1. Nucleophilicity: Quinuclidine is a stronger nucleophile than triethylamine. This is because the nitrogen atom in quinuclidine is more basic than the nitrogen atom in triethylamine. The more basic the nitrogen atom, the more readily it can donate a pair of electrons to form a new bond.
2. Steric hindrance: Triethylamine is a bulkier molecule than quinuclidine. This means that the three ethyl groups in triethylamine create more steric hindrance around the nitrogen atom, which makes it more difficult for the nitrogen atom to react with the isopropyl chloride. Quinuclidine, on the other hand, is a smaller molecule with less steric hindrance, which allows the nitrogen atom to react more easily with the isopropyl chloride.
3. Solvent effects: The reaction between quinuclidine and isopropyl chloride is typically carried out in a polar aprotic solvent, such as dimethylformamide (DMF). DMF is a good solvent for this reaction because it can solvate both the nucleophile and the electrophile, and it does not interfere with the reaction. Triethylamine, on the other hand, is a poor nucleophile in polar aprotic solvents. This is because the polar aprotic solvent molecules compete with the triethylamine for the isopropyl chloride, which reduces the concentration of the triethylamine-isopropyl chloride complex and slows down the reaction.
In summary, quinuclidine reacts faster than triethylamine with isopropyl chloride in an SN2 reaction because it is a stronger nucleophile, it has less steric hindrance, and it is more soluble in the reaction solvent.
