Two-phase protocol

Maye MM, Kariuiki NN, et al. 2004. Electrocatal3dic reduction of oxygen Gold and gold-platinum nanoparticle catalysts prepared by two-phase protocol. Gold Bull 37(3-4) 217-223. 

For the study of the electrocatalytic reduction of oxygen and oxidation of methanol, our approach to the preparation of catalysts by two-phase protocol " provides a better controllability over size, composition or surface properties in comparison with traditional approaches such as coprecipitation, deposition-precipitation, and impregnation. " The electrocatalytic activities were studied in both acidic and alkaline electrolytes. This chapter summarizes some of these recent results, which have provided us with further information for assessing gold-based alloy catalysts for fuel cell reactions. 

J. Luo, M. M. Maye, N. N. Kariuki, L. Wang, P. Njoki, Y. Lin, M. Schadt, H. R. Naslund, and C. J. Zhong, Electrocatalytic oxidation of methanol Carbon-supported gold-platinum nanoparticle catalysts prepared by two-phase protocol, Catal. Today 99, 291-297 (2005). 

Under such conditions re-use of the palladium catalyst would be difficult This was the motivation of Boche et al. to use a two-phase protocol by dissolving the sixfold sulfonated BlNAS-6 (1) and palladium acetate in water [3],... 

Reactions between A -(l-chloroalkyl)pyridinium chlorides 33 and amino acids in organic solvents have a low synthetic value because of the low solubility of the amine partner. A special protocol has been designed and tested in order to circumvent this drawback. Soon after the preparation of the salt, an aqueous solution of the amino acid was introduced in the reaction medium and the two-phase system obtained was heated under reflux for several hours. However, this was not too successful because sulfur dioxide, evolved during the preparation of the salt, was converted into sulfite that acted as an 5-nucleophile. As a result, A -(l-sulfonatoalkyl)pyridinium betaines such as 53 were obtained (Section IV,B,3) (97BSB383). To avoid the formation of such betaines, the salts 33 were isolated and reacted with an aqueous solution of L-cysteine (80) to afford thiazolidine-4-carboxylic acids hydrochlorides 81 (60-80% yields). 

While asymmetric approaches are certainly important, other synthetically significant epoxidation protocols have also been reported. For example, buffered two-phase MCPBA systems are useful for epoxidations in which the alkenes and/or resultant epoxides are acid-sensitive. Bicarbonate works quite well for cinnamate derivatives (e.g., 55) <96SC2235> however, 2,6-di-t-butyl-pyridine was shown to give superior results in the case of certain allyl acetals (e.g., 57) <96SC2875>. 

The two Phase II trials were Protocol 005 (N = 2391) and Protocol 007 (A = 551). The Phase III studies were FUTURE I (Protocol 013, A = 5442) and FUTURE II (Protocol 015, N = 12,157). Altogether, 20,541 women from 16 to 26 years of age were enrolled. Subjects were given Gardasil without prescreening for the presence of HPV infection. 

A recent synthesis of the phenylisoserine side-chain of taxol is shown in Scheme 18. The enone 21 was obtained in high yield by condensation of benzal-dehyde with pinacolone. Employing the non-aqueous two-phase epoxidation protocol, epoxide 22 was obtained in 76% yield and 94% e.e. Recrystallisation of the epoxide furnished the desired enantiomer in 97 % e. e. Subsequent manipulations of the epoxy-ketone gave the taxol side-chain 23 with the required stereochemistry (Scheme 18). 

Hatti-Kaul, R. Aqueous Two-Phase Systems Methods and Protocols, Humana Press Totowa, NJ 2000. 

We have employed two different protocols for the chemical fractionation of GSE obtained from MegaNatural-AZ based on the amounts needed for bioactivity-based assays. Batches of GSE (50 g) were extracted in acetone/water (7 3) under N2 with mechanical agitation for 12 h. The acetone was removed on a rotary evaporator and the aqueous phase was freeze-dried to yield 48 g of tannin crude extract (TCE). TCE was further fractionated following two different methods. 

There are enthalpies of formation for two phases of cumyl perbenzoate. However, the associated sublimation enthalpy that interconnects these phases, 43 kJ mol , is much too small. In that the enthalpy of sublimation must exceed the enthalpy of vaporization, and the latter is at least 75 kJmol using the CHLP protocol (from the number of carbons alone), the enthalpy of formation data loses credibility. Furthermore, lacking the enthalpy of formation of the corresponding cumyl benzoate (in any phase) disallows comparison. This would seem to be an altogether normal species until it is recognized that the archetype arylcarboxylate ester, methyl benzoate, has provided complications for the calorimetrist . 

