- Carboxylic Acid Participation in Amide Hydrolysis. Evidence That Separation of a Nonbonded Complex Can Be Rate Determining
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Maleamic acids derived from aliphatic amines of a wide range of basicity (compounds 1-8) undergo hydrolysis in solutions of acidity between 1E-4 M and 1 M hydrogen ion concentration by a mechanism involving participation of the carboxyl group at the adjacent amide.Kinetic analysis of the reaction (50 deg C) reveals that the identity of the rate-determining step (or steps) is a function of both the basicity of the leaving group and the acidity of the solution.At pH 4, the rate-determining step is O to N proton transfer to form a zwitterionic intermediate for compounds with weakly basic leaving groups.For compounds with more basic leaving groups, conversion of the zwitterionic intermediate to products is rate determining.In more acidic solutions, where proton transfer is facilitated, diffusion apart from the complex formed from C-N bond breakage of the zwitterionic intermediate is rate determining for compounds with the most basic leaving groups.C-N bond breakage is rate determining for compounds with the least basic leaving groups.This suggests that at pH 4 the breakdown of the zwitterion may also involve rate-determining diffusion.It is concluded that other facile elimination reactions may involve rate-determining diffusion and that changes in the rate-determining step can serve as an indicator of its occurrence and as a means of calibration of rate constants.It is also suggested that since pepsin may catalyze peptide hydrolysis by a carboxyl-participation mechanism, the occurrence of sequential covalent intermediates may exist to permit diffusion of the noncovalently held products.
- Kluger, Ronald,Chin, Jik
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- Investigation on the preparation of 2,2-difluoroethylamine by amination of 1-halo-2,2-difluoroethane
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The synthesis of 2,2-difluoroethylamine via the amination of 1-halo-2,2-difluoroethane (halogen = Cl or Br) without catalyst and solvent was studied by experiment and theoretical calculation. In order to compare the difficulty in the amination of 1-halo-2,2-difluoroethane with NH3, experimental investigations were carried through changing reaction temperature, molar ratio and reaction time. And experimental evidence demonstrated that 1-chloro-2,2-difluoroethane was more prone to amination than 1-bromo-2,2-difluoroethane under the same conditions. In addition, the reaction mechanism was investigated, and the formation complexity evaluated. Calculation of the transition states and rate constants, and analysis of the frontier molecular orbitals, indicated that the reaction rate of the amination of 1-chloro-2,2-difluoroethane was higher than that of 1-bromo-2,2-difluoroethane, which was consistent with the results of the experiment.
- Han, Xue,Qing, Feiyao,Zhang, Chengping,Jia, Xiaoqing,Quan, Hengdao
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- Method for synthesizing 2, 2-difluoroethylamine by using high-boiling residue in R142b as raw material
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The invention belongs to the technical field of fluorine chemical industry, and particularly relates to a method for synthesizing 2, 2-difluoroethylamine by using a high-boiling residue in R142b as araw material. The method is characterized in that under the catalytic action of a catalyst 1 and a catalyst 2, 2, 2-difluoro-1-chloroethane and an ammonia water solution react in a solvent to prepare2, 2-difluoroethylamine. According to the method, the use of expensive noble metal catalysts can be avoided, the adopted phase transfer catalyst can be dissolved in a water phase and an organic phaserespectively, and can be in full contact with reactants so that the reaction is relatively thorough, the reaction rate is increased, the reaction temperature, the reaction pressure and the reaction time are reduced, and the product yield is high; the method has the advantages of low reaction temperature, low reaction pressure, low equipment requirement strength and simple operation steps, and therectified solvent and ammonia water solution can be continuously recycled, thereby reducing the discharge of three wastes, lowering the environmental pollution, and lowering the production cost and post-treatment cost.
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Paragraph 0025-0032
(2021/01/24)
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- Preparation of 2,2-difluoro-ethylamine method (by machine translation)
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The present invention relates to a 2,2-difluoro-aminoethane preparation method, in particular a 1,1-difluoro-2-chloroethane reacts with ammonia water and preparing 2,2-difluoro-ethylamine method; heating 1,1-difluoro-2-chloroethane and an aqueous ammonia solution, and then are respectively and continuously into the respective coil preheater, and then through the respective coil superheater overheating, over-heat after the two-phase material mixed in the mixer into the reactor after the reaction, the reaction temperature is 80-240°C, the reaction pressure of 0.8-5 MPa; the reaction product after the reaction through the decompression pipeline into the distillation still in continuous pressure distillation, distillation product is 2,2-difluoro-ethylamine crude aqueous solution, after rectification to separate crude qualified products can be obtained; the preparation method of this invention does not use the extra catalyst, solvent, catalyst does not exist, such as solvent to the problem of pollution of the natural environment, but also reduces the production cost; the invention offers all in the preparation method of the aqueous solution are once again after rectifying liquid circulating absorption of pure ammonia into a different concentration of an aqueous ammonia solution to continue to use. (by machine translation)
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Paragraph 0024; 0025
(2017/03/14)
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- PROCESS FOR PREPARING 2,2-DIFLUOROETHYLAMINE FROM 2,2-DIFLUORO-1-CHLOROETHANE AND AMMONIA
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Process for preparing 2,2-difluoroethylamine, comprising the following steps: (i) mixing 2,2-difluoro-1-chloroethane and gaseous, liquid or supercritical ammonia in a pressure-stable, closed reaction vessel under a pressure in the range from 10 to 180 bar;(ii) reacting the reaction mixture at a reaction temperature in the range from 80° C. to 200° C.;(iii) letting down the reaction mixture and isolating 2,2-difluoroethylamine.
