Sigmatropiska

Sigmatropes are a class of chemical reactions in organic chemistry where a sigma bond is broken and a new sigma bond is formed in a concerted manner. The term "sigmatropic" is derived from the Greek word "sigmē," meaning "line" or "trace," referring to the movement of sigma electrons. These reactions are characterized by the movement of a sigma bond along a chain of atoms, typically involving the migration of a hydrogen atom or a group of atoms.

Sigmatropic reactions are further classified into two main types: pericyclic and non-pericyclic. Pericyclic reactions involve the simultaneous breaking and forming of multiple bonds, typically in a cyclic transition state. These reactions are further subdivided into two categories: suprafacial and antarafacial. Suprafacial reactions occur when the migrating group moves on the same face of the π-system, while antarafacial reactions occur when the migrating group moves on the opposite face.

Non-pericyclic sigmatropic reactions, on the other hand, involve the migration of a hydrogen atom or a group of atoms along a chain of atoms without the involvement of multiple bonds. These reactions are typically less common and less studied than pericyclic sigmatropic reactions.

Sigmatropic reactions are important in organic synthesis as they allow for the construction of complex organic molecules from simpler precursors. They are also used in the study of reaction mechanisms and the development of new synthetic methods.