Detailed interpretations of the spectra of endo-(Ia) and exo-(Ib) cyclopentadiene dimer, endo-cyclopentadiene trimer (VII), and endo-cyclopentadiene tetramer (IX) are given. The doublet found at τ 9·25 in the spectrum of the endo-trimer is assigned to 10-Hy(VII), the doublet coupling being due to 10-Hx which is situated at τ 7·76. A similar AB system is found in the spectrum of the endo-tetramer.
