Organic chemistry compounds with carbonyl group

For reviews of thiokelones and other compounds with C=S bonds, see Schaumann, in Patai Supplement A The Chemistry of Double-bonded Functional Groups, vol. 2, pt. 2 Wiley New York. 1989. pp. 1269-1367 Ohno. in Oae Organic Chemistry of Sulfur, Plenum New York, 1977. pp. 189-229 Mayer, in Janssen Organosulfur Chemistry Wiley New York, 1967, pp. 219-240 Campaigne, in Palai The Chemistry of the Carbonyl Group, pt. 1 Wiley New York, 1966, pp. 917-959. 

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 ... 

The cleavage of organic compounds from nucleophile-labile resins usually relies on the addition-elimination chemistry at the carbonyl group of the carboxylic acid derivative (i.e. an ester or thioester) that mediates the linkage between the assembled compound and the linker-resin. The overall reaction is a nucleophilic substitution that involves the release into the solution of the compound of interest with the attacking nucleophile generally incorporated. The linker-resin generally acts... 

We have now completed our survey of the basic organic chemistry compound classes, as defined by simple functional groups. In the remainder of the book, we shall examine compounds with multiple functional groups, whether they be the same or different. We shall see the amino group and amine derivatives again in these chapters, particularly when studying heterocycles, proteins, and nucleic acids. We shall learn that the combination of the amino and carbonyl groups underlies the molecular structure of life itself. 

The [ 2 + 4]-cycloaddition reaction of aldehydes and ketones with 1,3-dienes is a well-established synthetic procedure for the preparation of dihydropyrans which are attractive substrates for the synthesis of carbohydrates and other natural products [2]. Carbonyl compounds are usually of limited reactivity in cycloaddition reactions with dienes, because only electron-deficient carbonyl groups, as in glyoxy-lates, chloral, ketomalonate, 1,2,3-triketones, and related compounds, react with dienes which have electron-donating groups. The use of Lewis acids as catalysts for cycloaddition reactions of carbonyl compounds has, however, led to a new era for this class of reactions in synthetic organic chemistry. In particular, the application of chiral Lewis acid catalysts has provided new opportunities for enantioselec-tive cycloadditions of carbonyl compounds. 

Carbonyl reactions are extremely important in chemistry and biochemistry, yet they are often given short shrift in textbooks on physical organic chemistry, partly because the subject was historically developed by the study of nucleophilic substitution at saturated carbon, and partly because carbonyl reactions are often more difhcult to study. They are generally reversible under usual conditions and involve complicated multistep mechanisms and general acid/base catalysis. In thinking about carbonyl reactions, 1 find it helpful to consider the carbonyl group as a (very) stabilized carbenium ion, with an O substituent. Then one can immediately draw on everything one has learned about carbenium ion reactivity and see that the reactivity order for carbonyl compounds ... 

Compared to carboxylic and carbonic acid derivatives, the less highly oxidized carbonyl compounds such as aldehydes and ketones are not so widespread in nature. That is not to say that they are unimportant. To the contrary. Aldehydes and ketones are of great importance both in biological chemistry and in synthetic organic chemistry. However, the high reactivity of the carbonyl group in these compounds enables them to function more as intermediates in metabolism or in synthesis than as end products. This fact will become evident as we discuss the chemistry of aldehydes and ketones. Especially important are the addition reactions of carbonyl groups, and this chapter is mostly concerned with this kind of reaction of aldehydes and ketones. 

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