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Experiment 6

Experiment 6: Study of Two Nucleophilic Reactions Lab Report Form Part A: Formation of an Ether by an SN2 Reaction Mass of NaOH

0.55g

Mass of 2-Naphthol

1.05g

Volume of Ethanol

20mL

Volume of 1-Iodobutane

1.66g

Volume of Ice-Cold Water

50mL

Mass of Ice

27.78g

Mass of Product

0.26g

Melting point range of Product

24.1 - 32.1℃

Percent Yield of Product: 2-naphthol " Milimol of 2-naphthol " 1050 Mass = 1.05g = 1050mg" Molecular Weight = 144.17 g/mL = 144.17 mmol" = 7.283mmol Product " Mass = 0.26g = 260mg" Molecular weight = 200.26 g/mL

Milimol of product " =

260 mmol" 200.28

= 1.298mmol

Pr od uct (m m ol ) x 100%" 2 − n a ph th ol(m m ol ) 1.298m m ol = x 100%" 7.283m m ol

% Yield =

= 0.1782 x 100%" = 17.82%

Part B: Synthesis of 2,5-dichloro-2,5-dimethylhexane by an SN1 Reaction Part I: Synthesis of 2,5-dichlroo-2,5-dimethylhexane Mass of 2,5-dimethyl-2,5-hexanediol

0.26g

Mass of 2M HCl

2mL

Part II: TLC of 2,5-dichlroo-2,5-dimethylhexane

Experiment 6 TLC Plate:

Part III: Solubility Tests

Compound/ solvent

Methanol

2,5-dimethyl-2,5hexanediol

- Clear and transparent " - Clear and transparent " - Solvent fully - Solvent beads @

2,5-dichloro-2,5dimethylhexane

Both " - Clear and transparent " - Solvents completely - Clear and transparent " - Clear and transparent " dissolved - Solvent beads @ - Solvent fully bottom of tube (not dissolved dissolved) dissolved

Hexanes

bottom of tube (not dissolved)

Ethyl Acetate

Experiment 6 Discussion In this experiment the SN1 and SN2 reaction mechanisms were performed in order to produce different products which yielded from different reaction rates. The first part was the SN2 reaction, 2-naphthol was synthesized with NaOH and ethanol to create 1-iodobutane and water via reflux. The mixture was then distillates into a 25mL flask to extract 1-iodobutane, the percent yield was found to be 17.82%. In part two the SN1 reaction was performed, thus, synthesizing 2,5-dichloro-2,5-dimethylhexane. 2,5dimethyl-2,5-hexandiol and HCl were mixed together in a 25 mL flask, via vacuum filtration, washing and air drying, the melting point was found to be 24.1 - 32.1℃. A second test of TLC plate was performed with 95:5 hexane:ethyl acetate. It is seen that the starting material (SM) remained as a dot at the orgin line and the product did travel. Thus, due to the polar interactions between the two compounds and the hexane:ethyl acetate. The last test performed was solubility, both compounds were mixed into test tubes containing methanol, hexane, and ethyl acetate. 2,5-dimethyl-2,5-hexanediol dissolved fully int he methanol and ethyl acetate test tubes and 1,5-dichloro-2,5-dimethylhexane were soluble in hexane and ethyl acetate. These two compounds only dissolved in the compounds of like-polarity. Questions: 1. Explain each step in the synthesis and the purification process of the products for both types of SN reactions. SN1 reaction with 2,5-dichloro-2,5-dimethylhexane is a unimolecular nucleophilic substitution. It follows the pathway or carbocation formation and is followed by the attack of a nucleophile. Step 1 - attack of acid

OH

+OH₂ + HCl

OH

:OH

Step 2 - Neighboring group participation and cyclization - this step can be avoided, thus the direct attack of Hal would form the products. However, neighbouring group participation enhances the leaving group tendency o the OH group which facilitate the reaction.

+OH₂

H2 O +OH

:OH

Step 3 - Attack of anion to form the product.

OH +OH

HCl

Cl

+ ClCl

Cl

Experiment 6

SN2 bimolecular nucleophilic substitution yield the formation of an ether. The reaction proceeds by simultaneous attack by an incoming nucleophile and the emit of leaving group. The formation of intermediate takes place. O CH3

H

H2 O

ONa+

NaO:H

CH3

Step 2 - Attack of alkyl halide O-

O Na+

CH3

CH3

Cl

CH3

CH3

Ether

2. Give a detailed reaction mechanism for each chemical reaction in this experiment.

Experiment 6 3. Draw and label a reaction coordinate diagram for both types of SN reactions specific for the reactions of this experiment. You must label the starting structures of the initial state, the intermediates, the transition states and the final products as well as the activation energy and proper titles for the graphs and axes.

Experiment 6 4. Why is the product of part B soluble in hexanes but not the starting material 2,5dimethyl-2,,5-hexanediol? Explain. In part B, the two compounds 2,5-dimethyl-2,5-hexanediol (polar) and 2,5-dichrolo-2,5-dimethylhexane (non-polar) were used as solutes in three different solvents, methanol, hexane and ethyl acetate. Hexane is a non polar compound. Because polar compounds are soluble in polar solvents and non polar compounds are soluble in non-polar solvents (like dissolved like), hexane being non-polar only dissolved the polar compound (2,5-dimethyl-2,5-hexanediol).

Experiment 6 References Esteb, J. J., Magers, J. R., McNulty, L., Morgan, P., & Wilson, A.M. (2009). A Simple SN2 reaction for the Undergraduate Organic Laboratory. Journal of Chemical Eduction, 86(7), 850-852. Wanger, C. E., & Marshall, P. A. (2010). Synthesis of 2,5-DDichloro-2,5-dimethylhexane by an SN1 reaction. Journal of Chemical Education, 87(1), 81-83...