describe the reactions of alkenes – electrophilic addition;oxidation with cold dilute and hot concentrated KMO4; additionpolymerisation

Alkenes are hydrocarbons that contain a carbon-carbon double bond. They are unsaturated compounds and are generally more reactive than alkanes. Here are the reactions of alkenes:

1. Electrophilic Addition: This is the most common reaction of alkenes. In this reaction, an electrophile (a molecule that can accept a pair of electrons) reacts with the alkene, which acts as a nucleophile (a molecule that can donate a pair of electrons). The electrophile is attracted to the electron-rich double bond of the alkene, causing the double bond to break and the electrophile to add across the carbon atoms. For example, when bromine (Br2) is added to ethene (C2H4), 1,2-dibromoethane is formed.

2. Oxidation with Cold Dilute and Hot Concentrated KMnO4 (Potassium Permanganate): Alkenes can be oxidized by KMnO4 to form diols (compounds with two alcohol groups). In cold, dilute conditions, the reaction is typically mild and results in the formation of a vicinal (adjacent) diol. In hot, concentrated conditions, the reaction is more vigorous and can lead to the formation of carboxylic acids or even carbon dioxide, depending on the structure of the alkene.

3. Addition Polymerisation: Alkenes can also undergo a reaction called addition polymerisation, where many alkene molecules (monomers) join together to form a long chain (polymer). This reaction is initiated by a catalyst or by heat. For example, polyethylene, a common plastic, is made by the polymerisation of ethene.

Remember, the specific products of these reactions can vary depending on the structure of the alkene and the conditions of the reaction.