Carbonyl compounds definition

Instead of the definition in Eq. (7-82), the selectivity is often written as log k,). Another way to consider a selectivity-reactivity relationship is to compare the relative effects of a series of substituents on a pair of reactions. This is what is done when Hammett plots are made for a pair of reactions and their p values are compared. The slope of an LEER is a function of the sensitivity of the process being correlated to structural or solvent changes. Thus, in a family of closely related LFERs, the one with the steepest slope is the most selective, and the one with the smallest slope is the least selective.Moreover, the intercept (or some arbitrarily selected abscissa value, usually log fco for fhe reference substituent) should be a measure of reactivity in each reaction series. Thus, a correlation should exist between the slopes (selectivity) and intercepts (reactivity) of a family of related LFERs. It has been suggested that the slopes and intercepts should be linearly related, but the conditions required for linearity are seldom met, and it is instead common to find only a rough correlation, indicative of normal selectivity-reactivity behavior. The Br nsted slopes, p, for the halogenation of a series of carbonyl compounds catalyzed by carboxylate ions show a smooth but nonlinear correlation with log... 

This area of reactivity has been the subject of excellent reviews (J5). Silyl enol ethers are not sufficiently nucleophilic to react spontaneously with carbonyl compounds they do so under the influence of either Lewis acids or fluoride ion, as detailed above. Few clear trends have emerged from the somewhat limited number of definitive studies reported so far, with ambiguities in diastereoisomeric assignments occasionally complicating the issue even further. 

The reaction of carbonyl compounds to olefins often yields products difficult to obtain synthetically by other routes. The excellent yields obtainable under proper conditions make this reaction of definite preparative interest. Examples of some synthetic applications of oxetane formation follow ... 

The catalytically active species 31 was isolated and its structure definitively determined using X-ray analysis. The complex 31 was seen to be quite stable below 70 °C under an argon atmosphere at pH 2.0-6.0 and in the absence of any reducible carbonyl compounds [50]. When the reducing ability of isolated 31 in acidic media was examined, the catalytic reactions using cyclohexanone and acetophenone (31 ketones HCOOH = 1 200 1000) yielded the corresponding alcohols quantitatively in 2h at pH2.0 at 70°C (Scheme 5.17). 

Hydrosilylation of carbonyl compounds. The definitive report on reduction of carbonyl compounds by hydrosilylation catalyzed by Wilkinson"scatalyst is available.1 Hydrosilylation can be used to effect regioselective 1,2- or 1,4-reduction of a,/ -enals or -enones by proper choice of the hydrosilane. In general, monohydrosilanes favor 1,4-adducts, whereas dihydrosilanes favor 1,2-adducts. The regioselectivity is also influenced by the substituents on silicon and on the substrates. The presence of a phenyl group on the enone system can effect dramatic changes in the selectivity. Examples ... 

An optically active Grignard reagent has the ability to differentiate between the two enantiofaces of a carbonyl compound such as 45 [64], In the example shown, the (S)-enantiomer of the product alcohol, 46, is obtained with a high degree of optical purity (= specific rotation of mixture- - specific rotation of one pure enantiomer X 100 for definitions of other terms used in this work, see [65]). 

Although definitive evidence for the intermediacy of oxabicyclobutanes in the peracid oxidation of cyclopropenes is lacking, the production of conjugated carbonyl compounds from such reactions is most readily rationalized from the formation and spontaneous rearrangement of such species (equation Calculations suggest... 

The mixture probably contains the same trichloroethane as the peaks at 45.3 and 95.6 p.p.m. suggest (the chemical shifts of the mixture need not be quite the same as those of the pure compound as each compound is effectively dissolved in the other). The remaining peaks at 7.0, 27.3, 35.2, and 206.3 p.p.m. definitely belong to a carbonyl compound, probably a ketone since 206.3 p.p.m. is so large. Butanone fits the bill as it has one methyl and one CH2 group on the carbonyl group and one methyl away from any electronegative atoms. There are other possibilities. 

This relationship arises directly from our definitions of aldehydes and ketones, and our definitions of primary, secondary, and tertiary alcohols. The number of hydrogens attached to the carbonyl carbon defines the carbonyl compound as formaldehyde, higher aldehyde, or ketone. The carbonyl carbon is the one that finally bears the —OH group in the product here the number of hydrogens defines the alcohol as primary, secondary, or tertiary. For example ... 

Transacetalization in our opinion does not offer a definite advantage over the direct method except for those cases, such as that of cyclopropanone, where the 0,0-acetal is more accessible than the parent carbonyl compound (Scheme 71). The reaction, however, does not seem to be general (Scheme 71, b). 

The term Peterson alkenation has been used to describe the elimination of a functionalized organo-silicon compound with alkene formation for substrates synthesized by these methods. In accordance with the mechanistic definition outlined in the introduction to this cluq)ter, such topics are not considered in detail in this review. For the purpose of this discussion, the Peterson alkenation will be considered as the addition of an anion derivative to a carbonyl compound, followed by elimination to the alkene. 

Alcohols can be obtained from many other classes of compounds such as alkyl halides, amines, al-kenes, epoxides and carbonyl compounds. The addition of nucleophiles to carbonyl compounds is a versatile and convenient methc for the the preparation of alcohols. Regioselective oxirane ring opening of epoxides by nucleophiles is another important route for the synthesis of alcohols. However, stereospe-cific oxirane ring formation is prerequisite to the use of epoxides in organic synthesis. The chemistry of epoxides has been extensively studied in this decade and the development of the diastereoselective oxidations of alkenic alcohols makes epoxy alcohols with definite configurations readily available. Recently developed asymmetric epoxidation of prochiral allylic alcohols allows the enantioselective synthesis of 2,3-epoxy alcohols. 

In conclusion, the 1,3-dithiane unit still remains among the most valuable acyl anion equivalents, although that involving methyl methylthio sulfoxide or its diethyl analog offers the definite advantages of proceeding with metal hydride or even under phase-transfer catalysis conditions and of producing the carbonyl compound under reasonably mild conditions. 

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