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Alkenes - Coggle Diagram
Alkenes
Reactions
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Cracking- Breaking down of large Alkenes into smaller, more useful alkanes and alkenes
Oxidation by KMNO4
Alkenes can also be oxidised by acidified potassium manganate(VII) (KMnO4) which is a very powerful oxidising agent. Alkenes can be oxidised by both hot and cold KMnO4 which will result in different products being formed
When shaken with cold dilute KMnO4 the pale purple solution turns colourless and the product is a diol
When alkenes are reacted with hot concentrated KMnO4 the conditions are harsher causing the C-C double bond to completely break
Addition Polymerisation- Addition polymerisation is the reaction of many monomers containing at least one double C-C bond to form the long-chain polymers as the only product. In addition polymerisation reaction, the C-C double bond is broken to link together the monomers and form a polymer. This is a common method to make plastics
Properties
Chemical Properties
Polarity- Alkenes are weakly polar just like alkanes but are slightly more reactive than alkanes due to the presence of double bonds. The π electrons which make up the double bonds can easily be removed or added as they are weakly held.
Reactivity- Unsaturated alkenes compounds are highly reactive. They form a double bond between carbon-carbon atoms which makes them less stable due to loosely held pi bonds.
Physical Properties
These double-bonded compounds are colourless and odourless in nature. However, ethene is an exception because it is a colourless gas but has a faintly sweet odour.
Solubility- The alkenes are insoluble in water due to their nonpolar characteristics. But are completely soluble in nonpolar solvents such as benzene, ligroin, etc.
Boiling Point- The boiling points of the compounds increase as the number of carbon atoms in the compound increases.
Melting Point- The melting point of alkenes is similar to that of alkanes. However, cis-isomer molecules have a lower melting point than trans- isomers as the molecules are packed in a U-bending shape.
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Alkenes are a class of hydrocarbons unsaturated compounds with at least one carbon-to-carbon double bond. Alkenes are more reactive than alkanes due to the presence of the double bond.
