Final answer:
Aromatic rings do not readily undergo addition reactions; instead, they react with electrophiles under certain conditions. Unsaturated fatty acids can undergo oxidation differently than saturated fatty acids, involving isomerization of cis double bonds. Oxidation can lead to rancidity in fatty acids and is an important factor in diseases like cardiovascular disease.
Step-by-step explanation:
When attempting to oxidize alkyl and unsaturated chains of the aromatic rings in cold conditions, the aromatic compounds, which display a unique type of bonding, generally do not undergo addition reactions like alkenes do. Instead, these compounds often react with electrophiles in their most reactive cation form during aromatic substitutions. This reaction is facilitated by the generation of electrophilic cations through acid-base or Lewis acid-Lewis base reactions. For instance, halogen molecules can react with Lewis acids, such as AlX3 or FeX3, leading to the generation of a positive halogen ion through a heterolytic cleavage.
Furthermore, the oxidation of unsaturated fatty acids follows a slightly different pathway from that of saturated fatty acids during ß-oxidation. With unsaturated fatty acids, isomerization reactions may convert cis double bonds into more metabolically favorable trans double bonds. Due to the presence of double bonds in unsaturated fatty acids, these molecules yield slightly less ATP than saturated fatty acids, but still provide substantial energy.
Also, certain conditions can enhance oxidation, such as the presence of oxygen radicals that can react with fatty acids to create lipid peroxides which lead to rancidity and are associated with conditions like cardiovascular disease. In contrast, the reactivity of aromatic rings can be increased by the presence of electron-donating groups, which increase the electron density on the ring and facilitate the attack by electrophiles.