LAB REPORT EXAMPLE-DIELS ALDER
Abstract
The Diels Alder reaction is a cycloaddition reaction widely used to synthesize six-member rings. In our experiment we
conducted the synthesis of 9,10-Dihydroanthraceno-9,10-endo-α,β-succinic anhydride from anthracene and maleic
anhydride. We obtained X g of product (X% yield). The desired compound was analyzed by 1H NMR and TLC. Both
techniques showed that the compound was pure, and no starting material was present. The m.p was recorded, and it was
256-259 °C in agreement with values reported in literature.
Introduction
The Diels Alder reaction is a [4+2] cyclo-addition utilized to synthesize six-member ring. It requires the s-cis form of the
diene for the appropriate overlapping of the π of the diene and dienophile. A recent paper published by Amant et al
reports the use of Diels Alder in the conjugation of maleimide-containing drugs to antibodies. [1] Anthracene, one of the
reagents used in the experiment, acts as the diene; it is an aromatic compound consisting of three fused rings, often used
as backbone for dyes. [2] Maleic anhydride acts as the dienophile and it is commonly used in the synthesis of polymers and
resins.
Discussion
In this lab experiment we reacted anthracene (diene) with maleic anhydride (dienophile) to obtain 9,10- Dihydroanthraceno-9,10-endo-α,β-succinic anhydride. The reaction mixture was refluxed in xylene for 30 minutes,
followed by filtration of the precipitate. The product purity was tested by TLC comparing it with anthracene. TLC showed
that anthracene Rf was quite high (0.95) whereas the Rf of product was 0.65; therefore, a less polar eluent could be used.
We did not observe any starting material left over in the TLC analysis. 1 H NMR confirmed the presence of the compound,
showing 8 aromatic protons in the area between 7.2 ppm and 7.6 ppm. The two signals at 5ppm and 3.5 ppm are
characteristic of the newly formed six-member ring, therefore diagnostic for the formation of our desired compound. The
reaction is shown in the scheme below and involves a concerted mechanism for the formation of the final product.
Table of reagents:
Reagent MW Number of moles
anthracene
Maleic anhydride
Calculations: show calculations for the yield indicating the limiting reagent
Yield= number of moles of product/ number of moles of limiting reagent
% yield= Yield *100
Number of moles = weight in grams of compound / molecular weight of compound
Experimental:
0.2 g of anthracene and 0.1 g of maleic anhydride were refluxed in 2.5 ml of xylene for 30
minutes. After cooling the solution in ice, white crystals were collected. Mp (256-