Acid-Free Nitration of Benzene and Toluene in Zeolite NaZSM-5

Figure 5

Schematic molecular orbital diagram for NO₂, NO₂^𝛿+, and NO₂⁺. The grayed electron represents the diminished electron density in the HOMO because of donation to the zeolite Na⁺ cation. The result is a shift of the vibrational frequency to higher wave number. As δ increases, so does the frequency. The extent of the donation depends on the local environment of the cation in the zeolite.