<P> The reaction typically needs to be heated to initiate the process, however once started the Reimer - Tiemann Reaction can be highly exothermic; this combination makes it prone to thermal runaways . </P> <P> The direct formylation of aromatic compounds can be accomplished by various methods such as the Gattermann reaction, Gattermann--Koch reaction, Vilsmeier--Haack reaction, or Duff reaction; however, in terms of ease and safety of operations, the Reimer--Tiemann reaction is often the most advantageous route chosen in chemical synthesis . Of the prior mentioned reactions, the Reimer--Tiemann reaction is the only route not requiring acidic and / or anhydrous conditions . Additionally the Gattermann - Koch and Vilsmeier--Haack reactions are not applicable to phenol substrates . </P> <P> The Reimer--Tiemann reaction can be altered to yield phenolic acids by substituting the chloroform with carbon tetrachloride . For instance, the altered reaction with phenol would yield salicylic acid rather than the expected product, salicylaldehyde . </P>

The reaction intermediate generated during the mechanism of riemer tiemann reaction is