why doesn't carbon form quatrple bonds?
A quadruple bond is a type of chemical bond between two atoms involving eight electrons.
Carbon cannot form four bonds with another carbon atom because once they have the triple bond, there's no possible orbit left that would allow one more electron to orbit both the nuclei.
The first carbon to carbon bond is in that plane only. The second and the third carbon to carbon bond are above and below the ring. The fourth bond (quadruple bond) if formed would be pointing away from the two carbons. In order for this bond to exist, the other three bonds need to be tremendously bent and this is energetically very unfeasible. This strain thus resists the formation of the quadruple bond.