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psyloxy (Hive Addict) 10-08-03 17:37 No 463377 |
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alpha-bromopropanoic acid - a final word ? (Rated as: excellent) |
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propanoic acid + polyphosphoric acid + bromine __> alpha-bromopropanoic acid In the course of this study, the possibility of forming an anhydride and brominating in one step became the primary objective of the investigation. Aliphatic carboxylic acids were heated with polyphosphoric acid until solution of the acid was effected. Phosphoric acid was added as a diluent for the very viscous polyphosphoric acid. In lieu of the addition of phosphoric acid, several milliliters of water were added to the polyphosphoric acid prior to heating the reaction mixture. When solution of the carboxylic acid in the polyphosphoric acid was complete, bromine was added slowly to the stirred mixture which, in general, was maintained at a temperature near 100°. Two methods of isolating the products are feasible. The low boiling bromoacids can be distilled directly from the reaction mixture under reduced pressure. The higher boiling products can be isolated by diluting the reaction mixture with water in order to destroy the polyphosphoric acid. The alpha-bromoacid can then be extracted from the phosphoric acid solution with chloroform or other organic solvents which are insoluble in phosphoric acid. The formation of an anhvdride as the intermediate in this reaction may be postulated, The acyl phosphate type anhydride and the carboxylic acid anhydride are both possible intermediates. The former anhydride is considered to be the more probable postulate since bromination of butyric anhydride under the same conditions utilized for butyric acid did not give the dibromoanhydride but alpha-bromobutyric acid as the only product. This would support an assumption that a mixed anhydride was first formed and then destroyed to yield only the brominated acid. The yields of this reaction, in general, are equivalent to thosee obtained by the use of red phosphorus and bromine. Experimental The procedures described below are representative of those employed in the preparation of the acids listed in Table 1. With the butyric and valeric acids, the reaction mixture was heated to 100-120° during the addition of bromine and with butyric anhydride no diluent was used. A larger excess of bromine might be required if efficient condenser action is not obtained. incomplete Table 1 Yield from: AcOH : 67.6 % Bp: 100-105°C / 30 mmHg
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Antoncho (Official Hive Translator) 10-09-03 07:12 No 463508 |
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!!! | ||||||
Psyloxy, you're so damn good ![]() Where do you get all this stuff? ![]() Antoncho |
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psyloxy (Hive Addict) 10-09-03 21:26 No 463633 |
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propionic acid from n-propanol / HNO3 - 84% yield (Rated as: excellent) |
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I love you, too - Antoncho ![]() An excerpt from Patent GB771583 710 parts of 70% nitric acid and 50 parts of water were introduced into a vessel equipped with a mechanical stirrer. 144.5 parts of n-propanol were slowly added over a period of two hours, while the contents of the vessel were stirred vigorously and cooled to maintain the temperature at 30 to 35°C. A reflux condenser was attached to the vessel so as to prevent the loss of low-boiling products while allowing exhaust fumes, consisting primarily of nitrogen oxides and carbon dioxide, to escape. Propionic acid was obtained in 82.5% yield and acetic acid in 10.8% yield. The conversion of the n-propanol was 100%. The reaction products can be separated by distilling off the azeotropic mixture of the aliphatic acid and water from which the acid can be recovered by solvent extraction, e.g. with a mixture of benzene and ethyl acetate. Also check out Patent US1934648 n-PrOH + KOH/NaOH(fused) __> PrOO(Na/K) , 93% --psyloxy-- |
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Aurelius (Active Asperger Archivist) 10-10-03 08:01 No 463732 |
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Propanoic acid | ||||||
can also be had by OCl- added to MEK. (collect salt, acidify and distill) Act quickly or not at all. |
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Antoncho (Official Hive Translator) 10-10-03 08:28 No 463733 |
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? | ||||||
Hey, Aurelius, why don't you post something in Post 461624 (Antoncho: "Propionic acid from MEK - let's find it out!", Novel Discourse)? Do you know more than me? If so, you should share your knowledge! |
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Aurelius (Active Asperger Archivist) 10-11-03 00:26 No 463857 |
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Antoncho | ||||||
Rhodium's post in that thread seems to cover the subject well enough. What additional information do you really need? After all, (at least in the US- and I realize you're not a US bee) the materials, the hypochlorite powder and MEK, are extremely cheap. ~40-50% yields for chloroform and propionic both in the same reaction. what else is left? Act quickly or not at all. |
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Rhodium (Chief Bee) 10-16-03 10:33 No 464941 |
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Preparation of Propionic Acid | ||||||
All these methods now collected in Preparation of Propionic Acid (../rhodium /propio |
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psyloxy (Hive Addict) 06-21-04 01:14 No 514482 |
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J.Amer.Chem.Soc. : 76.1954;5805 (Rated as: good read) |
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![]() for the sake of completeness... --psyloxy-- |
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lugh (Moderator) 06-26-04 04:20 No 515475 |
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n-propanol from propane | ||||||
High Pressure Oxidation of propane to n-propanol Ind Eng Chem 26 267-76 (1934) ![]() ![]() Chemistry is our Covalent Bond |
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psyloxy (Hive Addict) 06-30-04 19:42 No 516571 |
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bromination/esterification of R-COOH w/ Br2/HSO3Cl (Rated as: good read) |
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![]() A mixture of aliphatic acid (10 mmol), bromine (10 mmol), chlorosulfonic acid (0,5 mL), and 1,2-dichloroethane (50 mL) were heated at 85°C for 2 h. After unreacted bromine and 20 mL 1,2-dichloroethane were distilled off, methanol (30 mL) was added to the mixture and the solution was refluxed for 10 h. [ After removal of methanol by distillation from the ester solution the residual mixture was washed with water, dried (Na2SO4) and distilled in vacuo. Yield of methyl ester of alpha-bromopropanoic acid from propanoic acid was 78.1% A 'general procedure for the preparation of...' is not included in the article, what I wrote above is headlined as 'Analysis of Products' - bear in mind that it was a kinetic study. Just read the article, you'll get the picture. I hope the most interesting part are the given references, looks like what they do here with Br2 / HSO3Cl can also be done with Cl2 and oleum. --psyloxy-- |
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