Ketones intensity

Fig. 7.12 FT-IR spectra (in KBr) C70H38 (top) when exposed to air for 1 day (second from top) shows the development of a sharp band ketone band at 1,737 cnr1 accompanied by the OFi stretching band at 3413 cm 1 and the OH bending band at 1,028 cm 1. Exposure of C70H38 for 1 month to air (third spectrum from top) causes a much more intense ketone band split at 1,733 and 1,709 cm 1 combined with intense OH stretching and bending respectively at 3,384 and 1,032 cm 1...

Sulphuric add test. Heat 0 5 g. of citric acid or a citrate with 1 ml. of H2SO4 CO and COg are evolved and the mixture turns yellow, but does not char. Acetone dicarboxylic acid, OC(CH2COOH)g, is also formed, and is tested for after heating the mixture for 1 minute cool, add a few ml. of water and make alkaline with NaOH solution. Add a few ml. of a freshly prepared solution of sodium nitroprusside and note the intense red coloration (see Test 4 a) for ketones, p. 346). 

Mass Spectrometry Aldehydes and ketones typically give a prominent molecular ion peak m their mass spectra Aldehydes also exhibit an M— 1 peak A major fragmentation pathway for both aldehydes and ketones leads to formation of acyl cations (acylium ions) by cleavage of an alkyl group from the carbonyl The most intense peak m the mass spectrum of diethyl ketone for example is m z 57 corresponding to loss of ethyl radi cal from the molecular ion... 

Acids generally absorb more strongly than esters, and esters more strongly than ketones or aldehydes. Amide absorption is usually similar in intensity to that of ketones but is subject to much greater variations. 

Raw Material and Energy Aspects to Pyridine Manufacture. The majority of pyridine and pyridine derivatives are based on raw materials like aldehydes or ketones. These are petroleum-derived starting materials and their manufacture entails cracking and distillation of alkanes and alkenes, and oxidation of alkanes, alkenes, or alcohols. Ammonia is usually the source of the nitrogen atom in pyridine compounds. Gas-phase synthesis of pyridines requires high temperatures (350—550°C) and is therefore somewhat energy intensive. 

When the a,P-unsaturated ketone is hydrogenated to the alcohol, a product with an intense sandalwood odor is produced (162). Many other examples of useful products have been made by condensation of campholenic aldehyde with ketones such as cyclopentanone and cyclohexanone. 

The most intensively studied oxidizing system is that developed by Pfitzner and Moflatt in which the oxidation is carried out at room temperature in the presence of dicyclohexylcarbodiimide (DCC) and a weak acid such as pyridinium trifluoroacetate or phosphoric acid. The DCC activates the DMSO which in turn reacts with the carbinol to give an oxysulfonium intermediate. This breaks down under mild base catalysis to give the desired ketone and dimethyl sulfide. 

The NMR study of steroidal epoxides (discussed in section II-F) parallels that of the analogous thiiranes. It is possible to relate the location and configuration of the thiirane group with the angular methyl and thiirane proton resonances. The proton NMR relationships for the intermediate thiocyanatohydrins have been included inageneral NMR study of steroids. Electronic spectra may be used in the analysis of steroidal thiiranes. Spectroscopic measurements have shown the existence of a low intensity absorption in the 240-260 m region. The regular patterns of rotatory contributions of thiiranes which are comparable with those of ketones prompted an accumulation of ORD and CD data for steroidal thiiranes. 

The first, and to this writing still only case of a ketone a-cleavage-recombi-nation sequence in the steroid field was reported by Butenandt, who found that 17-ketones epimerize at C-13. Ultraviolet irradiation of either stereoisomer produces an equilibrium mixture in which the thermodynamically more favored 13a-compound cf. (15)] with cw-fusion of rings C and D predominates at room temperature. As ultraviolet absorption energies and intensities of the two isomeric ketones are practically identical, the equilibrium composition depends largely on the rate of the competing recombination process from (14). For further examples of the photoisomerization at C-13 of 17-ketosteroids, see ref. 8, 12, 15 and 43. 

One of the most actively investigated aspects of enamine chemistry has been the acylation process (i). Initial intensive studies by Hiinig (373-375) showed the ease of preparing a variety of 9-diketones and particularly the synthetic potential of acylated cyclic ketones as intermediates in the preparation of aliphatic keto acids, keto dicarboxylic acids and diketo dicarboxylic acids (376-378). 

