Ketones carbonylation

Both the Clemmensen and the Wolff-Kishner reductions are designed to carry out a specific functional group transformation the reduction of an aldehyde or ketone carbonyl to a methylene group Neither one will reduce the carbonyl group of a carboxylic acid nor... 

Like aldehydes ketone functions take precedence over alcohol functions double bonds halogens and alkyl groups m determining the parent name and direction of numbering Aldehydes outrank ketones however and a compound that contains both an aldehyde and a ketone carbonyl group is named as an aldehyde In such cases the carbonyl oxy gen of the ketone is considered an 0x0 substituent on the mam chain... 

The carbonyl carbon of a ketone bears two electron releasing alkyl groups an aldehyde carbonyl group has only one Just as a disubstituted double bond m an alkene is more stable than a monosubstituted double bond a ketone carbonyl is more stable than an aldehyde carbonyl We 11 see later m this chapter that structural effects on the relative stability of carbonyl groups m aldehydes and ketones are an important factor m then rel ative reactivity... 

Consider first the electronic effect of alkyl groups versus hydrogen atoms attached to C=0 Recall from Section 17 2 that alkyl substituents stabilize C=0 making a ketone carbonyl more stable than an aldehyde carbonyl As with all equilibria factors... 

Keto ester a ketone carbonyl is 3 to the carbonyl group of the ester... 

The systematic lUPAC name of ethyl acetoacetate is ethyl 3 oxobutanoate The presence of a ketone carbonyl group is indicated by the designation oxo along with the appro priate locant Thus there are four carbon atoms m the acyl group of ethyl 3 oxobutanoate C 3 being the carbonyl carbon of the ketone function... 

In general the equilibrium represented by the sum of steps 1 to 3 is unfavorable (Two ester carbonyl groups are more stable than one ester plus one ketone carbonyl) However because the p keto ester is deprotonated under the reaction conditions the equilibrium represented by the sum of steps 1 to 4 does he to the side of products On subsequent acidification (step 5) the anion of the p keto ester is converted to its neutral form and isolated... 

Step 2 The ketone carbonyl of the acetoacetyl group is reduced to an alcohol function This reduction requires NADPH as a coenzyme (NADPH is the phosphate ester of NADH and reacts similarly to it)... 

Carbon-carbon bond formation then occurs between the ketone carbonyl of acetoacetyl coenzyme A and the a carbon of a molecule of acetyl coenzyme A... 

Ammonia reacts with the ketone carbonyl group to give an mine (C=NH) which is then reduced to the amine function of the a ammo acid Both mine formation and reduc tion are enzyme catalyzed The reduced form of nicotinamide adenine diphosphonu cleotide (NADPH) is a coenzyme and acts as a reducing agent The step m which the mine is reduced is the one m which the chirality center is introduced and gives only L glutamic acid... 

Step 1 The amine function of l glutamate reacts with the ketone carbonyl of pyruvate to form an mine... 

Ketose (Section 25 1) A carbohydrate that contains a ketone carbonyl group in its open chain form Kiliam-Fischer synthesis (Section 25 20) A synthetic method for carbohydrate chain extension The new carbon-carbon bond IS formed by converting an aldose to its cyanohydnn Reduction of the cyano group to an aldehyde function com pletes the synthesis... 

In Example 1 the solute, acetone, contains a ketone carbonyl group which is a hydrogen acceptor, i.e., solute class 5 according to Table 15-4. This solute is to be extracted from water with chloroform solvent which contains a hydrogen donor group, i.e., solvent class 4. The solute class 5 and solvent class 4 interaction in Table 15-4 is shown to give a negative deviation from Raonlt s law. 

The C NMR spectrum of the metabolite shows 16 signals instead of 8 as expected from the elemental composition determined by high-resolution mass spectrometry. Moreover, aromaticity of the 2,6-xylenol is obviously lost after metabolism because two ketonic carbonyl carbon atoms (5c = 203.1 and 214.4) and four instead of twelve carbon signals are observed in the shift range of trigonal carbon nuclei (5c = 133.1, 135.4, 135.6 and 139.4) in the C NMR spectra. To conclude, metabolism involves oxidation of the benzenoid ring. 

Crowns containing a ketonic carbonyl as part of the macroring.76... 

Ketonic carbonyl groups are commonly encountered in steroids and their reduction is facile, even in the absence of an alcohol. The lithium-ammonia reduction of androsta-l,4-diene-3,17-dione affords androst-4-ene-3,17-dione in 20% yield but concurrent reduction of the C-17 ketone results in formation of testosterone in 40% yield, even though the reduction is performed rapidly at —40 to —60° and excess lithium is destroyed with solid ammonium chloride. Similar reduction of the C-17 carbonyl group has been observed in other compounds. In the presence of an alcohol, a ketone is complete-... 

Ketose (Section 25.1) A carbohydrate that contains a ketone carbonyl group in its open-chain form. 

There are two methods for the introduction of a hydroxyalkyl group at position 5 of the pyrazol-3-one ring. Schmidt and Zimmer converted furanediones 258a-k into arylmethylenepyrazol-3-reaction with hydrazine hydrate or methylhydrazine (83Jmechanism proposed for the reaction involves nucleophilic attack of the hydrazine on the ketone carbonyl, followed by attack on the ester carbonyl and ring opening of the... 

Reduction of unsaturated aldehydes seems more influenced by the catalyst than is that of unsaturated ketones, probably because of the less hindered nature of the aldehydic function. A variety of special catalysts, such as unsupported (96), or supported (SJ) platinum-iron-zinc, plalinum-nickel-iron (47), platinum-cobalt (90), nickel-cobalt-iron (42-44), osmium (<55), rhenium heptoxide (74), or iridium-on-carbon (49), have been developed for selective hydrogenation of the carbonyl group in unsaturated aldehydes. None of these catalysts appears to reduce an a,/3-unsaturated ketonic carbonyl selectively. 

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