429-41-4Relevant articles and documents
Low-temperature NMR spectra of fluoride-acetic acid hydrogen-bonded complexes in aprotic polar environment
Golubev, Nikolai S.,Tolstoy, Peter M.,Smirnov, Sergei N.,Denisov, Gleb S.,Limbach, Hans-Heinrich
, p. 3 - 12 (2004)
Using low-temperature NMR (1H, 19F) technique in the slow exchange regime, the solutions containing tetrabutylammonium (TBA) acetate and HF have been studied in an aprotic freon mixture, CDF3/CDF 2Cl, exhibiting a dielectric permittivity, which increases strongly by lowering the temperature. Two different hydrogen bonded anionic clusters, a 1:1 cluster of the type AcOδ-?H?F -1+δ+ ([AcOHF]-) and a 2:1 cluster of the type AcOH?F-?HOAc ([(AcOH)2F]-) have been detected in equilibrium with each other, both forming ion pairs with the TBA countercation. [AcOHF]- exhibits an extremely strong hydrogen bond, with a proton shared between partially negatively charged oxygen and fluorine atoms. The NMR chemical shifts and scalar spin-spin coupling constants, 1J(FH), have been measured in the temperature range between 110 and 160 K, where separate NMR signals are observed for both species. In addition, H/D isotope effects on the 19F NMR chemical shielding have been measured for both clusters. In contrast to the related complexes [(FH) nF]- (n=1-4) studied previously, the NMR parameters of [AcOHF]- and of [(AcOH)2F]- depend strongly on temperature. This effect is associated with the increasing polarity of the solvent with decreasing temperatures, established earlier, which displaces the proton from fluorine to oxygen. As a motive power of this conversion, preferential solvation of the compact fluoride ion as compared to acetate is proposed.
Chastrette,Amouroux
, p. 323,326, 327 (1974)
Unraveling the cation and anion effects and kinetics for ionic liquid catalyzed direct synthesis of methyl acrylate under mild conditions
Wang, Gang,Li, Zengxi,Li, Chunshan,Zhang, Suojiang
, p. 7913 - 7923 (2020/12/01)
The direct synthesis of methyl acrylate (MA) from methyl acetate and trioxane at 350-380 °C is regarded as a supplementary route for the industrial propylene oxidation process; however, it suffers from rapid catalyst deactivation. Herein, a novel ionic liquid catalyzed mild liquid-phase system was developed for the direct synthesis of MA from methyl acetate and trioxane, where N,O-bis(trimethylsilyl)acetamide (BSA) was used as a probase for α-deprotonation and enol silyl etherification of methyl acetate. The trioxane decomposition to formaldehyde and methyl acetate enolization to 1-methoxy-1-trimethylsilyloxyethene proceeded with the catalysis of [Cation]Cl/MClx (M = Cu+, Fe3+, Zn2+ and Al3+) and [Cation]F, respectively. The cations and anions were observed to have significant effects on the yield and selectivity of MA, owing to the steric hindrance, acid site category and strength confirmed by pyridine probing FT-IR characterization. As a result, up to 60.2% yield with 94.6% selectivity of MA could be achieved when [N3,3,3,3]F and [N3,3,3,3]Cl/AlCl3 with 67 mol% AlCl3 were used in the presence of BSA at 25 °C. Kinetic studies indicated that the trioxane decomposition with the activation barrier of 41.2 ± 0.3 kJ mol-1 was the rate-determining step.
A naked eye detection of fluoride with urea receptors which have both an azo group and a nitrophenyl group as a signaling group
Dang, Nhat Tuan,Park, Jin Joo,Jang, Soonmin,Kang, Jongmin
body text, p. 1204 - 1208 (2010/09/10)
Anion recognition via hydrogen-bonding interactions could be monitored with changes in UV-vis absorption spectra and in some cases easily monitored with naked eye. Urea receptors 1 and 2 connected with both an azo group and a nitrophenyl group as a signaling group for color change proved to be an efficient naked eye receptor for the fluoride ion. The anion recognition phenomena of the receptors 1 and 2 via hydrogen-bonding interactions were investigated through UV-vis absorption and 1H NMR spectra.
