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synthesis of organic compounds
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Experiment No.: 8 Experiment Title: SYNTHESISING DIBENZALACETONE BY ALDOL CONDENSATION REACTION Surname: Matsididi First Names: Precious Olorato ID Number: 201903636 Day: Friday Lab Slot: 3-6pm Date of the experiment: 01 April 2022 CONTACTS; [email protected] +267 72 443 074
Synthesizing dibenzalacetone from acetone and benzaldehyde through the aldol condensation reaction. Method was proven successful as gave a yellow product of crystallizes which purity was proven using a TLC plate and identified using IR spectra. This product gave a melting point temperature range of 108.3 C-109.8 C and a 4.28g mass obtained giving a 67.1% of percentage⁰ ⁰ yield. AIM The aim of this experiment is to synthesize dibenzalacetone from acetone and benzaldehyde through the aldol condensation reaction. INTRODUCTION Aldol condensation reaction very useful synthesis method to organic chemistry founded in 1872 by Aleksandr Porfir'evich Borodin after observing formation of "aldol", 3-hydroxybutanal from an acetaldehyde in presence of other chemicals (Coulthard, Erb, & Aggarwal, 2012). This reaction occurs in aldehydes containing α-hydrogen in presence of a base to end up giving β-hydroxy aldehydes which are aldols. Here an enolate ion reacts with a carbonyl compound which is then followed by dehydration giving a conjugated enone. In this experiment the two carbonyl compounds used are Acetone and benzaldehyde which then the aldol condensation reaction then gives a dibenzalacetone compound also known as Dibenzylideneacetone. Dibenzalacetone is a yellow compound with melting temperature range of 107-113 °C (Cui, Ono, Kimura, Liu, & Saji, 2011). The reaction in this experiment proceeds as below;
2ml of acetone and 4ml of benzaldehyde solution were measured using a 10ml measuring cylinder and mixed into a 250ml conical flask, magnetic stirrer was added, and mixture was placed onto heat with stirring turned on. Into a 100ml beaker mixture of 20ml 95% ethanol and 20ml of 6M NaOH measured using 100ml measuring cylinder was mixed and then poured into the 250ml Erlenmeyer flask and continued to stir for 15minutes. Color change was noted. Suction filtration was then performed to obtain product and washed with cold ethanol and allowed to air dry for 10minutes. The crude product was weighed and its melting point determined as product into a capillary tube closed at one end and placed into the temperature measuring machine. The product was then recrystallized by dissolving in 15ml ethyl acetate and warmed using low heat and stirred until the whole product had dissolved. Then after 15ml of 95% of ethanol was added and removed from heat with stirring till crystals formed which were collected through suction filtration and air dried for 10 minutes. Product was dissolved and plotted on a TLC plate using capillary tube then placed into a beaker containing 2ml acetone and 8ml hexene to allow for development. The melting point of final product point determined as product into a capillary tube closed at one end and placed into the temperature measuring machine and run through the IR machine.
Table 1 of crude product mass and its properties Mass of petri dish + filter paper+ product 60.49g Mass of petri dish + filter paper 39.04g Mass of product 21.45g Product observation Yellow crystals Melting point range of product 101.5 C-103.1 C⁰ ⁰ Table 2 of final product and its properties Mass of petri dish + filter paper+ product 37.26g Mass of petri dish + filter paper 32.98g Mass of product 4.28g Product observation Yellow crystals Melting point range of product 108.3 C-109.8 C⁰ ⁰ Mass of acetone= density ×volume = 0.791g/cm^3 × 2cm^3 =1.58g Moles of acetone= mass / molar mass = 1.58g / 58.08g/mol =0.02724mol Mole ratio of acetone : dibenzalacetone 1 : 1
1661.63 C=O stretching Strong intensity, sharp peak 3077.73 C-H stretching Weak intensity, broad peak Rf= distance travelled by component disatnce travelled by solvent Spot 1=2.4cm/8cm=0.3 spot 2=0.3 spot 3=0.
