Title: The preparation of Dibenzylideneacetone

Date: Sep 22nd

Name:张瑾瑜

Student id:14321037

Objectives:

1. To prepare Dibenzylideneacetone by Claisen-Schmidt reaction

2. To measure the melting point of purified Dibenzylideneacetone

Principles:

Condensation reaction can be performed at the presence of alkaline as a catalyst to convert Aromatic aldehyde and aldehyde or ketone with α-hydrogen atom to unsaturated α,βaldehyde or ketone. The production rate should be high after dehydration.

Dibenzylideneacetone(dba、C17H14O) can be prepared by an aldol condensation of benzaldehyde and acetone with sodium hydroxide as a catalyst.

Reagents and apparatus

Benzaldehyde, 95% ethanol, 0.5M NaOH(aq) and acetone

250 mL round-bottomed flask, 10 mL pipet, reflux condenser, magnetic stirrer bar, hot-plate stirrer, clamp, suction flask, Buchner funnel

Physical constants

Theoretical mass of product = 2.87 g

Mass of crude product =

Mass of purified product =

Percent yield = (mass of purified product / theoretical mass of product) x 100% = ? %

Results

Color and shape of the purified product

Melting point of the final product = ?oC ~ ?oC

Answers to questions/ exercise

1.The introduction of extra impurities and the loss of production should be avoided so the solvent should be carefully chosen. Cold water can be used as a washing agent.

2.No, the productivity will not increase. The ratio between acetone andbenzaldehyde has reached the best ratio.

3. If the concentration of alkaline is too high, disproportion reaction of aldehyde will take place.

4. There are cis-cis isomer and cis-trans isomer. Nuclear Magnetic Resonance Spectroscopy can tell the difference.

Discussions

 

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