=== Adición de halóxenos ===
These occur between alkenes and electrophiles, often halogens as in [[halogen addition reaction]]s. Common reactions include use of bromine water to [[titration|titrate]] against a sample to deduce the number of double bonds present. For example, [[ethene]] + [[bromine]] → [[1,2-Dibromoethane|1,2-dibromoethane]]:
:C<sub>2</sub>H<sub>4</sub> + Br<sub>2</sub> → BrCH<sub>2</sub>CH<sub>2</sub>Br
This takes the form of 3 main steps shown below;<ref>Lenoir, D.; Chiappe, C. ''Chem. Eur. J.'' '''2003''', ''9'', 1036.</ref>
Image:Electrophilic addition of Br2.png|410px]]
Forming of a π -complex'''
The electrophilic Br-Br molecule interacts with electron-rich alkene molecule to form a [[pi -complex|π -complex]] '''1'''.
#'''Forming of a three-membered bromonium ion'''
The alkene is working as an electron donor and bromine as an electrophile. The three-membered [[bromonium ion]] '''2''' consisted with two carbon atoms and a bromine atom forms with a release of Br<sup>−</sup>.
Attacking of bromide ion'''
The bromonium ion is opened by the attack of Br<sup>−</sup> from the back side. This yields the [[Vicinal (chemistry)|vicinal]] dibromide with an [[antiperiplanar]] configuration. When other nucleophiles such as water or alcohol are existing, these may attack '''2''' to give an alcohol or an ether.
This process is called '''Ad<sub>E</sub>2 mechanism'''. [[ Iodine]] (I<sub>2</sub>), [[ chlorine]] (Cl<sub>2</sub>), [[ sulfenyl]] ion (RS<sup>+</sup>), [[ Mercury ( element)| mercury]] cation (Hg<sup>2+</sup>), and [[ dichlorocarbene]] (:CCl<sub>2</sub>) also react through similar pathways. The direct conversion of '''1''' to '''3''' will appear when the Br<sup>−</sup> is large excess in the reaction medium. A β-bromo [[ carbenium ion]] intermediate may be predominant instead of '''3''' if the alkene has a cation-stabilizing substituent like phenyl group. There is an example of the isolation of the bromonium ion '''2'''.<ref>Brown, R. S. Acc. Chem. Res. 1997, 30, 131.</ref>
=== Adición de haluros de hidróxeno ===