Advices For Studying Organic Chemistry

i) The antibonding orbital of the allyl radical is of highest energy and is empty in

the ground state of the radical.

Figure 13.2 Combination of three atomic p orbitals to form three π molecular
orbitals in the allyl radical. The bonding π molecular orbital is
formed by the combination of the three p orbitals with lobes of the
same sign overlapping above and below the plane of the atoms. The
nonbonding π molecular orbital has a node at C2. The antibonding π
molecular orbital has two nodes: between C1 and C2, and between C2
and C3. The shapes of molecular orbitals for the allyl radical
calculated using quantum mechanical principles are shown alongside
the schematic orbitals.

3. The structure of allyl radical given by MO theory:

C

C

C

H

HH

H 1 2 3 H

1/2 1/2

1) The dashed lines indicate that both C–C bonds are partial double bonds ⇒ there

is a π bond encompassing all three atoms.

i) The symbol 1/2• besides the C1 and C3 atoms ⇒ the unpaired electron spends