As from IR spectra of benzaldehyde peak wavenumbers of 1583.76, 1596.62, 1653.28, 1696.81, 2737.54, 2819.43 and 3064.21cm-1^ are seen and determined to be bonds of C=C bending, C=C bending, C=O stretch, C=O stretch, C-H stretching, C-H stretching and C-H stretching respectively which were extracted from the literature values (IR Spectrum Table & Chart, 2022) as well as literature of (Strouse, 1997). The wavenumber 1583.76cm-1^ gives a -C=C bending of an aromatic ring specifically benzene which is attached to carbon having and hydrogen and oxygen. Thus giving the - C-O at wavenumber 1653.28 and 1696.81cm-1^ which is of an aldehyde stretch of a conjugated bond that is interacting with benzene ring to stabilize it by movement of electrons. The -C-H bond is of an aldehyde and electrons are withdrawn from the hydrogen as carbon is more electronegative. Now looking at IR spectra of dibenzalacetone the peak wavenumbers are picked to be 1524.56, 1579.51, 1594.83, 1661.63 and 3077.73cm-1^ which from literature values of (Strouse, 1997) and (IR Spectrum Table & Chart, 2022) give bonds C=C bending, C=C bending, C=C stretching, C=O stretching and C-H stretching with respect to the wavenumbers. The C=C bond of 1524.56cm-1^ peak is bent giving signal of an aromatic ring which is known to be of benzene as well, with another C=C bond which is conjugated and showing to be attached to a cyclic alkene which is the benzene ring at wavenumber 1594.83cm-1. And a C=O bond of a conjugated ketone which also attached to a C=C bond that’s attached to the benzene ring giving movement of electrons to make it stable. Lastly the C-H bond stretching at 3079.73cm-1. From the two IR spectra of benzaldehyde and dibenzalacetone all bonds were present but with C=O bond in benzaldehyde being of an aldehyde group and that in the dibenzalacetone showing a ketone group presence but both were conjugated. 24.45g of crude product was extracted which were yellow crystals with a melting point temperature range of 101.5 C-103.1 C. the final product being dibenzalacetone gave a yellow product of mass of⁰ ⁰ 4.28g which gave a percentage yield of 67.1% which is good but could be explained that some of the product dissolved into the ethyl acetate during the purifying step. Dibenzalacetone gave a melting point temperature of 108.3 C-109.8 C which when compared to the literature value 107-⁰ ⁰ 113 °C as (Cui, Ono, Kimura, Liu, & Saji, 2011) which falls within the range. To compare the crude product and final product the crude product has a wide and lower melting point temperature range
Peak numbers of 1524.56, 1579.51, 1594.83, 1661.63 and 3077.73cm-1^ were observed and give bonds C=C bending, C=C bending, C=C stretching, C=O stretching and C-H stretching with respectively. Confirming the Dibenzalacetone which was yellow crystals with melting point temperature of 108.3 C-109.8 C and percentage yield of 67.1%. which gave 1 spot in TLC plate⁰ ⁰ considering it pure. The experiment proves on how the aldol condensation reaction is successful and necessary to organic chemistry as different products can be synthesis through aldehydes. REFERENCES REFERENCES Coulthard, Erb, & Aggarwal, 2012: , (Coulthard, Erb, & Aggarwal, 2012), (Cui, Ono, Kimura, Liu, & Saji, 2011: , (Cui, Ono, Kimura, Liu, & Saji, 2011), Santiago & Strobel, 2013: , (Santiago & Strobel, 2013), IR Spectrum Table & Chart, 2022: , (IR Spectrum Table & Chart, 2022), Strouse, 1997: , (Strouse, 1997), Cui, Ono, Kimura, Liu, & Saji, 2011: , (Cui, Ono, Kimura, Liu, & Saji, 2011),
