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Detailed study of mesomerism

Exercises on mesomerism (2)

"Candidat" atoms to mesomerism

Atoms candidates to mesomerism are those a) who have one or more solitary doublets b) who are the origin of one or more π bonds c) who do not have their full octet Furthermore to be candidates, two such atoms must be neighbors, except a) with a)

Find all the candidate atoms in the following molecule: Click for the answer! Atom 1. Complete octet (3 C-H bonds, une C-C bond), no π bond, no own doublet: not candidate Atom 2. Incomplete octet (1 C-H bond, 2 C-C bonds, no doublet because of +), the neighbour, atom 3 is candidate: candidate Atom 3. π bond, the two neighbors are candidates: candidate Atom 4. π bond, the two neighbors are candidates: candidate Atom 5. Own doublet (1 C-H bond, 2 C-C bonds, doublet because of -), the neighbour, atom 4 is candidate: candidate Atom 6. Complete octet , no π bond;, no own doublet: not candidate Atom 7. Own doublet , no π bond;, no neighbor candidate: not candidate

Displacement candidate and possible arrows

Simple candidates arrows - must be between "candidate" atoms - must transform a) an own doublet to a π doublet starting from the same atom or conversely b) a π doublet to a π doublet starting from the same atom Simple possible (allowed) arrows must also comply with the octet rule (no more than 8 electrons in an atom)

Draw a candidate arrow every time between candidate atoms in the following molecule and decide if it is allowed . Click three times!

Cascades of arrows

In the case of multiple sequential arrows, one arrow may ensure that the candidate arrow which follows may become allowed!

Arrow a: allowed Arrow b: The displacement induced by arrow a removes an electron from carbon 4 , the candidate arrow b is thereafter allowed