Aliphatic carbonyl carbon

NMR showed the presence of an aliphatic carbonyl carbon at 202ppm and a car-boxy carbon at 173 ppm. In the aromatic region of the spectrum, four signals were present. These are due to the four aromatic carbons in the thiophene rings. Signals at 162 and 110 to 135ppm indicated the isolated substance to be a trifluoroacetic acid salt. In the aliphatic part of the spectrum, two methyl carbons were at 14 ppm, and eight other aliphatic carbons were seen. 

An adjacent tnfluoromethyl group sharply increases the electrophilic character of the carbonyl carbon Compounds that readily form hydrates and hemiacetals show a time-dependent reversible mhibition of the en yme acetylcholinesterase (equation 2), in which the tight complex makes inhibition only partially reversible [75] In comparison with a nonfluormated analogue, several aliphatic ketones flanked by CFj and CF2 groups, are exceptionally potent reversible inhibitors of acetylcholinesterase, as documented by companson of inhibition constants shown in equation 3 [16 ... 

One further comparison aromatic aldehydes, such as benzaldehyde, are less reactive in nucleophilic addition reactions than aliphatic aldehydes because the electron-donating resonance effect of the aromatic ring makes the carbonyl group less electrophilic. Comparing electrostatic potential maps of formaldehyde and benzaldehyde, for example, shows that the carbonyl carbon atom is less positive (less blue) in the aromatic aldehyde. 

Carbonyl oxygen atoms of aldehydes can also be efficiently acylated by 1-acylbenzotriazoles 915 in the presence of mild bases (K2CO3, Et3N). The released benzotriazolide anions are consecutively attached to the aldehyde carbonyl carbon atoms to produce esters 944 (Equation 20). Aliphatic aldehydes react quickly at room temperature, but aromatic aldehydes require elevated temperatures. The yields are good to quantitative. The amounts of benzotriazol-2-yl isomers of esters 944 in the products mixtures is strongly dependent on the reaction conditions and the character of groups R1 and Rz, and it may vary from 5% to 25% <1999JHC777>. 

From the spectrum there are 7 carbon environments 4 carbons are in the typical aromatic/olefinic chemical shift range, 2 carbons in the aliphatic chemical shift range and 1 carbon at low field (167 ppm) characteristic of a carbonyl carbon. The molecular formula is given as C9HJJNO2 so there must be an element (or elements) of symmetry to account for the 2 carbons not apparent in the spectrum. 

Radical additions to alkenes and aromatic systems are well known reactions. The trapping in this manner of radicals obtained by reduction of the aliphatic carbonyl function has proved to be a versatile electrochemical route for the formation of carbon-carbon bonds. Such reactions are most frequently carried out in protic solvents so that the reactive species is a o-radical formed by protonation of the carbonyl radical-anion. Tlie cyclization step must be fast in order to compete with further reduction of the radical to a carbanion at the electrode surface followed by protonation. Cyclization can be favoured and further reduction disfavoured by a... 

Solid-state 13C NMR was employed to characterize intact samples of cutin and suberin biopolyesters. Although a considerable degree of structural heterogeneity was observed for both materials, it was possible nonetheless to resolve and assign many NMR peaks, even when the polyesters were accompanied by waxes or cell walls. Quantitative estimates for the various aliphatic, aromatic, and carbonyl carbon types indicated that cutin was primarily aliphatic in composition, whereas suberin had more aromatic and olefinic moieties. Additional analysis should be facilitated by the biosynthetic incorporation of selectively 13C-enriched precursors (26,27). 

Pickle, T., D. T. Allen, and S. E. Pratsinis, The Sources and Size Distributions of Aliphatic and Carbonyl Carbon in Los Angeles Aerosol, Atmos. Environ., 24A, 2221-2228(1990). 

