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Aldehydes analysis

Beer Samples. American lager beer samples used for the aldehyde analysis were stored at 30 °C for 4, 8, or 12 weeks. Control samples were stored for 12 weeks at 0 °C. [Pg.60]

A stainless steel autoclave filled with 80 mg (0.1 mmol) of [(-)-Diop]PtCl(SnCl,) is evacuated and cooled to -11 °C. 30 mL (1.77 g, 0.31 mol) of l-butene (measured in a Schlenk tube at — 60 C) and 25 mL of ethylbenzene are introduced by suction. The autoclave is pressurized with 19.95 bar of CO and heated at 100 X in an oil bath. After 1 h the reaction is started by introducing an equivalent amount of H2 and by connecting the autoclave to a reservoir to maintain the pressure in the reaction vessel constant at 81.13 bar. After a gas uptake of 12.5 L (corresponding to an olefin conversion of 70%) the reaction is stopped by cooling, first with water and then with ice to 0 X. The solution is analyzed by GC using a Carbowax column at 100 C for aldehyde analysis and adimethylsulfolanecolumnat r.t. for olefin analysis. The aldehyde yield (63%) is determined by using the solvent as internal standard. [Pg.321]

In a typical run, [Rh(CO)2Cl]2 and phosphane were weighed and introduced in the autoclave, which was then closed. The atmosphere was replaced by Ar and a toluene solution containing the required quantity of ethyl acrylate 32, and triethylamine was introduced through the ball valve. This valve was closed and the autoclave was pressurized with CO and H2 and heated to the required temperature in about 5 min. After the reaction time quoted in the Table, the autoclave was cooled to -40 °C in ca. 1 h in a well-ventilated hood. The reaction products were collected under argon into a Schlenk tube and analyzed by gas chromatography [3 m x 1/8 column 10% carbowax 20M on chromosorb 80-100 mesh] working at 150 °C and N2 as carrier gas (flow rate 10 Lh ) with 1,3,5-trimethylbenzene as internal standard for aldehydes analysis, working at 65 °C [0.4 Lh flow-rate of N2] with 2,2-dimethoxypropane as internal standard for ethyl propanoate analysis. [Pg.151]

Radiometric measurement of the C levels therefore, while requiring sophisticated instrumentation, is nonetheless the method of choice in our view. The normal procedure used in radiocarbon C analyses is to combust the sample, recover the resultant CO2, and convert it first to acetylene and then to benzene, as described above for the cinnamic aldehyde analysis. However, caffeine cannot be treated in this fashion due to its tendency to sublime from the combustion chamber to the catalyst traps before combustion is complete. Thus, a direct liquid scintillation counting technique was required, and the low-level liquid scintillation counting apparatus described by Noakes (18) was used to make all measurements. [Pg.463]

Aldehyde analysis based on bisulfite or hydroxylamine addition involves a nucleophilic attack on the carbonyl groups. As shown in Table 6. the aldehyde content determined this way is only half of what is to be expected from the periodate consumption and of what is determined via iodine oxidation in alkaline medium . The latter method does not involve a nucleophilic attack at the aldehyde carbon atoms and is valid for hemiacetal determination as well. [Pg.318]

Deng, C. Yao, N. Li, N. and Zhang, X. Headspace single drop microextraction with in-drop derivatization for aldehyde analysis. Journal of Separation Science 2005, 28 (17), 2301-2305. [Pg.656]

O Brien-Coker, I.C., Perkins, G. and Mallet, A.I. (2001) Aldehyde analysis by high performance liquid chromatography/tandemmass spectrometry. Rapid Commun. Mass Spectrom. 15, 920-928. [Pg.255]

Noth. The above method can be successfully applied only to dilute solutions of formaldehyde which are free in particular from other alfphatic aldehydes, since the latter, if present, would undergo a similar oxidation. Formaldehyde, if mixed with other aldehydes, should be estimated by quantitative addition of potassium cyanide for details, see advanced text-books of quantitative organic analysis. [Pg.458]

Analysis The a-hydroxy acid can best be made from an aldehyde and, then we can cany on as usual with a 1,3-dicarbonyl disconnection ... [Pg.43]

Analysis We must first decide whether to disconnect the ether ring or the a,p-imsaturated aldehyde. No doubt reasonable routes could be produced for both, but 1 shall give one only ... [Pg.98]

Alkenes are cleaved to carbonyl compounds by ozonolysis This reaction IS useful both for synthesis (preparation of aldehydes ketones or car boxyhc acids) and analysis When applied to analysis the carbonyl com pounds are isolated and identified allowing the substituents attached to the double bond to be deduced... [Pg.274]

FIGURE 14 2 Aretrosyn thetic analysis of alcohol preparation by way of the addition of a Grignard reagent to an aldehyde or ketone... [Pg.599]

This chapter is divided into two parts The first and major portion is devoted to carbohydrate structure You will see how the principles of stereochemistry and confer matronal analysis combine to aid our understanding of this complex subject The remain der of the chapter describes chemical reactions of carbohydrates Most of these reactions are simply extensions of what you have already learned concerning alcohols aldehydes ketones and acetals... [Pg.1026]

