The primary reaction products formed when metastable diacetylene (C4H2*) reacts with ground-state diacetylene (C4H2), ethylene (C2H4), and propene (CH3-CH=CH2) have been spectroscopically characterized using a laser pump-probe scheme. Reaction is initiated in a constrained expansion which limits reaction times to about 20 mu s. The molecular structures of the C6H2 product formed in the C4H2* + C4H2 reaction is identified from its R2PI spectrum and two-photon ionization threshold (9.49 +/- 0.01 eV) as triacetylene (H-C=C-C=C-C=C-H). The analogous scans of the C8H2 product show a clear two-photon ionization onset at 9.09 +/- 0.02 eV, but little resolved vibronic structure above this threshold, consistent with its assignment as tetraacetylene. The R2P1 spectra of the C6H4 product formed in the reactions of C4H2* with C2H4 and CH3-CH=CH2 lead to an identification of this product as 1-hexene-3,5-diyne (CH2=CH-C=C-C=CH). The C7H6 product formed in the reaction of C4H2* with CH3-CH=CH2 possesses an R2PI spectrum close to that of I-hexene-3,5-diyne, supporting its identification as a methylated derivative with the same ene-diyne structure. Two C7H6 isomers meet this criterion, 5-heptene-1,3-diyne (CH3-CH=CH2-C=C-C=C-H) and 2-methyl-1-hexene-3,5-diyne (H2C=C(CH3)-C=C-C=C-H), between which we cannot distinguish. Implications for the mechanisms for these C4H2* reactions are discussed.