Experiment 6 Metal Acetylacetonate Complex PDF

Preview

Summary

Experiment #6 for the fall chem labs (metal acetylacetonate complex/the one with the crystals)....

Description

1 Experiment 4 Report

Experiment 4.

(2 weeks) (LSM) Metal Acetyl-acetonate Complex

Purpose The purpose of week one of this lab is to use inorganic synthesis techniques to form Tris(acetylacetonato) Iron (III). Week two’s purpose is to measure the melting point of the crystalized complex and calculate percent yield.

Introduction PART ONE Acetylacetone (2,4-pentanedione) contains two ketones that are separated by carbon, which can be deprotonated to give an acetylacetonate anion. 1 Acetylacetonate can form a 6-membered ring due to its ability to act as a ligand towards metal ions. 2 In this experiment, iron (III) is used as the metal ion and is coordinated with the acetylacetonate ion to produce an octahedral complex. PART TWO Inorganic synthesis techniques are used to purify the product of part one. The conditions are set so that equilibrium is reached between the solid and the dissolved form. As it cools, more crystals will form and the molecules should push out the impurities. 3

Procedure Synthesis of Fe(acac)3

1

PubChem. (2021). Iron(III)Acetylacetonate. @Pubchem; PubChem. https://pubchem.ncbi.nlm.nih.gov/compound/4651115#section=3D-Conformer 2 Lab Manual Metal acetylacetonate Complexes web. (2015). http://www.magritek.com/wp-content/uploads/2015/03/Lab-Manual-Metal-acetylacetonate-Complexes-web.pdf 3 Queen’s Chemistry - First Year Laboratory Manual. (2021). Department of Chemistry, Queen’s University.

2 Experiment 4 Report

1. Donned safety equipment (goggles, lab coat, etc.) and took necessary safety precautions (tied long hair up, put on properly fitting gloves, positioned snorkel over the workstation). 2. Two large ice water baths were prepared. 3. 1 g of 𝐹𝑒𝐶𝑙3 · 6𝐻2𝑂 was measured out and put into a 125mL Erlenmeyer flask. 15 mL of 4.

5.

6. 7.

8.

9.

RO water is added to the flask and mixture is combined using a magnetic stirrer. 2 mL of acetylacetone was added into a beaker, ensuring the liquid does not come in direct contact of skin, and it was added via a Pasteur pipette into the iron chloride solution. Approximately 2.5 g of sodium acetate was weighed and added to a 50mL beaker with 10mL of RO water. This mixture was added to the solution via a Pasteur pipette, maintaining rapid stirring. The solution was then heated at 70 degrees Celsius for 10 minutes, maintaining rapid stirring. The mixture was then cooled on the bench for approximately 10 minutes and then cooled further in one of the prepared ice baths for another 10 minutes while the vacuum filtration unit was set up (ensuring the filter paper and watch glass are weighed and recorded). The product was filtered and washed four times with 15 mL of cold RO water. This was then let air dry for approximately 5 minutes, occasionally using a stir rod to break up clumps. The dried product was then weighed and the mass is recorded.

Recrystallization of Fe(acac)3 1. Donned safety equipment (goggles, lab coat, etc.) and took necessary safety precautions (tied long hair up, put on properly fitting gloves, positioned snorkel over the workstation). 2. Two hot baths (one 600mL and one 150mL) were prepared and headed to just above 70 degrees Celsius. 3. 0.3 g of the product of the previous week was transferred into a 50mL beaker and put into the 150mL hot bath. 4. 10mL of methanol was dispensed into a 150mL beaker and then put into the 600mL hot bath for 1 to 2 minutes. 5. 1 to 3 mL of the hot methanol was added to the previous week’s product via a Pasteur pipette. The mixture was left in the hot bath to evaporate some of the methanol. Once small crystals could be seen on the bottom of the beaker, it was immediately removed and placed on the bench to cool. 6. An ice water bath was then prepared and was used to further cool the mixture for approximately 10 minutes. 7. 5mL of methanol was dispensed into a 50mL beaker and put into the ice bath.

