How do I know which cyclohexdiene (?) is more stable? There's one where the double bonds are directly opposite each other (1,4) and another where they are almost next to each other but skip one side (1,3).

http://www.bluffton.edu/~bergerd/classes/CEM222/Handouts/cyclohexadiene_orbitals.pdf

thanks

To determine the relative stability of cyclohexadiene isomers, you can apply the concept of conjugation and the "double bond rule" also known as the "1,4 rule."

Step 1: Understand Conjugation
Conjugation refers to the presence of alternating single and multiple bonds, which creates a delocalized pi-electron system. This delocalization of electrons throughout the molecule contributes to its stability.

Step 2: Apply the 1,4 Rule
The 1,4 rule states that the most stable conformation of a diene (a molecule with two double bonds) is achieved when the double bonds are conjugated and separated by three carbon atoms or multiples thereof (1,4-disubstituted diene). This means that a diene with the double bonds precisely opposite each other (1,4) will be more stable than a diene with double bonds closer to each other but not exactly opposite (1,3).

Step 3: Compare the Isomers
In your specific case, the 1,4-conjugated isomer (double bonds directly opposite each other) will be more stable than the 1,3-conjugated isomer (double bonds almost next to each other but with one carbon atom between them). The 1,4 isomer allows for greater conjugation and delocalization of electrons, resulting in increased stability.

By understanding the concept of conjugation and applying the 1,4 rule, you can determine which cyclohexadiene isomer is more stable.