Surrogate - mixture

From Carter and Atkinson (1989) calculated using the EKMA model with low dilution and an eight-component surrogate mixture of organics chosen to be representative of emissions into California s South Coast air basin. Note that the absolute values used may have changed for some components since the original publication due to further refinement of the model. 

Figure 14.4 Gel image of proteins extracted from a mixed carbonic anhydrase lysozyme tissue surrogate. Lane M, molecular weight marker lane 1, a 1 2 mol ratio mixture of native, non-formalin-treated carbonic anhydrase and lysozyme lane 2, mixed surrogate with 1 2 mol ratio carbonic anhydrase lysozyme, solubilized and retrieved in 20mM Tris-HCl, pH 4.0, with 2% SDS lane 3, mixed surrogate with 1 2 mol ratio carbonic anhydrase lysozyme, solubilized and retrieved in 20mM Tris-HCl, pH 6.0, with 2% SDS. Protein bands corresponding to lysozyme monomer (a), carbonic anhydrase monomer (b), and the putative lysozyme-carbonic anhydrase heterodimer (c) are indicated. For more detail, see Reference 25.

The biological approach (whole effluent) to toxics control for the protection of aquatic life involves the use of acute and chronic toxicity tests to measure the toxicity of wastewaters. Whole effluent tests (WET) employ the use of standardized, surrogate freshwater or marine (depending on the mixture of effluent and receiving water) plants (algae), invertebrates, and vertebrates. 

The fate of four petroleum mixtures has been evaluated using three approaches—evaluating the fate of (1) indicator chemicals, (2) the mixture of the whole with a surrogate, and (3) the hydrocarbon mixture as a whole. The four mixtures were crude oil, JP-5, mineral spirits, and diesel. The choice of approach requires the consideration of availability and quality of data on the mixture, the mobility and toxicity of the mixture, and the availability of site data (Custance et al. 1992). 

The full potential of this C-H activation process, as a surrogate Mannich reaction, was realized in the direct asymmetric synthesis of threo-methylphenidate (Ritalin) 217 (Eq. 28) [140]. C-H insertion of N-Boc-piperidine 216 using second-generation Rh2-(S-biDOSP)2 and methyl phenyldiazoacetate resulted in a 71 29 diastereomeric mixture, where the desired threo-diastereomer was obtained in 52% yield with 86% enantiomeric excess. Winkler and co-workers screened several dirhodium tetracarboxami-dates and found Rh2(R-MEPY)4 to be the catalyst that gives the highest diastereoselec-tivity for this reaction [142]. 

Trialkyltin hydrides represent an important class of reagents in organic chemistry because of their utility in radical reactions. However, problems of toxicity and the difficulty of product purification made trialkyltin hydrides less than ideal reagents. Several workup procedures and structurally modified trialkyltin hydrides have been developed to facilitate the separation of tin residues from the reaction mixture. Tris(trimethylsilyl)silicon hydride has also been synthesized and is often used successfully in radical reactions. However, its reactivity is different from that of trialkyltin hydrides in a number of important respects. Other tin hydride surrogates are also available. ... 

Aliphatic and aromatic nitriles are often converted to the corresponding imidates that then react with amino alcohols to provide oxazolines. This two-step process offers milder conditions. Generally, a mixture of the imidate (free base or hydrochloride) is allowed to react with the amino alcohol in a solvent (alcohols, CH2CI2, CHCI3) with or without a tertiary base. As expected, the cylization proceeds with retention of stereochemistry when chiral amino alcohols are used. Representative examples are shown in Table g 17 33,62,63,139,216-225 ready availability of benzimidates and trimethyl orthobenzoates make them ideal surrogates for benzonitrile. ... 

Determination of the specific reactivity of the exhaust emissions requires accurate knowledge of both the types and amounts of compounds emitted as well as how each contributes to 03 formation. The latter factor, the ozone-forming potential, is treated in terms of its incremental reactivity (IR), which is defined as the number of molecules of ozone formed per VOC carbon atom added to an initial surrogate atmospheric reaction mixture of VOC and NOx ... 

Synthetic Mixture Approach. Robert Neal has been the chief proponent of the synthetic mixture approach (2). The advantages and disadvantages of using synthetic mixtures of chemicals as surrogates for mixtures found in actual waters are the following ... 

Other methods for the preparation of gem-diaminoalkyl residues have been reported. Some of them are directly applicable to synthesis of PMRI-peptides and some are only remotely related. Katritzky et al.1901 synthesized racemic, monoprotected diaminoalkyl derivatives by the Mannich reaction (Scheme 5). The diastereomeric mixtures of A-peptidyl gem-diaminoalkyl compounds were resolved to afford the diastereomerically pure retro-inverso surrogates. 

---