Non-derivatizing solvents

From the synthetic point of view, more flexibility is achieved by employing non-aqueous non-derivatizing solvents. Extensive work has been carried out on binary or ternary mixtures like inorganic or organic electrolytes in strongly dipolar aprotic solvents. The best known example is LiCl in DMA, in A-methyl-2-pyrrolidone (NMP), or in 1,3-dimethyl-2-imidazolidinone (DMI) [5]. The structure of these ceUulose/solvent system complexes has been described by several authors, differing essentially in the role played by the Li and CD ions, as comprehensively discussed in a specific review [6]. 

Functional Cellulose Materials Prepared from Non-derivatizing Solvents... 

Cellulose is very difficult to dissolve in common solvents due to its intramolecular and intermolecular hydrogen bonding networks. Lately, many new non-derivatizing solvents have been developed to dissolve cellulose. 

The utilization of ionic liquids provides a new opportunity for proeessing cellulose while minimizing the energy and environmental concerns, because ionic liquids are chemically and thermally stable, non-flammable and low in volatility [91, 92]. Several ionic liquids that serve as non-derivatizing solvents have been proposed such as 1-ally 1-3-methylimidazolium chloride (AmimCl) [93], 1-butyl-3-methylimidazolium chloride (BmimCl) [94], and 1,3-dialkylimidazolium formate [95]. Manufacturing cellulose fiber using ionic liquids has attracted attention in both academia and industry. For example, regenerated cellulose films... 

The sample (2-3 mg) is placed in a 5-ml tapered reaction vial. 3 ml of ethanol and 50 mg of the PNBTT reagent are added. The vial is covered loosely (nitrogen is evolved during the reaction, so the vial should not be sealed tightly) and heated in a bath at 65 °C until derivatization is complete (generally 1 h or less). The vial is then sealed and cooled to room temperature. The solution may be chromatographed directly or cleaned up as described above. The p-nitrobenzyl esters are non-polar compared with the parent acids and the by-products of reaction. For chromatography on silica gel, a non-polar solvent is used. 

The silylation of amino acids with BSTFA was studied in detail by Gehrke and coworkers [254—256]. BSTFA—acetonitrile (1 1) was applied first and fourteen amino acids were silylated at 135°C for 15 min. Glu, Arg, Lys, Trp, His and Cys, however, require up to 4 h, in order for measurable peaks to be obtained in the chromatogram. Despite such a long reaction, Gly and Glu gave two peaks and also it was difficult to separate the tris-TMS derivative of Gly from the derivatives of lie and Pro. The influence of polar and non-polar solvents was demonstrated later and was decisive mainly with respect to uniformity of the products. Only the bis-TMS derivative was produced in hexane, methylene chloride, chloroform and 1,2-dichloroethane bis- and tris-derivatives were produced in six more polar solvents. On the other hand, Arg did not provide any peak in the less polar solvents that were used and only one peak in the six more polar solvents. The best and most reproducible results were obtained when silylating seventeen amino acids with BSTFA—acetonitrile (1 1) at 150°C for 15 min 2.5 h at 150°C were necessary for the reproducible derivatization of Gly, Arg, and Glu. These reaction conditions were recommended for the analysis of all twenty amino acids. The TMS derivatives of amino acids were found to be stable on storing them in a sealed vial at room temperature for 8 days, with no decomposition. 

Solution formulations, however, do not typically have these same constraints, and complexation provides an alternative to the use of non-aqueous solvents or large volumes. A few derivatized CDs (e.g., hydro-xypropyl and sulfobutyl ether) can be safely administered by parenteral routes. This is often where complexation and its improvements in aqueous solubility can be most readily utilized. The derivatized CDs often can be used to replace cosolvents such as ethanol, polyethylene glycol, and lipids, as well as provide an alternative to the use of emulsions and liposomes. The hydroxypropyl and sulfobutyl ether derivatives are stable in solution and can be readily autoclaved, often improving the heat stability of drugs. There are however, reports of complexation of CDs with anti-oxidants and preservatives " with both decreased and increased efficacy. ... 

Most of the derivatives shown in Figure 8 are solvent extractable at low pH, and thus one of the classical methods used for antibiotic purification becomes accessible to cephalosporin C. To be commercially feasible, solvents should be selective and only slightly miscible with water. Extraction efficiency should be sufficiently high that multiple extractions are not required, and ideally should be efficient at low ratios so as to effect a concentration of the desired component. Emulsions and insoluble solids are anathema to extraction. Using these criteria, extraction of most of the cephalosporin C derivatives at low pH are far from ideal since mostly non-selective solvents (such as n-butanol and ethyl acetate) usually work best several extractions seem to be required, and derivatized cephalosporin C broth upon acidification will frequently result in emulsion formation. However, some derivatives behave better than... 

A. NMR of a non derivatized saponin in CD3OD (recorded at 300 MHz). At high field, one distinguishes the methyl resonances. The large peak at 4.7 ppm is OH (fi-om solvent and saponin). The 5.3 ppm signal is fi-om the triterpene double bond other signals in this area are anomeric protons from arabinose (5.7), rhamnose (5), xylose (4.5) and glucose (4.4 ppm). 

Extractive alkylation processes utilizing ion-pair distribution have been used in organic synthesis [61], as well as in derivatization for gas chromatographic assay. The technique is suitable for organic compounds containing active hydrogen, which are particularly reactive as ion-pairs in non-polar solvents. 

Derivatized carbohydrates possessing hydrophobic substituents are considered in the final sections. These compounds migrate rapidly on silica gel G with relatively non-polar solvents and resolution of a,j5-anomers and pyranose and furanose sugars is observed. 

The additional activation of the substrates is believed to arise from the hydrogen bonding interactions of ethylene glycol with the carbonyl of the aryl input. Therefore, other non-protic solvents result in trace amounts of product, unless a hydrogen-bond donor is added, such as [H2N Pr2][BF4]- Satisfactory yields (40-85%) of the indanones are accomplished from commercially available starting materials using a simple catalytic system that allows further derivatization. 

Reversed phase SPE separates analytes based on their polarity. The stationary phase of a reversed phase SPE cartridge is derivatized with hydrocarbon chains, which retain compounds of mid to low polarity due to the hydrophobic effect. The analyte can be eluted by washing the cartridge with a non-polar solvent, which disrupts the interaction of the analyte and the stationary phase. 

---