Reaction side product

Refluxing in presence of surfactant and other reaction side products always lead back to prismatic pariidles... 

Piperidine derivatives 161 and 164 could be cyclized to hexahydropyridooxadiazines 162, 165 via a dehydrogenation process by six oxidation equivalents of Hg(n)-EDTA. However, in both reactions, side products were also formed. From 161, piperidone derivative 163 was obtained, whereas starting from the amide 164, pyridopyrimidine 166 was isolated via cyclization by the amide nitrogen instead of oxime oxygen (Scheme 21) <1999ZNB632>. 

This procedure has been demonstrated to provide moderate yields and anomeric selectivity in oligosaccharide synthesis. For instance, the disaccharide 110 was obtained in 50% yield as a 1 2 a p ratio. The reaction side products were mainly the self-condensed donor (10-25%) and unreacted hemiacetal (5-10% or higher). Alternatively, the a-linked glycosides were favored with diethyl ether solvent. In this way, trisaccharide 111 was prepared from the disaccharide hemiacetal donor in 49% yield, favoring the a-anomer by 4 1. 

The purity of compounds in the library is an important factor. Reaction side products (e.g., triphenylphosphine from a Wittig reaction) should be completely removed from a compound in a library. Similarly, compounds should be free of any solvents used in their synthesis. Unfortunately, not all impurities are easily removed. Impurities can sometimes interfere with an assay and lead to inaccurate results.2... 

Another route to ten-vertex monometallocarboranes is through polyhedral expansion of 4,5-C2B7H9. A new isomer of C5H5C0C2B7H9 with carbon atoms in positions 3 and 10 is produced in this reaction. Side products included the nine-vertex species C5H5C0C2B6H8 (Section VIII) and the eleven-vertex C5H5C0C2B8H10 (24). 

Monomer is transferred via a pressurized pipe to the reactor top where reaction side products are flashed out. Higher conversion rates (97-99%) are achieved by a cascade of four to six reaction cups at decreasing pressures and increasing temperatures. 

Figure 3. Automated C-Terminal Sequencing of the Tripeptide, LAP (15 nmol), Covalently Attached to Carboxylic Acid Modified Polyethylene. Each thiohydantoin derivative is identified by comparison to the retention time of an authentic standard. Unlabeled peaks are background produced by reaction side products.

This square planar zinc complex is an excellent intermediate for the preparation of other BZO4 [16] octaene N4 complexes by metal exchange, and its use alleviates the problem of separating the desired complex from other reaction side products when o-aminobenzaldehyde is condensed in the presence of the appropriate metal ion. Complexes of nickel, cobalt, iron, and palladium have been prepared from this zinc compound. 

Now, the oxidation of cyclic and acyclic dienes at a glassy carbon electrode quite generally affords 1,4-addition reactions. Side products are also obtained. The table below summarizes [44] the different abilities of double bonds to react anodically (substitution versus addition). 

Amazingly, non-reduced catalysts exhibited high selectivity to unsaturated alcohol (COL), achieved a selectivity comparable to chemically reduced catalysts. The obtained results can be explained by low yields of reaction side-products (PPAL PPOL). High chlorine content resulted in formation of acetals. The promoting effect of chlorine in... 

Scheme 4 Isomerization of geraniol (11) into citronellal (12) and reaction side products (13 and 14).

Schemes Isomerization of prenol (15) into isovaleraldehyde (16) and reaction side product (17).

Contribution to the total or overall E-factor with respect to mass from reaction by-products, reaction side products, and unreacted starting materials (excludes excess reagents). 

Although there is an increasing trend toward precolumn derivatization methods, there are several advantages to an ion-exchange separation with postcolumn derivatization. The first is that there is little sample preparation protein hydrolysates can be injected directly into the column for analysis by LC. Unlike precolumn methods, it is not necessary to separate reaction side-products from the reaction mixture instead, they become a source of background. With postcolumn methods there is more sample-to-sample consistency because of the robustness of the ion-exchange separation and the fact that the reaction time is determined by the column size. 

In comparison with acyclic (phenyl and benzyl) diselenotetrasulfides, 6,6-dimethyl-l,4-diseleno-3,7-tetrasulfide gives cleaner sulfur-transfer products (both di- and tetrasulfides ) although the yields are comparable. Clean sulfur transfer is advantageous as some of the reaction side products, especially polymers and se-lenide adducts, are difficult to remove from the reaction mixture. 

Isomerization of a-pinene oxide to campholenic aldehyde is an important and complicated reaction. Side products like those described in Scheme 8.19 can be produced together with the product of interest. Working with a Zn(0Tf)2/Si02 catalyst calcined under N2 at 200°C prior to use, the selectivity was increased to 65% [97]. This increase in selectivity was attributed to loss of Brpnsted acid sites by dehydration of the catalyst surface, which, in turn, reduced the amount of side reactions. Further calcination at 400°C decreased the activity of the catalyst due to decomposition of Zn(OTf)2. 

Fluorescence detection offers the possibility of high sensitivity and, in the case of complex samples, improved selectivity. However, this mode of detection requires that the analyte exhibit native fluorescence or contain a group to which a fiuorophore can be attached by chemical deriva-tization. The number of compounds that fall into the former category are small, and while many analytes contain derivatizable groups (e.g., amino, carboxyl, hydroxyl), most derivatization chemistries are limited by one or more disadvantages (slow reaction kinetics, complicated reaction or cleanup conditions, poor yields, interference by matrix components, derivative instability, interference by reaction side products or unreacted derivatizing agent). 

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