Advices For Studying Organic Chemistry

2. The carbon-oxygen double bond consists of two electrons in a σ bond and two
   electrons in a π bond.

1. The π bond is formed by overlap of the carbon p orbital with a p orbital from the
   oxygen atom.


2. The electron pair in the π bond occupies both lobes (above and below the plane
   of the σ bonds).

Theπbondingmolecular

orbital of formaldehyde

(HCHO). The electron

pair of the π bond

occupies both lobes.

3. The more electronegative oxygen atom strongly attracts the electrons of both the σ
   bond and the π bond, causing the carbonyl group to be highly polarized ⇒ the
   carbon atom bears a substantial positive charge and the oxygen bears a substantial
   negative charge.

1. Resonance structures for the carbonyl group:

C

or

O +C O − Cδ+ Oδ−

Resonance structure for the carbonyl group Hybrid

2) Carbonyl compounds have rather large dipole moments as a result of the polarity

of the carbon-oxygen bond.

C

H 3 C

H 3 C

δ+ Oδ−

H

H

C O

+¡÷

H 3 C

H 3 C

C

+¡÷

O

Formaldehyde Acetone An electrostatic potential
μ = 2.27 D μ = 2.88 D map for acetone