Experiment 11 - Grade: A PDF

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Experiment 11: Reaction of 3,4-Dimethoxybenzaldehyde and 1-Indanone to Explore “Crossed” Aldol Condensation

Introduction The overall aim of this experiment was to use 3,4-dimethoxybenzaldehyde with 1idanone to make an alpha, beta-unsaturated carbonyl compound (Weldegirma, 2020). This type

of reaction is called a crossed aldol condensation reaction. In this reaction, an enol compound or an enolate compound reacts with a carbonyl group in hopes to form a beta-hydroxyaldehyde compound or a beta-hydroxyketone compound. This type of reaction is very important in organic chemistry because it is a good way to form C-C bonds (Aldol Condensation, 2020). There are two types of aldol condensations, self and crossed. Self-aldol condensation is when the carbonyl group present in the reaction can act as both a nucleophile and an electrophile. This reaction is considered to be one of the side reactions, so it Is important to try and prevent it. When making an enolate using an aldehyde, NaOH is used as the base forming one product. When wanting to make an enolate from a ketone, a stronger base must be used. A common strong base to use in this reaction is Lithium diisopropyl amide (Self Condensation, 2020). A crossed aldol condensation reaction is a reaction where two carbonyl compounds react with each other. This type of reaction is very successful because aldehydes are more reactive than ketones and since they do not have an alpha hydrogen present, this reduces the number of products formed (Crossed Aldol Condensation, 2015). In this experiment, a crossed aldol condensation is being done and an aldehyde and a ketone are reacting together and NaOH is being used as the base. This type of reaction is considered to be apart of green chemistry because no solvent is needed, it has a high atom economy, and it releases minimal waste (Weldegirma, 2020).

Mechanism

Side Reaction

Experimental

10mL Round Flask +250mg 3,4dimethoxybenzaldehyde +200mg 1-inandone +Crush the 2 compounds with metal spatula or glass rod until they form an oil +Reaction takes place without solvent

Melting Mixture +50mg finely ground NaOH +Continue grinding mixture until it becomes a solid mass +Let it stand for 15 minutes to continue reaction +acidify with 2mL 10% HCl, use litmus for pH check +Isolate product by vacuum filtration +Wash with cold H2O Crude Product

Analysis +Determine mass of product, % yield +Obtain melting point +Collect IR spectrum +Obtain H NMR Desired Product

Table of Chemicals

Recrystallization +Dissolves product with 30mL of 90% EtOH +Heat solution +Cool reaction to room temperature +Place flask in ice bath +Collect crystals with vacuum filtration +Wash crystals with cold 90% EtOH +Vacuum filter crystals Final Desired Product

Chemical

Formula

Molar Mass (g)

Boilin g Point (°C) 281

3,4dimethoxybenaldehy de

C9H10O3

166.1 7

Sodium hydroxide

NaOH

39.99 7

1-indanone

C9H8O

Hydrochloric acid

Meltin g Point (°C)

Structure

Color

Toxicity

IUPAC

43

Peach

-harmful if swallowed

Ventraledhyde

1388

323

Colorles s

Sodium hydroxide

132.1 6

243

42

White to yellow

HCl

36.46

-85.1

-114.2

Colorles s

Ethanol

CH3CH2O H

46.07

78.2

114.14

Colorles s

-causes skin burns and eye damage -harmful if swallowed -causes skin and eye irritation -causes respiratory irritation -causes skin burns and eye damage -toxic if inhaled -flammable

Chloroform-D

CHCl3

120.3 8

60.9

-64

Colorles s

-harmful if swallowed -causes skin and eye irritation -toxic if inhaled carcinogeni c

Trichloro(deuteri o) methane

2,3-dihydroinden1-one

Chlorane

Ethanol

Results Mass of crude product Mass of pure product Melting point of crude Melting point of pure Percent Yield

400 mg 350 mg 171-176 °C 175-178 °C 95%

Calculations Limiting Reagent 0.25 g C 9 H 10 O 3=

1 mol 1 mol product =0.001504429 × 1 mol 166.17

g product mol 1 mol product

280.318 0.001504429 mol product ×

Percent Yield 0.4 g ×100=95 % Crude 0.4217 g

0.35 ×100=83 % pure 0.4217

= 0.4217 product

Figure 1. H NMR spectrum of final product

Figure 2. IR spectrum of final product.

