- Solvolysis in 2,2,2-Trifluoroethanol-Water and 2,2,2-Trifluoroethanol-Etanol Mixtures. Selectivity of the Intermediates and N Values
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Solvolysis of 1-adamantyl bromide (1-Br) in eight TFE-EtOH mixtures gave a Grunwald-Winstein mGW value of 1.50, and the ethyl (1-OEt) and trifluoroethyl (1-OTFE) ethers.The selectivity ratios for reaction with the solvent components kTFE/kEtOH are medium dependent, being 2.60-0.83.In TFE-H2O, mGW = 0.56 and the kTFE/KH2O ratios increase with ΧH2O from 0.49 to 2.04.Solvolysis of 1-anisyl-2-methylpropen-1-yl tosylate (2-OTs) in TFE-EtOH gives mGW = 0.89 and an average kTFE/kEtOH value of 0.086.Methyl tosylate was solvolyzed in several TFE-EtOH and TFE- H2O mixtures and new values of the nucleophilic parameter N were determined.Products were derived from the free cation in the solvolysis of 2-OTs and from the solvent-separated ion pair in the solvolysis of 1-Br, and the selectivities of these species were analyzed.The nucleophilicities of TFE-H2O and TFE-EtOH mixtures and the recent use of the comparison od TFE-H2O and EtOH-H2O mixtures for evaluating solvent participation in solvolysis reactions were discussed.
- Kaspi, Joseph,Rappoport, Zvi
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Read Online
- Method for preparing hydrofluoroether through two-step process
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The invention discloses a method for preparing hydrofluoroether through a two-step process. With the method provided by the invention, p-toluensulfonyl chloride and fluorine-containing alcohol are subjected to a reaction to obtain p-toluenesulfonate, and the p-toluenesulfonate and sodium alkoxide are subjected to a Williamson ether synthetic reaction to obtain the hydrofluoroether. The method disclosed by the invention has the advantages of cheap and low-toxicity raw materials, mild and controllable reaction conditions, and high yield.
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Paragraph 0055; 0057
(2019/07/10)
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- Preparation of Methyl Fluoroalkyl Ethers
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Methyl fluoroalkyl ether can be produced by the reaction of a fluoroalkyl alcohol with chloromethane. The process involves reacting an alkoxide of a fluoroalkyl alcohol with chloromethane.
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Page/Page column 4
(2010/12/29)
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- Hydrogen bonding lowers intrinsic nucleophilicity of solvated nucleophiles
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The relationship between nucleophilicity and the structure/environment of the nucleophile is of fundamental importance in organic chemistry. In this work, we have measured nucleophilicities of a series of substituted alkoxides in the gas phase. The functional group substitutions affect the nucleophiles through ion-dipole, ion-induced dipole interactions and through hydrogen bonding whenever structurally possible. This set of alkoxides serves as an ideal model system for studying nucleophiles under microsolvation settings. Marcus theory was applied to analyze the results. Using Marcus theory, we separate nucleophilicity into two independent components, an intrinsic nucleophilicity and a thermodynamic driving force determined solely by the overall reaction exothermicity. It is found that the apparent nucleophilicities of the substituted alkoxides are always much lower than those of the unsubstituted ones. However, ion-dipole, ion-induced dipole interactions, by themselves, do not significantly affect the intrinsic nucleophilicity; the decrease in the apparent nucleophilicity results from a weaker thermodynamic driving force. On the other hand, hydrogen bonding not only stabilizes the nucleophile but also increases the intrinsic barrier height by 3 to ～4 kcal mol-1. In this regard, the hydrogen bond is not acting as a perturbation in the sense of an external dipole but more directly affects the electronic structure and reactivity of the nucleophilic alkoxide. This finding offers a deeper insight into the solvation effect on nucleophilicity, such as the remarkably lower reactivities in nucleophilic substitution reactions in protic solvents than in aprotic solvents.
- Chen, Xin,Brauman, John I.
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scheme or table
p. 15038 - 15046
(2009/03/12)
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- Methyl hypofluorite (MeOF) reactions with various fluoroolefins
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The reaction of methyl hypofluorite (MeOF) with certain fluoroolefins, such as CF2=CF2, CF2=CFCF3, CF2=CFOCF3, CF2=CFOMe, CF2=CClF, CF2=CHF, CF2=CH2, CHF=CH2, CF2=CFCF=CF2, occurred in CD3CN or in the presence of NaF. Using neat MeOF in the presence of NaF was a novel method and gave good results. We observed that when more than three fluorine atoms are bonded to the C-C double bond, the addition products were obtained in mostly good yields.
