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Mechanisms of Alkenes
12 December 2012
19:00

Electrophilic addition
- Double bond has many electrons so its easily attracted by electrophiles- electron deficient
- Double bond is nucleophilic- electron rich

- Shake an alkene with orange bromine
water- solution decolourises
- Bromine is added across double bond to
form dibromoalkane
Why are potassium manganate and bromine water
decolourised when they react with alkenes?
- The structure that gives them their colour eg
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- In the presence of a nucleophile, eg
...


The polarised bromine acts as an
electrophile and attracts an electron pair
from the double bond to form a C -- Br
bond

Bromine ion acts as nucleophile- attacks
carbocation to give away electrons

- HBr adds to an unsymmetrical alkene--> two possible products
- Amount of product produced- depends on how stable the carbocation is
- More stable carbocation is more likely to form- the secondary product is more stable because it has
electron densities on either side of the carbon that the Bromine is attached to whereas the primary
product has the electron density from one carbon that is attached to it
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7 Organic Chemistry Page 2

Diol- two OH groups

Addition reaction



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