Here's why:

* Polarity: Methylene chloride (CH₂Cl₂) is less polar than acetone (CH₃COCH₃). Caffeine is a relatively polar molecule due to its nitrogen-containing rings and carbonyl groups.

* "Like Dissolves Like": The principle of "like dissolves like" states that substances with similar polarities are more likely to dissolve in each other. Since caffeine is more polar, it will have a stronger affinity for a less polar solvent like methylene chloride.

In summary:

* Acetone is more polar, so caffeine will be less soluble in it.

* Methylene chloride is less polar, so caffeine will be more soluble in it.

This is why methylene chloride is often used to extract caffeine from coffee beans or tea leaves.