Please enable JavaScript.
Coggle requires JavaScript to display documents.
Alkene (Halogenoalkane (Hydrogen halides, such as HCl and HBr, react with…
Alkene
Halogenoalkane
Hydrogen halides, such as HCl and HBr, react with alkenes to produce halogenoalkanes. These reactions take place rapidly in solution at room temperature.
All the hydrogen halides are able to react in this way, but the reactivity is in the order HI > HBr > HCl due to the decreasing strength of the hydrogen halide bond down Group 17. So HI, with the weakest bond, reacts the most readily.
-
Alcohols
The reaction with water is known as hydration, and converts the alkene into an alcohol. In the laboratory, it can be achieved using concentrated sulfuric acid as a catalyst. The reaction involves an intermediate in which both H+ and HSO4− ions are added across the double bond, but this is quickly followed by hydrolysis with replacement of the HSO4− by OH− and reformation of the H2SO4.
-
Conditions: heat with steam and catalyst of concentrated H2SO4
This reaction is of industrial significance because ethanol is a very important solvent, and so is manufactured on a large scale.
Alkane
-
This process, known as hydrogenation, is used in the margarine industry to convert oils containing many unsaturated hydrocarbon chains into more saturated compounds which have higher melting points. This is done so that margarine will be a solid at room temperature. However, there are now widespread concerns about the health effects of so-called trans fats, produced by partial hydrogenation.
-
Dihalogenoalkane
Halogens react with alkenes to produce dihalogeno compounds. These reactions happen quickly at room temperature, and are accompanied by the loss of colour of the reacting halogen. Note that the name and structure of the product indicates that a halogen atom attaches to each of the two carbon atoms of the double bond.
-
Addition polymers
Because alkenes readily undergo addition reactions by breaking their double bond, they can be joined together to produce long chains known as addition polymers. The alkene used in this reaction is known as the monomer, and its chemical nature determines the properties of the polymer. Polymers, typically containing thousands of molecules of the monomer, are a major product of the organic chemical industry and many of our most familiar and useful plastics are polymers of alkenes.
As polymers are such large molecules, their structures are shown using a repeating unit, which has open bonds at each end. It is put in a bracket with n as subscript to denote the number of repeating units.
For example, ethene polymerizes to form poly(ethene), commonly known as polythene.
-
Similarly, propene polymerizes to form poly(propene), often called polypropylene.
-
-
Other common addition polymers include poly(chloroethene), also known as PVC, and PTFE, poly(tetrafluoroethene), often marketed as Teflon®.
