Functional group compounds with carbonyl groups

Combined glc and mass spectrometry provide the capability to deal with the complex mixtures of closely related compounds often found in plant cuticles. Even though identification of new compounds solely by their mass spectra cannot be considered reliable, mass spectrometry has become an invaluable tool in identifying known types of compounds in cuticular lipids. For example, methyl branches in alkanes can be located by cleavage on both sides of the substituted carbon (Fig. 5). Mass spectrometry is also the most suitable technique for identifying branched fatty acids (Tulloch, 1976 Jack-son and Blomquist, 1976 Nicolaides and Apon, 1977). Functional groups such as carbonyl groups and hydroxyl groups in the aliphatic chain can be... 

Many functional groups besides the carbonyl group react with hydrazoic acid to give tetrazoles. In most of these reactions no catalyst is required. The tetrazoles thus obtained frequently are formed by rearrangement of intermediate azides. Since it may be desired to apply the Schmidt reaction to a molecule containing other functional groups or to a mixture of compounds, a few of the reactions leading to the formation of tetrazoles will be discussed briefly. 

A major difference between alcohols and thiols concerns their oxidation We have seen earlier m this chapter that oxidation of alcohols gives compounds having carbonyl groups Analogous oxidation of thiols to compounds with C=S functions does not occur Only sulfur is oxidized not carbon and compounds containing sulfur m various oxida tion states are possible These include a series of acids classified as sulfemc sulfimc and sulfonic according to the number of oxygens attached to sulfur... 

For reviews of the addition of organometallic compounds to carbonyl groups, see Eicher, T. in Patai, Ref. 2, p. 621 Kharasch, M.S. Reinmuth, O. Grignard Reactions of Nonmetallic Substances, Prentice-Hall Englewood Cliffs, NJ, 1954, p. 138. For a review of reagents that extend carbon chains by three carbons, with some functionality at the new terminus, see Stowell, J.C. Chem. Rev., 1984, 84, 409. 

Secondary amines can be prepared from the primary amine and carbonyl compounds by way of the reduction of the derived Schiff bases, with or without the isolation of these intermediates. This procedure represents one aspect of the general method of reductive alkylation discussed in Section 5.16.3, p. 776. With aromatic primary amines and aromatic aldehydes the Schiff bases are usually readily isolable in the crystalline state and can then be subsequently subjected to a suitable reduction procedure, often by hydrogenation over a Raney nickel catalyst at moderate temperatures and pressures. A convenient procedure, which is illustrated in Expt 6.58, uses sodium borohydride in methanol, a reagent which owing to its selective reducing properties (Section 5.4.1, p. 519) does not affect other reducible functional groups (particularly the nitro group) which may be present in the Schiff base contrast the use of sodium borohydride in the presence of palladium-on-carbon, p. 894. 

Carbohydrates are the most abundant of all organic compounds in the biosphere. Many members of the carbohydrate class have the empirical formula Cx(H20)y, and are literally hydrates of carbon. The fundamental units of the carbohydrate class, the monosaccharides, are polyhydroxy aldehydes or ketones and certain of their derivatives. As with other classes of biologically important compounds, much of the function of the carbohydrates derives from the ability of the monosaccharides to combine, with loss of water, to form polymers oligosaccharides and polysaccharides. The chemistry of carbohydrates is, at its core, the chemistry of carbonyl and hydroxyl functional groups, but these functional groups, when found in the same compound, sometimes exhibit atypical properties. The discussion that follows is designed to review the aspects of carbohydrate chemistry that are especially important for isolation, analysis, and structure determination of biologically important carbohydrates. 

Oxidation of ethylene to acetaldehyde by palladium compounds according to eq. (2) can be applied to other olefins and olefinic compounds with functional groups [1,7]. This is often called the Wacker reaction , and occurs regiospecifically. The carbonyl group is formed at that C-atom of the double bond where the nucleophile in a Markovnikov-like addition would enter (eq. (3)). Thus, primary olefins give methyl ketones. 

For GC or FIPLC quantification, or GC-MS identification, neutral compounds are of necessity analyzed without further chemical treatment. For compounds with functional groups such as hydroxyl, amino, carboxylic add, or reactive carbonyl groups, however, it may be convenient to prepare suitable derivatives. This has a long tradition in organic chemistry highlighted by the use of crystalline phenylosazones of carbohydrates to prepare and separate otherwise intradable mixtures of noncrystalline carbohydrates (Fischer 1909). In the present context, there are several advantages in using such procedures ... 

Acetattzation. Diethyl acetals are formed from carbonyl compounds by functional group exchange with triethyl orthoformate (EtOH also present) under the influence of DDD." Benzylic activation. Hydride abstraction by DDQ from benzyl ethers, where the benzylic position is also activated by a nuclear substitutent (e.g., methoxy group), prepares such compounds to be attacked by nucleophiles. The reaction constitutes an important step in a synthesis of deoxyfrenolicin. ... 

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