The Baldwin rules are a set of organic chemistry guidelines that indicate the relative p of cyclization reactions for alicyclic compounds. They were first introduced by Jack Baldwin in 1976.
The rules classify ring closures in three ways:
For example, a ring closure can be named as 5-exo trig. 5-endo trig can look correct in theory, but is not favorable according to the Baldwin rules:
Baldwin discovered that the required orbital overlap for bonding only favored certain combinations of ring size and exo / endo / dig / trig / tet parameters.
It is important that the Baldwin rules are guidelines, with exceptions. Cations often ignore Baldwin rules. Rules
The favorable and unfavorable Baldwin ring closure rules are shown below.
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