Advices For Studying Organic Chemistry

Solomons/SoloCh01

1. Maximum overlap between the p orbitals of a π bond occurs when the axes of the
   p orbitals are exactly parallel ⇒ Rotation one carbon of the double bond 90°
   breaks the π bond.


2. The strength of the π bond is 264 KJ mol–1 (63.1 Kcal mol–1)⇒ the rotation
   barrier of double bond.


3. The rotation barrier of a C–C single bond is 13-26 KJ mol–1 (3.1-6.2 Kcal mol–1).

Figure 1.25 A stylized depiction of how rotation of a carbon atom of a double
bond through an angle of 90° results in breaking of the π bond.

1.13B. Cis-Trans Isomerism

Cl

Cl

Cl

Cl

H

H

H

H

cis-1,2-Dichloroethene trans-1,2-Dichloroethene

1. Stereoisomers
   
   
   1. cis-1,2-Dichloroethene and trans-1,2-dichloroethene are non-superposable ⇒
      Different compounds ⇒ not constitutional isomers
   
   
   2. Latin: cis, on the same side; trans, across.