Abstract
Trihalogenomethyl anions, generated by decarboxylation of trichloro- and tribromo-acetic acid in dimethyl sulphoxide solution, react with added aldehydes. In the presence of 1,3,5-trinitrobenzene, the reaction with aldehydes competes with the formation of the coloured Meisenheimer adduct. The reduction in absorbance from the value in the absence of aldehyde has been used to measure the reactivity of trihalogenomethyl anions towards a series of aldehydes relative to their reactivity towards trinitrobenzene. For 4-substituted benzaldehydes, the reactivities obey a linear ρσ– relationship. The most reactive aldehyde used is only two times less reactive towards CCl3– or CBr3– than hydrogen ions, and it is concluded that, in dimethyl sulphoxide solutions, the reaction between trichloromethyl anions and hydrogen ions is not encounter-controlled. The reactions with aldehydes have been used to prepare several new compounds of the formula RCH(OY)CX3 where R = aryl or pyridyl, X = Br or Cl, and Y = H or COCH3.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have