NaCN is without doubt a useful reagent. Formylation of phenol ethers (with ZnCN made from ZnCl2/NaCN) and synthesis of phenylacetonitriles from benzylhalides comes to mind. The two preparations on Rh.ws have disadvantages. The synth starting from K4[Fe(CN)6]3 produces volatile HCN as intermediate. The alternative BaO + 3C + N2 ----> Ba(CN)2 + CO just doesn't look too appealing. A FSE session didn't turn up any hits where either KCN/KSCN or NaCN/NaSCN were mentioned together in the same post so I assume that topic was not discussed before though NaSCN __> NaCN seems like a favorable reaction. Here is a snipple from Patent DE89607 (http://l2.espacenet.com/dips/viewer?PN=DE89607&CY=gb&LG=en&DB=EPD)
which claims to be an improvement of Patent US507753 (http://l2.espacenet.com/dips/viewer?PN=US507753&CY=gb&LG=en&DB=EPD)
:
97Kg KSCN and 65Kg Zn dust are heated (to 300-400°C) in an iron-pan with stirring. As soon as the mass begins to gleam the external heating is discontinued and one lets the reaction run till the end. The stripped alkaline solution is to contain 60Kg KCN, i.e. ~90% yield. 1-2% NaOH is said to help the reaction immensley.
Well, that's the only info I have available right now. I'd like to hear some opinions / additional knowledge on that reaction. After all it doesn't seem to be too uncommon.
--psyloxy--