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Page/Page column 4
(2012/07/28)
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- PROCESS FOR THE PREPARATION OF 2,2-DIFLUOROETHYLAMINE STARTING FROM PROP-2-EN-1-AMINE
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A process for the preparation of 2,2-difluoroethylamine of the formula (I) [in-line-formulae]CHF2CH2NH2??(I)[/in-line-formulae] comprising the stages (i) and (ii): stage (i): reaction of 2,2-difluoro-1-haloethane of the formula (II) [in-line-formulae]CHF2—CH2Hal??(II)[/in-line-formulae] in which Hal is chlorine, bromine or iodine, with prop-2-en-1-amine of the formula (III) to give N-(2,2-difluoroethyl)prop-2-en-1-amine of the formula (IV) preferably in the presence of an acid scavenger, and stage (ii): removal of the allyl group from the N-(2,2-difluoroethyl)prop-2-en-1-amine of the formula (IV) obtained in stage (i) to give 2,2-difluoroethylamine of the formula (I) or a salt thereof.
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Page/Page column 6
(2012/06/16)
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- PROCESS FOR THE PREPARATION OF 2,2-DIFLUOROETHYLAMINE STARTING FROM A BENZYLAMINE COMPOUND
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Process for the preparation of 2,2-difluoroethylamine of the formula (I) [in-line-formulae]CHF2CH2NH2??(I)[/in-line-formulae] comprising the stages (i) and (ii): stage (i): reaction of 2,2-difluoro-1-haloethane of the general formula (II) [in-line-formulae]CHF2—CH2Hal??(II),[/in-line-formulae]with a benzylamine compound of the formula (III) in the presence of an acid scavenger, in which, in formula (II), Hal is chlorine, bromine or iodine, and, in the formulae (III), R1 is hydrogen or C1-C12-alkyl, and R2 is hydrogen, halogen, C1-C12-alkyl or C1-C6-alkoxy; stage (ii): catalytic hydrogenation of the N-benzyl-2,2-difluoroethanamine compound obtained in the stage (i) to give 2,2-difluoroethylamine of the formula (I) or a salt thereof.
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Page/Page column 8
(2012/05/21)
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- Process for Preparing 2,2-Difluoroethylamine
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The present invention relates to a process for preparing 2,2-difluoroethylamine proceeding from 2,2-difluoro-1-haloethane using ammonia in a solvent which has a maximum water content of 15% by volume and in the presence of a catalyst which accelerates the reaction with ammonia.
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Page/Page column 3
(2011/04/18)
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- Structural effects on reactivity in intramolecular catalysis. The hydrolysis of N-alkylated monoamides derived from norbornene-2,3-dicarboxylic acid
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Monoamides of 2,3-endo-cis-5-norbornene dicarboxylic acid (compounds 1-5) were prepared by addition of primary alkyl amines (n-propyl-, 2-methoxyethyl-, 2-fluoroethyl-, 2,2-difluoroethyl-, 2,2,2-trifluoroethyl-) to 2,3-endo-cis-5-norbornene dicarboxylic anhydride.The rates of hydrolysis of each compound in solutions whose acid concentration ranged from 0.01 M to 9 M were determined.Rates increase with acidity above 0.1 M until a maximum rate is achieved in strong acid.The results are consistent with a mechanism involving intramolecular catalysis of the hydrolysis of the amide by the adjacent carboxylic acid.The dependence of rate on acidity can be interpreted in terms of a multistep mechanism involving formation of an intramolecular tetrahedral adduct, tautomerization of the adduct, and expulsion of the amine to give the anhydride.The identity of the rate-determining step is a function of the basicity of the substrate and the acidity of the medium.Analysis of the data in terms of the proposed mechanism suggests that the effective molarity of the groups involved in tautomerization of the tetrahedral internal addition intermediate is higher than in other rigid systems which lack the norbornene structure.It is proposed that ring strain and rotational entropy control cyclization and elimination steps.Interactions of the solvent with the entire substrate control reorganization of the intermediate.Conjugation of the interacting functional groups does not appear to have a significant effect upon their reactivity.
- Kluger, Ronald,Brandl, Michael
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p. 2515 - 2520
(2007/10/02)
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