Aldehydes characteristic chemical properties

The chemical properties of monosaccharides are further complicated by the fact that they can exhibit tautomerism in aqueous basic solutions (Figure 1.15). This means that after a short time a basic aqueous solution of a monosaccharide will also contain a mixture of monosaccharides that will exhibit their characteristic chemical properties. For example, a solution of fructose will produce a silver mirror when treated with an ammoniacal solution of silver nitrate (Tol-len s reagent). This is because under basic conditions fructose undergoes tautomerism to glucose, whose structure contains an aldehyde group, which reduces Tollen s reagent to metallic silver. 

Behera et al. (2004) concluded that the optimum conditions for the conventional roasting method were 125°C for 10 min and, in the microwave processing method, the best conditions were 730 W for 10min. The yields and physico-chemical properties of the volatile oils were similar in both cases. Changes were observed in the optical rotation values, which indicated differences in the chemical compositions. GC and GC-MS analysis of optimized condition samples showed that microwave-heated samples could better retain the characteristic flavour compounds of cumin (i.e. total aldehydes) than conventionally roasted samples (Table 11.5). Earlier GC reports showed cuminaldehyde as the only major aldehyde present in Indian cumin oil, but this study revealed the... 

The most outstanding chemical property of 2-pyrazolin-5-ones is the activity of the hydrogen atoms at C-4. This position is very reactive, undergoing the characteristic condensations and substitutions of the active methylene group. Aldehydes and ketones react readily at this position, giving in the simpler cases a mixture of products as shown in eq 04 22.34.110.296.311.333,633.702.809.980,1123.1241.1250.1263,1288,1351 This... 

Cinnamic aldehyde possesses the chemical properties characteristic of aldehydes and of unsaturated compounds. It forms an addition-product with bromine, which readily loses hydrogen bromide. It boils at 129° (20 mm.). 

Oxidizability is a chemical property characteristic of aldehyde functions. The aldehyde function of glucose makes it capable of reducing copper salts, and this property is widely used to assay sugars. Furthermore, many aldehydes oxidize to form carboxylic acid with oxidizing agents as weak as silver oxide ... 

With improved analytical methods there has been a large increase in the number of compounds identified in wines. Volatile compounds from different families (such as alcohols, esters, aldehydes, terpenes, etc.) play an important role in the organoleptic characteristics of wines. This wide variety of compwimds with different chemical properties and with different concentrations makes the flavour pa-ofile of wines very complex. Therefore, it is necessary to standardise the terminology so as to facilitate the knowledge of the aromatic profile of wines. 

Each aldehyde has distinct physical and chemical properties as well as specific toxicology characteristics. Specific toxicology information on an aldehyde is available in the solvent s MSDS and from the solvent producer. 

Butyl Aldehyde Chemical Formula CHjCHjCHjCHO. Observable Characteristics — Physical State (as normally shipped) Liquid Color Colorless Odor Pungent aldehyde pungent and intense. Physical and Chemical Properties... 

Acetaldehyde — (i) Chemical Designations — Synonyms Acetic Aldehyde Ethanal, Ethyl Aldehyde Chemical Formula CHjCHO (iil Observable Characteristics — Physical State (as normally shipped) Liquid Color Colorless Odor Penetrating, fruity sharp pungent (iii) Physical and Chemical Properties — Physical State at 15 C and 1 atm. Liquid Molecular Weight 44.05 Boiling Point at 1 atm. 68.7, 20.4, 293.6 Freezing Point -189, -123, 150 Critical Temperature 370, 188, 461 Critical Pressure 820, 56, 5.7 Specific Gravity 0.780 at 20 C (liquid) Vapor (Ckis) Density 1.5 Ratio of Specific Heats of Vapor (Gas) 1.182 Latent Heat of Vaporization 245. 136, 5.69 Heat of Combustion -10600, -5890, -246.4 Heat of Decomposition Not pertinent (ivl Health... 

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