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Aaron DyneCHEM204 Exp. 1

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Aaron DyneCHEM204 Exp. 1

Friedel-Crafts alkylation of p-dimethoxybenzene

Method

p-dimethoxybenzene (213.2mg) was combined with 0.40mL of t-butanol and 0.6mL of glacial acetic acid and cooled. 0.8mL of cooled sulfuric acid was then slowly added dropwise with stirring over the ice bath. Precipitation was observed and the solution was brought to room temperature with occasional stirring. The solution was diluted with a small amount of ice to absorb excess heat, then filled with deionised water until container was approximately two-thirds full. Resultant off-white solid was collected via vacuum suction and washed with deionised water. Solid was recrystalised with boiling methanol and recollected upon cooling via vacuum suction. Final product was then dried via vacuum suction for additional 10 minutes before final collection. Final product was a white crystalline mass (197.3mg), melting range was measured (90.3-92.4C) and IR spectrum was obtained.

Yield Calculation

Note: product obtained is 2,5-di(t-butyl)-1,4-dimethoxybenzene

MW (p-dimethoxybenzene) = 138.17g/mol

MW (product) = 250.38g/mol

m (p-dimethoxybenzene) = 213.2mg

n (p-dimethoxybenzene) = 0.2132g / 138.17g/mol = 0.001543 mol

Stoichiometry: 1 mol p-dimethoxybenzene (limiting reagent): 1 mol product

n (product, theoretical) = n(p-dimethoxybenzene) = 0.001543 mol

m (product, theoretical) = 0.001543 mol * 250.38g/mol = 0.3863g

m (product, obtained) = 0.1973g

% yield = (0.1973g / 0.3863g) * 100% = 51.1%

Characterisation

IR:

p-dimethoxybenzene

The sharp peak at 825cm-1 confirms the p-substitution of the aromatic ring, due to the C-H out-of-plane stretching. Some weak absorption just below the 3000cm-1 due to the sp3 C-H bonds [1].

2,5-di(t-butyl)-1,4-dimethoxybenzene

Although there appears to be some interference in this reading, can still make out the characteristic sp3 C-H stretching in the region just below 3000cm-1. This activity is stronger in the product than the initial reactant, indicated the presence of more alkyl bonds in the product. The additional sharp peaks at 766cm-1, 851cm-1 and 877cm-1 are also indicative of the additional substitutions made on the aromatic system [2].

NMR:

p-dimethoxybenzene

2,5-di(t-butyl)-1,4-dimethoxybenzene

Melting Point

Product melting point: 90.3-92.4C

Literature melting point: 103-104C [3]

Discussion

The calculated yield of only 51.1% was likely influenced by several factors during the experiment. Due to the microscale setup, losses due to spilling or transfer would have significantly affected the yield. There was slight spilling when transferring the final product to its container. Removing the crude product from the flask walls after cooling also proved difficult. There was also concern that too much hot solvent may have been used during recrystallization. The lower melting point of the final product than that of the literature value couldve been due to trapped water within the crystals, suggesting that vacuum drying was not fully successful. This could have been due to other experimenters also utilizing vacuum drying machinery concurrently. There was also some interference/error shown on the IR spectra. This could have been due to operator error, however the lower melting point of the final product when compared to the literature value suggests the presence of possible impurities within the product that couldve altered the IR spectrum.

The IR spectrum does however show evidence of some success at synthesising the desired product, as evidenced by the stronger absorption in the region just below 3000cm-1 when compared to the starting material, suggesting the presence of the additional alkyl (C-H) bonds having been formed, as well as the difference in absorbances in the 600-800cm-1 range showing a change in substitution patterns on the aromatic ring.

[1] McMurry, J. (2015). Organic Chemistry; (9th edition). Cengage Learning.

[2] Weigel, U. M and Herges, R. Automatic interpretation of infrared spectra: recognition of

aromatic substitution patterns using neural networks. J. Chem. Inf. Comput. Sci. 1992, 32, 6,

723731.

[3] Chemical Book. 1,4-DI-TERT-BUTYL-2,5-DIMETHOXYBENZENE. https://

www.chemicalbook.com/ChemicalProductProperty_EN_CB2290115.htm Accessed 29/04/24Aaron DyneCHEM204 Exp. 2

Diels-Alder reaction: preparation of cis-cyclohex-4-ene-1,2-dicarboxylic acid

Reaction Mechanism

Method

Part 1 Preparation of cis-cyclohex-4-ene-1,2-dicarboxylic anhydride

2.56g of 2,5-dihydrothiophene-1,1-dioxide and 2.08g of maleic anhydride were combined with 2.0mL of bis(2-methoxyethyl) ether. The mixture was heated slowly with a heat gun until exothermic reaction started to occur, confirmed via bubbling of solution. Solution was maintained between 15-160C with heat gun until reaction stopped (approximately 10 minutes). Solution was then slowly cooled to room temperature and then transferred to water bath where crystallisation was induced by stirring. 25mL of cold deionised water was then added, and then filtered via suction. Crystals were washed with two additional rounds of cold deionised water and left to suction dry for 10 minutes. Of this, 1.003g of moist product was removed for Part 2. The remaining moist product was dried via vacuum oven.

Part 2 Hydrolysis of initial anhydride adduct to cis-cyclohex-4-ene-1,2-dicarboxylic acid1.003g of moist adduct from Part 1 was combined with 5mL deionised water and boiled until crystals fully dissolved. Solution was then cooled in ice bath to induce crystallisation. Crystals were filtered via suction and dried in vacuum oven.

