Other Carbonyl Compounds

Ph3P=CHCOAr + SCNCOPh —Ph3p=cCOAr ArCOCOCSNHCOPh 

Organometallics. Methylenetriphenylphosphoranes form stable 2 1 complexes (38)40 and 1 1 complexes (39)41 when treated with copper(i) or silver(i) chlorides. Stable adducts (40) can also be obtained from the reaction of methylenetrimethyl-phosphorane and metal trialkyls.42 

Silylated ylides (41) are produced from alkylidenetrialkylphosphoranes and 1,3-disilacyclobutanes.43 These reactions are thought to proceed via penta-alkylphos-phorane intermediates since cleavage of 1,1-dimethylsilacyclobutane gave only (42). 

The mechanism of hydrolysis of benzylidenetriphenylphosphorane is similar to that of the corresponding phosphonium salt.52 It is proposed that the low polarities of the solutions in which ylides are usually hydrolysed increase the equilibrium 

Yoshida, H. Matsuura, T. Ogata, and S. Inokawa, Bull. Chem. Soc. Japan, 1975,48, 2907. 

The major ban is which appear in the infrared spectrum of carboxylic acids (which contain the COOH group) are summarised in Table 4.3h.  

1715-1680 3500-2500 1300-1200 1400 900 C=0 stretching O—H stretching C—O stretching C—O—in-plane bending C—O—out-of-plane bending 

The two most polar bonds in esters (containing the —CO—O—C— group) are the C=0 and C—O bonds, and these produce the strongest peaks in the spectrum of any ester (see Table 4.3i). 

---

Other carbonyl compounds are within the scope of the reaction ketones give amides, and aldehydes yield nitriles and formyl derivatives of amines ... 

So far in this section we have combined enolate anions with other carbonyl compounds by direct attack at the carbonyl group. We can expand the scope of this reaction by using a,p-unsaturated carbonyl compounds as the electrophiles. This is the Michael reaction. Remind yourself of tliis by writing out the mechanism of a Michael reaction such as ... 

Acetaldehyde can be isolated and identified by the characteristic melting points of the crystalline compounds formed with hydrazines, semicarbazides, etc these derivatives of aldehydes can be separated by paper and column chromatography (104,113). Acetaldehyde has been separated quantitatively from other carbonyl compounds on an ion-exchange resin in the bisulfite form the aldehyde is then eluted from the column with a solution of sodium chloride (114). In larger quantities, acetaldehyde may be isolated by passing the vapor into ether, then saturating with dry ammonia acetaldehyde—ammonia crystallizes from the solution. Reactions with bisulfite, hydrazines, oximes, semicarb azides, and 5,5-dimethyl-1,3-cyclohexanedione [126-81 -8] (dimedone) have also been used to isolate acetaldehyde from various solutions. 

Acetylene is condensed with carbonyl compounds to give a wide variety of products, some of which are the substrates for the preparation of families of derivatives. The most commercially significant reaction is the condensation of acetylene with formaldehyde. The reaction does not proceed well with base catalysis which works well with other carbonyl compounds and it was discovered by Reppe (33) that acetylene under pressure (304 kPa (3 atm), or above) reacts smoothly with formaldehyde at 100°C in the presence of a copper acetyUde complex catalyst. The reaction can be controlled to give either propargyl alcohol or butynediol (see Acetylene-DERIVED chemicals). 2-Butyne-l,4-diol, its hydroxyethyl ethers, and propargyl alcohol are used as corrosion inhibitors. 2,3-Dibromo-2-butene-l,4-diol is used as a flame retardant in polyurethane and other polymer systems (see Bromine compounds Elame retardants). 

In the case of nicotinamide, the color yield is often low. This problem can be circumvented by either hydrolysis to nicotinic acid or by conversion of the amide to a fluorescent compound. Treatment of nicotinamide with methyl iodide yields the quaternary ammonium salt, /V-methyl nicotinamide (5). Reaction of this compound with acetophenone yields a fluorescent adduct (49). Other carbonyl compounds have also been used (50—54). 

Cyclohexanone purity is most readily deteanined by gas-Hquid chromatography over DC-710 or carbowax 20M-on-chromosorb. Impurities such as cyclohexane, ben2ene, cyclohexanol, and phenol do not interfere. In the absence of other carbonyl compounds cyclohexanone may be deterrnined by treatment with hydroxylamine hydrochloride, which forms the oxime, as follows ... 

BS ISO 16000 Indoor formaldehyde and other carbonyl compounds Active and diffusive sampling... 

Fluoroalkyl ketones may be used as the electrophilic partners in condensation reactions with other carbonyl compounds The highly electrophilic hexafluo-roacetone has been used in selective hexafluoroisopropyhdenation reactions with enol silyl ethers and dienolsilyl ethers [f] (equation 1)... 

