Carbonyl group, 787 table

The oxidation of starch in aqueous suspension with H202 in the presence of iron phthalocyanine gives both carboxylic and carbonyl groups (Table 3.1). The best yields were obtained with a molar ratio 12900/1 (0.0078 mol%), but the oxidation was still quite efficient with 0.0039 mol% of catalyst [25800 per anhydroglucose unit (AGU)/catalyst ratio]. The oxidized starch had almost the same final Fe-content as the initial potato starch. Still, the efficiency of this method in view of scaling up was limited by comparatively low activity and product isolation problems. 

Each alcohol has a saturated carbon atom next to oxygen, all close together. Then there are carbons next door but one to oxygen they are back in the 0-50 p.p.m. region but at its low field end— about 30-35 p.p.m.. Notice the similarity of these chemical shifts to those of carbons next to a carbonyl group (Table 3.5 on p. 63). In each case we have C-C-O and the effects are about the same. Two of the alcohols have carbon(s) one further away still at yet smaller chemical shift (further upfield, more shielded) at about 20 p.p.m., but only the n-butanol has a more remote carbon still at 15.2. The number and the chemical shift of the signals identify the molecules very clearly. 

A theoretical determination of vibrational absorption and Raman spectra of 3-methylindole radicals has been carried out in comparison to experimentally measured spectra for 3-methylindole (Table 28) to provide specific spectroscopic markers for the detection of neutral or cationic tryptophan radicals in biological systems <2001CPH(265)13>. Among isatin derivatives, substitution at C-5 has relatively greater influence on the electron density and the force constant of the amide than of the ketone carbonyl group (Table 29) <2001SAA469>. 

The sole exception of preferential endo attack is seen in the reaction of cuprates with oxanorbornenyl ketones [106]. The unusual and unprecedented endo delivery of the nucleophile is proposed to proceed via a prior complexation of the bridgehead oxygen with one equivalent of the cuprate on the less hindered side, followed by addition of another equivalent of cuprate from the more hindered endo face of the carbonyl group. Table 2 shows the reactions of 88 with various cuprates to give the exo alcohols (entries 1 -3). The remote olefin shows a positive effect in promoting endo nucleophilic attack, as shown by the reactions of 88 and 89 respectively (entry 1 vs. 4). 

Many other reagents have been used to cleave hydrazones and to regenerate carbonyl groups. Table 1 lists some of these other examples of procedures to regenerate carbonyl compounds from their N,N-d -alkylhydrazones. 

Net retention of configuration is observed for the corresponding catalytic allylations of the ketone lithium, zinc, potassium borate, and tin enolates with various allyl esters depicted in Table 21 h-8. The relative configuration of the additional stereogenic center adjacent to the ketone carbonyl group (Table 21, entry 4) has not been assigned. 

It is well known that carbonyl groups increase the acidity of the proton(s) adjacent (a-) to the carbonyl group. Table 1.1 shows the pA a values for some unsaturated compounds and for some common solvents and reagents. 

Notably, fluorine may also exert a substantial effect on the conformation of a molecule [19]. On the other hand, an excellent match is found for the carbonyl group (Table 35.1) [20, 21]. 

The existence of [Rh2( 0)8] under normal conditions has not been confirmed, although its synthesis from dispersed metal under pressure (28 MPa) and at 473 K had been reported. However, it was shown that [Rh2( 0)8] exists in solutions only at high pressures and at low temperatures.[Rh2(CO)8] and [Ir2( 0)8] were also prepared by reactions of atomic Rh and Ir with carbon monoxide in 0 matrices. During condensation at 10 K, [Rh( 0)4] or [Ir( 0)4] are formed first, and subsequently at 50 K react to give [M2( 0)8] compounds. At 223 K, the dinuclear carbonyls are transformed into [M4( 0)i2]. This means that with respect to tetranuclear compounds, the dinuclear complexes are thermodynamically unstable. [Rh2( 0)8] in solutions as well as in the matrix and [Ir2( 0)8] in the matrix have bridging carbonyl groups (Table 2.26). 

A further study of the rate of reduction of various ketones reveals that the reactivity varies with electronic and positional environments of carbonyl groups (Table 25.11) [33]. 

Recall that a carbonyl group produces a very strong signal between 1650 and 1850 cm in an IR spectrum. The precise location of the signal depends on the nature of the carbonyl group. Table 21.3 gives carbonyl stretching frequencies for each of the carboxylic acid derivatives. 

In grapes affected by rot, Guillou-Largeteau (1996) identified molecules with two carbonyl groups (Table 8.8). They are probably formed during the development of Botrytis cinerea and other microorganisms involved in various types of rot. In view of the fact that concentrations do not... 

