Structure and Reactivity of alkenes.

https://www.youtube.com/watch?v=Df3tpeeJtHQ

When do sigma bonds form

When electron orbitals directly overlap

Key facts about alkAnes

The bond angles are tetrahedral (109.5 degrees)

Sigma bonds are freely rotational.

What are alkenes

Unsaturated hydrocarbons with the general formula CnH2n

What is ethene

A planar molecule, they are flat with all of the atoms lying on the same plane

There are 3 bonding regions around each carbon atom, they repel and move as far apart as possible, so bond angles ar ound carbon atoms are are around 120 degrees.

What is difference between ethane and ethene

Just like ethane, there are sigma bonds between the carbon and hydrogen atoms

However, when double bond forms ,a pi bond is formed. it is above and below the sigma bond, its only1 pi bond

So double bond in alkenes consists of sigma and pi bond

What is key points about alkenes

Pi bonds cannot rotate, this means structure of alkene across double bond is locked, This means alkenes can stereoisomers

Alkenes are highly reactive, this is due to double bond. The bond enthalpy of pi bond is less than the sigma bond, thats because pi bond is sideways overlap of orbitals, sigma bond is direct overlap,so pi bond takes less energy and is easier to break,,

Double bond has two pairs of electrons, one pair of electrons in sigma bond , one in pi bond, sothey have high electron density in double bond