The intermolecular McMurry reaction is first of all a suitable method for the synthesis of symmetrical alkenes. With a mixture of carbonyl compounds as starting material, the yield is often poor. An exception to this being the coupling of diaryl ketones with other carbonyl compounds, where the mixed coupling product can be obtained in good yield. For example benzophenone and acetone (stoichiometric ratio 1 4) are coupled in 94% yield. ... 

The precursors for >C6 acids (namely, >C6 oi-dicarbonyls) are assumed to form by aldol condensation of ot-dicarbonyl compounds with other carbonyl compounds (route 7), and termination of this oligomerization is... 

Other carbonyl compounds exhibit rotation about sp -sp bonds, including amides. In M-acetyl-iV-methylaniline, the cis conformation (i ) is more stable than... 

Both singlet and triplet n,n states undergo the reaction." The intermediate diradical can also cyclize to a cyclobutanol, which is often a side product. Carboxylic esters, anhydrides, and other carbonyl compounds can also give this... 

The catalytic hydrosi(ly)lations of other C=X functional groups (X = O, NR) constitute alternative routes to the reduction of aldehydes, ketones, imines and other carbonyl compounds (Scheme 2.9), circumventing the use of molecular hydrogen or occasionally harsh transfer hydrogenation conditions. 

The enolates of other carbonyl compounds can be used in mixed aldol reactions. Extensive use has been made of the enolates of esters, thiol esters, amides, and imides, including several that serve as chiral auxiliaries. The methods for formation of these enolates are similar to those for ketones. Lithium, boron, titanium, and tin derivatives have all been widely used. The silyl ethers of ester enolates, which are called silyl ketene acetals, show reactivity that is analogous to silyl enol ethers and are covalent equivalents of ester enolates. The silyl thioketene acetal derivatives of thiol esters are also useful. The reactions of these enolate equivalents are discussed in Section 2.1.4. 

Although the reaction of ketones and other carbonyl compounds with electrophiles such as bromine leads to substitution rather than addition, the mechanism of the reaction is closely related to electrophilic additions to alkenes. An enol, enolate, or enolate equivalent derived from the carbonyl compound is the nucleophile, and the electrophilic attack by the halogen is analogous to that on alkenes. The reaction is completed by restoration of the carbonyl bond, rather than by addition of a nucleophile. The acid- and base-catalyzed halogenation of ketones, which is discussed briefly in Section 6.4 of Part A, provide the most-studied examples of the reaction from a mechanistic perspective. 

Organopalladium intermediates are also involved in the synthesis of ketones and other carbonyl compounds. These reactions involve acylpalladium intermediates, which can be made from acyl halides or by reaction of an organopalladium species with carbon monoxide. A second organic group, usually arising from any organometallic reagent, can then form a ketone. Alternatively, the acylpalladium intermediate may react with nucleophilic solvents such as alcohols to form esters. 

Hydrazide-containing compounds also can be coupled to carboxylate groups using a carbodiimide-mediated reaction. Using bifunctional hydrazide reagents, carboxylates can be modified to possess terminal hydrazide groups able to conjugate with other carbonyl compounds (Chapter 4, Section 8). 

When considered as a part of the photochemistry of carbonyl compounds, irradiations of esters constitute a minor component. The more frequent photolyses of other carbonyl compounds, in particular ketones, is not surprising, as, even though parallels exist between ester and ketone photochemistry (for example, both experience a-cleavage and hydrogen abstraction-reactions), esters require radiation of higher energy for reaction, and typically produce more-complex mixtures of products. In addition to their similarity to other carbonyl compounds in their reactivity, esters also experience reactions that are uniquely their own. 

A reaction unknown for other carbonyl compounds occurs when es-... 

More generally, double bonds between two carbons or one carbon and a heteroatom, possibly conjugated with other unsaturated moieties in the molecule, are eligible for two-electron/two-proton reactions according to Scheme 2.20. Carbonyl compounds are typical examples of such two-electron/two-proton hydrogenation reactions. In the case of quinones, the reaction that converts the quinone into the corresponding hydroquinone is reversible. With other carbonyl compounds, the protonation of the initial ketyl anion radical compete with its dimerization, as discussed later. 

B-Allenyl-9-BBN has also been shown to react cleanly and efficiently with other electrophiles [27]. Not surprisingly, aldehydes show the highest reactivity. In a competition experiment between benzaldehyde and acetophenone at -78 °C, the aldehyde adduct predominated by more than 30 l(Eq. 9.22). Competition experiments with other carbonyl compounds showed a similar bias for aldehyde adducts. 

Other Carbonyl Compounds. The reaction of alkylidenetriphenylphosphoranes with lactones (Scheme 8) affords betaines (32), which can be thermally decomposed to eliminate triphenylphosphine, giving lactones in which the alkylidene grouping of the starting ylide is incorporated into the ring.34... 

As mentioned previously, the scope of photochemical oxidants extends to organic nitrates and other carbonyl compounds. Among the organic nitrates, the one most often cited is peroxyacetylnitrate (PAN). Electron-capture detector techniques applied to the gas chromatt aph were used to measure PAN concentrations in Los Angeles late in 1%5. ... 

