The reaction of an aromatic heterocycle with a proton is called a protonation. One of articles about this theory is 《Condensation of crotonaldehyde with secondary amines. I》. Authors are Hunig, Siegfried.The article about the compound:2-Bromopriopionaldehydediethylacetalcas:3400-55-3,SMILESS:CC(Br)C(OCC)OCC).Product Details of 3400-55-3. Through the article, more information about this compound (cas:3400-55-3) is conveyed.
Acid-free crotonaldehyde (I), b. 101°, was prepared by distilling the tech. product over pyrogallol and NaOH, collecting the fraction b. 95-105°, and redistg. in a Widmer column in a N atm. All amine-catalyzed condensations of I were done by adding the amine to I, always under dry O-free N. E.g., 0.4 mol. I and 0.004 mol. Et2NH were heated at 152°; the reaction occurred with spontaneous boiling and could be followed easily in a graduated reactor by the volume decrease (about 27%). It was nearly complete in about 90 min.; at lower temperatures it was much slower. At the same temperature, 2-mol.-% of Et2NH or Pr2NH were equally effective, the rate declining sharply with lower amine concentrations Under like conditions, the effectiveness of different amines decreased in this order: BuNH2, hexamethylenimine, pyrrolidine, Me2NH, Et2NH, Bu2NH, Pr2NH. Of secondary amines, the effectiveness decreased thus: Et2NH, piperidine, (PhCH2)2NH, morpholine. Bu3N was not effective. Solvents increased the condensation rate, H2O most (reaction of 2 mols. H2O + 1 mol. I complete in 40 min.), followed in order of decreasing effect by BuOH + H2O, BuOH, dioxane, PhMe, methylcyclohexane. The reaction followed 1st-order kinetics. A few min. after mixing, the mixture turned yellow-green, and the bomb tube was transferred to a glass tube which served as bath for the heating liquid (e.g. PhBr, b. 152°); the highest point reached by the meniscus on heating provided a zero point from which to reckon contraction, i.e. rate of reaction. After the removal of other products, the residual resin was extracted with CCl4; it contained little bound -CHO. The paper includes a discussion of the possible structure of the condensed product.
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Reference:
Piperazine – Wikipedia,
Piperazines – an overview | ScienceDirect Topics