Gas phase hydrolysis

Analysis of some experimental results [527, 528, 532] suggests that niobium oxides are first formed as gaseous components resulting from the pure gas-phase hydrolysis ... 

Percentage of the gas-phase hydrolysis reaction occurring by the BAC2 and SN2 mechanism"... 

NM Meltzer, GI Tous, S Gruber, S Stein. Gas-phase hydrolysis of proteins and peptides. Anal Biochem 160 356-361, 1987. 

R Knecht, JY Chang. Liquid chromatographic determination of amino acids after gas-phase hydrolysis and derivatization with (dimethylamino)azobenzenesulfonyl chloride. Anal Chem 58 2375-2379, 1986. 

DEH Palladino, RM House, KA Cohen. Measurement of amino acid compositions of glycoprotein systems by gas-phase hydrolysis and reversed-phase high-performance chromatography. J Chro-matogr 599 3-11, 1992. 

Determination of oxidized amino acids in urine is usually performed by isotope dilution gas chromatography-mass spectrometry (L9). DOPA is estimated by HPLC separation of acid protein hydrolysates with fluorescence detection (excitation 280 nm, emission at 320 nm) (A15). Other methods are based on borate-hydrochloric acid difference spectroscopy (this method suffers interference from tyrosine and tryptophan) (W2), derivatization of DOPA with nitrite and subsequent coulometric determination (W3), and fluorometric detection after derivatization with ethylenediamine (A15). 3-Hydroxylysine is quantitated by HPLC with 9-fluorenylmethyl chloroformate precolumn derivatization (M25) of amino acids obtained by gas-phase hydrolysis of proteins (F21). Other general methods to detect amino acid damage are mass spectometry methods applied to protein hydrolysates, such as tandem mass spectrometry (F6). 

Conventional hydrolysis exposes the polypeptide to 6M HCl acid under vacuum at 110°C for 20-24 h [1,2]. Protective agents, such as 0.1% phenol, are added to improve recovery. Gas-phase hydrolysis, in which the acid is delivered as a vapor, gives comparable results to the liquid phase. Additionally, the gas phase minimizes acid contaminants and allows parallel hydrolysis of standards and samples within the same chamber. 

The co-production of water in CO oxychlorination has been given as a reason for the disbelief that such a process could be feasible [455,456,457]. Although the hydrolysis of phosgene is highly favoured thermodynamically, the rates of reaction are found to be slow even at elevated temperatures, unless the reaction is suitably catalysed (see Section 9.10.3.1) [615,2207]. Indeed, the gas phase hydrolysis of phosgene has been studied [708] and... 

It is well documented that N02 can be transformed in the air to particulate nitrate. For this reason the nitrate content of aerosol particles in clear air is around 0.1 fig m 3 (Soderlund and Svensson, 1976). This gas-to-particle conversion process is initiated either by reaction [3.24] or by the gas phase hydrolysis of nitrogen dioxide ... 

A simple APCVD process for deposition of Ti02 thin films by the gas phase hydrolysis of TiCU yields films at 130-150°C [132]. Nitrogen was used as the carrier gas in a rotating disc reactor. The film quality was sufficient for use as an anti-reflective coating in silicon solar cells, however, no application as a dielectric was reported. 

Combining the halogenation of methane with catalytic, preferentially gas-phase hydrolysis, methyl alcohol (and dimethyl ether) can be obtained in high selectivity (Scheme 18) . The hydrolysis of methyl chloride with caustic was first carried out by Berthelot in the mid 1800 . This first preparation of methyl alcohol, however,... 

Gas phase hydrolysis under special conditions yields unstable phosphenous acid, H0-P=0 (4.209), which can be detected by infrared spectroscopy. 

