Why do radicals attack polyunsaturated fatty acids?

[sameeralord]

Is it because they are unsaturated and can unfold. I understand how one radical would create another radical but I don't know exactly how radical could spread in a fatty acid chain. Any diagram would be useful. Thank you

 

[Ygggdrasil]

The double bonds in unsaturated fattly acids are especially vulnerable to reaction with radicals while radicals react much more slowly with aliphatic hydrocarbons (hydrocarbons with no double bonds).

 

[sameeralord]

The double bonds in unsaturated fattly acids are especially vulnerable to reaction with radicals while radicals react much more slowly with aliphatic hydrocarbons (hydrocarbons with no double bonds).

Thank you for the reply but you are surely capable of telling me why that is so I read theory about hybridisation so you can use that if you want. Thanks Is this something to do with a pi bond?

 

[espen180]

I think this can be sufficiently explained through the mechanism of addition reactions.

Let's say Br₂ dissociates to two electrically neutral Br atoms. Notice these are radicals because of the unpaired electron on each.

Since the double bond has a paticularily high electron density, it is a prime target for radicals, as orbitals can overlap and form covalent bonds. Because of electron-electron repulsion, "stealing" on of these electrons is much easier than in a C-C single bond. Simply put the bond enthalpy of the C-Br bond is lower than the bond enthalpy of the C=C double bond, so the Br radical has little trouble stealing one of the electrons from the C=C double bond. Then the Br^- ion bonds to one of the carbons from the double bond through attraction on opposite charges (stealing the electron makes the acid a carbokation). The other karbon from the double bond now has an unpaired electron (see fig), and the other Br atom from the Br₂ molecule can bond with it and complete the addition reaction.

http://img408.imageshack.us/img408/73/addisjon.png

 

[LudusRex]

I can explain why radicals attack polyunsaturated fatty acids. Radicals are highly reactive chemical species that have an unpaired electron in their outermost shell. This makes them highly unstable and eager to react with other molecules in order to stabilize themselves.

Polyunsaturated fatty acids (PUFAs) have multiple double bonds in their carbon chain, making them unsaturated. These double bonds create kinks or bends in the fatty acid chain, making it easier for radicals to attack and break the bonds. This is because the double bonds weaken the overall stability of the fatty acid chain, making it more susceptible to attack.

When a radical attacks a PUFA, it causes a chain reaction known as lipid peroxidation. This process involves the radical stealing an electron from the PUFA, creating a new radical in the process. This new radical can then go on to attack other PUFA molecules, creating a chain reaction.

The attack of radicals on PUFAs is also known as oxidative stress, and it can have damaging effects on cells and tissues. The resulting lipid peroxidation can lead to cell membrane damage, which can disrupt important cellular processes and potentially lead to cell death.

I understand your confusion about how radicals can spread in a fatty acid chain. Here is a simplified diagram to help illustrate the process:

[Diagram of a PUFA chain with double bonds and arrows representing the attack of radicals and the creation of new radicals]

In conclusion, radicals attack polyunsaturated fatty acids because these fatty acids are unsaturated and have weaker bonds due to their double bonds. This makes them easier targets for radicals, which can lead to a chain reaction of lipid peroxidation and potential damage to cells and tissues. I hope this explanation and diagram have helped to clarify the process for you.