Why is dibenzalacetone yellow

Synthesis of E,E-dibenzalacetone (E,E-DBA)

Abstract

The preparation of E,E-dibenzalacetone (Scheme 1), from benzaldehyde and acetone in the presence of ethanol and Ethanolic sodium hydroxide, is described. Crude E,E-dibenzalacetone was purified by recrystallization .the results showed that purified E,E-dibenzalacetone was obtained in 67.1% yield and 63.7% yield for crude E,E-dibenzalacetone. The crude and purified products were characterized by melting point determination.

Introduction

The purpose of this experiment was to use a based-catalyzed aldol condensation in the synthesize of E,E-dibenzalacetone and to characterize the crude and purified samples of E,E-dibenzalacetone by melting point determination. As shown in Scheme 1 this involved allowing benzaldehyde to react with acetone in the presence of ethanol and Ethanolic sodium hydroxide.

../Desktop/lab%20report/Unit%205%20reaction%20scheme.gif Scheme 1

Results

The results of the synthesis of E,E-dibenzalacetone are summarized in Table 1.

Compound

molar mass (g/mol)

volume/mass moles

yield

Melting point (OC)

benzaldehyde (density 1.043g/mL)

106.2 g/mole

0.25 ml

0.26 g

0.002 mole

N/A

N/A

acetone (density 0.788 g/mL)

580.08 g/mole

0.1 ml

0.07 g

0.001 mole

N/A

N/A

E,E-DBA
(a yellow solid)

234.24 g/mole

N/A

Theoretical

0.234 g

0.001 mole

Literature value

110-111oC

E,E-DBA


(a yellow solid)

234.24 g/mole

N/A

Actual

crude*

0.645 g

63.7%

purified**

0.14 g

67.1

Actual

Crude

109-110 Oc

purified

110-111 Oc

* a yellow solid ** a yellow crystal solid

Discussion


E-E dibenzalacetone is prepared from Benzaldehyde and acetone, and ethanol, as well as ethanolic sodium hydroxide, is added. The result is a yellow solid which needs to be separated from the crude sample to have a pure sample. After being purified by crystallization, the total yield that was obtained was 67.1 %. The following sample gives an experiment of the whole procedure;

../Desktop/lab%20report/Unit%205%20reaction%20scheme.gif Scheme 1

The crude products were separated by crystallization method. The melting points of these different products are different. The one which melted first was removed while the one which has a higher melting point remained. After the reaction of Benzaldehyde with acetone in the presence of ethanol and Ethanolic sodium hydroxide, a yellow solid is formed. The solid must undergo crystallization such that the pure sample is made of yellow crystals. In the purification process, the crude sample is subjected to a source of heat, and the other products melt first because they have lower melting points. E-E dibenzalacetone will remain as yellow crystals. After the other products are removed, the sample is then purified by crystallization to have pure crystals of the sample. Immediately after the reaction, the resulting crude sample had a weight of 0.645 grams, and it was 63.7 %. However, after the purification process, the pure sample reduced its mass to 0.14 grams and a total of 67.1 %. The mass fell because the crude sample had some tracks of the other products which reacted and which had not been removed. However, after the purification process, all the traces of the other products were removed, and the mass fell while the purity of the sample rose to 67.1 % from 63.7 %.

Experimental Procedure

“The preparation was carried out according to the prescribed method”

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