Ethers alkyl thiocyanation

Kamal and Chouhan prepared the TSIL [bmim][SCN] to convert alkyl halides to alkyl thiocyanates. This [bmim][SCN] was prepared by ion exchange of [bmim][Cl] with KSCN in acetone. Alkyl halides were reacted with this TSIL to give quantitative amounts of the corresponding alkyl thiocyanates with high yields. Scheme 31. The product was then easily extracted with ether. 

Cleavage of thioethers. von Braun found that a dialkyl thioether is cleaved by cyanogen bromide at a somewhat elevated temperature (60-70°, sealed tube) to an alkyl thiocyanate and an alkyl bromide. Results for the first three mixed ethers disclose a clear relationship of Haftfestigkeit to size of group ... 

Effluents from the manufacture of Pb(CH3)4 can be treated with an alkali metal borohydride, e.g., NaBH4 at pH 8 to 11 to substantially reduce the level of dissolved lead compounds, like [Pb(CH3)3][145, 146]. Zn can also be used [147]. Liquid NH3 and toluene are used to remove solid NH4Clfrom the apparatus for producing Pb(CH3)4 by the NH3- or amine-catalyzed reaction of CH3CI with a PbNa alloy [148]. Stabilization of Pb(CH3)4, and of antiknock fluids containing Pb(CH3)4, is accomplished by addition of compounds, like toluene [149], xylene [141, 150], styrenes [151], naphthalenes [149, 151, 152], anthracenes [152], substituted phenols [141, 152 to 155], olefinic hydrocarbons [152], alcohols [141, 152], amines [155], hydroquinones [156], ethers [141], saturated or unsaturated carboxylic acids [141, 152], esters of phosphoric acid [152], or of sulfuric acid [157], or of sulfonic acids [141], imidazoles [158], alkyl halides and alkyl thiocyanates [141], or tall oil [159] see also Organolead Compounds , Vol. 2, Section 1.1.1.2, to be published. 

On the basis of infrared shift values we may conclude that ethyl nitrate is a very weak base while the alkyl nitrites are quite strong ones (150) and that the alkyl thiocyanates and isothiocyanates are of comparable and rather weak basicity. The low basicity of nitrate esters is confirmed by the Henry s law constant of HCl over ethyl nitrate which places it between n-heptane and biphenyl ether by this criterion (331). 

Silver fluoborate, reaction with ethyl bromide in ether, 46, 114 Silver nitrate, complexing with phenyl-acetylene, 46, 40 Silver oxide, 46, 83 Silver thiocyanate, 45, 71 Sodium amide, in alkylation of ethyl phenylacetate w ith (2-bromo-ethyl)benzene, 47, 72 in condensation of 2,4-pentanedione and 1 bromobutane to give 2,4-nonanedione, 47, 92 Sodium 2 ammobenzenesulfinate, from reduction of 2 mtrobenzenesul-finic acid, 47, 5... 

ABS AE AE/P AES AG AOS APEO APG AS BiAS BM c6(EO)3 CNPEC CTAS D DATS DCPEG DEEDMAC branched alkylbenzene sulfonate alcohol ethoxylate alcohol ethoxylate/propoxylate alkylether sulfate alkyl glucamide a-olefin sulfonate alkylphenol ethoxylate alkyl polyglucoside alkyl sulfate bismuth active substances alkyldimethylbenzyl ammonium triethylene glycol monohexyl ether carboxylated nonylphenoxy carboxylates cobalt thiocyanate active substances R2S10(o.5)2 dialkyl tetralinsulfonate dicarboxylated PEG ditallow ester of di(hydroxyethyl)dimethyl ammonium chloride... 

Subsequently, it was shown that the reaction was catalyzed by base (48M(79)106). Dicyandiamide reacts with nitriles (the most valuable method), amidines, cyanamides, ammonia, cyanates, thiocyanates, carboxylic acids and anhydrides to yield 1,3,5-triazines (Table 13). This synthetic route has been reviewed thoroughly several times (59HC(13)1, p. 219,61MI22000, p. 650, 73ZC408). The base-catalyzed reaction of dicyandiamide with alkyl or aryl nitriles (Scheme 65) proceeds via the imino ether anion and the rate determining step is solvent dependent. In DMSO the formation of the imino ether is rate determining, but in 2-methoxyethanol the reaction between the anion and dicyandiamide controls the rate (66T157). 

General procedure An alkyl bromide (1 mole) is dropped into a stirred, boiling mixture of finely powdered KSCN (1.5 moles) and ethanol (340 ml about one-third of the KSCN dissolves), and the mixture is kept at the b.p. for 2 h. Then part of the solvent is distilled off, the remaining mixture is diluted with water, the thiocyanate is extracted in ether, and the ethereal solution is dried over CaCl2 or Na2S04 and worked up by vacuum-distillation. Yields for pentyl to tridecyl thiocyanate are about 80-90 %.850... 

Alkylthiocyanates have been prepared in higji yield by reaction of alkali metal thiocyanates with various primary and secondary alkyl halides under phase transfer conditions. Quaternary alkylammonium salts [12—14], crown ethers [15], cryptates [16], and tertiary amines [14] have all proved effective phase transfer catalysts for this reaction (Eq. 13.7 and Table 13.4). The mechanism of the thiocyanate displacement is probably similar to that of the cyanide displacement reaction (see Sect. 7.2). 

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