LEC ALKENES

• Alkenes are unsaturated hydro carbon containing carbon carbon double bond
• The general formula of alkenes are CnH2n
• The alkenes are also callled as olefins meaning oil forming
• Carbon carbon double bond of alkenes consists of

  1 strong sigma bond (397kJmol-1) due tohead on overlapping of sp2 hhybridised orbitals

  1 weak pi bond (284kJmol) obtained lateral or sideways overlapping of 2 2p orbitals of two carbon atom
• Double bond is shorter in bond length than single bond

  Double bond - 134 pm

  Single Bond -154 pm
• Alkenes are easily attacked by reagents or compounds which are in search of electrophilic reagents or compounds which are in search of electron because they behave as a source of loosely held mobile electron
• The presence of weaker pi bond makes alkenes unstable molecule in comparison to alkenes
• Alkenes can be changed into single bond compounds by combining the electrophilic reagents
• ISOMERISM IN ALKENES

  Structural isomerism - chain and position

  Geometrical Isomerism - cis and trans
• Structural Isomeris

  Chain Isomerism - the isomers differe with respect to the chain of carbon atom.

  Same molecular formula differ in skeleton

  Position Isomerism- differ in position of double bond
• Geometrical isomerism

  Have the same molecular formula but differ in spatial arrangement of atoms or group of atom about the double bond

  Same side - cis isomers

  Opposite side - trans isomerism
• Cis isomers is more polar than trans isomers. This is distinguished on properties