Discovery of CH₂CHCCH and detection of HCCN, HC₄N, CH₃CH₂CN, and, tentatively, CH₃CH₂CCH in TMC-1

We present the discovery in TMC-1 of vinyl acetylene, CH 2 CHCCH, and detection, for first time a cold dark cloud, HCCN, HC 4 N, 3 CN. A tentative detection CCH is also reported. The column density acetylene (1.2 ± 0.2) × 10 13 cm −2 , which makes it one most abundant closed-shell hydrocarbons detected TMC-1. Its abundance only three times lower than that propylene, CHCH . densities derived HCCN N are (4.4 04) 11 (3.7 0.4) respectively. Hence, HCCN/HC ratio 1.2 0.3. For ethyl cyanide we derive (1.1 0.3) These results compared with state-of-the-art chemical model TMC-1, able to account observed abundances these molecules through gas-phase routes.