Aldol Lab Report PDF

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Lab report for aldol lab...

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Solventless Aldol Reaction Experiment #9

Madison Bradley Section 3 TA: Maddie Parker December 4, 2020

Discussion The purpose of the experiment was to perform an aldol reaction using 1-indanone and ventraldehyde, to form 2-(3,4-dimethoxybenzilydine)-2,3-dihyddroinden-1-one. The melting point of the recrystallized product was 160-163C. The literature value was 183-185C (Rothenberg et al., 2001). The lower melting point indicated that impurities were present. The reaction had a 53% yield for the crude product, and a 21% yield for the recrystallized product. This is fairly high, especially since a significant amount of solid was left behind on the walls of the reaction tube and the glass stirring rod. This could have further suggested that impurities were present in the product. The IR spectrum of the recrystallized product (Appendix B) did not match up with the literature spectrum of (E)-2-(3,4-dimethoxybenzylidene)-2,3-dihydroinden-1-one from the course website (Appendix B); this confirmed that the product was impure. The obtained spectrum showed an alcohol, which was not present in either of the reactants or the product; the alcohol could potentially have come from a product of the aldol reaction that did not yet undergo dehydration. The obtained spectrum did show a carbonyl; the stretching frequency (1680 cm-1) was likely too high for a ketone (1-indanone) or aldehyde (ventraldehyde), and lined up better with an alpha,beta-unsaturation carbonyl, like is present in the product. This suggested that the desired product was formed, and no reactants were present in the recrystallized product Based on the IR data, the purpose of the experiment (producing (E)-2-(3,4dimethoxybenzylidene)-2,3-dihydroinden-1-one) was likely successful, but the reaction perhaps did not run to completion. However, based on IR, melting point, and percent yield, the recrystallization process was unsuccessful at removing the impurities (such as an alcohol) from the crude product. A potential reason for this was that the crude product would not completely dissolve in the ethanol/water solvent, even though a seemingly large amount of solvent had been added, as using too-much or too-little solvent can cause recrystallization to be unsuccessful.

References: CHEM:2410 Course Website Rothenberg, G; Downie, A. P.; Raston, C. L.; Scott, J.L. J. Am. Chem. Soc. 2001, 123, 87018708.

Appendix A

Theoretical yield of (E)-2-(3,4-dimethoxybenzylidene)-2,3-dihydroinden-1-one: 0.26 g indanone×

280.3 g 1 mol indanone 1 mol product =0.55 g × × 1 mole indanone 1mol product 132.162 g

0.28 g ventraldehyde×

280.3 g 1 mol product 1 mol ventraldehyde =0.47 g × × 1mol ventraldehyde 1 mol product 166.176 g

After determining that ventraldehyde was the limiting reactant, the theoretical yield of product was determined to be 0.47 g.

Percent yield of crude (E)-2-(3,4-dimethoxybenzylidene)-2,3-dihydroinden-1-one: 0.25 g =0.53=53 % 0.47 g

Percent yield of recrystallized (E)-2-(3,4-dimethoxybenzylidene)-2,3-dihydroinden-1-one: 0.10 g =0.21=21 % 0.47 g

Appendix B

IR spectrum of recrystallized product:

Wavenumbers 3410.68 cm-1 1680.97 cm-1

Functional group Alcohol O-H Carbonyl C=O

IR spectrum of 2-(3,4-dimethoxybenzilydine)-2,3-dihyddroinden-1-one (from course website):

Wavenumbers 3054.45 cm-1 2986.82 cm-1 1694.22 cm-1 1626.62 cm-1 1597.65 cm-1 1265.38 cm-1

Functional Group Sp2 hybridized C-H Sp3 hybridized C-H Alpha-beta unsaturated ketone C=O Alkene C=C Aromatic ring C-C Ester C-O

H-NMR of 2-(3,4-dimethoxybenzilydine)-2,3-dihyddroinden-1-one (from course website):

Shift 7.9 ppm 7.6 ppm 7.4 ppm 7.3 ppm 7.2 ppm 7.0 ppm 4.1 ppm 4.0 ppm

Integration 1 3 1 1 1 1 2 6

Splitting Doublet Multiplet Triplet Doublet Singlet Doublet Singlet Singlet

Proton A B C D E F G H

Appendix C

Describe the role of the melting point depression phenomenon in this experiment. 1-indanone and ventraldehyde are solid at room temperature, so they would be unlikely to react without intervention. Their melting points are 42C and 44C, which are not far above room temperature. When the 2 solids are crushed into a finely-ground mixture, the newfound impurities will lower each substance’s melting point to below room temperature. Because of this, they will both be liquids at room temperature. In a liquid mixture, the molecules of each substance can react with each other much easier. If this melting point depression to below room temperature did not occur, we would have had to use a solvent to carry out this reaction. Organic solvents tend to be flammable and toxic, so it’s beneficial for safety purposes that we did not have to use one. The lack of solvent also reduced the amount of waste produced in our reaction. Additionally, it saved us time in the long run, because we did not have to take extra measures to remove the solvent when we isolated the product. All of these features are principles of green chemistry.

Draw the structures of the precursors you would use to prepare the compound below, assuming the same solventless aldol reaction conditions are used in this experiment.

In preparing the compound shown above from the precursors you’ve identified, would mixtures of different crossed aldol products be likely to form? No. In the reaction I proposed above, only the ketone can from an enolate ion; this is because the aldehyde has no alpha protons. Though there is a concern of the enolate reacting with a ketone that has not been enolized, this will likely only occur in small amounts because ketones are less reactive towards nucleophilic attacks. This is because the alkyl groups on each side of the ketone’s carbonyl carbon act as electron density donors, making the carbon less electrophilic. If this type of reaction occurring was significant, we would have seen it occur in our experiment....