The substituent effects of X- in 1-X-hexatrienes, which are chain π-systems with conjugated double bonds, was compared with those in PhX, which are ring π-systems, using core electron binding energy shifts (ΔCEBE) of the carbon atoms in the molecules. The ΔCEBE of C 1C 4 in 1-X-hexatrienes are generally close to ΔCEBE of C 1C 4 in PhX. The ΔCEBE of carbon atoms in the 1-X-hexatrienes are not only highly correlated to the Hammett σ substituent constants, but their numerical values are also close to each other. The core electron binding energies (CEBE) of the six carbons in 1-X-hexatriynes, which are the chain π-systems with conjugated triple bonds, were calculated by density functional theory (DFT) and the substituent effect was investigated. Average ΔCEBE of the five carbon atoms between C 2 and C 6 in 1-X-hexatriyne were calculated. 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