SOLIS

We studied the line emission from CH3CN and its deuterated isotopologue CH$_2$DCN towards prototypical Class I object SVS13-A, where deuteration of a large number species has already been reported. Our goal is to measure CH$_3$CN in protostar, for first time, order constrain formation pathways chemical evolution early prestellar core 0 evolved stages. imaged CH2DCN SVS13-A using IRAM NOEMA interferometer at 3mm context Large Program SOLIS (with spatial resolution 1.8"x1.2"). The images have complemented by spectra collected IRAM-30m ASAI, that provided an unbiased spectral survey 3mm, 2mm, 1.3mm. observed analysed LTE non-LTE LVG approaches. NOEMA/SOLIS show this emits unresolved area centered continuum peak, suggesting methyl cyanide isotopologues are associated with hot corino previously via other iCOMs. In addition, we detected 41 11 ASAI transitions CH2DCN, respectively, which cover upper level energies (Eup) 13 442 K 18 200 K, respectively. derived [CH2DCN]/[CH3CN] ratio $\sim$9\%. This value consistent those measured cores factor 2-3 higher than protostars. Contrarily what expected molecular species, does not decrease respect measurements younger Finally, discuss why our new results suggest was likely synthesised gas-phase reactions frozen onto dust grain mantles during cold phase.