Reactions under Strongly Acidic Conditions pH

Under these conditions, the methylol groups are very unstable and benzylic carbenium ions (2) result, which then react very fast with phenol, yielding dihydroxydiphenylmethane (3) (Eqs. 4 and Thus, in acidic 

Malhotra et have proposed that the protonated methylolphenol forms an activated complex with another phenol molecule at the ortho or para position without the formation of a benzylic carbenium ion and support this argument with some entropy of activation data. The rate equation shown in Eq. (6) has been developed for the reaction.  

Drumm and Le Blanc have determined that, in acidic media, the apparent functionality of phenol is 2.32, which is in agreement with the observation by Knop and Scheib that, according to GPC data, mainly linear chain molecules are formed, with molecular weights below 2,000. 

In the presence of alcohols, the reactive species is a carbenium ion (4), formed from the hemiacetal (5) (Eq. 7). Efforts to synthesize model compounds continue the work started by Bender and coworkers. A series of new dimeric and trimeric compounds, derived from o-cresol, have been synthesized and their structures determined by IR, NMR, and elemental analysis. Additional homologues of p-cresol have been prepared by Kammerer and Niemann, to study the melting behavior of a wide range of methylene-bridged phenol oligomers. Prepolymer formation, namely novolac production, has been studied in batch and continuous flow reac- 

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