Isocyanic Acid

(HNCO) [75-13-8] CHNO (MW 43.03) InChI = 1S/CHNO/c2-1-3/h2H InChIKey = OWIKHYCFFJSOEH-UHFFFAOYSA-N (HOCN) [420-05-3] CHNO (MW 43.03) InChI = 1S/CHNO/c2-1-3/h3H InChIKey = XLJMAIOERFSOGZ-UHFFFAOYSA-N (KOCN) [590-28-3] CKNO (MW 81.12) InChI = 1S/CHNO.K/c2-1-3;/h3H;/q;+1/p-1 InChIKey = GKKCIDNWFBPDBW-UHFFFAOYSA-M (NaOCN) [917-61-3] CNNaO (MW 65.01) InChI = 1S/CHNO.Na/c2-1-3;/h3H;/q;+1/p-1 InChIKey = ZVCDLGYNFYZZOK-UHFFFAOYSA-M (AgOCN) [3315-16-0] CAgNO (MW 149.89) InChI = 1S/CHNO.Ag/c2-1-3;/h3H;/q;+1/p-1 InChIKey = DWBPIWPCOSHWCK-UHFFFAOYSA-M (synthesis of isocyanates, allophanates, and some heterocyclic compounds) Physical Data: mp −86 °C; bp 23.5 °C (by extrapolation); d 1.14 g cm−3; pKa 3.66. Solubility: poorly sol aliphatic hydrocarbons; sol benzene, toluene, CCl4, ether, THF, etc. Drying: over P2O5. Analysis of Reagent Purity: see Belson and Strachan.1c Preparative Methods: by the depolymerization of cyanuric acid,1a,b or by heating urea.1c The gas can be absorbed in ether, THF, CHCl3, or CCl4. Aqueous solutions of HNCO can be prepared in situ by reacting NaOCN or KOCN with 1 equiv of dil HCl or AcOH at temperatures of approx 0–15 °C. Handling, Storage, and Precautions: isocyanic acid (gas, liquid, or as concentrated solution in anhyd organic solvents) readily polymerizes from −20 °C to rt to give an easily separable mixture of cyanuric acid and cyamelide (a polymer whose structure is as yet unknown), but dilute solutions in ether or CCl4 can be kept at rt without serious decomposition.1c In contact with moisture, even at 0 °C, it hydrolyzes to NH3 and CO2.1c Stored at dry ice or liquid nitrogen temperature, it is quite stable.1c Besides being a strong acid, lacrymator, and vesicant, it possesses an acrid odor. The highly toxic character of isocyanic acid requires that it should be used only in a well-ventilated fume hood.