Chromatography of alcohols

For the higher alkoxy groups, standard carbon and hydrogen analysis may be used, although careful sample preparation is required because of the ease of hydrolysis. Quantitative vapor-phase chromatography of alcohol Hberated during hydrolysis may also be used, but care must be taken in this case to ensure that hydrolysis is complete before the estimation is carried out. 

Gas chromatography of alcohols offers no particular problems, and there is much literature on separating and identifying alcohols. 

Gas Chromatography of Alcohols This procedure will identify and quantify the common alcohols in blood and mine. The column used is 0,3% Carbowax 20M on Carbopak C, The system is the same as System GI for Solvents and Other Volatile Compounds (p. 199) except that for this purpose it is operated isothermally at 120°. identification of alcohols... 

Purification of cAM P-dependent protein kinase holoenzyme Affinity chromatography of alcohol dehydrogenases on a hydrophobic... 

In addition to ease of removal after serving to protect a hydroxyl group from unwanted reaction, placement of trialkylsilyl groups on oxygen serves the added function of decreasing the polarity of the (former) hydroxyl group. This is a major aid in chromatography of alcohols. 

Control in the affinity chromatography of alcohol dehydrogenase and in demonstrating the absence of interactions with an n-hexyl spacer arm... 

FIG. 3 A. Ethylene oxide distribution (via supercritical liquid chromatography) of methyl ester ethoxylate obtained with conventional (NaOH) catalyst. B. Ethylene oxide distribution (via supercritical liquid chromatography) of methyl ester ethoxylate obtained with Ca/Al-alkoxide catalyst. (From Ref. 23.) C. Ethylene oxide distribution (via supercritical liquid chromatography) of alcohol ethoxylate obtained with conventional (NaOH) catalyst. D. Ethylene oxide distribution (via supercritical hquid chromatography) of alcohol ethoxylate obtained with Ca/Al-aUcoxide catalyst. (From Ref. 23.)... 

RO—CF=CF2, are obtained by reaction with sodium salts of alcohols (26). An osone—TFE reaction is accompanied by chemiluminescence (27). Dimerization at 600°C gives perfluorocyclobutane, C Fg further heating gives hexafluoropropylene, CF2=CFCF2, and eventually perfluoroisobutylene, CF2=C(CF2)2 (28). Purity is deterrnined by both gas—Hquid and gas—soHd chromatography the in spectmm is complex and therefore of no value. 

FIGURE 4.24 Adsorption chromatography of small molecules with a TSK-GEL G2500PWxl column. Column TSK-GEL G2500PWxl, 6 /tm, 7.8 mm X 30 cm. Sample (I) phenylacetic acid. (2) 3-phenylpropionic acid, (3) 4-phenylbutyric acid, (4) benzylamine, (5) 2-phenylethylamine, (6) 3-phenylpropylamine, (7) benzyl alcohol, (8) 2-phenylethanol, and (9) 3-phenyl-1 -propanol. Elution 0.1 M NaCIO, in water. Flow rate 2.0 ml/min. Temperature 65 C. Detection UV at 215 nm. 

A large number of silylating agents exist for the introduction of the trimethylsilyl group onto a variety of alcohols. In general, the sterically least hindered alcohols are the most readily silylated, but are also the most labile to hydrolysis with either acid or base. Trimethylsilylation is used extensively for the derivatization of most functional groups to increase their volatility for gas chromatography and mass spectrometry. 

V. Schubert, R. Diener and A. Mosandl, Enantioselective multidimensional gas chromatography of some secondary alcohols and their acetates from banana , Z C. Naturforsch. C. 46 33-36 (1991). 

To a solution of (5)-ester 6 (0.566 g, 1.90 mmol) in 20 mL of THF at 0°C is added tetrabutylammonium fluoride (3.0 mL, 3.0 mmol) (Note 19). After 15 min, the reaction mixture is warmed to room temperature. After 3 hr, 20 mL of aqueous saturated NH4C1 is added and the mixture is extracted with three 10-mL portions of Et20. The combined organic extracts are washed with 20 mL of brine, dried over MgS04, filtered, and concentrated under reduced pressure. The residue is purified by chromatography on silica gel (elution with 20% EtOAc/hexanes) to afford 0.271 g (78%) of alcohol 7 (Note 20). 

