Derivatization Experiments

As is evident in Figure 2.22, significant dispersion exists between the different series of experiments, which is most likely related to some uncontrolled aspect of the derivatization experiments, possibly including the effects of uncontrolled chloride co-adsorption in the different experiments. Nevertheless, the experiments provide an order of magnitude estimate of the consumption parameters and, equally important, reveal the potential dependence of the catalyst deactivation process. The potential... 

N- 0 anionic rearrangement has also been observed in monosilylhydroxylamines, and the results of derivatization experiments provide good evidence for equilibrium between N and O anions (2). For instance, lithiation of 0-trimethylsilylhydroxylamine followed by reaction with tert-butyldimethylchlorosilane produces a 3 1 mixture of rearranged and unrearranged products 23). 

Klinger also investigated the photoreaction of 1,4-benzoquinone (5) for which he expected analogue monoesters. Based on skilled derivatization experiments, the products from this reaction turned out to be acylated hydroquinones 6 accompanied by quinhydrone (7) as a major side-product (Scheme 3 Table 88.1). He also studied control reactions in the dark, which yielded only trace amounts of quinhydrone (7) after several months, unambiguously proving that light was essential for the activation. ... 

This experiment describes a quantitative analysis for the active ingredients in a prescription antipsychotic medication. The separation makes use of a cyanopropyl derivatized column and a mobile phase of 70% v/v acetonitrile, 5% v/v methanol, and 25% v/v 0.1 M aqueous KH2PO4. A UV detector set to 215 nm is used to measure the eluent s absorbance. 

Weber, P. L. Buck, D. R. Capillary Electrophoresis A Past and Simple Method for the Determination of the Amino Acid Composition of Proteins, /. Chem. Educ. 1994, 71, 609-612. This experiment describes a method for determining the amino acid composition of cyctochrome c and lysozyme. The proteins are hydrolyzed in acid, and an internal standard of a-aminoadipic acid is added. Derivatization with naphthalene-2,3-dicarboxaldehyde gives derivatives that absorb at 420 nm. Separation is by MEKC using a buffer solution of 50 mM SDS in 20 mM sodium borate. 

The thiazolecarboxylic acid structure (40) was also guessed in a similar way, from tracer experiments. The unknown compound was converted into the thiamine thiazole by heating at 100°C and pH 2. On paper electrophoresis, it migrated as an anion at pH 4. Tracer experiments indicated that it incorporated C-l and C-2 of L-tyrosine, and the sulfur of sulfate. The synthetic acid was prepared by carboxylation of the lithium derivative of the thiamine thiazole, and the derivatives shown in Scheme 19 were obtained by conventional methods. Again, the radioactivity of the unknown, labeled with 35S could not be separated from structure 40, added as carrier, and the molar radioactivity remained constant through several recrystallizations and the derivatizations of Scheme 17. 

As previously discussed, solvents that dissolve cellulose by derivatization may be employed for further functionahzation, e.g., esterification. Thus, cellulose has been dissolved in paraformaldehyde/DMSO and esterified, e.g., by acetic, butyric, and phthalic anhydride, as well as by unsaturated methacrylic and maleic anhydride, in the presence of pyridine, or an acetate catalyst. DS values from 0.2 to 2.0 were obtained, being higher, 2.5 for cellulose acetate. H and NMR spectroscopy have indicated that the hydroxyl group of the methy-lol chains are preferably esterified with the anhydrides. Treatment of celliflose with this solvent system, at 90 °C, with methylene diacetate or ethylene diacetate, in the presence of potassium acetate, led to cellulose acetate with a DS of 1.5. Interestingly, the reaction with acetyl chloride or activated acid is less convenient DMAc or DMF can be substituted for DMSO [215-219]. In another set of experiments, polymer with high o -celliflose content was esterified with trimethylacetic anhydride, 1,2,4-benzenetricarboylic anhydride, trimellitic anhydride, phthalic anhydride, and a pyridine catalyst. The esters were isolated after 8h of reaction at 80-100°C, or Ih at room temperature (trimellitic anhydride). These are versatile compounds with interesting elastomeric and thermoplastic properties, and can be cast as films and membranes [220]. 

In Situ Derivatization. To demonstrate that a group of alcohols could be derivatized at low alcohol concentration, the following experiment was performed. First, 6 x 10 mole of each of the alcohols used to form derivatives was dissolved in 100 ml of acetonitrile. Then 2 x 10" mole of compound V was added, and the solution was heated at 70°C. This solution was then diluted by taking 1.0 mL of the reaction mixture and diluting to 10 mL with water and acetonitrile, and the diluted solution was analyzed. After 4 h the methanol and ethanol were completely derivatized, but it took 6 h for the n-propanol and n-butanol derivatives to form. 

To demonstrate that a group of alkyl bromides could be derivatized at low alkyl bromide concentration, a similar experiment... 

Heterocyclic fluorophores based on the benzoxadiazole nucleous, namely 4-nitrobenz-2-oxa-l,3-diazole (NBD) 14 derivatives/analogs, have been widely used as derivatization reagents for analysis purposes. Examples include the amino- or thiol reactive 4-fluoro-7-nitrobenz-2-oxa-l,3-diazole (NBD-F) 15 and 4-chloro-7-nitrobenz-2-oxa-1,3-diazole (NBD-C1) 16 [45-50] and the thiol-reactive /V-((2-(iodoacetoxy)ethyl)-/V-methyl)amino-7-nitrobenz-2-oxa-1,3-dia-zole (IANBD ester) 17 [51] and 7-chlorobenz-2-oxa-l,3-diazole-4-sulfonate (SBD-C1) 18 [52], NBD-F and NBD-C1 derivatives can be excited at about 470 nm by using the relatively inexpensive and reliable argon ion lasers or newer diode pumped solid state (DPSS) lasers. NBD-F has been used as a labeling tag in various capillary electrophoresis (CE) experiments for amino acids [53-57] including the monitorization of in vivo dynamics of amino acids neurotransmitters [58]. 

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