The synthesis and chromatography arecompleted on the first day. The melting temperature analysis is completed on the second day.

8. >ssemble the drying tube by placing a small piece of glass wool or cotton near the tip, fill with

4rierite

5

, and cover with a second piece of glass wool or cotton.

3. 7repare cold distilled water by placing wash bottles with distilled water in an ice water bath.

cetic anhydride: trongly irritating and corrosive. 'oderate fire risk (flash point



odium bicarbonate: 'ay be harmful by ingestion or inhalation. 'ay cause eye and skin irritation.1'! Classification: 1ealth ha%ard", Flammability*, 7hysical ha%ard*.

1exanes: erious fire ha%ard (flash point 83DC. evere eye and skin irritant. 'oderately toxicby ingestion. ?apor causes weakness, fatigue, nausea and headache. 1'! Classification: 1ealthha%ard8, Flammability3, 7hysical ha%ard*.

>cetone: Fire ha%ard (flash point ".*DC. tore in dedicated flammables cabinet. 'oderatelytoxic by inhalation or ingestion. 'oderately toxic by ingestion. ?apor causes weakness, fatigue,nausea and headache. kin and eye irritant. 1'! Classification: 1ealth ha%ard8,Flammability3, 7hysical ha%ard*.

4iethyl ether: erious fire ha%ard (flash point


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Compound Chemical formula.oiling temperature

range (C)Molar mass

(g'mol)/ensity

(g'm0) at $1C

he2ane(mi2ture ofisomers)

CH"4 &*"& *#$

acetone C3HO 1 1&*& *#"

diethyl ether C4H"O 34* #4*"" *#

acetic anhydride C4HO3 "3&"4 "$* "*&

phosphoric acid(&1)

H3PO4in H$O "1& &* "*&1

SAMPLE RES%LTS

"elting temperature graph of acetylferrocene



"elting temperature graph of ferrocene

14-friedel crafts acylation ferrocene

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