Aqueous micellar solutions of many nonionic surfactants, with an increase in temperature, become turbid over a narrow temperature range, which is referred to as their cloud-point [17,277]. Above the cloud-point temperature, such solutions separate into two isotropic phases. Cloud-point extraction (CPE) is also referred to as a particular case of ATPE [278,279] and more specifically as aqueous micellar two-phase systems [10,277]. Very recently, in an extensive review, Quina and Hinze [280] have discussed in detail the emergence of CPE as an environmentally benign separation process, highlighting the basic features, experimental protocols, recent applications, and future trends in this area. 

The most popular method for measuring the polarity of a solute entails determination of the distribution constant between water and a water-immiscible solvent, e.g., octanol. However, because there is difficulty in dissolving proteins in the solvent, a two-phase aqueous system was developed (Shanbhag and Axelson, 1975). Albertson (1986) reported the construction of various aqueous phase systems for partitioning proteins, other macromolecules, and even cells. Recently, simpler aqueous biphase systems were selected for hydrophobic partitioning of proteins (Hachem et al., 1996). However, because of restrictions similar to those for HIC, as discussed above, it may be premature to replace the method used in Basic Protocol 5. The definition of hydrophobicity is based on the polarity of chemical compounds, which is closely related to the distribution between solvents of different polarities. This theory is similar to the elution mechanism of phase distribution chromatography as well as phase partition. However, complexity in the partition system and procedure hampers the broad use of the phase partition approaches. 

While the measurement protocol is fairly simple, there are a number of important factors that need to be considered when using the drop shape analysis method. First, a sufficient visual contrast between the drop and the surrounding liquid is required to be able to extract the drop profile. If the external phase is slightly turbid, or if the refractive indices of the two phases match each other, it may be difficult or even impossible to extract the drop profile. If possible, the more turbid phase should be chosen as the internal drop-forming... 

In a more recent study, Westman and Lundin described the solid-phase synthesis of aminopropenones and aminopropenoates, respectively30 as intermediates for heterocyclic synthesis. Two different three-step methods for the preparation of heterocycles have been developed. The first method involved formation of a polymer-bound ester from a IV-protected glycine derivative and Merrifield resin (Scheme 7.10a), while the second method employed an interesting approach utilising simple aqueous methy-lamine solution for functionalisation of the solid support (Scheme 7.10b). In this latter approach, a variety of hetero cycles were readily synthesised from the generated polymer-bound benzylamine using a two-step protocol (see Section 5.3.3). 

Employing two resin-bound amines and three different anhydrides in the above solid-phase protocol, a set of six cyclic imides (see Fig. 7.15) were synthesised in good yields. 

In connection with an interest in generating /i-turn dipeptide mimetics, Piscopio and co-workers developed a solid-phase approach to the Freidinger lactam 86 via a solid-phase Ugi condensation and ring-closing metathesis (RCM) methodology [72], The resin-bound amine 85 is the equivalent of a traceless linker and the two-step protocol proceeds in good yield (Scheme 11.17). 

In the final phase of LCA, inferences are drawn especially from LCI analysis and LCIA. From an analysis of the results, conclusions can be drawn and limitations defined, and recommendations for producers and policy-makers can be made. In general, the purpose of an LCA is to make inferences that can support a decision or provide a basis for a viewpoint. This means that the process of drawing conclusions is perhaps the most important step in any LCA. The relevant issue of interpretation is dealt with in ISO 14043. This phase will be exemplified as a case study comparing the results of LCA for two analytical protocols. 

An uncommon experiment of cage self-assembly in a liquid-liquid two-phase system has been described. Cavitand 31b (1 equiv) dissolved in 1,1,2,2-tetrachlor-oethane was exposed to an aqueous solution of Pd(en)(N03)2 (2.5 equiv) in a test tube. Immediately, a solid formed at the interface, which became more abundant over time.1H NMR analysis of the recovered solid indicated the formation of cage 32h in pure form. A MALDI-TOF experiment performed directly on the solid sample confirmed the attribution. This last result is particularly interesting since liquid-liquid interfaces represent another potentially useful field of action for self-assembly protocols, which has barely been explored so far [42]. 

The mixture of phenol and water (45 50, v/v) can be used to extract LPS (Westphal and Jann, 1965). This mixture is a single phase above 65°C but separates into two phases below 65°C. LPS and proteins can be extracted from bacteria by this mixture above 65°C. When cooled down, phase separation occurs. The phenol phase mainly contains proteins, while the water phase contains LPS, polysaccharides, and nucleic acids. The following protocol is the most used for phenol-water extraction of LPS (Johnson and Perry, 1976). 

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