Nucleophilic reagents attack the carbonyl carbon atom the subsequent course of this reaction parallels that in aliphatic chemistry. If the carbonyl group and the heteroatom are adjacent, the ring is usually opened. If they are not adjacent, a carbonyl addition compound results, which often eliminates water spontaneously. The reactions of carbonyl groups in both environments are discussed. 

The nature of carbonyl groups in coal is not yet known unambiguously. It may be quinonoid and/or ketonic (13) in character. In the latter case, the carbonyl carbon will have to be grouped with the aliphatic carbon, and in... 

Alcohols, amines, and thiols add readily to the electrophilic carbon of the carbonyl group to form hemiacetals, carbinolamines, hemiketals, and hemimercaptals. An example is the formation of ring structures of sugars (Eq. 4-1). Water can also add to carbonyl groups and most aliphatic carbonyl compounds... 

Fluorination ot carbon adjacent to heteroatoms invariably increases lipophilt-city, as does fluorination of double bonds (Table 10), but ot-fluorination of aliphatic carbonyl groups is an exception a-Fluoroketones or aldehydes that form stable... 

Anodic oxidation of aliphatic aldehydes and ketones is generally difficult because their oxidation potentials are very high (>2.5 V). However, silylation at the carbonyl carbon causes a marked decrease in the oxidation potential as shown in Table 933,40. This silicon effect is much smaller in the case of aromatic carbonyl analogues40. The silicon effect is attributed to the rise of the HOMO level by the interaction between the C—Si a orbital and the nonbonding p orbital of the carbonyl oxygen, which in turn favors the electron transfer. 

Carboxylic adds where the R group is an alkyl group are called aliphatic acids. Tire salts of carboxylic adds are named with the suffix -ate. The -ate replaces the -ic (or -oic in lUPAC names), so that "acetic" becomes "acetate". (Acetate is sometimes abbreviated -OAc.) In IUPAC rules, the carbonyl carbon of a carboxylic acid takes priority over all groups discussed so far. 

Such a mechanism can explain why aromatic R1 acids have a higher reactivity than aliphatic ones. AH is a Lewis base, which carries an unshared pair of electrons on the A atom. Hence an increase in its nucleophilic character should facilitate the addition to the electron-poor carbonyl carbon atom and should make easier the elimination of X as a negative ion. 

In the aliphatic region of the 10-oxocancentrine spectrum the signal at 20.4 ppm corresponding to C-10 in cancentrine was absent. Both C-9 and C-14 were deshielded as in the model discussed above. These results confirmed the location of the carbonyl at C-10 in oxocancentrine. The assignments made to the quaternary aromatic and carbonyl carbons were considered to be tentative by the authors. 

JK 1 mol"1 (Stewart and Teo, 1980). For this series also, a plot of log k for reduction against log K for hydration yields a line of slope 1.12, consistent with a transition state with substantial hydride bonding to carbonyl carbon. A correlation (r = 0.9785) between logk for reduction of a series of aliphatic ketones and log K for equilibration of the ketone and alcohol has a slope of 1.1, which has also been taken to support a productlike transition state (Muller and Blanc, 1980, 1981 Boyer et al., 1979). 

Inhibitory action was associated with a wide variety of structural groups substituted on the carbonyl carbon of the amide moiety. In general, derivatives with nonpolar side chains were more active than those with polar side chains. The most active inhibitors, represented by diuron, possessed a dialkyl-amino substituent. However, derivatives with aliphatic side chains, such as propanil, and alicyclic side chains, such as cypromid, were also strong inhibitors (6). 

The width estimated from the AFM image is in good agreement with the line width of surface initiator micropatterns. The formation of a PMMA layer was further confirmed by XPS measurement, in which the characteristic peaks attributed to aliphatic carbon, the ether carbon, and carbonyl carbon were observed at 285, 286.5, and 288.8 eV, respectively. 

Aldehyde dehydrogenases have been isolated from a variety of sources, the most important being the liver. With a series of linear aliphatic aldehydes, the rate of oxidation increases as the carbonyl carbon becomes more positive. 

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