Wednesday, July 20, 2011

Alkenes



In alkenes ,
  • the pi bond is weaker than the sigma bond.
  • trans alkenes are generally more stable than cis alkene.
  • stability in creases as the number of R groups connected to the double bond increases.
Have Van der Waals interactions.
Therefore melting point(mp) s and boiling point(bp)s are low.
Mp and bp increases as the number of C atoms increases. This is due to the increasing surface area.
C-C bond between an alkyl bond and one of the double bond carbons is slightly polar because sp3 hybridized carbon donates electron density to the sp2 hybridized carbon.

Reactions
Characteristic reaction of Alkenes is Addition.
Pi bond is broken and two sigma bonds are formed.
Because alkenes are electron rich they react with Electrophiles.
Simple alkenes do not react with nucleophiles or electron rich reagents.
Because the C atoms of the double bond are trigonal planar addition can occur from either from the same side(syn) or both sides(anti).

Important Addition reactions of Alkenes
  1. Hydrohalogenation
  2. Hydration
  3. Halogenation
  4. Halohydrin formation
  5. Hydrocarbonation ( Oxidation)

2 comments:

  1. shaaaa niyamay ne oka therena sinhalen demma nam thawath hoday anyway maru :P :P

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  2. thanks :) welaawak hambunoth sinhalen daannam :-)

    ReplyDelete