Ford GP, Smith CT (1987) Gas-phase hydrolysis of protonated oxirane. Ab initio and semiempirical molecular orbital calculations. JAm Chem Soc 109(5) 1325-1331 Coxon JM, Maclagan DGAR, Rauk A, Thorpe AJ, Whalen D (1997) Rearrangement of protonated propene oxide to protonated propanal. J Am Chem Soc 119(20) 4712 718 Korzan R, Upton B, Turnbull K, Seybold PG (2010) Quantum chemical study of the energetics and directionality of acid-catalyzed aromatic epoxide ring openings. Int J Quant Chem 110(15) 2931 2937... 

In the gas-phase hydrolysis of esters, a competitive channel appears associated with an attack not on the carbonyl but rather on the alkyl carbon atom [1] ... 

Wet hydrolysis may not yield good results when using pure proteins, especially when the sample size is limited. Pure proteins can be hydrolyzed by gas-phase hydrolysis (Meltzer et al., 1987). With gas-phase hydrolysis, the HCl is placed in a separate container from the sample. The containers are then sealed into a secondary container. The secondary container is commonly a glass desiccator sealed with a Teflon gasket and placed in a desiccator cage. The desiccator is cycled between an inert gas, commonly nitrogen, and a vacuum, with the final cycle maintaining a vacuum in the desiccator. The desiccator is then placed in an oven at 110°C for the appropriate time. 

On heating, the HCl gas is released from the 6 HCl, and the gas then hydrolyzes the protein. This is a good technique for pure proteins of limited quantity, since most contaminants present in the 6 A HCl are usually nonvolatile and therefore cannot contaminate the samples. Another advantage is that the HCl and moisture that may condense on the samples can easily be removed with vacuum, leaving the hydrolyzed protein in a state ready for precolumn derivatization or to be dissolved in the appropriate solvent for chromatography. The disadvantage is that some of the protective agents that can be added to the 6 A HCl are not volatile and are therefore ineffective with gas-phase hydrolysis. 

The disadvantage of precolumn derivatization is increased manipulation of the sample before it can be chromatographed. Most autosamplers today can automate the derivatization reaction, thus freeing lab personnel for other activities. However, the derivatization reaction will usually not occur on the still very acidic hydrolyte. This necessitates the prior removal of the acid and water from the sample. This is commonly done by a vacuum. To completely remove the acid from the sample, the sample often has to be dried, ledissolved (usually in water), and then dried a second time. Once dried, the sample is ledissolved using a solvent compatible with the derivatization reaction. The additional time required by these steps can offset the savings achieved by using reversed-phase chromatography. Gas-phase hydrolysis of pure proteins eliminates the need to remove the acid from the sample. 

Novo Nordisk s lipozyme IM has been used for gas-phase hydrolysis of ethyl acetate (10% (v/v) in aq. sat. He). At 25-35 °C, 30% yield has been obtained after 5 min. However, the biocatalyst loses 90% activity in 30 min. This reaction, which clearly bears potential for being optimized, should be regarded as a novel approach for unusual reactions under itions [24]. 

Perez, V.H., Miranda, E.A., and Valenca, G.P. (2006) Kinetics of gas phase hydrolysis of ethyl acetate catalyzed by immobilized lipase. Appl. Biochem. Biotechnol, 136, Ih-in. 

Theoretical studies of the gas-phase hydrolysis or methanolysis of methylsul-fonyl chloride indicated a concerted Sn2 process involving a four-membered cyclic transition state. The tertiary amine-catalysed hydrolysis of benzenesul-fonyl chloride was shown to be inhibited by chloride ion and a nucleophilic mechanism of catalysis was favoured. Kinetic studies" of the solvolysis of p-substituted benzenesulfonyl chlorides in aqueous binary mixtures with acetone, methanol, ethanol, acetonitrile and dioxime showed that the reactions were third order processes, with first order rate constants determined mainly by the molar concentrations of the protic solvent, so that the reaction rates appear to be dominated by solvent stoichiometry. The solvolyses in methanol and ethanol yield both an alcoholysis (ap) and a hydrolysis product (hp). Solvolyses of electron-rich arylsulfonyl chlorides, under neutral or acidic conditions, exhibited surprising maxima in solvent-dependent S values as defined by Equation 15. 

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