Hydrolysis studies of phosphodichloridate and thiophosphodichloridate ions

We report the pH-k(obs) profiles for the hydrolyses of phosphodichloridate and thiophosphodichloridate ions in aqueous solutions. Both species show broad pH-k(obs) plateaus that extend to high pHs.     

Hydrolysis of organomercury compounds in dimethylformamide,catalyzed by iodide ions

Russian Chemical Bulletin -     

Hydrolysis of 2-alkoxyalk-2-enals

Hydrolysis of 2-alkoxyalk-2-enals with equimolar amount of water (in an organic solvent) and with an excess of water has been studied with the aim of synthesizing 2-oxopropanal (methylglyoxal). 2-Oxopropanal obtained in an excess of water exists in the hydrate from. In organic solvents, the cyclic trimer of 2-oxopropanal, 2,4,6-triacetyl-1,3,5-trioxane, predominates (NMR data). Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2547–2549, December, 1998.     

Hydrolysis of imidazole-2-ylidenes

The direct reaction of an imidazole-2-ylidene in a predominantly aqueous environment [about 0.1 M solution in a H(2)O (>60%)/THF solvent system] was investigated for the first time. The reaction yielded a stable solution of the corresponding imidazolium-hydroxide of pH 13, which is in agreement with results from an ab initio molecular dynamics simulation. In contrast, hydrolysis of the carbene in a mainly aprotic environment (>80% THF) gives a hydrogen-bridged carbene-water complex which could be detected by NMR and IR spectroscopies for the first time. This complex converts slowly to two isomeric ring opened products and is at higher water concentration in dynamic equilibrium with the imidazolium hydroxide. A computational mechanistic study of the carbene hydrolysis with a gradually increasing number of water molecules revealed that the imidazolium-hydroxide structure can only be optimized with three or more water molecules as reactants, and with the increasing number of water molecules its stability is increasing with respect to the carbene-water complex. In agreement with the experimental results, these findings point out that solvent stabilization and basicity of the hydroxide ion plays a crucial role in the reaction. With increasing number of water molecules the barriers connecting the reaction intermediates are getting smaller, and the ring opened hydrolysis products can be derived from imidazolium-hydroxide type intermediates. Computational studies on the hydrolysis of a nonaromatic imidazolidine-2-ylidene analogue clearly indicated the analogous ring-opened product to be by 10-12 kcal/mol more stable than the appropriate ion pair and the carbene-water complex, in agreement with the known aromatic stabilization of imidazol-2-ylidenes. Accordingly, these molecules hydrolyze with exclusive formation of the ring-opened product.     

Hydrolysis constants of tervalent lanthanum and lanthanide ions in 0.1 M KNO3 solution

The hydrolysis constants K _h of tervalent lanthanum and lanthanide ions at 25°C have been determined by pH titration against the background of 0.1 M KNO₃. pK _h values change monotonically from 8.53 for La(OH)²⁺ to 7.41 for Lu(OH)²⁺ and from 26.56 for La(OH)₃ to 21.43 for Lu(OH)₃.     

Hydrolysis of 2-acetyl-substituted fluoroalkyl 3-ketoesters

Conclusions Fluoroalkyl 2-acetyl-3-ketoesters are hydrolyzed by a) aqueous KOH regioselectively with cleavage of the C²-C³ bond, b) aqueous ethanolic KOH and aqueous pyridine with cleavage of the C²-C³ and C²-C⁴ bonds, and c) in neutral aqueous and acid media with cleavage of the C¹-C² and C²-C⁴ bonds.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 2112–2113, September, 1987.     

Formation of iminium ions by fragmentation of a2 ions

Tandem mass spectrometric experiments have been carried out on the protonated amides H-Gly-Ala-NH2, H-Ala-Gly-NH2, H-Ala-Val-NH2, H-Val-Ala-pNA, H-Leu-Phe-NH2, H-Phe-Leu-NH2, H-Phe-Tyr-NH2 and H-Tyr-Phe-NH2 with particular emphasis on the fragmentation of the isomeric a2 ions derived therefrom. Primary fragmentation reactions of the protonated amides involve formation of the y1" and b2 ions with further fragmentation of the b2 ion to form the a2 ion which fragments to form iminium ions. Collision-induced dissociation studies of the mass-selected a2 ions were carried out. For the Gly-Ala, Ala-Gly and Val-Ala a2 ions, weak signals were observed corresponding to loss of CO from the a2 ion. With the exception of the Gly-Ala, Ala-Gly and Val-Ala a2 ions, both possible iminium ions (a1 and the internal iminium ion) are observed with the most abundant being that formed by proton attachment to the imine of higher proton affinity. The results provide strong support for the recently proposed (El Aribi et al. J. Am. Chem. Soc. 2003; 125: 9229) mechanism of fragmentation of a2 ions which involves elimination of CO from the a2 ion to form a proton-bound complex of two imines. Based on this mechanism ab initio calculations of the total energies of the a2 ions and the transition states for fragmentation have been carried out giving the energy barrier for fragmentation of each a2 ion. The experimental results are interpreted in terms of these energetics data, unimolecular rate constants calculated by using the RRKM theory, and the imine proton affinities.     

