acetylene in the Gas Phase and in Solution in the Range 1100 to 4000Summary. The electronic spectra of the title compounds I(n), n = 1 to 5, were recorded under standard conditions for quantitative comparison. Spectra of 1(1) to 1(4) in the gas phase and of I(2) to 1(5) in nonpolar solutions are presented in a computer plotted form, and wave length maxima and intensities are listed. Tcntative assignments of the medium-intensity, first transition (A band) and the ultrahigh-intensity, second transition (B band) are given. Finally, spectra of I(2) to 1(5) rccorded at -150" are presented and discussed (A band). The syntheses of 1(3) to 1(5) are given in detail. treatment will appear in a separate paper [12].

The PE.‐spectra of triacetylene 1 (3), methyldiacetylene 2 (2), dimethylacetylene 3 (1) and dimethyldiacetylene 3 (2) have been recorded. The π‐ionization potentials of the unsubstituted acetylenes can be parametrized in terms of a LCBO‐model.

Kfingclbergstrasee 80, CH-4056 Basel. Switzcrlmd (20. XI. 74) Summauy. 1,.5-Cyclooctadiyne 1 was isolated in 2 pcrcent yield from polymerized butatrieno 5. Other oligomcrs of 5 wcre dctected in the reaction mixture by combined GLC./MS. analysis but have not been identified. Diets-Aldev adducts of I with two equivalents of 1,J-butadiene and of 2,3-dimethyI-l.J-butarli~ne have bcan preparcd. In the prescnce of strong base 1 isomorizcd to cyclooctatctraenc. 5 was rcformcd by photolysis of 1. Attcmpts to preparc transition mctal complexes of 1 failed. Effrxts of ring strain and of transannular interaction on the rcactivity of 1 arc discusscd. The dirnerization of 5 to 1 is predicted to be strongly cxothcrmic.The synthesis of medium-sized cyclic alkynes [l] and the investigation of their chemical reactivity as a function of geometric ring strain have been the object of considerable effort during the past twenty years. The smallest unsubstituted cycloalkyne yet isolated is cyclooctyne which was first prepared by Bloquist in 1953 [2], Evidence for the intermediate existence of the lower homologues cycloheptyne, .-hexyne, and -pentyne is limited to trapping and self-trapping reactions [3aJ. ' 1 2 3 4 ---1) Permanent addrcss: