Chloroform reaction with phenoxide

Mono-substitution occurs most readily in the stepwise replacement of the halogen substituents of 2,4,6-trichloro-s-triazine with aqueous methanol and sodium bicarbonate (30°, 30 min), the monomethoxy derivative (324) is obtained on heating (65°, 30 min), the disubstitu-ted derivative is formed and on brief heating (65°) with the more basic sodium carbonate or methanolic sodium hydroxide (25°, 3 hr) complete methoxylation (320) occurs. Ethanolic ethoxide (25°, 1 hr) or sodium carbonate (35°) is sufficient to give complete ethoxy-dechlorination. The corresponding phenoxy derivatives are obtained on treatment with one (0°), two (15°, 1 hr), or three equivalents (25-70°, 3 hr) of various sodium phenoxides in aqueous acetone. The stepwise reaction with phenols, alcohols, or thiols proceeds in better yield in organic solvents (acetone or chloroform) with collidine or 2,6-lutidine as acid acceptors than in aqueous sodium bicarbonate. ... 

A general method of synthesis of the aryl chloroformates involves the reaction of phosgene with phenoxide, M[OAr], dissolved in a suitable solvent at low temperatures [1442] ... 

Scheme 8.45. An example of the Reimer-Heman reaction. Dichlorocarbene is known to be generated from the reaction of trichloromethane (chloroform, HCClj) with, for example, aqueous sodium hydroxide. Introduction of sodium phenoxide solution results in the formation of orfho-hydroxybenzaldehyde. Substitution via either carbene insertion or electrophiUc addition resnlts.

Although 4-hydroxybenzaldehyde can be made by the saligenin route, it has been made historically by the Reimer-Tiemann process, which also produces sahcylaldehyde (64). Treatment of phenol with chloroform and aqueous sodium hydroxide results in the formation of benzal chlorides, which are rapidly hydrolyzed by the alkaline medium into aldehydes. Acidification of the phenoxides results in the formation of the final products, sahcylaldehyde and 4-hydroxybenzaldehyde. The ratio of ortho and para isomers is flexible and can be controlled within certain limits. The overall reaction scheme is shown in Figure 1. Product separation is accomphshed by distillation, but this process leads to environmental problems because of the quantities of sodium chloride produced. 

Treatment of a phenol with chloroform (trichloromethane) in the presence of hydroxide ion results in the synthesis of a 2-hydroxybenzalde-hyde through C-formylation. Dichlorocarbene, CCl2, is generated by the action of base on chloroform and this highly reactive electrophile then attacks the phenoxide. The mechanism of the Reimer-Tiemann reaction, is given in Scheme 4.12. 

Phenols react with chloroform in the presence of hydroxide ion in water to give o- and jp-hydroxybenzaldehydes. The steps of the reaction are (1) the formation of dichlorocarbene, as shown in Example 4.22 (2) nucleophilic reaction of the phenoxide with the electrophilic carbene and (3) hydrolysis. 

The Reimer-Tiemann reaction involves electrophilic substitution on the highly reactive phenoxide ring. The electrophilic reagent is dichlorocarbene, CCl2, generated from chloroform by the action of base. Although electrically neutral, dichlorocarbene contains a carbon atom with only a sextet of electrons and hence is strongly electrophilic. 

Originally, polycarbonate was produced by interfacial (organic/aqueous) polycondensation of phosgene (COClj) with disodium salt of a bisphenol, such as 2,2-bis(4-hydroxyphenyl)propane (bisphenol A or BPA). Initially, the reaction produces an intermediate chloroformate R0C(0)C1 (Eq. (12.1)), which subsequently reacts with another phenoxide molecule, growing a polymer chain... 

PMMA cross-linked by ethylene dimethacrylate with immobilized side oligooxy-ethylene chains were used as interfacial transfer catalysts [80]. Also studied was the formation of benzyl acetate, benzyl bromide and alkali metal acetates in boiling chloroform and of n-octylphenyl ester from n-octyl iodide and K or Na phenoxide in toluene at 100 °C in the presence of a catalytic polymer amount. The product yield increased with an increase in the reaction time and the catalyst/acetate or catalyst/ phenoxide molar ratio. The conversion of benzyl bromide increased according to the following sequence of acetates Napolymeric catalyst could be regenerated and used many times. 

Fig. 10. Hammett correlation between a-values and the logarithms of the relative rate constants of the S 2 alkylation reaction of substituted pyridinium-N-phenoxides with methyl iodide in chloroform at 25°C Ig (k /k q) = 0.40 a + 0.0003...

---