Acetylation+of+Ferrocene

= = Acetylation of Ferrocene

=Introduction:= The purpose of the lab was to perform an electrophilic aromatic substitution of ferrocene. Acetic acid is used along with phosphoric acid as the catalyst to produce monoacetylferrocene. The reagent and catalyst used produce less hazardous byproducts and are considered a much safer greener approach to the traditional method which involves strong Lewis acids and acetyl-halides. The product is two cyclopentene rings joined by and iron atom in the idle and an acetyl group bound to a carbon on one of the cyclopentene rings. The reagents and products are shown below.



= Procedure: = Procedure and link provided by Professor Carol Higginbotham Central Oregon Community College, Organic Chemistry II CH 242/335 []

I. Place a heating stir plate on a lab jack and fill a dish with water then place on top. Put a stand behind the apparatus and attach two clamps. Clamp a reflux condenser to the top clamp and a 20ml round bottom flask to the lower clamp. II. Weigh out 1.5g of ferrocene and place it into the flask along with a magnetic stir bar. When the water bath is nearly to the boiling point lower the round bottom flask into the water bath and add 5.0ml of acetic anhydride. III. Then add 1.0 ml of 85% phosphoric acid to the flask. The mixture will darken in color as it is heated. Swirl the flask until the ferronce is completely dissolved. IV. Lower the reflux condenser into the neck of the round bottom flask and attach the water supply to the lower port on the water jacket and then attach a drain hose to the upper water jacket port. V. Heat the mixture for 10 min and note any changes in color and condensation characteristics during the process. VI. In a 200 ml beaker add 25 g of ice and pour the reaction mixture over the ice. Rinse the flask with 5ml portions of ice water. There will be iron colored deposits left behind in the 20 ml round bottom however try to rinse as much of the mixture onto the ice bath as possible. Stir the mixture in the ice bath with a glass stirring rod for a few minutes. VII. Placing the beaker onto a stir plate without heat begin the magnetic stir bar and add 37.5 ml of 3M aqueous NaOH. Slowly add sodium bicarbonate to neutralize the acid in solution. Less than 8 grams will be required. IIX.Place the solution aside for 20 min allowing the mixture to separate into the four distinct layers as shown in picture below. IX. Assemble a vacuum filtration device and after 20 min has passed collect the crude product. Continue the vacuum filtration for several min to allow for the product to dry. Place two sheets of filter paper on the bench and empty the product onto one of them. Then place the other filter paper on top and press the remaining moisture out of the product. X. Place a small sample of the product aside for TLC testing later on. XI. Place the solid into a small Erlenmeyer flask along with the stir bar and add 20 ml of hexanes. Do Not Heat the mixture at this point or the hexanes will boil off and leave a black sludge at the bottom of your flask and really mess everything up from there on out. Allow while stirring the hexanes to evaporate off for 5-10 min. XII. Decant the dark orange solution into another Erlenmeyer flask leaving behind the black solids on the bottom of the flask. Gently warm the solution and add a small amount of decolorizing carbon to the flask and stir gently with glass stirring rod. XIII.Remove from heat and allow cooling slowly. Red brown crystals will begin to form in the solution. When the solution has reached room temperature then place in ice bath and then empty the solution into vacuum filtration device to collect the crystals. Wash the flask with small amounts of cooled hexanes. Allow to dry in the vacuum filtration device for several minutes.

Apparatus set up for the hot bath and mixture of ferrocene, acetic anhydride and 85% phosphoric acid

= =

__Step__ six of the procedure the mixture setting for 20 minutes. Before filtration where the crude product is collected by vacuum filtration. = = = =  The photos are a nice addition. I think that, since they document what you observed during the lab, they are best put in the "Data" section. = Data: = Ferrocene = 1.513g 38ml NaOH 8.008g Sodium Bicarb 25.442g ice 5.0 ml acetic anhydride 1.0ml 85% phosphoric acid 20ml hexanes

Weigh the final product for yield. Ferrocene 186.04g/mol Acetylferrocene 228.07g/mol Final yield= 0.075g acetylferrocene (0.075 g acetylferrocene) X (1mol acetylferrocene / 228.07 g acetylferrocene) = 0.00033mol 1.513g Ferrocene X (1mol/186.04g Ferroncene) X (1mol Ferroncene/1mol acetylferrocene) X (228.07g acetylferrocene/1mol acetylferrocene) = 1.855g theoretical yield. (0.075g final product/1.855g theoretical yield) X 100% = 4.0% recovery L Yikes! A low yield. That's a shame. Did you weigh your crude product? Did you never get many crystals, or did you lose them along the way, somewhere? Melting point data: Sweat at 74.4°C Melting at 79.2°C Finished at 80.3°C = =

The TLC results shown below

 * C**-Crude product
 * F**-Ferrocene
 * P**-Recrystallized Recovered Product

= Analysis/Discussion = According to the theoretical percentage yield recovered which is 4.0% recovery there is significant error involved. Further analyzing of the collected product the melting point range 74.4°C-80.3°C which is a good indicator that the recovered product is significantly pure according to the literature melting points provided in the procedure 82-83°C and 84-85°C. **TLC**-results show the Ferrocene took a straight shot up faster than the other two products, the Crude products shot up but didn't go as far as the ferrocene. Traces of a small amount of yellow which can be identified as ferrocene was identifed in the Crude material. The collected finish product appeared to have a darker orange color and when up little further than the crude product it appeared to have no other materials in its path therefore can safe say it was a pure product collected. Yes. The TLC tells a story here....the crude product contains a lot of ferrocene, which indicates your reaction didn't go to completion. This could be due to too little time heating, or having your hot water bath too cool, or other factors. Then when you purified you probably lost a lot of your material, since that ferrocene got separated out from the acetylferrocene. = = = Conclusion: = The purpose of this laboratory experiment was to conduct a greener approach at Friedal-Crafts actylation reaction which was a electrophillic aromatic substitution that allows for a reaction of acyl chlorides. This procedure appeared to be very informative for students allowing them to experiment with less vigorous acylations that tend to afford mixtures of mono- and diacylated products. Usually boiling off the hexanes just leaves some burnt up crud, wtih no solvent, and can also cause some deterioration of your product (extreme heat damages the product).
 * The lack of pure product could have resulted from the beginning of the experiment when dissolving the Ferrocene in the 20 mL round-bottom flask. The 1.0 mL of 85% phosphoric acid was added to the 5.0 mL of acetic anhydration minutes before the hot water bath was boiling therefore the ferrocene was not dissolved completely.
 * During the filtaration process a lot of the crude product and pure product was washed through the filter paper.
 * During the work up the addition of the 20 mL of hexanes and boiled for 5 minutes, the procedure says to boil a full 5 minutes, during lab the instructor mentioned not to boil the full five. This group did not here the procedure and ended up boiling off asl the hexanes and possibly all its products. This could be the reason for such a low yield of crystals collected.

= Post-lab Questions: = 1. Describe the physical properties (color and state) of the crude product: The crude product was in a solid form the color was a bright orange the picture above in the medium beaker is a good reference to the collect crude product after filtration of course.

2.The finished recovered recrystallized product was a small amount due to errors in procedure but appeared as a dark orange-reddish color, the collected mass 0.075g acetylferrocene and percentage of theoretical yield 4.0%

=Reference:=

K.M. Doxsee and J.E Hutchison, Thompson Brooks/Cole. Green Organic Chemistry- Strategies, Tools, and laboratory Experiments. Experiment #18 The Friedel-Crafts Reaction: Acetylation of Ferrocene, 2004; pp 228-230