Kolbe-Schmitt reaction: Sodium phenoxide + CO2 (125°C, 4-7 atm) -> sodium salicylate (ortho-hydroxybenzoic acid after acidification). CO2 acts as electrophile on the activated ring. At higher temperature: para-hydroxybenzoic acid predominates. This is used industrially to make aspirin (acetylsalicylic acid). Reimer-Tiemann reaction: Phenol + CHCl3 + NaOH -> o-hydroxybenzaldehyde (salicylaldehyde). Mechanism: NaOH deprotonates CHCl3 to form dichlorocarbene (:CCl2), which attacks the activated phenol ring. The :CCl2 is the electrophile. With CCl4 instead of CHCl3: trichlorocarbene attacks, eventually yielding salicylic acid (not aldehyde). Important JEE distinction: CHCl3 -> aldehyde; CCl4 -> acid.