pericyklisen

Pericyklisen is a term that can refer to several distinct concepts, primarily in chemistry and biology. In organic chemistry, a pericyclic reaction is a type of concerted chemical reaction in which all bond breaking and bond forming occur in a single, cyclic transition state. These reactions are characterized by their stereospecificity and regioselectivity, and are often predictable through the Woodward-Hoffmann rules, which utilize molecular orbital symmetry to determine whether a reaction is allowed or forbidden under thermal or photochemical conditions. Common examples include cycloadditions, electrocyclic reactions, and sigmatropic rearrangements. The term highlights the cyclic nature of the transition state involved.

In a biological context, particularly in the study of blood vessels, the term can relate to pericytes. Pericytes are cells that surround the endothelium of capillaries and venules. They are often described as being "perivascular," meaning they are located around blood vessels. While not a direct chemical reaction, their close association with the vasculature gives rise to the potential for related terminology. These cells play crucial roles in blood vessel stability, blood flow regulation, and tissue repair. The specific usage of "pericyklisen" might therefore allude to processes or structures associated with these perivascular cells, though this usage is less standardized than in organic chemistry. It is important to consider the context to understand the precise meaning of the term.