dehydration of 2- methylcyclohexanol, Papers of Organic Chemistry

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Dehydration of Alcohol with Phosphoric Acid

Catalyzed Reaction into Alkenes.

Gilberto Sosa 09/28/

Acid Catalyzed Dehydration of 2-

methylcyclohexanol

INTRODUCTION

Acid-catalyzed reactions use strong mineral acids that increase kinetics (speed of reaction) but do not increase thermodynamic properties (amount of product) that is produced. Additionally, this acid is also regenerated during reaction and does not get consumed. This Beta Elimination reaction of a secondary alcohol with the strong acid produces an alkene that is more substituted due to carbocation stability trends. Given that protonation is needed for the better leaving group to be produced this confirms the E1 mechanism that relies soley on [reactant] concentration in rate law equation

Real World Applications

The product of this secondary alcohol methylcyclohexanol dehydrating is an alkene following the E1 mechanism. Alkenes are very important and mostpresent molecule in manufacturing. The applications of alkene have ranged from fruit ripening molecule ethylene, ethane diol anti-freeze, and lastly, plastic Overall Reaction

Structures of Organic Molecules Reactant Major Products Minor Products PROCEDURE DATA TABLE 1: PHYSICAL PROPERTIES OF COMPOUNDS Compound Formula Molar Mass g/mol Boiling Point (°C) Melting Point (°C) Refractive Index, nD^20 Density g/mL Mass/Vol/Conc. Used in expt. Reactant C 7 H 14 O(2- methylcyclohexanol) 114.19 165-166 -38.0 0.93 750 L or mcL

Solvent H3PO4(phosphoric acid) Major Product

C7H12(1-

methylcyclohexane)

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Minor Org. Product

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Minor Org. product

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Inorg. Prod. H 2 O

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Catalyst H3PO4(phosphoric acid)

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Other Reagent

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Other Reagent

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Special Equipment (include those used to characterize the product(s)) FIGURE 1: (LEFT) HICKMAN STILL FRACTIONAL DISTILLATION SET UP (CENTER) MICROPIPETTE (RIGHT) MICROPIPETTE DISPOSABLE TIPS

CALCULATIONS/RESULTS: Attention: For these calculations assume, hypothetically, 100% conversion to only the major organic product and NO minor products were produced. Theoretical Yield. Show your calculations. If you produced 0.190g of your final product, what is the %Yield? Show your calculations. Note on Refractive Index (RI) Small amounts of impurities can cause significant changes in the refractive index of a substance. Anything within ± 0. of the literature value is acceptable. One possible source of error is miscalibration of the refractometer. This is checked using deionized water and zeroing out the refractometer. Look up the nD^20 of water: __________________ CONCLUSION/POST-LAB QUESTIONS Answer the following questions.

1. What are the major and, if applicable, minor products – Label them as such - of the dehydration of each of the following compounds? a. 4-methylcyclohexanol b. 2-methyl-3-hexanol c. 3-methylcyclohexanol d. 1-pentanol e. 2,3-dimethyl-2,3-butanediol (Hint: Pinacole rearrangements involve a methyl migration)
2. List the function or role of each of the compounds used in this experiment. All of those same compounds that should be listed in your DATA TABLE 1 in the main body of the Lab Report. Compound Function or Purpose Reactant Solvent ??? (^) Catalyst Other Reagent Other Reagent Other Reagent Other Reagent

3. (a) What is the difference between a simple Distillation and a fractional distillation. (b) Why did we use a fractional distillation technique in this lab instead of a simple distillation?
4. Referring to IR spectra in Figures A and B, label each according to whether it is the Reactant or a product. You don’t have to specify which of the three possible products. Explain how you arrived at your conclusion by pointing to a specific peak or peaks in the spectra. FIGURE (A): SPECTRUM FIGURE (B): SPECTRUM

A = B=

7. Refer to the images in Figures 7. Assume that these were your results. Explain what these mean. Is the test positive or negative for your expected product(s)? How do you know? FIGURE 7: POTASSIUM PERMANGANATE TEST (LEFT) KMnO 4 solution + reactant (RIGHT) KMnO 4 + Products TABLE 4: POTASSIUM PERMANGANATE TEST RESULTS Test tube containing Appearance before addition of KMnO 4 Appearance after addition of KMnO 4 Reactant Clear and colorless Products Clear and colorless

FIGURE 10: EXPLANATION OF THE PERMANGANATE TEST