ethanethioic S-acid thioacetic acid ethanethioic O-acid C2H4OS chebi_ontology InChI=1S/C2H4OS/c1-2(3)4/h1H3,(H,3,4) CHEBI:46800 Beilstein:1733298 ethanethioic O-acid 76.11856 0 75.99829 DUYAAUVXQSMXQP-UHFFFAOYSA-N CC(O)=S Gmelin:1216872