Lead thiocyanate, reaction with acid

Thiocyanates are rather stable to air, oxidation, and dilute nitric acid. Of considerable practical importance are the reactions of thiocyanate with metal cations. Silver, mercury, lead, and cuprous thiocyanates precipitate. Many metals form complexes. The deep red complex of ferric iron with thiocyanate, [Fe(SCN)g] , is an effective iadicator for either ion. Various metal thiocyanate complexes with transition metals can be extracted iato organic solvents. 

Previously, the reaction of 3,4,6-tri-0-acetyl-l,5-anhydro-2-deoxy-D-arabino-hex-l-enitol (D-glucal triacetate) (20) with lead thiocyanate in a mixture of acetic acid, acetic anhydride, and carbon tetrachloride had been reported by Igarashi and Honma.37 They observed formation of isothiocyanate 21 as the main product, accompanied by a mixture of four isomeric thiocyanates. 

For reasons already outlined, it is not possible to evaluate single-ion solvent activity coefficients, Vy-, with any degree of certainty. It is more satisfactory to choose one anion as a standard. We have chosen thiocyanate ion as a standard, and this leads to the linear free energy expressions (49) for solubilities of silver salts to (50) (cf. 29) for rates of reaction with methyl iodide and to (51) for acid strengths. In these equations, the value for an anion Y on transfer from DMF to... 

Construction of the simplest fused heterocyclic system that shows some anabolic activity starts by epoxidation of the olefin at C2 in 23-1 with peracetic acid buffered with sodium acetate (23-2) (Scheme 5.23). Reaction of this intermediate with potassium thiocyanate and phosphoric acid, essentially thiocyanic acid, leads to diaxial opening of the oxirane to form the 3a-hydroxy-2/8-cyanate 23-3. Treatment of the product with base leads to formation of the /3-thioepoxide 23-5. Formation of that product can be rationalized by assuming that the first step involves removal by base of a proton on the hydroxyl group. That alkoxide then proceeds to add to the cyano group at C2 to form a transient five-membered ring as in... 

LEAD DINITRATE (10099-74-8) A strong oxidizer. Violent reaction with reducing agents, combustible materials, ammonium thiocyanate, potassium hexanitrocobalite(III) (C.I. pigment yellow), cyclopentadienyl sodium, red hot carbon, lead(II) phosphinate, phosphorus, tin(II) chloride. Incompatible with aluminum, ammonia, citric acid, hydrozoic acid, metal phosphinates, methyl isocyanoacetate, sodium peroxyborate, potassium acetate, strong oxidizers, trinitrobenzoic acid, urea nitrate. 

Type K Syntheses (C—C—N—C—S). The reaction between jS-(ethoxycar-bonyl)acryloyl isothiocyanates (obtained from the acid chloride and lead thiocyanate) and aromatic amines gives the 2-arylamino-A -thiazolin-4-ones (48) in good yield.2-(Substituted amino)-A -thiazolines may also be obtained in high yields by allowing vicinal iodo-isothiocyanates to react with amines e.g. PhCH(NCS)CH2l with amines, in the absence of light, gives (49). ... 

One of the most valuable methods for the preparation of A2-thiazolines is of this class. The reaction of 2-haloalkylamines (334) with thioamides, metal thiocyanates or carbon disulfide give 2-alkyl- or -aryl- (335), 2-amino- (336), and 2-mercapto- (337) A2-thiazolines, respectively (Scheme 218) (17CB804). A method derived from the last procedure leads to a convenient synthesis of 2-phenyl-A2-thiazolines (340) under very mild conditions and consists of the condensation between a-aminothiols (338) and thiobenzoylmercaptoacetic acid (339 Scheme 219) (74TL1863) (this method could be better classified under Type E, Section 4.19.3.2.5). 

Sulphide. Reduce a portion of the residue with zinc and dilute sulphuric acid. If hydrogen sulphide is evolved (lead acetate paper test), sulphide is present. It is preferable to employ the sodium carbonate residue rather than the original mixture in testing for sulphide, for the latter may contain sulphite and thiocyanate, both of which give hydrogen sulphide when reduced (cf. Section IV.4, reaction 8 and Section IV.10, reaction 5). 

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