Absorption ketones

It is possible to monitor the reaction and determine the end point by the absence of an a,/S-unsaturated ketone absorption in the UV or by the determination of the consumption of ca. one molar equivalent of hydrogen peroxide by permanganate titration. 

It has been shown that CD measurement is a proper tool to determine the absolute configuration of the C-3 stereo center in corynantheine and yohimbine alkaloids (300). The chiroptical properties of stereoisomeric yohimbanes and 17-ketoyohimbanes also have been studied. Cotton effects due to aromatic and ketone absorptions have been considered in terms of the appropriate sector and... 

The spectra of 2-butanone (ethyl methyl ketone, No. 18), acetone (No. 17), and cyclohexanone (No. 19) in Appendix B illustrate ketonic absorptions. 

Oxonine 1, a derivative of the diterpene alkaloid aconitine, undergoes smooth oxidation when treated with exactly one equivalent of periodic acid. The product thus obtained, which shows no aldehyde or ketone absorption in the ir spectrum, is converted into 2 when heated in dilute aqueous base with air passing through the solution. 

The ketone IR absorption of 3-methyl-2-cyclohexenone occurs near 1690 cm-1 because the double bond is next to the ketone group. The ketone IR absorption of 3-cyclopentenyl methyl ketone occurs near 1715 cm-1, the usual position for ketone absorption. 

The IR of Compound B shows a ketone absorption. The splitting pattern of the H NMR spectrum indicates an isopropyl group and indicates that the compound is a methyl ketone. 

Liquid acetoin stored for a long period of time has a well-developed ketonic absorption band at 275 nm, indicating the prevalent form (A), whereas liquid acetoin freshly prepared by melting or dissolving the dimer shows no such absorption, which indicates that based on the dimer structure the latter liquid can be expected to consist of the oxide form (B), and that the equilibrium between the keto form and the oxide form is reached very slowly (in a matter of days). 

After isolation as sedoheptulosan, the free sugar can be recovered through its acetate. Acetolysis of sirupy sedoheptulosan tetraacetate, in the presence of a catalytic proportion of perchloric acid, gives a crystalline sedoheptulose hexaacetate which, since its ultraviolet spectrum shows no ketonic absorption, was designated hexa-O-acetyl-a-n-alfro-heptulopyra-nose. Cautious deacetylation of this product gave sirupy sedoheptulose,... 

Epitestosterone has been identified in the urine of men and women by Korenman eta/. (1964). Infrared techniques were used in the characterization. The a,)S-unsaturated ketone absorption was found at 1677 cm ... 

Look for the presence or absence of a saturated ketone absorption in the product. 

Absorption Spectrum and Cross Sections of HCHO For carbonyl compounds such as aldehydes and ketones, absorption bands due to the electronic transition called n — r transition, in which the isolated pair of lone-pair electrons on the O atom of carbonyl group (—C = O) is excited to the excited Jt orbital of the double bond, appears around 300 nm. Since this transition is a forbidden transition, the absorption cross sections are not very large ( 10 cm molecule ) in general. However, since the absorption bands extend to near 350 nm where solar actinic flux grows, their photolyses are very important in the troposphere. 

Simple esters have an absorption at about 1740 cm, a higher wavenumber than aldehyde and ketone absorptions. Esters also have a C—O stretching absorption in the 1000—1300 cm" region. Because other absorptions also occur in this region, such data are useful only as a confirmation when an ester is suspected from other data such as the carbonyl stretching absorption. We recall that alcohols, ethers, and carboxylic acids have C—O absorptions in the same region. Figure 2.14 shows the infrared spectrum of ethyl acetate. 

Table IX-F-7. Methyl vinyl ketone absorption cross sections in the gas-phase (Gierczak et al, 1997) and recommended quantum yields for photodecomposition units for cr are cm molecule ...

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