In a similar scheme, acylation of 2-methoxynaphthalene gives ketone, 15. This is then converted to the acetic acid by the Wilgerodt reaction. Esterification, alkylation of the carbanion (sodium hydride methyl iodide), and finally saponification affords naproxen (17). The intense current effort on nonsteroid antiinflammatory agents and acrylacetic acids in particular make... 

Flowever, ionic liquids acting as transition metal catalysts are not necessarily based on classical Lewis acids. Dyson et al. recently reported the ionic liquid [BMIM][Co(CO)4] [38]. The system was obtained as an intense blue-green colored liquid by metathesis between [BMIM]C1 and Na[Co(CO)4]. The liquid was used as a catalyst in the debromination of 2-bromoketones to their corresponding ketones. 

Carbonyl functional groups are the easiest to identify of all IR absorptions because of their sharp, intense peak in the range 1670 to 1780 cm-1. Most important, the exact position of absorption within the range can often be used to identify the exact kind ot carbonyl functional group—aldehyde, ketone, ester, and so forth. 

Carvone (Problem 12.39) has an intense infrared absorption at 1690 cm-1. What kind of ketone does carvone contain ... 

All carbonyl-containing compounds have intense IR absorptions in the range 1650 to 1850 cm-1. As shown in Table 21.3, the exact position of the absorption provides information about the specific kind of carbonyl group. For comparison, the IR absorptions of aldehydes, ketones, and carboxylic acids are included in the table, along with values for carboxylic acid derivatives. 

When present in macro quantities, aldehydes and ketones can be determined by conversion to the 2,4-dinitrophenylhydrazone which can be collected and weighed. When present in smaller quantities (10 3M or less), although hydrazone formation takes place, it does not separate from methanol solution, but if alkali is added an intense red coloration develops the reagent itself only produces a slight yellow colour. Measurement of the absorbance of the red solution thus provides a method for quantitative determination. 

The stereochemical outcome of nucleophilic addition reactions to cyclic ketones is the subject of numerous experimental and theoretical studies, with substituted cyclohexanones and cy-clopcntanones having been intensively studied. In addition reactions to substituted cyclohexanones 1 the problem of simple diastereoselectivity is manifested in the predominance of cither axial attack of a nucleophile, leading to the equatorial alcohol 2 A. or equatorial attack of the nucleophile which leads to the axial alcohol 2B. 

Molecular ion The MW of aliphatic ketones can be determined from its prominent molecular ion. In general, the intensity of the molecular ions of ketones is greater for C3-C8 than for CVC u. A molecular ion is usually observed for methoxime derivatives. 

Molecular ion Molecular ions of cyclic ketones are relatively intense. Characteristic fragment ions of cyclic ketones occur ai m/z 28, 29, 41, and 55. Cyclic ketones also lose CO and/or C>H (m/z 28) from the molecular ion (Q and higher). Low-abundance ions corresponding to loss of H20 are frequently observed. Keto-steroids are a special class of cyclic ketones and have abundani molecular ions. 

Characteristic fragment ions Aliphatic ketones also give abundant McLafferty rearrangement ions at m/z 58, 72, 86, and so forth. Methyl ketones produce an abundant ion at m/z 43. Low-intensity ions at m/z 31, 45, 59, 73, and so on reveal oxygen in the unknown ketone and are especially useful in distinguishing ketone spectra from isomeric paraffin spectra. Subtract 43 from the mass of the rearrangement ion to determine R. 

The photolysis of carbonyl compounds is one of the most intensively studied areas of photochemistry. Since CIDNP studies have been concerned mostly with aldehydes and ketones we shall confine these brief introductory remarks to such compounds. More extensive reviews are available (e.g., Simons, 1971). 

The ratio of the isomeric amino ketones in the crude product can be determined from the relative intensities of the signals for the (CH3)2C grouping in a proton magnetic resonance spectrum taken in trifluoroacetic acid (see Note 10). In chloroform-d these absorptions overlap. 

Several studies, however, conclusively showed that the intensity of the sweet taste depends strongly upon the number of hydroxyl groups in the A-ring. - - For example, compound 85 and its sodium salt, which have only one hydroxyl group in the A-ring, are less sweet than the 2,6-dihydroxy compound. Furthermore, there is also a requirement for an orrto-hydroxy ketone system in ring A, as compound 86 is tasteless, and because it had already been shown that the alkoxy-hydroxy substituents on ring B are also... 

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