Reduction of Nitro Groups and Aryl Ketones

Electrophilic nitration and Friedel-Crafts acylation reactions introduce deactivating, meta-directing substituents on an aromatic ring. The attached atoms are in a high oxidation state, and their reduction converts these electron withdrawing functions into electron donating amino and alkyl groups. Reduction is easily achieved either by catalytic hydrogenation (H₂ + catalyst), or with reducing metals in acid. Examples of these reductions are shown here, equation 6 demonstrating the simultaneous reduction of both functions. Note that the butylbenzene product in equation 4 cannot be generated by direct Friedel-Crafts alkylation due to carbocation rearrangement. The zinc used in ketone reductions, such as 5, is usually activated by alloying with mercury (a process known as amalgamation).

Several alternative methods for reducing nitro groups to amines are known. These include zinc or tin in dilute mineral acid, and sodium sulfide in ammonium hydroxide solution. The procedures described above are sufficient for most cases.

مواضيع ذات صلة

Organic compounds are more soluble in water as ions

Heterocyclic aromatic compounds

Hückel’s rule tells us if compounds are aromatic

Molecular orbitals and aromaticity

The π molecular orbitals of other conjugated cyclic hydrocarbons

Benzene has six π molecular orbitals

Varying the number of electrons

Heats of hydrogenation of benzene and cyclooctatetraene

? What makes benzene special

Aromaticity

Conjugation and reactivity: looking forward to Chapter 10

The amide group