what is the first and second step in a alkene halogenation reaction
Go to the following site, scroll about half way down the page. The site talks about halogenation in general, then gives you a site you can click on to obtain the mechanism. The mechanism you want is there.
what site dr bob
OOPS!
Sorry. Here it is.http://www.chemguide.co.uk/organicprops/alkenes/halogenation.html
The first step in alkene halogenation is the initiation step, where a halogen molecule (e.g., Cl2 or Br2) is split into two halogen atoms (e.g., Cl∙ or Br∙). The second step is the propagation step, where the halogen atom reacts with the alkene to form a halogenated alkane.
To carry out a halogenation reaction, you would typically follow these steps:
1. Initiation: The reaction is usually initiated by introducing a source of energy, such as heat or light, to break the diatomic halogen molecule into halogen atoms. For example, in the case of chlorine (Cl2), exposure to ultraviolet (UV) light causes the Cl-Cl bond to break, resulting in two chlorine radicals (Cl∙).
2. Propagation: In the propagation step, the alkene molecule reacts with the halogen radical, forming a halogenated alkane and a new halogen radical. For example, if we have an alkene (e.g., ethene, C2H4) and a chlorine radical (Cl∙), the reaction can proceed as follows:
C2H4 + Cl∙ → CH2=CHCl
This creates a new alkyl radical (CH2∙) and a molecule of hydrogen chloride (HCl). The process repeats as the alkyl radical generated in the above step reacts with another molecule of the halogen (e.g., chlorine) to produce the halogenated alkane and a new halogen radical. The reaction continues until all the alkene has been consumed or until it is terminated by adding a suitable terminating agent (e.g., an antioxidant) to quench the radical reactions.
It's important to note that there may be variations in reaction conditions depending on the specific alkene, halogen, and desired reaction outcome. Additionally, the regioselectivity and stereoselectivity of the reaction may also need to be considered.