= Solution
\b[The large negative <activation entropy> is consistent with a strongly organized bimolecular <cycloaddition>.] Two separately translating and rotating molecules must approach with a restricted orientation to form a compact ring-forming transition state. Losing relative positional and orientational freedom lowers entropy.
Internal conformational restrictions and solvent rearrangement can contribute too. In a nonpolar solvent, a simple association picture is more plausible than assigning the whole effect to strong ionic solvation, but the numerical value is not a direct count of molecular orientations alone.
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