"This reaction gave a different product than expected."
Kana showed her notebook.
Rei looked at the reaction equation. "Carbocation rearrangement."
"Carbocation?"
"Carbon cation. A highly reactive intermediate with positive charge."
Milia drew a diagram. "Carbon with only three bonds. Planar structure with an empty p orbital."
"Looks unstable," Kana said.
"Exactly. So it tries to stabilize," Rei continued.
"How?"
"Attracts electrons. From nearby bonds."
Milia added explanation. "Primary, secondary, tertiary carbocations. More substituents means more stable."
"Why?"
"Hyperconjugation. Electrons from adjacent C-H bonds partially flow into the empty p orbital."
Rei drew a diagram. "Electron density disperses. Energy decreases."
Kana began understanding. "So tertiary is most stable?"
"Yes. Three substituents, so hyperconjugation effect is large."
Milia introduced another stabilization mechanism. "Resonance is also important. When there's a double bond nearby, the positive charge delocalizes."
"Allylic cation, benzylic cation. These are particularly stable."
Rei added. "Multiple resonance structures can be drawn. Actual structure is a hybrid of those."
Kana asked. "But what's rearrangement?"
"Carbocation moving to a more stable position," Rei answered.
Milia drew the mechanism. "Secondary carbocation forms. But there's a tertiary carbon nearby."
"Hydrogen or carbon migrates to become tertiary carbocation."
Kana was surprised. "They move on their own?"
"Because it's energetically favorable," Rei explained. "Reactions aim for more stable states."
"Wagner-Meerwein rearrangement," Milia named it. "A classical example."
Rei drew a reaction diagram. "Energy curve. From secondary cation to tertiary cation. Downhill."
"But why say they wander?" Kana asked.
Milia laughed. "Because carbocations have many options. Hard to predict which path they'll choose."
"React with nucleophile, rearrange, or eliminate."
Rei added. "Reaction conditions, solvent, temperature. Everything affects it."
"A probabilistic process."
Kana pondered. "But does this happen in living organisms too?"
"It does," Milia nodded. "Terpenoid biosynthesis. Carbocations rearrange successively."
"From squalene to cholesterol. Complex polycyclic structures form through a series of cation rearrangements."
Rei was impressed. "Enzymes control those pathways. Not random, produces only specific products."
"Amazing precision," Kana murmured.
Milia gave another example. "Carbocations are involved in drug metabolism too."
"Cytochrome P450 catalyzes oxidation reactions. Sometimes carbocations form."
"Does that become a problem?" Kana asked.
"If they react with DNA or proteins, toxicity appears," Rei answered.
"So in drug design, we try to avoid carbocation formation."
Kana reviewed her notebook. "My reaction is also a result of carbocation wandering."
"Yes. But unexpected products sometimes lead to new discoveries," Milia encouraged.
Rei said quietly. "Chemistry is always full of surprises."
"Carbocations exist for only an instant. But that instant determines the reaction's fate."
Kana stared at the diagram. Arrows pointing in multiple directions.
"Each wandering path has meaning."
Milia and Rei nodded.
"Chemistry's beauty," Rei said.
The three continued thinking about the journey of invisible intermediates.