Thin-layer chromatography (TLC) is used both for characterization of alcohol sulfates and alcohol ether sulfates and for their analysis in mixtures. This technique, combined with the use of scanning densitometers, is a quantitative analytical method. TLC is preferred to HPLC in this case as anionic surfactants do not contain strong chromophores and the refractive index detector is of low sensitivity and not suitable for gradient elution. A recent development in HPLC detector technology, the evaporative light-scattering detector, will probably overcome these sensitivity problems. 

The ion spray liquid chromatography/mass spectrometry (LC-MS) interface coupled via a postsuppressor split with an ion chromatography (IC) has been used in the analysis of alcohol sulfates. The IC-MS readily produces the molecular weight while the tandem mass spectrometric detection IC-MS-MS provides structural information [305]. 

The alkyl chain distribution of the base alcohol in alcohol sulfates is easily determined by gas chromatography. However, alcohol sulfates and alcohol ether sulfates are not volatile and require a previous hydrolysis to yield the free alcohol. The extracted free alcohol can be injected directly [306] or converted to its trimethylsilyl derivative before injection [307]. Alternatively, the alcohol sulfate can be decomposed by hydroiodic acid to yield the alkyl iodides of the starting alcohols [308]. A preferred method forms the alkyl iodides after hydrolysis of the alcohol sulfate which are analyzed after further extraction of the free alcohol, thus avoiding the formation of hydrogen sulfide. This latter method is commonly used to determine the alkyl chain distribution of alcohol ether sulfates. 

Secondly it is possible to carry out functional chromatography within the framework of a two-dimensional development [6-8]. The first separation is followed by an in situ reaction of the sample substance on the layer the chromatogram is then developed perpendicular to the direction of the first chromatogram (SRS technique). The decision concerning the type of alcohol, is then made on the basis of the positions of the chromatogram zones esters migrate appreciable further than their parent alcohols and acids. 

Katayama, M., Masuda, Y., and Taniguchi, H., Determination of alcohols by high-performance liquid chromatography after pre-column derivatization with 2-(4-carboxyphenyl)-5,6-dimethylbenzimidazole,/. Chromatogr., 585,219, 1991. 

Lange, H.W. and Hempel, K., Automated chromatography of aromatic acids, aldehydes, and alcohols with an amino acid analyzer, /. Chromatogr., 59, 53,1971. 

Paskach, T. J., Lieker, H.-R, Reilly, P. J., and Thielecke, K., High-performance anion-exchange chromatography of sugars and sugar alcohols on quaternary ammonium resins under alkaline conditions, Carb. Res., 215,1, 1991. 

Jandera, P., Holcapek, M., Theodoridis, G. (1998). Investigation of chromatographic behavior of alcohol ethoxylate surfactants in normal-phase and reversed-phase systems using high-performance liquid chromatography-mass spectrometry. J. Chromatogr. A 813(2), 299-311. 

Because of the exceptional C-F bond strength, the successful preparation of a-halocyclopropyl c-complexes is realized by substitution of 1-bromo-l-fluoro-trans-2,3-dimethylcyclopropane 179 with Fp [90], Silica gel column chromatography of the thus obtained cr-complex 180 results in ring opening to the alcohol 181 as a single stereoisomer. The allene complex 182 is produced by treatment with BF3OEt2, indicating that 181 is derived from 182 and water. The 7i-allyl complex 183 is formed by photolysis via a disrotatory process. 

J.J. Jimenez, J.L. Bemal, S. Aumente, L. Toribio, J. Bernal, Quality assurance of commercial beeswax II. Gas chromatography electron impact ionization mass spectrometry of alcohols and acids, Journal of Chromatography A, 1007, 101 116 (2003). 

The detailed composition, referring to classes of compounds, is shown for C6 in Figure 9.3 with and without precolumn hydrogenation. In addition to paraffins, there are olefins—mainly with terminal double bond—and small amounts of alcohols (and aldehydes). The low detection limit of gas chromatography (GC) analysis allows precise determination even of minor compounds and provides exhaustive composition data also for use in kinetic modeling. Because of the short sampling duration of ca. 0.1 s,8 time-resolved selectivity data are obtained. 

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