Yield

[insert handwritten yield calculations here use guide in lab manual]

Characterisation

[Insert annotated IR and NMR spectra here]

Discussion

Aaron DyneCHEM204 Exp. 3

Preparation of H2Salen and reduction to H4Salen

Method

Part 1 Preparation of H2Salen

0.39g of ethylenediamine and 1.59g of salicylaldehyde was combined with 75.0mL of ethanol and refluxed under heat for 60 minutes. Solution was then cooled to room temperature and then placed in ice bath where crystalisation occurred. Crystals were collected under vacuum and washed with cold ethanol.

Part 2 Reduction of H2Salen

1.002g of H2Salen from Part 1 was combined with 50mL of methanol and stirred until partially dissolved. 0.6g of NaBH4 was slowly added to the mixture while under continuous stirring over 10 minutes. Solution was kept under stirring for additional 10 minutes until reaction subsided. TLC was then performed (see below). Remaining solvent was removed via rotary evaporation until off-white solid remained. Solid was then resuspended in 30mL deionised water and transferred to separating funnel for extraction. Product was extracted three times with 25mL ethyl acetate. The combined organic extracts were then washed twice with 30mL deionised water. The organic extract was then dried with sodium sulfate. Product was then filtered and remaining solvent removed via rotary evaporation. Crude H4Salen was then recrystallised using hot methanol and collected upon cooling and dried in vacuum oven.

Results

[yield calculations, IR spectra , NMR Spectra]

Discussion

Aaron DyneCHEM204 Exp. 4

Column Chromatography

0.102g of 1:1 fluorene:fluorenone mixture, dissolved in 0.5mL of dichloromethane, was placed in 25cm x 1cm dry column chromatography column prepared using dry silica gel 60 and petroleum spirit. The first product was isolated using 30mL of 20% dichloromethane in petroleum spirits. Progression was observed using watch-glass evaporation. When first product was believed to have completed extraction, an intermediate isolate was obtained while using dichloromethane to rapidly move the second isolate to the bottom of the column. After replacing the intermediate isolate flask, the second product was then elucidated using dichloromethane as eluent. The three collected fractions were left to evaporate over 2 days. TLC was performed with the solutions prior to this (see below). After evaporating, the yields of remaining solids in fractions 1 and 3 were obtained for characterisation.

Recovered massesCharacterisations

Spectra

TLC

Discussion [dont forget post-lab questions].

Aaron DyneCHEM204 Exp. 5

Extraction of Euagenol and Acetyl eugenol from cloves

Method

25.54g of crushed dry cloves was placed under steam distillation for 90 minutes. The cloudy distillate was then cooled to room temperature before placed in separating funnel for extraction process. The initial distillate was first extracted with three 25mL portions of DCM. 0.5mL of organic layer was retained for GC analysis. Remaining organic layer was then extracted first with three 25mL portions of 5% sodium hydroxide. Aqueous layer was retained for further extraction. Organic layer was dried with anhydrous sodium sulfate, filtered and then rotary evaporated until small amount of colourless solution obtained (eugenol acetate). The previously retained aqueous layer was then acidified slowly using concentrated HCl (8mL) added dropwise until solution appeared cloudy. Solution was then extracted using two 25mL portions of DCM. This organic layer (containing eugenol), was then dried with sodium sulfate, filtered, and rotary evaporated until oily product remained.

Yield

Characterisations

Discussion

Aaron DyneCHEM204 Exp. 6

Aldol Condensation

Reaction Mechanism

[insert reaction mechanism]

Method

A solution of 1.03g KOH in 10mL deionised water was prepared and combined with 10mL ethanol and kept at room temperature. 3.02g of acetophenone and 2.65g of benzaldehyde was then added to this mixture and stirred vigorously for 1 hour, producing a yellow-tinted oil. Solution was then cooled in an ice bath and crystallisation was induced. Solid then filtered over vacuum and washed with cold ethanol. Solid was then recrystalised with hot ethanol and dried over vacuum for additional 10 minutes.

Yield

Characterisation

[IR , NMR , UV]

Discussion

Aaron DyneCHEM204 Exp. 7

Biomimetic synthesis of benzoin the benzoin condensation

Method

Part 1 Purification of benzaldehyde

10.32g of benzaldehyde was dissolved in 25mL ethyl acetate. Solution was then washed 40mL of 5% NaOH solution, aqueous layer was then discarded. Organic layer washed twice with 50mL deionised water. Organic layer was then isolated and dried with sodium sulfate. Solution was then filtered and placed into rotary evaporator until remaining ethyl acetate was removed. Resultant benzaldehyde was then distilled using a heat gun, and distillate that was obtained after system reached 160C was isolated. The resultant distillate (purified benzaldehyde) was then analysed and retained for Part 2.

Part 2 Synthesis of Benzoin

0.32g of thiamine hydrochloride was dissolved in 0.45mL of deionised water. 3.0mL of ethanol was then added and stirred until solution was homogenous, then cooled in ice bath. 0.9mL of 2M NaOH was then added dropwise until solution turned pale yellow and kept at below room temperature. 0.946g of purified benzaldehyde (from Part 1) was then added and mixed. Solution was then sealed and placed in darkroom for 2 days. Resultant crystalline mass was then transferred to vacuum and washed three times with cold deionised water. After air drying for 5 minutes, solid product transferred to vacuum oven. Crude benzoin was then crystalised using 95% hot ethanol.

Yield

Characterisation

Discussion

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