Discussion The melting point of the product obtained when 3,4-dimethoxybenzaldehyde and 1indanone react with each other ranges between 178-181°C. The melting point obtained in the experiment for the pure product ended up being 175-178°C and the melting point obtained for the crude product ended up being 171-176°C. These ranges are a little low which means there could have been possible impurities in the sample. The percent yield of the amount of crude product obtained was 95%. This yield is way over 50% and very close to 100% making this a really good yield. The percent yield obtained for the pure product was 83%. This is also a very good yield because it is so close to 100%. The loss of product could have been from the transfer process or due to possible side reactions. The IR spectrum is a good tool to use when wanting to determine if the wanted product was obtained. The final products IR spectrum should have peaks around 2850-3000 which represents the sp3 carbons as well as the sp2 carbons. It should also have a very prominent peak around 1700 which represents the carbonyl group on the molecules. Another peak should be around 1450-2000 which represents the benzene rings. When looking at the IR spectrum provided to us (figure 2), all of these peaks are present which gives supporting information that the wanted product was indeed obtained. The H NMR spectrum is another tool to use when wanting to determine if the wanted product was obtained. The final product H NMR spectrum should have peaks at around 6.5-8 which would represent the protons on the benzene ring. Also, there should be peaks at around 4.5-6.5 which would represent the vinylic proton off on the carbon connecting the rings together. There should also be some peaks between 2-4 ppm which represent the protons on the methyl groups coming off of the oxygens as well as the

protons on the cyclopentanes. When looking at the H NMR spectrum provided to us (figure 1), All of the predicted peaks are presents which gives us more information to support that the final product was indeed obtained. Conclusion The overall aim of this experiment was to use 3,4-dimethoxybenzaldehyde with 1idanone to make an alpha, beta-unsaturated carbonyl compound (Weldegirma, 2020). The data obtained in this experiment revealed that the wanted product was indeed obtained with a few impurities. This was known by looking at the melting points of the crude and pure samples as well as using the H NMR spectrum and the IR spectrum. The crossed aldol condensation reaction used in this experiment can be used in many real-world situations. One of these ways is scientists rely on this reaction when wanting to make synthetic versions of natural products (Aldridge, 2006). Overall this experiment was a success because the wanted product was obtained and I was able to learn more about the crossed aldol condensation reaction.

References

1-Indanone. (n.d.). Retrieved November 03, 2020, from https://pubchem.ncbi.nlm.nih.gov/compound/1-Indanone Aldridge2006-03-24T15:19:52+00:00, S. (2006, March 24). Chemists imitate nature. Retrieved November 03, 2020, from https://www.chemistryworld.com/features/chemists-imitatenature/3004541.article Chloroform-D. (n.d.). Retrieved November 03, 2020, from https://pubchem.ncbi.nlm.nih.gov/compound/Chloroform-D Ethanol. (n.d.). Retrieved November 03, 2020, from https://pubchem.ncbi.nlm.nih.gov/compound/Ethanol Hydrochloric acid. (n.d.). Retrieved November 03, 2020, from https://pubchem.ncbi.nlm.nih.gov/compound/Hydrochloric-acid Libretexts. (2020, July 14). 18.6: Crossed Aldol Condensation. Retrieved November 03, 2020, from https://chem.libretexts.org/Bookshelves/Organic_Chemistry/Map:_Organic_Chemistry_(V ollhardt_and_Schore)/18:_Enols,_Enolates,_and_the_Aldol_Condensation:_a,bUnsaturated_Aldehydes_and_Ketones/18.06:_Crossed__Aldol__Condensation Libretexts. (2020, September 13). Aldol Condensation. Retrieved November 03, 2020, from https://chem.libretexts.org/Bookshelves/Organic_Chemistry/Supplemental_Modules_(Orga nic_Chemistry)/Reactions/Organic_Reactions/Aldol_Condensation Self-condensation. (2020, July 22). Retrieved November 03, 2020, from https://en.wikipedia.org/wiki/Self-condensation Sodium hydroxide. (n.d.). Retrieved November 03, 2020, from https://pubchem.ncbi.nlm.nih.gov/compound/Sodium-hydroxide Veratraldehyde. (n.d.). Retrieved November 03, 2020, from https://pubchem.ncbi.nlm.nih.gov/compound/Veratraldehyde Weldegirma, S. Experimental Organic Chemistry Lab Manual; University of South Florida: Tampa, FL, 2020; p 125-127...