Acid reflux

An alternative method of conducting the preparation consists in treating 100 g. of cycZohexanol with 250 ml. of concentrated hydrochloric acid, refluxing slowly whilst a stream of hydrogen chloride gas is passed into the mechanically stirred... 

Ethyl acetate. Use 58 g. (73-5 ml.) of absolute ethyl alcohol, 225 g. of glacial acetic acid and 3 g. of concentrated sulphuric acid. Reflux for 6-12 hours. Work up as for n-propyl acetate. B.p. 76- 77°. Yield 32 g. Much ethyl acetate is lost in the washing process. A better yield may be obtained, and most of the excess of acetic acid may be recovered, by distilhng the reaction mixture through an efficient fractionating column and proceeding as for methyl acetate. 

Ethyl n-butyrate. Use a mixture of 88 g. (92 ml.) of n-butyric acid, 23 g. (29 ml.) of ethanol and 9 g. (5 ml.) of concentrated sulphuric acid. Reflux for 14 hours. Pour into excess of water, wash several times with water, followed by saturated sodium bicarbonate solution until all the acid is removed, and finally with water. Dry with anhydrous magnesium sulphate, and distU. The ethyl n-but3rrate passes over at 119 5-120-5°, Yield 40 g. An improved yield can be obtained by distilhng the reaction mixture through an efficient fractionating column until the temperature rises to 125°, and purifying the crude ester as detailed above under methyl acetate. 

Ethyl benzoate sulphuric acid as a catalyst). Use 30 g. of benzoic acid, 115 g. (146 ml.) of absolute ethyl alcohol and 5 g. (2 7 ml.) of concentrated sulphuric acid. Reflux the mixture for 4 hours and work up as for Methyl Benzoate. The yield of ethyl benzoate, b.p. 212-214°, is 32 g. 

Fission of ethers with hydriodic acid. Reflux 1 ml. of the compound with 5 ml. of freshly distilled constant b.p. hydriodic acid (b.p. 126-128°) for 2-3 hours in a small flask fitted with a double surface condenser. Add 10 ml. of water, distil and collect about 7 ml. of liquid. Decolourise the distillate by the addition of a little sodium bisulphite and separate the two layers by means of a dropper pipette. If the original compound is suspected to be an aliphatic ether, determine the b.p. of the iodide by the Siwoloboff method (Section 11,12) if the amount of product is insufficient, repeat the original experiment. 

Hydrolysis of a substituted amide. A. With 10 per cent, sulphuric acid. Reflux 1 g. of the compound (e.g., acetanilide) with 20 ml. of 10 per cent, sulphuric acid for 1-2 hours. Distil the reaction mixture and collect 10 ml. of distillate this will contain any volatile organic acids which may be present. Cool the residue, render it alkaline with 20 per cent, sodium hydroxide solution, cool, and extract with ether. Distil off the ether and examine the ether-soluble residue for an amine. 

B. With 70 per cent, sulphuric acid. Reflux 1 g. of the substance (e.g., benzanilide) with 10-15 ml. of 70 per cent, sulphuric acid (4 3 by volume) for 30 minutes. Allow to cool and wash down any acid which has sublimed into the condenser with hot water. Filter off the acid, wash it with water, and examine for solubility, etc. Render the filtrate alkaline... 

Hydrolysis of a nitrile to an acid. Reflux 1 g. of the nitrile with 6 ml. of 30-40 per cent, sodium hydroxide solution until ammonia ceases to be evolved (2-3 hours). Dilute with 5 ml. of water and add, with coohng, 7 ml. of 50 per cent, sulphuric acid. Isolate the acid by ether extraction, and examine its solubility and other properties. 

Cyanide compounds are classified as either simple or complex. It is usually necessary to decompose complex cyanides by an acid reflux. The cyanide is then distilled into sodium hydroxide to remove compounds that would interfere in analysis. Extreme care should be taken during the distillation as toxic hydrogen cyanide is generated. The cyanide in the alkaline distillate can then be measured potentiometricaHy with an ion-selective electrode. Alternatively, the cyanide can be determined colorimetricaHy. It is converted to cyanogen chloride by reaction with chloramine-T at pH <8. The CNCl then reacts with a pyridine barbituric acid reagent to form a red-blue dye. 

HOCH2CH2OH, MgS04, PhH, L-tartaric acid, reflux, 20 h. 97% yield. These conditions were optimized for the protection of unsaturated aldehydes to prevent double-bond migration. ... 

Reaction of 2-aminoethanethiol hydrochloride with hydroxymethylfurazan 61 in 48% aqueous hydrobromic acid (reflux, 24 h) gave a salt that on treatment with an equimolar amount of 3,4-dimethoxy-l,2,5-thiadiazole 1,1-dioxide and another amine gave compound 62 (84USP4471122) (Scheme 30). 

MP 191° to 192,5°C, Two recrystallizations from aqueous ethanol gave the cinchonidine salt of the L-acid, MP 192,5° to 194°C. To the salt (2.9 g) in warm ethanol (50 ml) was added water (50 ml) and a slight excess (ca 10 ml) of N aqueous sodium hydroxide. The mixture was diluted with water, cooled, filtered from the precipitated base and the filtrate acidified with hydrochloric acid. Refluxing with 2 N ethanolic hydrogen chloride yielded p-nitro-N-phthaloyl-L-phenylalanine ethyl ester, according to U.S. Patent 3,032,585. 

The proton pump inhibitors are used for treatment or symptomatic relief of various gastric disorders, including gastric and duodenal ulcers, GERD, or pathological hypersecretory conditions. Painful, persistent heartburn 2 or more days a week may indicate acid reflux disease which can erode the delicate lining of the esophagus,... 

Hydrocinnamic acid. Reflux a mixture of 53 5 g. of propiophenone (Section IV,137), 20-6 g. of sulphur and 46 g. (46 ml.) of morpholine for 6 horns. Pour the reaction product into 400 ml. of 10 per cent, alcohohc sodium hydroxide solution and reflux for 7 hours. Distil off the alcohol, dilute with water, acidify with hydrochloric acid (to Congo red paper), and extract three times with ether. Wash the ether extracts with water, dry, remove the ether and distil. Collect the hydrocinnamic acid at 125-129°/ 6 mm. it solidifies completely on cooling, m.p. 46-47°. The yield is 39 g. 

Transfer the aqueous fraction from the hexane-aqueous partition (25-30 mL) into a 50-mL round-bottom flask. Add 3-3.5 mL of concentrated HCl (such that the final acid concentration is > 1N and several boiling chips to the round-bottom flask and reflux the sample for 1 h under a water-cooled condenser. This acid reflux step will cleave any conjugated acid metabolites in the crop matrices. 

SBA Materiaf N Loading (mmol N/g) Acid Reflux (mmol N/g) Base Treatment (mmol N/g)... 

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