Table 4.

Bond distances (C-C and C≡C in Å) for the central linear C-C≡C-C unit of propellanes III-C₄ ÷ VII-C₄ and two di-substituted acetylenes R- C≡C-R (R=2-Adamantyl (VIII) and R=Methyl (IX)). Frequency of Raman-active C≡C stretch (in cm⁻¹).

C-C≡C-C	III-C4	IV-C4	VIII	IX	VI-C4	V-C4	VII-C4
R(C-C)	1.506	1.475	1.469	1.463	1.459	1.450	1.418
R(C≡C)	1.225	1.212	1.213	1.210	1.208	1.202	1.191
ν(C≡C)	2286	2384	2390	2426	2423	2478	2581