Diels-Alder Reaction

Topics: Alkene, Chemical bond, Maleic anhydride Pages: 5 (798 words) Published: April 1, 2014
Brittany Martin
2/13/2014
Diels Alder reaction of anthracene and Maleic anhydride

Reaction Scheme:
Figure one shows the reaction scheme for Diels Alder reaction of anthracene and maleic anhydride

Theory/Background:
The Diels-Alder reaction was created in 1928 by two German chemists Otto Diels and Kurt Alder (Wade, Jr., 2013). This reaction is best used for making six membered rings with different functional groups. The reaction is called a 4+2 cycloaddition because a ring is formed by four pi electrons in the diene interacting with two pi electrons of the alkene or alkyne (Wade, Jr., 2013). In this experiment anthracene was used as the diene and considered to be electron rich in the reaction. Maleic anhydride was the electron poor dienophile used in the reaction. The reaction converted two pi bonds into two sigma bonds forming 1,9 dihydroanthracene-9, 10-,  succinic anhydride (Wade, Jr., 2013).

Procedure:
Step 1: Weighed 0.5g of anthracene and 0.25g of maleic anhydride Step 2: Added 6mL of xylene
Step 3: Allowed the mixture to boil for 30 minutes
Step 4: Placed 6mL of xylene in ice bath
Step 5: Cooled down reaction to room temperature for 5 minutes and placed in ice bath for 5 minutes to recrystallize Step 5: Collected crystals by vacuumed filtration
Step 6: Mixed 6mL of xylene with crystals and heated the mixture Step 7: Allowed the mixture to cool to room temperature
Step 8: Cooled the solution in an ice bath for 5 minutes
Step 9: Collected the crystalized solid by vacuum filtration Step 10: Measured the melting point for the crystalize solid

Reagent Table:

Table 1: The chemicals and properties used in the reaction
Compound
Quantity
Molar Mass
(g/mol)
Melting Point (C)
Boiling Point (C)
Anthracene
0.5g
178.23
216-218
340
Maleic Anhydride
0.25g
98.06
54-56
200
Potassium Bromide
100
119
63.38
759
Xylene
6mL
106.17

137-144
9,10 dihydroanthracene-9, 10-,  succinic anhydride

276.23
262-264

Observations:
Mixture in ice bath and product precipitated is slightly yellow. The crystals that are collected in vacuum filtration are a crystal clear color.

Results:

Table 2: The weight and melting point 9,10 dihydroanthracene-9, 10-,  succinic anhydride Product
Weight
Melting Point
9,10 dihydroanthracene-9, 10-,  succinic anhydride
Pure: 1.05g
Crude: .95g
260C

Calculations:

-Anthrancene
Theoretical yield
0.5g ( 0.003 mol) of anthrancene
Anthrancene: MW: 178.23 g/mol
Theoretical yield: 0.25g/mol x 98.06g/mol maleic = 24% anthrancene -Maleic anhydride
Theoretical yield
0.25g (0.0025mol) of Maleic anhydride
Maleic anhydride MW: 98.06 g/mol
Theoretical yield: 0.0025mols x 178.23 g/mol of anthrancene = 0.45% of Maleic anhydride

Discussion of Results
The purpose of this experiment was to create a Diels Alder reaction. For this experiment, is was clear that Anthracene is the electron-rich diene. Maleic anhydride was the electron-poor dienophile. The dienophile contained two carbonyls that are withdrawing groups. A good dienophile is described to have two or more withdrawing groups (Wade, Jr., 2013). Dienophiles commonly contains carbonyl or cyano groups to enhance the Diels-Alder reactivity (Wade, Jr., 2013). The two functional groups contributed to the reaction by pulling the electron density away from the pi bond.

The mechanism for the Diels-Alder reaction is a concerted cyclic movement. For this experiment, the reaction was carried out in xylene. The boiling point for xylene is 140C (Wade, Jr., 1998). Xylene was used for three reasons because it provided a decent reaction temperature, it did not freeze in the ice bath, and the reactants were more soluble in it (Wade, Jr. 1998). The reaction begun by mixing 0.5g of anthrancene with 0.25g of maleic and 6mL of xylene. The mixture was heated for 30 minutes. The mixture was heated because when a conjugated diene is heated in the presence of an alkene it forms a cyclohexane...
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