Organic Chemistry

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 (256-258 °C),

Rf (product): 0.65. 1H NMR (CDCl3, 300 MHz) δ: 7.6-7.4 (m, 4H, ArHa), 7.3-7.1 (m, 4H, ArHb),

4.82 (s, 1H, CH), 3.52 (s, 1H, CH)

Conclusions

In conclusions, our experiment showed an application of the Diels Alder reaction in the formation of 9,10-

Dihydroanthraceno-9,10-endo-α,β-succinic anhydride. The yield obtained was X% and the purity of the compound was

confirmed by TLC, 1H NMR and m.p.

Alternative (if you did not get a good result): In conclusions, our experiment showed an application of the Diels Alder

reaction in the formation of 9,10-Dihydroanthraceno-9,10-endo-α,β-succinic anhydride; The yield and the purity were not satisfactory. We believe that a longer reaction time (this is just an example of an explanation you can give!!!) or a different

ratio of the reagents could improve the yield.

References (showing one of the format) General format. ACS style: Author, A. A; Author, B. B; Author, C. C. Title of Article. Journal Abbreviation (italics) [Online if online] Year (bold), Volume (italics), Pagination.

1. Amant, A.H; Lemen, D; Florinas, S; Mao S; Fazenbaker, C; Zhong, H; Wu, H; Gao C; Christie R.J; Read de Alaniz. Tuning

the Diels-Alder Reaction for Bioconjugation to Maleimide Drug-Linkers. J. Bioconjug Chem. 2018, 7, 2406-2414.

2. Thomas, K.R.J; Singh, P. Electro-optical properties of new anthracene based organic dyes for dye-sensitized solar cells.

Dyes and Pigments. 2011, 15, 254-256.