Experiments Essay

1814 Words Aug 11th, 2011 8 Pages
EXPERIMENT 1: REACTIONS OF ENOLATE IONS WITH CARBONYL GROUPS

Aims
In this experiment we used two techniques for the reactions of enolate ions with carbonyl groups. One technique used was Doebner reaction and the other technique used was Claisen-Schmidt reaction. Therefore the aim of this experiment is to synthesize trans p-methoxycinnamic acid and to synthesize dibenzalacetone via an aldol condensation reaction between acetone and benzaldehyde. The products would be recrystallized using ethanol, then characterized using melting point analysis.

Introduction:
In this experiment we learnt on carbonyl compounds, enols and enolates. We also learnt two different techniques to test the reactions of enolate ions with carbonyl groups which
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The crude product was air dried and weighed. Lastly the crude product was recrystallized from methanol and the weight and melting point was determined. The table below shows the mass of the crude product, mass of dibenzaldehyde and the melting point rage of dibenzaldehyde.

mass of the crude product 3.33g mass of dibenzalacetone 2.4g the melting point rage of dibenzalacetone 108.7,110.1
Table 4

Results and Discussions:
Results and discussions for experimental part a and b are discussed below. Experimental part a:
Q1. Comment on the temperature of the reaction solution when it is heated under reflux (i.e. at its boiling point) in an oil bath at 120ₒC vs a Bunsen burner, with temperature of 4ooₒC.
ANS: When heated with Bunsen burner will not be effective and the temperature will not be constant throughout as compared to when heating with reflux at 120 degrees Celsius. Heating under reflux is more constant .
Q2. Why does p-methoxycinnamic acid precipitate upon acidification?
ANS: it is because the precipitate contains water and thus when acid was added to p-methoxycinnamic acid it reacts to remove the water molecules in the form of precipitate to make the solution more acidic.

Experimental part b:
Q1. Explain the principal of recrystallization as a purification technique.
ANS: Crystallization depends on the values of solubility: compounds (solutes) tend to be more soluble in hot

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