The quantum yields of the Norrish Type II process depend on the chain length and structure of the ketone carbonyl group (Table 3.7) [859]. For a methyl or phenyl ketone, the quantum yield remains almost independent of chain length, regardless of whether it is in a polymer or a small molecule whereas, if it is in the centre of a chain, the quantum yield decreases with chain length. A side chain ketone shows a considerably higher efficiency, which is more or less independent of molecular weight. 

It s fortunate that even small variations in the position of the band can be interpreted in terms of the type of carbonyl group (Table 5.5). Anhydrides show two bands because the carbonyl vibrations are coupled, and they can vibrate in phase or out of phase (5.7, 5.8) these are called the symmetric and antisymmetric stretches. The carbonyl stretching frequency can also be used to establish ring size if the carbonyl carbon atom is part of the ring. Cyclohexanone shows an entirely normal stretching frequency of 1716 cm"h the values for cyclopentanone, cyclobutanone, and cyclopropanone are, respectively, 1748,1783, and 1850 cm b Similar differences are noted for lactones (cyclic esters) and lactams (cyclic amides). 

Many compounds contain more than one functional group Prostaglandin Ei a hormone that regulates the relaxation of smooth muscles con tains two different kinds of carbonyl groups Classify each one (aldehyde ketone carboxylic acid ester amide acyl chloride or acid anhydride) Identify the most acidic proton in prostaglandin Ei and use Table 1 7 to estimate its pK ... 

Two aldehydes two ketones or one aldehyde and one ketone may be formed Let s recall the classes of carbonyl compounds from Table 4 1 Aldehydes have at least one hydrogen on the carbonyl group ketones have two carbon substituents—alkyl groups for example—on the carbonyl Carboxylic acids have a hydroxyl substituent attached to the carbonyl group... 

As Table 12 2 indicates a variety of substituent types are meta directing and strongly deactivating We have already discussed one of these the trifluoromethyl group Several of the others have a carbonyl group attached directly to the aromatic ring... 

The type of alcohol produced depends on the carbonyl compound Substituents present on the carbonyl group of an aldehyde or ketone stay there—they become sub stituents on the carbon that bears the hydroxyl group m the product Thus as shown m Table 14 3 (following page) formaldehyde reacts with Grignard reagents to yield pri mary alcohols aldehydes yield secondary alcohols and ketones yield tertiary alcohols... 

The reaction of alcohols with acyl chlorides is analogous to their reaction with p toluenesulfonyl chloride described earlier (Section 8 14 and Table 15 2) In those reactions a p toluene sulfonate ester was formed by displacement of chloride from the sulfonyl group by the oxygen of the alcohol Carboxylic esters arise by displacement of chlonde from a carbonyl group by the alcohol oxygen... 

Table 17 2 summarizes the reactions of aldehydes and ketones that you ve seen m ear her chapters All are valuable tools to the synthetic chemist Carbonyl groups provide access to hydrocarbons by Clemmensen or Wolff-Kishner reduction (Section 12 8) to alcohols by reduction (Section 15 2) or by reaction with Grignard or organolithmm reagents (Sections 14 6 and 14 7)... 

A number of compounds of the general type H2NZ react with aldehydes and ketones m a manner analogous to that of primary amines The carbonyl group (C=0) IS converted to C=NZ and a molecule of water is formed Table 17 4 presents exam pies of some of these reactions The mechanism by which each proceeds is similar to the nucleophilic addition-elimination mechanism described for the reaction of primary amines with aldehydes and ketones... 

The characteristic reactions of aldehydes and ketones involve nude ophihc addition to the carbonyl group and are summarized m Table 17 5 Reagents of the type HY react according to the general equation... 

The mechanisms of all the reactions cited m Table 20 1 are similar to the mecha nism of hydrolysis of an acyl chlonde outlined m Figure 20 2 They differ with respect to the nucleophile that attacks the carbonyl group... 

Conversions of acid anhydrides to other carboxylic acid derivatives are illustrated m Table 20 2 Because a more highly stabilized carbonyl group must result m order for nucleophilic acyl substitution to be effective acid anhydrides are readily converted to carboxylic acids esters and amides but not to acyl chlorides... 

Nucleophilic acyl substitutions at the ester carbonyl group are summarized m Table 20 5 on page 849 Esters are less reactive than acyl chlorides and acid anhydrides Nude ophilic acyl substitution m esters especially ester hydrolysis has been extensively mves tigated from a mechanistic perspective Indeed much of what we know concerning the general topic of nucleophilic acyl substitution comes from studies carried out on esters The following sections describe those mechanistic studies... 

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