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Questions and Answers
What type of reaction is the synthesis of dibenzalacetone?
What type of reaction is the synthesis of dibenzalacetone?
- Esterification
- Claisen-Schmidt Reaction (correct)
- Friedel-Crafts Alkylation
- Grignard Reaction
Which of the following reagents are required for the synthesis of dibenzalacetone?
Which of the following reagents are required for the synthesis of dibenzalacetone?
- Ethanol, water and sodium chloride
- Benzaldehyde and ethanol
- Acetone and sodium chloride
- Benzaldehyde, acetone, and NaOH (correct)
What property of trans,trans-dibenzalacetone makes it useful in sunscreens?
What property of trans,trans-dibenzalacetone makes it useful in sunscreens?
- It's insolubility in ethanol
- Its ability to absorb UV light (correct)
- Its high melting point
- Its solubility in water
What role does recrystallization play in the purification of dibenzalacetone?
What role does recrystallization play in the purification of dibenzalacetone?
Why is it essential to find the limiting reagent in the synthesis of dibenzalacetone?
Why is it essential to find the limiting reagent in the synthesis of dibenzalacetone?
How do impurities affect the melting point of dibenzalacetone?
How do impurities affect the melting point of dibenzalacetone?
Which physical characteristic is associated with the cis,cis isomer of dibenzalacetone?
Which physical characteristic is associated with the cis,cis isomer of dibenzalacetone?
During recrystallization, why is it important to use just enough hot solvent to dissolve the solid?
During recrystallization, why is it important to use just enough hot solvent to dissolve the solid?
In the context of recrystallization, what does 'hot filtration' achieve?
In the context of recrystallization, what does 'hot filtration' achieve?
Which factor primarily influences the actual yield of a reaction?
Which factor primarily influences the actual yield of a reaction?
If a student synthesizes dibenzalacetone and obtains a melting point range of 100-102°C, what does this indicate about the product's purity?
If a student synthesizes dibenzalacetone and obtains a melting point range of 100-102°C, what does this indicate about the product's purity?
Why is ethanol considered flammable, requiring the use of a hood during experiments?
Why is ethanol considered flammable, requiring the use of a hood during experiments?
What should be done with soluble compounds after an experiment involving dibenzalacetone synthesis?
What should be done with soluble compounds after an experiment involving dibenzalacetone synthesis?
How does the Claisen-Schmidt reaction contribute to the synthesis of dibenzalacetone?
How does the Claisen-Schmidt reaction contribute to the synthesis of dibenzalacetone?
What is the purpose of using NaOH in the synthesis of dibenzalacetone?
What is the purpose of using NaOH in the synthesis of dibenzalacetone?
Flashcards
Mixed Aldol Condensation Reaction
Mixed Aldol Condensation Reaction
A reaction involving both an aldehyde and a ketone to form new carbon-carbon bonds.
Claisen-Schmidt Reaction
Claisen-Schmidt Reaction
A specific type of mixed aldol condensation that involves the reaction between an aldehyde and a ketone.
Dibenzalacetone
Dibenzalacetone
An organic compound with the formula C17H14O, often used in sunscreens due to its UV light absorption properties.
Recrystallization
Recrystallization
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Melting Point
Melting Point
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Theoretical Yield
Theoretical Yield
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Actual Yield
Actual Yield
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Percent Yield
Percent Yield
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Limiting Reagent
Limiting Reagent
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Handling Hot Glassware
Handling Hot Glassware
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Study Notes
- The experiment is MED-108 Organic Chemistry Lab, Experiment 1
- The experiment is the synthesis of Dibenzalacetone, conducted by Dr. Stella Loizou
Learning Objective
- Synthesize a crystalline organic compound and purify it through recrystallization.
Synthesis of Dibenzalacetone
- Mixed Aldol Condensation Reaction also known as Claisen-Schmidt Reaction
- Aldehyde + ketone with NaOH yields mixed aldol
- Benzaldehyde (M.W:106,13 g/mol) + Acetone (M.W:58,08 g/mol) with NaOH (aq.) / EtOH at 20-25 degrees Celsius yields trans, trans-dibenzalacetone (M.W:234,29 g/mol)
- The yield is 90%
Properties of trans,trans-dibenzalacetone
- Insoluble in Hâ‚‚O
- Soluble in EtOH
- Double bonds absorb UV light, which leads to it being used in sunscreens
Isomers
- It forms three isomers
- cis,cis isomer: liquid that flushes out on the initial filtration of the crystals
- cis,trans isomer: formed in very small amounts, M.P.: 60°C due to inefficiency in packing into a crystal
- trans,trans isomer: main product, formed in large amounts, M.P.: 110-111°C because it is a highly symmetric molecule that packs very well
Purification by Recrystallization
- Purification of a solid by recrystallization from a solvent relies on different substances having different extents of solubility in a given solvent
- Impurities present in a solid sample are much more insoluble in the chosen solvent and so they remain in the filter , whereas in the solution is the pure product
- Complete dissolution resulting in a clear solution with solvent added, impurities are undissolved and removed by hot filtration.
Purity Assessment
- Determination of Melting Point (M.P.).
- Impurities in the product make the M.P. lower than the literature value.
Yields
- Theoretical Yield is the amount of product obtained when the limiting reagent reacts completely.
- Theoretical Yield (g) = n(mol) x M.W. (g/mol) of product, where "n" refers to the amount of product when the limiting reagent is used.
- Actual Yield (g): amount of product that is produced.
- Percent Yield (%) = (actual yield (g) / theoretical yield (g)) x 100
Waste disposal
- Be careful with HOT glassware
- EtOH is flammable, use a HOOD to avoid fire
- NaOH can cause skin irritation
- Soluble compounds should be washed down the drain.
- Solid materials should be placed in the dustbin.
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