Photolytic. Major products reported from the photooxidation of butane with nitrogen oxides under atmospheric conditions were acetaldehyde, formaldehyde, and 2-butanone. Minor products included peroxyacyl nitrates and methyl, ethyl and propyl nitrates, carbon monoxide, and carbon dioxide. Biacetyl, tert-butyl nitrate, ethanol, and acetone were reported as trace products (Altshuller, 1983 Bufalini et al, 1971). The amount of sec-butyl nitrate formed was about twice that of n-butyl nitrate. 2-Butanone was the major photooxidation product with a yield of 37% (Evmorfopoulos and Glavas, 1998). Irradiation of butane in the presence of chlorine yielded carbon monoxide, carbon dioxide, hydroperoxides, peroxyacid, and other carbonyl compounds (Hanst and Gay, 1983). Nitrous acid vapor and butane in a smog chamber were irradiated with UV light. Major oxidation products identified included 2-butanone, acetaldehyde, and butanal. Minor products included peroxyacetyl nitrate, methyl nitrate, and unidentified compounds (Cox et al., 1981). 

As expected, cyclohexanone hydrogenation performed in an IL has a longer reaction time than in solventless conditions. Where using iridium nanoparticles dispersed in an IL, the biphasic hydrogenation of cyclohexanone could be performed at least 15 times, without any considerable loss in catalytic activity this contrasted with the use of nanoparticles in solventless conditions, when the catalytic activity begins to decHne after the third cycle. The standard experimental conditions established for the hydrogenation of other carbonyl compounds were 75 °C, 4atm of H2 and a molar substrate Ir ratio of 250. 

The carbon dioxide anion-radical was used for one-electron reductions of nitrobenzene diazo-nium cations, nitrobenzene itself, quinones, aliphatic nitro compounds, acetaldehyde, acetone and other carbonyl compounds, maleimide, riboflavin, and certain dyes (Morkovnik and Okhlobystin 1979). The double bonds in maleate and fumarate are reduced by CO2. The reduced products, on being protonated, give rise to succinate (Schutz and Meyerstein 2006). The carbon dioxide anion-radical reduces organic complexes of Co and Ru into appropriate complexes of the metals(II) (Morkovnik and Okhlobystin 1979). In particular, after the electron transfer from this anion radical to the pentammino-p-nitrobenzoato-cobalt(III) complex, the Co(III) complex with thep-nitrophenyl anion-radical fragment is initially formed. The intermediate complex transforms into the final Co(II) complex with the p-nitrobenzoate ligand. 

Aldehydes and ketones, and other carbonyl compounds having hydrogen atoms on the a-carbon, exist in solution as equilibrium mixtures of two or more isomeric forms. These isomers are termed the keto form, which is how we normally represent a carbonyl compound, and the enol form, which takes its name from the combination of double bond and alcohol. 

Another important part of Organic 11 is carbonyl chemistry. We look at the basics of the carbonyls in Chapter 9. It s like a family reunion where 1 (John, one of your authors) grew up in North Carolina — everybody is related. You meet aldehydes, ketones, carboxylic acids, acyl chlorides, esters, cimides, and on and on. It s a quick peek, because later we go back and examine many of these in detail. For example, in Chapter 10 you study aldehydes and ketones, along with some of the amines, while in Chapter 11 we introduce you to other carbonyl compounds, enols and enolates, along with nitroalkanes and nitriles. 

Acyl halides and anhydrides are important reactants for the formation of other carbonyl compounds, but you don t need to take up valuable brain space with information about any other acyl halide or anhydride reactions at this time. 

The enolates of other carbonyl compounds can be used in mixed aldol condensations. Extensive use has been made of the enolates of esters, thioesters, amides, nitriles, and nitroalkanes. Scheme 2.4 gives a selection of such reactions. 

Similarly, benzhy dr azide (324) and solidified hydrazine (163) react quantitatively in the solid state with aldehydes, ketones, and other carbonyl compounds. Thus, quantitative yields of the hydrazones 325 and fully specific 327... 

Other carbonyl compounds, such as acetaldehyde or propionaldehyde can also be polymerized to high-molecular-weight products however, their stability is lower than that of polyoxymethylenes with protected end groups. 

Reaction of (159) with other carbonyl compounds was monitored by H NMR spectroscopy <90JHC1993>. Acetophenone and benzophenone in CDCI3 at 60 °C gave within 2 h a small amount of (179) analogues but mainly thermal decomposition products of the latter. Benzaldehyde reacts at room temperature but the resulting analogue (179) decomposes completely. 

An alternative method to TBARS for determination of MDA is formation of the DNP derivative and quantitation by RP-HPLC with DA-UVD, recording in the 195 to 500 nm range. Other carbonyl compounds present in the sample also form the corresponding DNP compounds and are also determined. The method was applied to MDA determination in plasma of rats, after they were subjected to oxidative stress by intraparental injection of a dose of bacterial lipopolysaccharide" . 

---