tokens: Herschel /HIFI guaranteed time CHESS key program (Ceccarelli et al. 2010 ). On the scale of individual envelopes, N 2 D + is seen only towards A (Jørgensen et al. 2011 ). Most recently, the distribution of N 2 D + has been analysed by Murillo et al. ( 2018b ) on the scale of the individual protostars and the circumbinary envelope. C2.31 Glycolonitrile (HOCH<sub>2</sub>CN), <italic>m</italic> = 57 Glycolonitrile was detected towards source B by Zeng et al. ( 2019 ). C2.32 Aminoacetonitrile (NH<sub>2</sub>CH<sub>2</sub>CN), <italic>m</italic> = 56 An upper limit was derived towards source B by Zeng et al. ( 2019 ). C2.33 Formyl cyanide (CHOCN), <italic>m</italic> = 55 An upper limit was derived towards source B by Zeng et al. ( 2019 ). C2.34 Ethenimine (CH<sub>2</sub>CNH), <italic>m</italic> = 41 An upper limit was derived towards source B by Zeng et al. ( 2019 ). C2.35 Nitrous acid (HONO), <italic>m</italic> = 47 Coutens et al. ( 2019a ) detected HONO towards source B and derived an accurate column density. C2.36 Nitrogen dioxide (NO<sub>2</sub>), <italic>m</italic> = 46 Coutens et al. ( 2019a ) derived an upper limit for NO 2 towards source B. C2.37 Nitrosyl cation (NO<sup>+</sup>), <italic>m</italic> = 30 Coutens et al. ( 2019a ) derived an upper limit for NO + towards source B. C2.38 Nitric acid (HNO<sub>3</sub>), <italic>m</italic> = 63 Coutens et al. ( 2019a ) derived an upper limit for HNO 3 towards source B. C3 S-bearing molecules C3.1 Hydrogen sulphide (H<sub>2</sub>S), <italic>m</italic> = 34 H 2 S was detected on envelope scales (Blake et al. 1994 ), as was HDS (van Dishoeck et al. 1995 ; Caux et al. 2011 ). It was also observed towards the two protostars individually (Chandler et al. 2005 ; Jørgensen et al. 2011 ). On large cloud and core scales, H 2 S is also observed, but at lower abundances than closer to the binary source (Wakelam et al. 2004 ). H 2 S was detected on envelope scales in the infrared with the Herschel /HIFI guaranteed time CHESS key program (Ceccarelli et al. 2010 ). Baryshev et al. ( 2015 ) reported a line of H 2 S in absorption from the foreground cloud. HDS and HD 34 S were detected towards source B by Drozdovskaya et al. ( 2018 ) with accurate column densities provided. C3.2 Carbon monosulphide (CS), <italic>m</italic> = 44 C 32 S was the second molecule studied in IRAS 16293-2422. Its emission line profile showed strong self-absorption and prominent asymmetry, which was interpreted as a signature of infall (Walker et al. 1986 ; van Dishoeck et al. 1995 ). C 34 S was observed soon thereafter (Menten et al. 1987 ). CS, like CO, is present on the large cloud and core scales; and the smaller circumbinary envelope and disc-A and -B scales (Mizuno et al. 1990 ; Walker, Carlstrom Bieging 1993 ; Blake et al. 1994 ; Narayanan et al. 1998 ; Caux et al. 2011 ; Jørgensen et al. 2011 ; Takakuwa Kamazaki 2011 ; van der Wiel et al. 2019 ). It also traces the outflows (Walker et al. 1990 ; Girart et al. 2014 ), and shocks,
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