diels-alder reaction with a-Terpinene and an N-phenylmaleimide

Question

I conducted a diels-alder reaction using a-Terpinene and an N-phenylmaleimide derivative and I am to come up with a structure for the incomplete dienophile. I've been given an nmr table that corresponds to the end product and done an IR scan on my cycloadduct. I've come up with a potential structure, however I am not sure if it is correct and I am having a hard time corresponding the protons with the given peaks. Please if you have any knowledge or way to help me it would be greatly appreciated!

Answer 1

Hi Noe, based on the information and spectra provided, your reaction between α-terpinene and N-phenylmaleimide appears to have formed the expected Diels-Alder product with a bicyclic structure. The IR spectrum strongly supports the presence of a carbonyl group (C=O stretch around 1700 cm⁻¹), which aligns with the maleimide functional group in the product. Additionally, the peaks in the aromatic C-H stretch region (~3000 cm⁻¹) and C=C stretch region (1500-1600 cm⁻¹) confirm the retention of the phenyl group and double bonds in the structure. The NMR spectrum shows distinct peaks in the aromatic region (6.0-8.0 ppm) that likely correspond to the protons on the phenyl group, with splitting patterns indicating the substitution pattern. The aliphatic region (0.5-3.0 ppm) reveals signals corresponding to protons on the bicyclic framework derived from α-terpinene, such as methyl, methylene, or bridgehead protons.

Hi Noe, based on the information and spectra provided, your reaction between α-terpinene and N-phenylmaleimide appears to have formed the expected Diels-Alder product with a bicyclic structure. The IR spectrum strongly supports the presence of a carbonyl group (C=O stretch around 1700 cm⁻¹), which aligns with the maleimide functional group in the product. Additionally, the peaks in the aromatic C-H stretch region (~3000 cm⁻¹) and C=C stretch region (1500-1600 cm⁻¹) confirm the retention of the phenyl group and double bonds in the structure. The NMR spectrum shows distinct peaks in the aromatic region (6.0-8.0 ppm) that likely correspond to the protons on the phenyl group, with splitting patterns indicating the substitution pattern. The aliphatic region (0.5-3.0 ppm) reveals signals corresponding to protons on the bicyclic framework derived from α-terpinene, such as methyl, methylene, or bridgehead protons.

Your proposed structure seems reasonable, but it’s essential to ensure the integration values match the number of protons for each signal in the NMR spectrum. For example, the singlet or doublet near 4.0-5.0 ppm could correspond to a proton on a carbon adjacent to the electronegative nitrogen of the maleimide. Additionally, the IR fingerprint region confirms the aromatic and bicyclic framework, as well as other functional group vibrations. If you’re having trouble matching specific protons to peaks, start with the phenyl group in the aromatic region and work toward assigning the aliphatic protons. Your approach is on the right track, and further refinement should focus on precise peak assignments. Let me know if you’d like additional clarification or assistance!