Hydrohalogenation

A simple example of a hydrochlorination is that of indene with hydrogen chloride gas (no solvent):[4] Alkynes also undergo hydrohalogenation reactions.[6] This regioselectivity is rationalized by the resonance stabilization of a neighboring carbocation by a lone pair on the initially installed halogen.Depending on relative rates of the two steps, it may be difficult to stop at the first stage, and often, mixtures of the mono and bis hydrohalogenation products are obtained.By reaction with tertiary amines, long-chain alkyl bromides such as 1-bromododecane, give quaternary ammonium salts, which are used as phase transfer catalysts.[10] Recent research has found that adding silica gel or alumina to H-Cl (or H-Br) in dichloromethane increases the rate of reaction making it an easy one to carry out.
Addition of HCl to acrolein
Addition of HCl to acrolein
electrophilic additionhydrogen halideshydrogen chloridehydrogen bromidealkeneshaloalkanesMarkovnikov's rulealkenecarbocationindenevinyl cationelectrophilealkenyl halideFree-radical additionperoxideschain reactionfree radical halogenationbrominealkylating agentsdimethyl aminefatty tertiary aminesquaternary ammonium saltsphase transfer catalystsMichael acceptorsnucleophilic conjugate additionacroleinsilica gelaluminadichloromethaneJ. Am. Chem. Soc.Organic SynthesesMarch, JerryOrganic ReactionsUllmann's Encyclopedia of Industrial Chemistry