The quote of the post title comes from R. B. Woodward explaining the genesis of the discovery of what are now known as the Woodward-Hoffmann rules for pericyclic reactions.[cite]10.1021/ja01080a054[/cite] I first wrote about this in 2012, noting that “*for (that) blog, I do not want to investigate the transition states”.* Here I take a closer look at this aspect. I will start by explaining my then reluctance to discuss transition states.
A set of accurate scale models has been developed for use in studies of the structures of amino acids, peptides, and proteins. Models representing atoms or groups of atoms built from hard wood to the scale 1 in.=1A are connected by a clamping device which maintains desired molecular configurations. These accurate models have been used as substitutes for calculation in investigations of the probable configuration of the polypeptide chain in proteins. Analogous models constructed of rubber-like plastic to the scale 1 in.=2A and connected by snap fasteners are designed for qualitative studies of protein structure.