- Suzuta, Tetsuya,Abe, Takashi,Sekiya, Akira
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- Synthesis of trifluoroethyl ethers from 2,2,2-trifluoroethyl chloride (HCFC-133a) in high temperature aqueous medium
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Treatment of 2,2,2-trifluoroethyl chloride (HCFC-133a) with alcohols (phenols) and aqueous KOH in autoclave at 240-280 C gives the corresponding 2,2,2-trifluoroethyl (2-chloro-1,1-difluoroethyl) ethers in good yields.
- Wu, Kai,Chen, Qing-Yun
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- Matrix-isolation and ab initio molecular orbital study of 2,2,2-trifluoroethylidene
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Photolysis of 2,2,2-trifluorodiazoethane (2) in an argon matrix at 12 K generates triplet 2,2,2-trifluoroethylidene (1) in addition to a significant amount of trifluoroethylene (3) and small amounts of trifluoromethyldiazirine (4). These compounds were identified by IR and UV spectroscopy. Short-wavelength - photolysis of the carbene 1 converts it to trifluoroethylene, while slowly warming the matrix to 35 K results in dimerization to the isomeric hexafluorobut-2-enes. High-level ab initio calculations (QCISD(T)6-311(2D,2P)//MP2-FC/6-31G**) are reported for the singlet and triplet states of 2,2,2-trifluoroethylidene as well as for methylene and ethylidene. The calculated IR spectrum for triplet 2,2,2-trifluoroethylidene is in good agreement with the experimental one, but the UV/vis spectrum calculated using the CIS method does not match very well. The transition structures for the 1,2-fluorine atom rearrangement of the single and triplet states of carbene 1 to trifluoroethene were calculated at the QCISD(T)-FC/6-311(2D,2P)//MP2-FC/6-31G** level of theory. The calculated barrier for 1,2-fluorine atom migration in the singlet carbene, 21.5 kcal/mol, is less than suggested by recent experimental results (29 ± 4 kcal/ mol). The calculated barrier for the corresponding rearrangement in the triplet system was 51 kcal/mol. Previous reports concerning the energies and geometries of these calculated transition structures are shown to be in error.
- O'Gara, John E.,Dailey, William P.
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p. 12016 - 12021
(2007/10/03)
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- Gas-phase SN2 and E2 reactions of alkyl halides
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Rate coefficients have been measured for the gas-phase reactions of methyl, ethyl, n-propyl, isopropyl, tert-butyl, and neopentyl chlorides and bromides with the following set of nucleophiles, listed in order of decreasing basicity: HO-, CH3O-, F-, HO- (H2O), CF3CH2O-, H2NS-, C2F5CH2O-, HS-, and Cl-. For methyl chloride the reaction efficiency first falls significantly below unity with HO- (H2O) as the nucleophile and for methyl bromide with HS- as the nucleophile; in both cases the overall reaction exothermicity is about 30 kcal mol-1. Earlier conclusions that these halides react slowly with stronger bases are shown to be in error. In the region where the rates are slow oxygen anions react with the alkyl chlorides and bromides by elimination while sulfur anions of the same basicity react by substitution. This difference is due to a slowing down of elimination with the sulfur bases; sulfur anions show no increased nucleophilicity as compared to oxy anions of the same basicity. Rate coefficients have also been measured for reaction of methyl fluoride with HO- and CH3O- and ethylene oxide with HO-, CH3O-, and F-. All of these rates are slow but measurable; combining the results of these experiments with those of the alkyl chlorides and bromides suggests that the gas-phase barrier to the symmetrical SN2 reaction of F- with methyl fluoride is lower than previous estimates. We have also measured rates for reaction of allyl chloride with F-, H2NS-, and HS-, chloromethyl ether with H2NS- and HS-, chloroacetonitrile with F-, H2NS-, HS-, and 37Cl-, bromoacetonitrile with Cl- and 81Br-, and α-chloroacetone with H2NS-, HS-, and 37Cl-. Our results also imply that the gas-phase SN2 barrier for Br- reacting with methyl bromide is nearly equal to the ion-dipole attraction energy of the reactants, in agreement with previous estimates.
- DePuy, Charles H.,Gronert, Scott,Mullin, Amy,Bierbaum, Veronica M.
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p. 8650 - 8655
(2007/10/02)
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