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