Lab Report 2

docx

School

Northeastern University *

*We aren’t endorsed by this school

Course

2312

Subject

Chemistry

Date

Jan 9, 2024

Type

docx

Pages

Uploaded by ElderSnow12035

Experiment #2 Oxidation of Cyclohexanol Date Preformed—October 4, 2023 Date Due—October 11, 2023 Experimental Objective

By performing this experiment, we took knowledge from our classroom learning of interpreting infrared spectrum graphs and applied that knowledge to a real-world experiment to determine if the reaction had properly occurred and if our product was pure. We will use simple distillation which we learnt in organic chemistry I labs, the rotary evaporator, and FTIR. By using sodium dichromate, we were able to oxidize cyclohexanol, a 2° alcohol, to cyclohexanone, a ketone. Reagents Used Cyclohexanol Cyclohexanone Sodium Dichromate Sulfuric Acid MW: 100.158 g/mol MW: 98.14 g/mol MW: 261.97 g/mol MW: 98.08 g/mol Density: 0.96 g/mL Density: 0.95 g/mL b.p: 160.8 °C b.p: 155.4 °C Reaction Scheme Figure 1 . Oxidation of cyclohexanol to cyclohexanone from Pre-lab Balanced equation: 7C 6 H 12 O + Na 2 Cr 2 O 7 → 7C 6 H 10 O + 7H 2 O Procedure A hot plate was set to heat, and both a sand bath and steam bath were placed onto the hot plate. Sodium dichromate (1.5 g) and 2M sulfuric acid (7 mL) were collected. The sulfuric acid was poured into a beaker (50 mL) and then the sodium dichromate was added and mixed until dissolved. Cyclohexanol (0.75 g) was collected in an Erlenmeyer flask (50 mL) and the sodium dichromate solution was then added to the Erlenmeyer flask and a thermometer was placed in the flask. The mixture was then swirled over the steam bath to maintain a temperature of 55-60°C for 15-20 minutes. While the reaction was taking place a simple distillation apparatus was set up. Once the reaction time had passed, the Erlenmeyer flask solution was transferred to a round bottom flask (10 mL) and placed into the sand bath. The distillate was collected from the Hickman stillhead using a Pasteur pipette and placed into a test tube and was extracted until about 2.5 mL of solution was in the test tube. Two layers were formed in the test tube and sodium chloride (0.3 g) was added to the distillate. The solution was stirred until the sodium chloride completely dissolved. The top, organic, layer was removed using a Pasteur pipette and placed into a centrifuge tube. T-butyl methyl ether (0.5 mL) was added to the remaining distillate, this was done twice. Each time the top layer was removed via Pasteur pipette and placed into the same centrifuge tube. Saturated sodium chloride (1 mL) was then added to the centrifuge tube and mixed gently. The top, organic, layer of the centrifuge tube was removed using a

Pasteur pipette and placed into a beaker (20 mL). This layer contained ether and cyclohexanone. Calcium chloride pellets were added to the beaker to dry the ether/cyclohexanone mixture. The mass of an empty conical vial (3 mL) was recorded, and the dried ether/cyclohexanone mixture was then added to the vial. The calcium chloride pellets remained in the beaker and were washed with t-butyl methyl ether (0.5 mL). The t-butyl methyl ether from the beaker was then added to the conical vial containing the ether/cyclohexanone mixture. The conical vial was then taken to the rotary evaporator and the t-butyl methyl ether was evaporated from the vial while the cyclohexanone remained in the vial. The mass of the conical vial was recorded again, and this was the mass of the product. The product was then taken to the FTIR station to obtain an infrared spectrum of the product to determine if the reaction had occurred properly. Results I. Theoretical yield Limiting reagent: Cyclohexanol 0.768 g cyclohexanol ( 1 mol cyclohexanol 100.158 gcyclohexanol )( 1 mol cyclohexanone 1 molcyclohexanol )( 98.14 gcyclohexanone 1 mol cyclohexanone ) = 0.753 g cyclohexanone II. Observations The sodium dichromate solution was an orange color and when the cyclohexanol was added the new solution changed to a dark green color and consistently was like that of olive oil and balsamic vinegar. When the solution was heated it remained the same dark green color, but the consistency of the liquid was uniform throughout and had more of an olive oil consistency. Once the solution was distilled the liquid was clear with a water like consistency. When the solution was put into the test tube the organic layer was white while the aqueous layer was a light-yellow color. When sodium chloride was added to the test tube the color became clear and the layers were separated by a small line which looked like the meniscus. Throughout the rest of the experiment the color remained clear with a water like consistency. III. Characterization Percent yield : 0.400 gcyclohexanone 0.753 gcyclohexanone × 100% = 53.1% Physical Description of Final Product : The final product was a clear liquid with a water like consistency. Results and Analysis : FTIR; There is a large peak at ~1700 cm -1 which indicates a carbonyl group was present and therefore it is likely cyclohexanol was oxidized to cyclohexanone.

Your preview ends here

Eager to read complete document? Join bartleby learn and gain access to the full version

Access to all documents
Unlimited textbook solutions
24/7 expert homework help

Figure 2. FTIR of final product from the experiment Conclusion The results of the FTIR are expected to be cyclohexanone because of the peak around 1700 cm -1 which represents a carbonyl group. In this case the carbonyl peak represented the formation of a ketone in the form of cyclohexanone. There is a small surge around 3500 which could indicate a small amount of cyclohexanol. This could have been caused by some aqueous layer being extracted during the extraction process. During the experiment, there was an excess of solution prior to the rotary evaporator, this would not have been likely to cause a negative effect on the experiment. Cyclohexanone was obtained in a 53.1% yield which indicates the product was not impure because the percent yield was not over 100%. The oxidation of cyclohexanol to cyclohexanone was successful. References National Center for Biotechnology Information (2023). PubChem Compound Summary for CID 7967, Cyclohexanone. Retrieved October 6, 2023 from https://pubchem.ncbi.nlm.nih.gov/compound/Cyclohexanone . National Center for Biotechnology Information (2023). PubChem Compound Summary for CID 7966, Cyclohexanol. Retrieved October 4, 2023 from https://pubchem.ncbi.nlm.nih.gov/compound/Cyclohexanol . National Center for Biotechnology Information (2023). PubChem Compound Summary for CID 1118, Sulfuric Acid. Retrieved October 6, 2023 from https://pubchem.ncbi.nlm.nih.gov/compound/Sulfuric- Acid . National Center for Biotechnology Information (2023). PubChem Compound Summary for CID 25408, Sodium Dichromate. Retrieved October 6, 2023 from https://pubchem.ncbi.nlm.nih.gov/compound/Sodium-Dichromate .