Aldehydes, enals, dienals, ketones, and hydrocarbons, which are responsible for disagreeable odors, generally bok at lower temperatures than fatty acids. Analysis showkig a free fatty acid concentration of less than 0.05% is an kidication that deodorization is sufficientiy complete. Some of the dienals have very low odor thresholds and sensory evaluation of the finished ok is a judicious quaHty assurance step. [Pg.127]

Polyester composition can be determined by hydrolytic depolymerization followed by gas chromatography (28) to analyze for monomers, comonomers, oligomers, and other components including side-reaction products (ie, DEG, vinyl groups, aldehydes), plasticizers, and finishes. Mass spectroscopy and infrared spectroscopy can provide valuable composition information, including end group analysis (47,101,102). X-ray fluorescence is commonly used to determine metals content of polymers, from sources including catalysts, delusterants, or tracer materials added for fiber identification purposes (28,102,103). [Pg.332]

Oxidation of a glycol can lead to a variety of products. Periodic acid quantitatively cleaves 1,2-glycols to aldehydes and is used as an analysis method for glycols (12,13). The oxidation of propylene glycol over Pd/C modified with Pb, Bi, or Te forms a mixture of lactic acid, hydroxyacetone, and pymvic acid (14). Air oxidation of propylene glycol using an electrolytic crystalline silver catalyst yields pymvic aldehyde. [Pg.366]

Ana.lytica.1 Methods. Various analytical methods involve titration with oxidants, eg, hexacyanoferrate (ferricyanide), which oxidize dithionites to sulfite. lodimetric titration to sulfate in the presence of formaldehyde enables dithionite to be distinguished from sulfite because aldehyde adducts of sulfite are not oxidized by iodine. Reductive bleaching of dyes can be used to determine dithionite, the extent of reduction being deterrnined photometrically. Methods for determining mixtures of dithionite, sulfite, and thiosulfates have been reviewed (365). Analysis of dithionite particularly for thiosulfate, a frequent and undesirable impurity, can be done easily by Hquid chromatography (366). [Pg.151]

Vanillin, being an aldehyde, is able to form acetals and hemiacetals. Therefore, in flavor formulations using high concentrations of vanillin in conjunction with carriers such as propylene glycol, a glc analysis often shows a reduced vanillin peak after storage of the compounded flavor, and the presence of new peaks indicating acetal formation. Addition of about 0.5% of water to the formula reverses the reaction, ie, there is a reduction of acetal, and the reappearance of vanillin peaks. [Pg.399]

The thermal glass-transition temperatures of poly(vinyl acetal)s can be determined by dynamic mechanical analysis, differential scanning calorimetry, and nmr techniques (31). The thermal glass-transition temperature of poly(vinyl acetal) resins prepared from aliphatic aldehydes can be estimated from empirical relationships such as equation 1 where OH and OAc are the weight percent of vinyl alcohol and vinyl acetate units and C is the number of carbons in the chain derived from the aldehyde. The symbols with subscripts are the corresponding values for a standard (s) resin with known parameters (32). The formula accurately predicts that resin T increases as vinyl alcohol content increases, and decreases as vinyl acetate content and aldehyde carbon chain length increases. [Pg.450]

The aldehyde is separated from the lower aqueous layer as a colorless liquid and dried over 10 g. of anhydrous sodium sulfate. The drying agent is removed by filtration, and the product is distilled under reduced pressure using a Claisen distillation apparatus to give 92-94 g. (82-84%) of cyclohexanecarboxaldehyde, b.p. 52-63° (18 mm.), 1.4484 (Notes 10, 11). A purity of about 98% was established by gas chromatographic analysis (Note 12) the product is suitable for synthetic use without further purification (Note 13). [Pg.12]

This cleavage reaction is more often seen in structural analysis than in synthesis. The substitution pattern around a double bond is revealed by identifying the carbonyl-containing compounds that make up the product. Hydrolysis of the ozonide intermediate in the presence of zinc (reductive workup) permits aldehyde products to be isolated without further oxidation. [Pg.710]


See other pages where Aldehydes analysis is mentioned: [Pg.311]    [Pg.2]    [Pg.38]    [Pg.166]    [Pg.311]    [Pg.2]    [Pg.38]    [Pg.166]    [Pg.108]    [Pg.62]    [Pg.738]    [Pg.739]    [Pg.346]    [Pg.78]    [Pg.53]    [Pg.27]    [Pg.208]    [Pg.287]    [Pg.524]    [Pg.486]    [Pg.360]    [Pg.133]    [Pg.59]    [Pg.83]    [Pg.83]    [Pg.684]    [Pg.738]    [Pg.739]   
See also in sourсe #XX -- [ Pg.65 , Pg.66 ]

See also in sourсe #XX -- [ Pg.630 , Pg.632 , Pg.634 , Pg.639 , Pg.645 ]

See also in sourсe #XX -- [ Pg.630 , Pg.632 , Pg.634 , Pg.639 , Pg.645 ]

See also in sourсe #XX -- [ Pg.164 ]




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