Ultraviolet absorption aldehydes

One of the more important areas of use of ultraviolet instruments is the identification and determination of biologically active substances. Many components in body fluids can be determined either directly or through colorimetric methods. Drugs and narcotics can be measured both in the body as well as in formulations. Vitamin assay is another related activity. Nearly all metals and nonmetals can be determined through their ultraviolet absorption or by colorimetric methods. In recent years, ultraviolet instruments have been used extensively for the determination of air and water pollutants, such as aldehydes, phenolics, and ozone ... 

Wavelengths tor Maximum Ultraviolet Absorption of Some Carboxylic Acids, Aldehydes, and Ketones (n--- n )... 

The Pharmacopea and the Essential Oil Association of the United States require the following analyses as an index of oil purity refractive index, optical rotation, refractive index and optical rotation of a 10% distillate, specific gravity, aldehyde content, evaporation residue and ultraviolet absorption spectrum (Kesterson et al. 157 and Sale 29). 

Kuhota, M. and Kitada, I., Studies on the bridging reaction of collagen molecules with aldehydes. III. Bridging rcacuon with foniial-dehyde and ultraviolet absorption of bridging compounds, Hikaku Kagaku. 27, 137, 1981 Chem. Absir.. 96, 144875, 1982. 

The highly levorotatory y-hexaacetate would have to be a structural isomer of the two anomeric a and /3 hexaacetates. It was pointed out that the aldehyde structure XLIII was improbable from the mode of its formation moreover it was excluded by the fact that the compound failed to give rise, on treatment with thiosemicarbazide, to the ultraviolet absorption band at 2700 A characteristic of tiuosemicarbazones. Since ring isomerism in the N-methyl-L-glucosamine portion or a 1,3-orthoacetate structure did not seem probable, the 1,6-furanose structure (XLIV) was tentatively proposed for this compound. 

The solution frequently becomes warm,12 and its refractive index,1 viscosity,2 freezing point-composition curve,3 and ultraviolet absorption spectrum 36 are not those which would be expected if no reaction took place. Usually hydrates or hemiacetals of simple aldehydes are too unstable to be isolated, but a number of them are actually known and their physical properties have been determined.4 When the carbonyl group is attached to an electron-attracting group (making the carbonyl carbon atom abnormally positive), stable hydrates are frequently formed. Glyoxal, chloral, and ketomalonic acid are common examples. 

An increase of the ultraviolet absorption at 285 nm on exposure of nylon-6,6 to sunlight has been observed [105], The chromophore responsible for this absorption is already introduced to a slight extent during manufacture (Fig. 21). Absorption in this region could tentatively be assigned to aldehyde groups produced in reaction (10), which could further initiate or sensitize the photodegradation of polyamides. 

Poison in which the aldehyde component of the Schiff s base has a strident green character, creating a sharp contrast with the heavy sweetness of the methyl anthranilate. The pale yellow colour of methyl anthranilate is darkened when a Schiff s base is formed from it. This is because of the hypsochromic shift in the ultraviolet absorption maximum resulting from the extension of conjugation. This colour has an effect on the colour of any fragrance in which it is incorporated and has to be taken into account if colour would be deleterious in the final product. Many Schiff s bases are available commercially but some perfumers prefer to formulate their fragrances using aldehydes and free methyl anthranilate and allow the Schiff s base to form spontaneously in the perfume. 

The constitution (XXI) was confirmed by a synthesis of dl-cus-pareine, which was identical with the alkaloid in boiling point, in ultraviolet absorption spectrum, and in its sensitivity to hot mineral acid which caused reddening and resinification. dl-Norcuspareine (XXIV) was formed by the catalytic reduction of the products obtained by the condensation of veratric aldehyde with quinalcfine or with o-nitrobenzal-acetone, or of o-nitrobenzaldehyde with veratralacetone, and on methyla-... 

UV-VIS Aldehydes and ketones have two absorption bands in the ultraviolet region Both involve excitation of an electron to an antibonding tt orbital In one called a TT TT transition the electron is one of the tt electrons of the C=0 group In the other called an n ir transition it is one of the oxygen lone pair electrons Because the tt electrons are more strongly held than the lone parr electrons the transition is of... 

UV-VIS Aldehydes and ketones have two absorption bands in the ultraviolet region. 

The carboxyl function does absorb ultraviolet radiation, but the wavelengths at which this occurs are appreciably shorter than for carbonyl compounds such as aldehydes and ketones, and, in fact, are out of the range of most commercial ultraviolet spectrometers. Some idea of how the hydroxyl substituent modifies the absorption properties of the carbonyl group in carboxylic acids can be seen from Table 18-2, in which are listed the wavelengths of maximum light absorption (Amax) and the extinction coefficients at maximum absorption (emax) of several carboxylic acids, aldehydes, and ketones. 

It was long ago suggested that the low extinction coefficient absorption band of ketones and aldehydes occurring in the 280-360 m i region of the ultraviolet corresponds to an excitation process in which a nonbonding (hence n ) electron is promoted to the antibonding t (i.e., ir ) orbital. This constitutes the n ir process and is conveniently depicted in three dimensions using an atomic orbital representation ... 

The carbonyl group. Acetone (in cyclohexane solution) exhibits two absorption bands one appears at 190nm (e 1860) and corresponds to the n - n transition, while the second is at 280 nm (e 13) and corresponds to the n - n transition. The absorption maxima of these bands are solvent-dependent. Ultraviolet spectra of saturated aldehydes, carboxylic acids, esters and lactones exhibit a similar absorption profile, and in general are of little diagnostic value. 

In an analytical experimental series (Fig. 1), the effluent was collected in fractions. These fractions were analyzed with respect to pH, fermentable sugars, furan aldehydes, phenolic compounds, aliphatic acids, sulfate, and ultraviolet (UV) absorption at 280 nm. 

A number of points regarding the chemical behavior of the streptose moiety are anomalous and will bear comment. Although a free carbonyl group seems established, streptomycin itself shows no carbonyl absorption in the ultraviolet region. Derivatives of the acyclic or aldehydo structure have hitherto exhibited such absorption. Oxidation of this aldehyde substituent to the carboxyl stage or its reduction to either the carbinol or hydrocarbon did not affect the resistance of the tertiary hydroxyl toward acetylation. However, conversion of both aldehyde functions in streptose to the carboxyl stage of oxidation made the tertiary hydroxyl easily esterifiable. ... 

Oxydextran showed no carbonyl absorption in the infrared or ultraviolet spectra hydration of the aldehyde groups was assumed. Many other polysaccharides have been oxidized with periodate, but only in purely structural work and no reactions have been studied (other than hydrolysis of the oxypolysaccharide or its oxidation or reduction products). 

Oxygen saturated polyethylene glycol (283) shows an absorption band in the ultraviolet which is ascribed to a CT-absorption. Photolysis induces the formation of peroxidlc compounds. Glycol-aldehyde is an Important end product. 

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