My question is why is benzene less reactive than 1,3,5-cyclohexatriene?
I know that benzene does not undergo addition reactions and is extremely stable to oxidizing reagents. C atoms in benzene are connected by delocalized double bonds which make them available to all carbon atoms at the same time. This makes the ring system unusually stable.
I cannot find anything on 1,3,5-cyclohexane and why it is more reactive.
To understand why benzene is less reactive than 1,3,5-cyclohexatriene, let's first clarify some basics about their structures and reactivity.
Benzene is a six-membered ring molecule consisting of alternating single and double bonds. It has a delocalized electron system, commonly referred to as aromaticity, where the π electrons are spread out over the entire ring. This delocalization of electrons creates an exceptionally stable structure for benzene, making it less reactive.
On the other hand, 1,3,5-cyclohexatriene (also known as cyclohexatriene or simply triene) is a molecule that has three double bonds within a six-membered ring. The presence of these isolated double bonds in triene increases its reactivity compared to benzene.
Now, let's explore why benzene's delocalized electron system contributes to its stability. In benzene, the π electrons are spread out over the entire ring, making them available to all the carbon atoms simultaneously. This leads to a phenomenon called resonance. Resonance describes the delocalization of electrons between different possible structures (also known as resonance forms) without breaking any bonds.
Resonance in benzene results in the distribution of electron density throughout the entire ring, creating a system of electron clouds above and below the plane of the molecule. This delocalization of electrons enhances the stability of benzene by decreasing the energy required to disturb the electron system or break any of the bonds.
In contrast, 1,3,5-cyclohexatriene lacks this delocalized π electron system found in benzene. The presence of isolated double bonds in the triene structure makes it more reactive because these double bonds are susceptible to addition reactions. Addition reactions involve breaking the existing double bond(s) and forming new bonds. Since triene has three isolated double bonds, it is more prone to undergo addition reactions compared to benzene.
Moreover, the presence of isolated double bonds makes triene less stable compared to benzene. The double bonds in triene are fixed, and any reagent that can attack double bonds can potentially react with triene. In contrast, benzene's delocalized π electrons are less accessible to electrophilic or nucleophilic reagents, making it less reactive.
In summary, the delocalized π electron system in benzene makes it more stable and less prone to undergo addition reactions compared to 1,3,5-cyclohexatriene, which lacks this electron delocalization. Triene's isolated double bonds make it more reactive since these double bonds are more readily attacked by electrophilic or nucleophilic reagents.