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US 5,208,361 AGranted
Method of preparing alkylisothiocyanic acid esters
AssigneeDegussa AG
InventorsGunter Giesselmann, Kurt Gunther
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AssigneeDegussa AG
InventorsGunter Giesselmann, Kurt Gunther
Estimating the term…
Alkylisothiocyanic acid esters having the formula R--N.dbd.C.dbd.S can be prepared by reacting N-alkyldithiocarbamates with hydrogen peroxide in aqueous phase at 95.degree. to 130.degree. C. The aqueous solution of N-alkyldithiocarbamate is reacted with a 20 to 40% by weight aqueous solution of hydrogen peroxide in a volumetric ratio of 1 to 0.8 to 1 while maintaining a pH of 1.5 to 4.5. The solutions are preferably sprayed into a reactor, at which time the alkylisothiocyanate formed distills off in vapor form and an aqueous phase containing the byproducts collects in the reactor. The method is capable of significantly increasing the space-time yield because much less sulfur is formed in comparison to the previously known method, which takes place at pH 5 to 9, thereby minimizing the shutdown times previously required for cleaning the reactor.
In a method of preparing alkylisothiocyanic acid esters of the formula R--N.dbd.C.dbd.S, in which R signifies a methyl or ethyl group, from an aqueous solution of an N-alkyldithiocarbamate of the formula R--NH--C(S)--S--Me, in which R stands for a methyl or ethyl group and Me for an alkali-metal atom or an ammonium or alkylammonium group, and from an aqueous solution of hydrogen peroxide, using at least one mole hydrogen peroxide for each mole of N-alkyldithiocarbamate, the reaction being carried out at a temperature of 95.degree. to 130.degree. C. and the alkylisothiocyanic acid ester formed being separated in known manner from the mixture;
Dependencies are inferred from the claim text.