OCHEM 2, Postlab 2, Conversion of Carvone to Carvacrol PDF

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This is the postlab with the prelab report for the lab of The Conversion of Carvone to Carvacrol. Includes all the information....

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Snehal Kancharlawar Xena Mansoura Chem 2212L 2/10/2022 Conversion of Carvone to Carvacrol Introduction: The purpose of this lab is to perform an acid-catalyzed isomerization of (R)-carvone to carvacrol. The techniques used in this experiment are reflux, liquid/liquid extraction, suction filtration, and IR spectroscopy. Reflux is a technique where a solution is heated without the loss of the solvent. In reflux the solvent evaporates, then recondenses due to the condenser, and finally falls back into the solution. Liquid/liquid extraction is used to separate a mixture and remove it from one solvent to another in order to isolate it. Suction filtration is used to separate a solid and liquid mixture in order to obtain the solid and involves the use of suction. IR Spectroscopy is used to identify functional groups in a compound by measuring the interaction of infrared radiation with matter. A real world example is the isomerization of straight-chain hydrocarbons into branched-chain isomers for use in gasoline manufacturing. Balanced Equation:

Reaction Mechanism:

Table of Reagents:

Structure

MW

BP

MP

Density

Safety Information

(R)-(-)carvone

150.22 g/mol

25.2°C

0.959

Combustible

g/mL at

liquid,

25 °C

hazardous gas, can cause allergic reactions on skin.

Carvacrol

150.22 g/mol

236.8°C

1.0 °C

0.976

Harmful if

g/mL at

swallowed

20 °C

and can cause skin irritation.

Sulfuric acid

Diethyl ether

98.079 g/mol

74.12 g/mol

337°C

34.6°C

1.840

Can cause eye

g/mL at

and skin

25 °C

burns.

0.706

Flammable

g/mL at

liquid and

25 °C

vapor, vapor can cause dizziness.

Sodium bicarbonate

84.007 g/mol

300 °C

1.1g/mL

Can cause eye

at 25 °C

and skin irritation.

Sodium

142.04 g/mol

884°C

sulfate

Water

18.02 g/mol

100 °C

2.68

Can cause eye

g/mL at

and skin

25 °C

irritation.

1.0 g/mL

Brine

76.46

20 °C

1.202

Can cause eye

g/ml at

and skin

25 °C

irritation.

Procedure: ● 2.0 g of R-(-)carvone was added to a 100 mL round bottom flask containing a magnetic stir bar. ● 25 mL of 6M H 2SO4 was added to the flask. ● The solution was refluxed for 45 minutes. ● The heat was removed and the solution was allowed to stir for 10 minutes. ● The solution was placed in the ice bath for 10 minutes. ● The solution was extracted twice with 25 mL portions of diethyl ether. ● The solution was washed with 15 mL of water and then 15 mL of saturated NaHCO 3 solution. ● The organic layer was washed with 15 mL of brine. ● The solution was dried with sodium sulfate. ● Vacuum filtration was done, the filtrate was transferred to a 24/40 round bottom flask and rotovapped, then the mass, IR and HNMR was recorded. Data and Observations: Starting weight of (R)-(-)carvone: 2.017g Starting volume of 6M sulfuric acid: 25.0 mL Reflux time: 45 min Volume of diethyl ether extractions: 50.0 mL Volume of water washes: 15.0 mL

Volume of saturated sodium bicarbonate washes: 15.0 mL Volume of brine wash: 14.0 mL Weight of the recovered product: 1.642g Observations: The reaction mixture in the beginning was a pale yellow color. After the mixture was put through the rotovap it turned into a viscous, orange liquid. Results: Limiting Reagent: 25.0 mL H 2SO4 x (1.84g/1 mL) x (1 mol H2SO4/98.079g) x (1 mol Carvacrol/1 mol H2SO4) x ( 150.22 g/1 mol Carvacrol)= 70.5g Carvacrol 2.017g Carvone x (1 mol Carvone/ 150.22g) x ( 1 mol Carvacrol/ 1 mol Carvone) x (150.22g/ 1 mol Carvacrol) = 2.017g Carvacrol Carvone is the Limiting Reagent. Percent Yield: (1.642g/2.017g) x 100 = 81.41%

Discussion and Conclusion:

Graph 1. IR spectrum of product Carvacrol

3372.18 cm-1

O-H stretch, Alcohol

2959.53 cm-1

C-H stretch, sp3 Carbon

Table 1. IR peaks in IR spectrum of Carvacrol

Graph 2. IR spectrum of Carvone

~2990 cm-1

C-H stretch, sp3 Carbons

~1680 cm-1

C=O stretch

Table 2. IR peaks in the IR Spectrum of Carvone

Graph 3. HNMR of Carvacrol

In this lab the limiting reagent was carvone and the percent yield was 81%. This percent yield is very reasonable. In order to increase the percent yield we could have extracted the reaction mixture with diethyl ether more accurately, so that none of the aqueous portion fell into the organic portion when draining out the separatory funnel. Graph 1 and 2 show the IR spectra for the experimentally obtained carvacrol and for carvone, respectively. Graph 1 has peaks at 3372.18 cm-1 and 2959.53 cm-1 which represent an O-H stretch and C-H stretch, respectively. Graph 2 has peaks at 2990 cm-1 and 1680 cm-1, which represent a C-H stretch and a C=O stretch, respectively. The reaction can be deemed as successful since the IR spectrum for the product, carvacrol, shows the O-H stretch and doesn’t show the C=O stretch. The major difference in the two IR graphs is that the carvone graph shows the C=O and the carvacrol graph only shows the O-H stretch that represents the alcohol and not a C=O stretch. Graph 3 shows the HNMR for the product, carvacrol. There are four types of hydrogens in carvacrol. The multiplicity of each of the peaks is quartet, multiplet, singlet, and doublet. For peak number 4, there are 6 hydrogens and they are split by one other hydrogen. For peak number 3 there are 3 hydrogens and they are not split by any hydrogens. For peak number 2 there is one hydrogen and it is split by 6 hydrogens. For peak 1 there are actually three different kinds of hydrogens that are very similar in ppm and appear as only 1 peak. They are all split by one other hydrogen. The hydrogens on peak 4 are the most upfield and shielded, while the hydrogens on peak 3 are the second most shielded. Peak 1 is the most deshielded because it is the closest to the electronegative oxygen atom. Post-Lab Questions: 1. The driving force behind this reaction is the formation of an aromatic compound, the benzene ring, which is more stable than the initial reactant. Since the reaction product is unusually stable, the tautomerization favors enol over the keto form for an acid-catalyzed reaction.

2. 3. We could have substituted the enantiomer of R-carvone for the starting material since the final product is achiral, so the chirality of the starting material does not affect the final product. The product would have still been carvacrol.

4. These two compounds are enantiomers and the optical rotation for S-thalidomide would be -27°. 5. The neutralization reaction between sodium bicarbonate and the sulfuric acid caused the bubbling to form. The gas created was carbon dioxide....