Definitions for hydrohalogenation
hy·dro·halo·gena·tion

WiktionaryRate this definition:4.5 / 4 votes

1. hydrohalogenationnoun

   The electrophilic addition of hydrohalic acids to alkenes to yield the corresponding haloalkanes.

WikipediaRate this definition:0.0 / 0 votes

1. Hydrohalogenation

   A hydrohalogenation reaction is the electrophilic addition of hydrohalic acids like hydrogen chloride or hydrogen bromide to alkenes to yield the corresponding haloalkanes. If the two carbon atoms at the double bond are linked to a different number of hydrogen atoms, the halogen is found preferentially at the carbon with fewer hydrogen substituents, an observation known as Markovnikov's rule. This is due to the abstraction of a hydrogen atom by the alkene from the acid (HX) to form the most stable carbocation (relative stability: 3°>2°>1°>methyl), as well as generating a halogen anion. A simple example of a hydrochlorination is that of indene with hydrogen chloride gas (no solvent): Alkynes also undergo hydrohalogenation reactions. Depending on the exact substrate, alkyne hydrohalogenation can proceed though a concerted protonation/nucleophilic attack (AdE3) or stepwise by first protonating the alkyne to form a vinyl cation, followed by attack of HX/X− to give the product (AdE2) (see electrophile for arrow pushing). As in the case of alkenes, the regioselectivity is determined by the relative ability of the carbon atoms to stabilize positive charge (either a partial charge in the case of a concerted transition state or a full formal charge for a discrete vinyl cation). Depending on reaction conditions, the main product could be this initially formed alkenyl halide, or the product of twice hydrohalogenation to form a dihaloalkane. In most cases, the main regioisomer formed is the gem-dihaloalkane. 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.

WikidataRate this definition:3.0 / 2 votes

1. Hydrohalogenation

   A hydrohalogenation reaction is the electrophilic addition of hydrohalic acids like hydrogen chloride or hydrogen bromide to alkenes to yield the corresponding haloalkanes. If the two carbon atoms at the double bond are linked to a different number of hydrogen atoms, the halogen is found preferentially at the carbon with fewer hydrogen substituents, an observation known as Markovnikov's rule. This is due to the abstraction of a hydrogen atom by the alkene from the acid to form the most stable carbocation, as well as generating a halogen anion. The subsequent reaction proceeds by an SN1 mechanism due to the presence of the electrophilic carbocation and a nucleophilic halide anion, thus resulting in the final product. A simple example of a hydrochlorination is that of indene with hydrochloric acid gas:

How to pronounce hydrohalogenation?

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Numerology

1. Chaldean Numerology

   The numerical value of hydrohalogenation in Chaldean Numerology is: 3

2. Pythagorean Numerology

   The numerical value of hydrohalogenation in Pythagorean Numerology is: 2

References

1. ^ Wiktionary
   https://en.wiktionary.org/wiki/Hydrohalogenation
2. ^ Wikipedia
   https://en.wikipedia.org/wiki/Hydrohalogenation
3. ^ Wikidata
   https://www.wikidata.org/w/index.php?search=hydrohalogenation