3 Experiment 4 Report

8. The product was then filtered for 5 minutes using the vacuum filtration system (larger crystals were broken up with a stirring rod) and the chilled methanol was used to wash it down. 9. A watch glass was weighed and the dried product was transferred onto it and weighed. The mass was recorded. 10. A small amount of the recrystallized product and the crude product were put into a Mel-temp apparatus and the melting point was found and recorded. Observations

PART ONE -

-

-

𝐹𝑒𝐶𝑙3 - yellow crystal - highly soluble in water Sodium acetate - opaque white crystal powder - highly soluble in water - translucent when mixed with water acetylacetone - blueish and translucent when acetylacetone was added to the 𝐹𝑒𝐶𝑙3 · 6𝐻2𝑂, solution turned dark red and opaque when sodium acetate mixture was added, solution turned bright red and began to separate.

PART TWO -

crude product is a bright red colour - when mixed with the methanol, became a deep red colour less than a minute after adding the methanol and swirling the mixture, crystals began to form on the sides when left on the bench to cool, solution turned dark red and slightly yellow on the sides crystals began to form from the center, creating a thin and clumpy layer after filtering the substance, some material ended up in the filtrate (possible source of error)

DATA SHEET Crude Fe(acac)3

4 Experiment 4 Report

Experimental Observations: [These should be written directly into your lab notebook.] Mass of FeCl3∙6H2O /g Mass of watch glass /g Mass of watch glass and crude product /g (before recrystallization) Recrystallized Fe(acac)3 Mass of watch glass /g Mass of watch glass and pure product /g (after recrystallization)

1.02g 39.42g 40.73

30.060g 30.336g

5 Experiment 4 Report

Calculations

6 Experiment 4 Report

Questions From Part I 1. What is the limiting reagent? 𝐹𝑒𝐶𝑙 · 6𝐻 𝑂 3

2

2. What is the percent yield of the crude product? 103.5% 3. Give three reasons why you did not get 100% yield. -

-

Due to a problem with the temperature probe, the mixture was allowed to get too hot and even boiled for a moment while heating it, which may have contributed to the discrepancy between the actual yield and theoretical yield. There may have been some error in measuring the substances. Impurities (like dust) may have added to the final weight.

From Part II 4. What is the percent yield of the pure product? 92% 5. Compare your crude vs. pure product yield. List three reasons why they may be different/same. -

The processes for the crude product vs the recrystallized product were different (one had a chemical reaction, one didn’t), which may have contributed to the discrepancy. - Some material ended up in the filtrate, which may have contributed to the lower percent yield. - Another source of discrepancy could have also been any product left when transferring the paper. 6. What can you say about the difference, if any, between the crude and the recrystallized product in your observed melting point data? Recrystallization brings the substance closer to the pure product, therefore the melting point will be closer to the known value. The crude product was recorded to have melted at a lower temperature than the recrystallized product. The known melting point for Fe(acac)3 is between 180 and 182 °C4, and the melting point we recorded for the recrystallized product was 181.4 °C.

4

American Elements. (2016, August 22). Iron(III) Acetylacetonate | AMERICAN ELEMENTS ®. American Elements. https://www.americanelements.com/iron-iii-acetylacetonate-14024-18-1

7 Experiment 4 Report

References 1. PubChem. (2021). Iron(III)Acetylacetonate. @Pubchem; PubChem. https://pubchem.ncbi.nlm.nih.gov/compound/4651115#section=3D-Conformer 2. Lab Manual Metal acetylacetonate Complexes web. (2015). http://www.magritek.com/wp-content/uploads/2015/03/Lab-Manual-Metal-acetylacetonat e-Complexes-web.pdf 3. Queen’s Chemistry - First Year Laboratory Manual. (2021). Department of Chemistry, Queen’s University. 4. American Elements. (2016, August 22). Iron(III) Acetylacetonate | AMERICAN ELEMENTS ®. American Elements. https://www.americanelements.com/iron-iii-acetylacetonate-14024-18-1...