Hydrogen chloride molecular sieve

The chloride is usually (but not always) stabilised in storage by addition of aqueous alkali or anhydrous amines as acid acceptors. A 270 kg batch which was not stabilised polymerised violently when charged into a reactor. Contact of the chloride (slightly hydrolysed and acidic) with rust led to formation of ferric chloride which catalysed an intermolecular Friedel-Craft reaction to form polybenzyls with evolution of further hydrogen chloride. Contact of unstabilised benzyl chloride with aluminium, iron or rust should be avoided to obviate the risk of polycondensation. See Benzyl bromide Molecular sieve... 

This compound is usually made and used in situ. A 5 g sample was allowed to sit in a screw top vial for a couple of days, one morning it was found to have blown a hole in the lid and extruded a 20 ml plume of polymeric foam [1], An attempt to dry anisyl chloride over molecular sieves pressurised the container, presumably with hydrogen chloride evolved during polymerisation [2],... 

Acetyl-3-methyl-4,5-dihydrothiophen-4-one Benzyl alcohol, Hydrogen bromide, Iron Benzyl bromide, Molecular sieve Benzyl chloride, Catalytic impurities Benzyl fluoride l,2-Bis(chloromethyl)benzene Ethylene oxide, Contaminants Furoyl chloride... 

In the sequence of reactions shown above TMCS acts in step a as catalytic activator in the coupling leading to the dinucleoside phosphorfluoridite. In step b the same compound acts as a reagent to give the corresponding phosphite, MeaSiF and HCl. Hydrogen chloride formed can be trapped by 4-A molecular sieves or trialkylamine. 

Dimethylformamide (99.8%), mthenium chloride hydrate (RUCI3 XH2O, 35 0% Ru), hydrogen chloride (4 M solution in 1,4-dioxane), and triphenyl-phosphine (99%) are purchased from Aldrich and used as received. DMF is conveniently dried with activated 4-A molecular sieves. As RUCI3 XH2O is a hygroscopic salt, it should be handled only briefly under ambient conditions. 

Acetalization. /7-Chloropropionaldchydc diethyl acetal can be prepared from acrolein in 88% yield by reaction of ethanol in the presence of hydrogen chloride dissolved in ether and with a 4 A molecular sieve as water scavenger.2 In the absence of a molecular sieve the yield drops to 65%. If elhanolic hydrogen chloride is used the yield is 34%.3... 

Hydrogen chloride in diethyl ether at room temperature was added to a mixture of 7 [34] (1.00 g, 2.16 mmol) and sodium cyanoborohydride (1.70 g, 27.0 mmol) in tetrahydrofuran (30 mL, distilled from LiAlH ) containing 3-A molecular sieves, until the evolution of gas biased. Use of TLC [silica gel, light petroleum (bp 40-60°)/ethyl acetate 5 1] after 5 min, PrHcated complete reaction. The mixture was diluted with CHjClj (50 mL) and water, [filtered, and the solution was extracted with water and then with saturated aqueous... 

Reduction of acetals (if, 8, 454). 4,6-O-Benzylidene-hexopyranosides (1) are reduced by NaBU, ( N and hydrogen chloride in the presence of 3 A molecular sieves lo 6-hen/yl ethers with a free (-hydroxyl group (2).1... 

To a stirred suspension of 3 g of methyl 2-endo-hydroxy-l-exo-hydroxymethyl-3a, 8b-cis-2,3,3a,8b-tetra hydro-1 H-5-cyclopenta[ bjbenzofuran-carboxylate in 30 ml of anhydrous tetrahydrofuran was added 1.5 ml of a solution which is obtained by dissolving 10 ml of 1,1-diethoxyethane and 200 mg of p-toluenesulfonic acid monohydrate into 10 ml of tetrahydrofuran followed by drying over molecular sieves, and the mixture was stirred for 14 hours at 60°C and then cooled. To the reaction mixture was added 100 mg of sodium hydrogen carbonate, and the mixture was stirred for 10 min at room temperature. Then, water was added to the reaction mixture and the mixture was extracted three times with ethyl acetate. The combined organic layers were washed with water and aqueous saturated solution of sodium chloride, was dried, and was concentrated to give 3.5 g of the crude crystals. The crude crystals were recrystallized from benzene-hexane to yield 2 g of the title compound (m.p. 162-163°C). 

Acetylation of tertiary hydroxyl groups. Midecamycin (1), a macrolide antibiotic from S. mycarofacience, is readily converted into the 9,2 -diacetyl derivative by Ac20-Py forcing conditions required for acetylation of the 3"-hydroxyl group result in decomposition. However, reaction of the diacetate with acetyl chloride in ethyl acetate in the presence of a 4 A molecular sieve to scavenge the hydrogen chloride... 

Hydrogen chloride is corrosive and toxic TLV 5ppm. Prepare by adding concentrated sulphuric acid to anhydrous ammonium chloride and dry by passage over molecular sieves. Dispose by dissolving in water. 

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