This is the IR spectrum of the adduct of Maleic Anhydride + alpha-terpinene (Diels Alder reaction of the Diene from eucalyptus oil). I need to interpret this data for my results report. What are the important points (so I can make a table with it) and give a short interpretation of it.
The Correct Answer and Explanation is :
The IR spectrum of the adduct of Maleic Anhydride + α-Terpinene (a Diels-Alder reaction product) provides key insights into the functional groups present in the product. Below are the key peaks and their interpretations:
Important IR Absorption Peaks and Their Assignments
| Wavenumber (cm⁻¹) | Functional Group | Interpretation |
|---|---|---|
| ~1780 & ~1850 | Anhydride (C=O stretch) | Strong peaks due to asymmetric & symmetric stretching of cyclic anhydride carbonyl groups. |
| ~1700 | Ketone (C=O stretch) | Possible additional carbonyl presence from rearrangement or impurities. |
| ~2950 | C-H Stretch (Aliphatic) | Strong peaks from CH3 and CH2 groups in the terpenoid structure. |
| ~1450 | CH2 bending (Alkane) | Confirms presence of aliphatic groups. |
| ~1200–1300 | C-O-C stretch (Anhydride) | Anhydride characteristic stretching vibrations. |
| ~900 | Alkene out-of-plane bending | Presence of non-conjugated double bonds. |
Interpretation of the IR Spectrum
The IR spectrum confirms the formation of the Diels-Alder adduct between α-terpinene (the diene) and maleic anhydride (the dienophile). The strong absorption bands at ~1780 cm⁻¹ and ~1850 cm⁻¹ confirm the presence of an anhydride functionality, which is expected since maleic anhydride remains intact in the product. The absence of a broad O-H stretch (~3200-3600 cm⁻¹) indicates no hydrolysis of the anhydride.
The peaks around 2950 cm⁻¹ and 1450 cm⁻¹ confirm the presence of aliphatic CH3 and CH2 groups, indicating that the terpenoid structure remains largely unchanged. The peak around ~900 cm⁻¹ suggests the presence of an isolated alkene, likely from part of the terpenoid framework that was not involved in the reaction.
The successful appearance of the anhydride peaks and absence of maleic anhydride’s characteristic C=C stretch (~1600 cm⁻¹) confirms the reaction has proceeded as expected, leading to the formation of a bicyclic adduct without significant side reactions.
Would you like me to format this for your report?