See image — Reaction Mechanism Chemistry Question

💡 Solution & Explanation

Concept: The Reimer-Tiemann reaction involves the treatment of phenol with a trihalomethane (CHX3) in the presence of a base (NaOH). The trihalomethane generates a dihalocarbene intermediate in situ, which reacts with the phenol ring. Step 1: Identify the reagent. The question states that CCl4 (carbon tetrachloride) is used in place of CHCl3 (chloroform). Note: 'pyrene' here appears to be a misprint or colloquial reference; the reagent specified in parentheses is CCl4. Step 2: Reaction of CCl4 with base. When CCl4 reacts with NaOH (the base used in Reimer-Tiemann conditions), it generates :CCl2 (dichlorocarbene) just as CHCl3 does, but in a different manner. Actually, CCl4 under basic conditions generates trichloromethyl anion (CCl3^-) or can form :CCl2 differently. More precisely, CCl4 with NaOH gives CCl3^- which can act as an electrophilic species. The key distinction: when CHCl3 is used, the product is salicylaldehyde (an aldehyde, -CHO after hydrolysis of the intermediate -CH(OH)- or -CCl2- group). When CCl4 is used instead, the carbene intermediate is :CCl2 which, upon insertion and subsequent hydrolysis, gives a -CCl2OH intermediate that hydrolyzes to -COOH (a carboxylic acid group) rather than an aldehyde. Step 3: Mechanistic reasoning. With CHCl3 → :CHCl → after ortho attack and hydrolysis → -CHO (aldehyde = salicylaldehyde). With CCl4 → :CCl2 → after ortho electrophilic attack on phenol and hydrolysis of the -CCl2- group → -COOH (carboxylic acid = salicylic acid). The extra chlorine on the carbene means that upon hydrolysis, a carboxylic acid rather than an aldehyde is formed. Step 4: Elimination of other options. (a) Salicylaldehyde is the product of the standard Reimer-Tiemann reaction with CHCl3, not CCl4. (b) Phenolphthalein is formed from phenol and phthalic anhydride (Pechmann-type condensation), unrelated here. (d) Cyclohexanol is not a product of any Reimer-Tiemann variant with phenol. Therefore, the correct answer is C.