Compilation of the CCH (y-axis) and CH₃OH (x-axis) total column densities, derived with single-dish observations towards WCCC objects, hot corinos, molecular clouds, and PDRs. The points refer to measurement towards: the WCCC object prototype L1527 (blue open circle: Sakai et al. 2008); the hot corino prototype IRAS 16293-2422 (filled blue circle: Van Dishoeck et al. 1995); the sources in the Perseus cloud (black: Higuchi et al. 2018); the known hot corinos among the Perseus sources (filled pink circle: Higuchi et al. 2018), the sources in OMC-2/3 (red: this work); various PDRs (green): Horsehead nebula (Teyssier et al. 2004; Guzmán et al. 2013), OMC-1 Ridge PDR and core (Ungerechts et al. 1997), Orion Bar (Cuadrado et al. 2015, 2017), IC63 (Jansen et al. 1994; Teyssier et al. 2004), and Mon R2 (Ginard et al. 2012); various pre-stellar cores (light blue): L1498 (Padovani et al. 2009, Daprà et al. 2017), TMC-1 (Friberg et al. 1988, Pratap et al. 1997, Soma et al. 2015), L1521E (Nagy et al. 2019) and L134N (Dickens et al. 2000) as representatives of cold molecular clouds. Upper limits are represented by arrows.