alkenes have a high electron density at the C=C bonds.
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And so they can be attacked by substances we call electrophites (electron deficit species) some substances are added to the carbon atoms with the double bond.
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hydrogenation/addition of hydrogen
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alkenes react with hydrogen in the presence of a nickel catalyst at about 152 degrees to form alkanes e.g
this type of reaction is useful in converting unsaturated oils into margarine.
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with steam
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they react with steam in the presence of phosphoric acid (catalyst) to form alcohols.
ethene reacts to form ethanol:
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with hydrogen halide
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react with hydrogen halide to form a halogenoalkane the reactivity decreases with the bond strength of the hydrogen halide.
Ethene reacts with hydrogen chloride chloroethane:
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with halogens
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they react very fast with halogens to form (di)halogeno alkane. the reaction between bromine and alkenes is used as a test for unsaturation. And also potassium promanganate.
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with dilute manganate 7
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alkenes are quickly oxidised by dilute manganate 7 to form diol (contains OH) in this reaction the OH group is added to the carbons which had the C=C.
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self addition polymerisation
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in the presence of a catalyst, right temperature and pressure they undergo polymerisation to form polyalkenes.
some compounds containing C=C may also undergo polymerisation to form polymers.
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