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Alkylhalides: Substitution reactions 6 (Sn1)


Alkylhalides: Substitution

Nucleophile substitution reaction (Sn1 reaction)
Sn1 side reactions
I will now discuss some side reactions that can occur when a Sn1 reaction takes place.


Carbocation shift
Illustrated in the scheme below:


Benzyl- and allylhalides 
Benzyl- and allylhalides can undergo Sn1 AND Sn2 reactions. How to distinct them?

  • Sn1 conditions: protic solvent and by adding a weak attacking nucleophile. Note: Benzyl- and allylhalides easily undergo Sn1 reactions, because their carbocations are very stable.
  • Sn2 conditions: aprotic solvent and by adding a strong attacking nucleophile. Note: tertiary benzylhalides and tertiary allylhalides will NOT undergo a Sn2 reaction because of the steric effects (see chapter Sn2 reaction blogposts).
Sn2 reaction examples


Sn1 reaction examples


Sn1 and Sn2 reactions in biology, nature and medicines

S-Adenosyl methionine
This is a biological methylating agens, also known as SAM.
It is a frequently used cosubstrate involved in methyl transfer reactions. For more details I would suggest to look on more specified articles around this substance. A sulfide is the leaving group in this molecule.


Methyltetrahydrofolate
This is like SAM also a biological methylating agens, the amine group is the leaving group of this molecule.

Sulfur mostard
Most commonly used for Chemical Warfare. This is a very very toxic molecule and can cause severe pains and can have devastating consequenses for the body.


Temozolomide
This molecule is an alkylating agent that is used to treat aggressive brain tumors, its most famous use was for treatment of the brain tumor of Ted Kennedy.


Comments

  1. Anonymous27 July 2022 at 12:29

    Thanks for the information. I really like the way you express complex topics in lucid way. It really helps me understand it much better way. adenosyl methionine

    ReplyDelete

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