Hydrolysis of 2-ethyl-1,2-oxaphospholan-5-one 2-oxide

Conclusions Hydrolysis of 2-ethyl-1,2-oxaphospholan-5-one 2-oxide proceeds via attack of water at both reactive centers, the phosphorus atom and the carbonyl carbon.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2314–2315, October, 1969.     

Hydrolysis of 2-substituted and 1,2-disubstituted imidazolines

The mechanism and kinetics of hydrolysis of 2-substituted and 1,2-disubstituted imidazolines in acid, neutral, and alkaline solutions were studied. The influence of the substituents at the 1-and 2-positions of the imidazoline ring on the hydrolytic resistance of these compounds was demonstrated.     

Preparation of TiO2 Powder by Modified Two-Stage Hydrolysis

Nano-sized TiO₂ powders were synthesized by modified hydrolysis reaction using two-stage treatments of acid/base catalyst. Using an acidic catalyst, the primary particle size of assynthesized TiO₂ was smaller than using basic catalyst, but rutile ratio and the particle size were increased after heat treatment due to the dense packing of particles. However, in the synthesized TiO₂ powder using a basic catalyst persist the anatase phase and a loosely aggregation of particle after heat treatment. It was found that the catalyst used in the first stage determines the primary particle size. However the phase, the packing density and degree of dispersion of TiO₂ powder were determined by the secondly applied catalyst. Therefore, the addition sequence of catalysts is the most important key to prepare fine powders for photocatalytic use and solar cell. In this study, an acid treatment followed by a base is suggested as best route to obtaining fine size and distribution of particles and high content of anatase phase.     

Hydrolysis of 2-Hydroxyethyl Methacrylate in Concentrated Aqueous Solutions

Hydrolysis of 2-hydroxyethyl methacrylate in aqueous solutions, as influenced by pH, temperature, and substrate concentration, was studied. In concentrated solutions, the monomer forms associates, which promotes its hydrolysis.     

Hydrolysis of 1-methyl-2-methylthio-Δ2-imidazoline

New results in SN methyl transfer reaction in the series of Δ₂-imidazoline with and without quaternary salt catalyst are reported. The hydrolysis of monocyclic compounds containing the 2-alkyl thio, uronium group leads to the formation of a salt. Rearrangement reactions observed in the “uncatalysed reaction” may be due to a true catalytic reaction.     

甲基丙烯酸(2-烷基-2-金刚烷)酯的合成及水解研究

甲基丙烯酸(2-甲基-2-金刚烷)酯和甲基丙烯酸(2-乙基-2-金刚烷)酯是两个重要的193nm光刻胶主体树脂的单体.两个化合物是由2-金刚酮与碘甲烷、碘乙烷的格氏试剂反应得到2-甲基-2-金刚醇、2-乙基-2-金刚醇,然后在氢化钠的作用下与甲基丙烯酰氯发生酯化反应制得.酯化产率50%—60%.产品结构经¹HNMR、IR、MS和元素分析表征.在对甲基苯磺酸-水合物的催化作用下对两个单体进行了水解测试,探讨了水解机理,计算出水解速率常数k,k值分别为-1.52和-3.90.     

Application of Chemoenzymatic Hydrolysis in the Synthesis of 2-Monoacylglycerols

The selective biocatalyzed synthesis of 2-monoacylglycerols (2-MAGs) through the use of commercially available immobilized Candida antarctica (Novozym435) and Rhizomucor miehei is explored. Reactions at room temperature result in the formation of a 2-MAG and a corresponding ethyl ester of the fatty acid with immobilized Candida antarctica within 2h with yields ranging from 36%-83%. Similar reaction conditions with immobilized Rhizomucor miehei yielded exclusively the 2-MAG after 24h with yields ranging from 37% to 88%. Yields vary on the acyl group at the sn-2 position and choice of enzyme involved.     

Enantioselective Hydrolysis of 2-Aryloxypropionyl Derivatives by Penicillin V Amidase

Selective hydrolysis of 2-aryloxypropionyl derivatives 1a-1e and 2-phenyloxybutyrate 1f catalyzed by an immobilized penicillin V amidase, Semacylase, was found to show moderately to low enantiomeric excess.     

Enantioselective Hydrolysis of 2, 2-Disubstituted Oxiranes Mediated by Microsomal Epoxide Hydrolase

2-Aryl-2-methyloxiranes are enantioselectively hydrolyzed with microsomal epoxide hydrolase from pig liver to provide 1, 2-diols containing a tertiary benzylic alcohol stereogenic centre upto 34% enantio-meric purities.