Carbonyl functional groups ketones

Although carbohydrates exist almost entirely as cyclic hemiacetals m aqueous solution they are m rapid equilibrium with their open chain forms and most of the reagents that react with simple aldehydes and ketones react m an analogous way with the carbonyl functional groups of carbohydrates... 

Carbonyl functional groups are the easiest to identify of all IR absorptions because of their sharp, intense peak in the range 1670 to 1780 cm-1. Most important, the exact position of absorption within the range can often be used to identify the exact kind ot carbonyl functional group—aldehyde, ketone, ester, and so forth. 

Aldehydes and ketones both have the carbonyl functional group. An aldehyde is an organic compound that has a double-bonded oxygen on the last carbon of a carbon chain. The functional group for an aldehyde is... 

Since aldehydes and ketones both possess the carbonyl functional group, they undergo similar chemical reactions. 

Aldehydes and ketones both contain the carbonyl functional group ... 

Although the structures of many carbohydrates appear to be quite complex, the chemistry of these substances usually involves only two functional groups —ketone or aldehyde carbonyls and alcohol hydroxyl groups. The carbonyl groups normally do not occur as such, but are combined with hydroxyl groups to form hemiacetal or acetal linkages of the kind discussed in Section 15-4E. 

Different types of carbonyl groups give characteristic strong absorptions at different positions in the infrared spectrum. As a result, infrared spectroscopy is often the best method to detect and differentiate these carboxylic acid derivatives. Table 21-3 summarizes the characteristic IR absorptions of carbonyl functional groups. As in Chapter 12, we are using about 1710 cm-1 for simple ketones and acids as a standard for comparison. Appendix 2 gives a more complete table of characteristic IR frequencies. 

Aluminum atom reactions are relevant to interfacial chemistry associated with aluminum-polyimide junctions. Al deposited under ultra high vacuum will reduce surface carbonyl functional groups (22). MVS co-condensation experiments show that besides ketones, aldehydes and epoxides, atomic aluminum will deoxygenate ethers. Chapter 7 of the monograph by Klabunde (12) includes tables of deoxygenation products of a variety of cyclic and acyclic ketones and ethers. 

With 1,4-diketones the distribution of the reduction products is dependent on the stereochemical situation of the two carbonyl functions. In acyclic derivatives, with no stereochemical interaction between the two carbonyl functions, the ketone groups are independently reduced to give methylene products in the usual manner. On the other hand, cyclic 1,4-diketones react differently. For example, cyclohexane-1,4-dione (22) suffers ring opening to give hexane-2,5-dione and hex-5-en-2-one derivatives, and products of further reduction are also detectable (equation 11). A 1,4-diketone (23) in which the two carbonyls are stereochemically close, gave the diketone (24) under relatively mild conditions (Zn/AcOH, 25 C), formed by the same C—C bond cleavage as seen in cyclohexane-1,4-dione. Under Clemmensen conditions this derivative was then converted to cyclobutane-1,4-diol (25 equation 12) in 98% yield, which is closely related to the aforementioned cyclopropanediol intermediate. ... 

Fig. 4. Plot of the carbonyl NMR chemical shift for aryl acids O (33), aryl amides (33), aryl esters (33), aryl acid chlorides ffl(37), and aryl ketones (32) verus torsion angle between the aryi ring and the carbonyl functional group.

As Scheme 9 shows, an aromatic ketone-derived hydrazone bond was introduced between PEG and PE. The presence of a methyl group (electron donating) on the carbonyl functional group would provide a sufficient lability of the hydrazone bond under mildly acidic conditions while an immediate aromatic ring (electron withdrawing) next to the hydrazone bond would offer... 

Monosaccharides are identified by their carbonyl functional group (aldehyde or ketone) and by the number of carbon atoms they contain. The simplest monosaccharides are the two trioses glyceraldehyde (an aldotriose) and dihydroxyacetone (aketotriose). Four-, five-, six-, and seven-carbon-containing monosaccharides are called tet-roses, pentoses, hexoses, and heptoses, respectively. Structures of some monosaccharides are shown in Figure 9-1. All monosaccharides, with the exception of dihydroxyacetone, contain at least one asymmetrical or chiral carbon atom, and therefore two or more stereoisomers are... 

The Homer-Wadsworth-Emmons reaction is among the most important reactions for effecting a two-carbon chain elongation of a carbonyl functional group - " It can be described as a general synthetic protocol for the conversion of aldehydes and ketones into aji-unsaturated carbonyl compounds and their derivatives " ... 

Ketones. Compounds with a carbonyl functional group and the general formula RR CO, where R and R are alkyl and/or aromatic groups. (24.4)... 

The carbonyl functional group provides an electrophilic site for nucleophilic attack. As none of the naturally occurring amino acids contains a ketone or aldehyde moiety, it is not possible for a protein-bound carbonyl group to be present at an enzyme active site, unless it is provided by a cofactor. The most commonly seen reactive carbonyl group in enzymes is that provided by the pyridoxal phosphate cofactor which is derived from vitamin B6." The carbonyl serves as a site for covalent adduct formation with a nucleophilic substrate, often an amine or the amino group of amino acid substrates. An alternative strategy for introduction of a reactive carbonyl at an enzyme active sight has been described for a class of enzymes that possess a covalent pyruvoyl cofactor. 

Solution A characteristic of both ketones and aldehydes is the carbonyl functional group they possess. Thus, to characterize and identify ketones and aldehydes, reactions with the carbonyls are often done. Since oxygen is more electronegative, (electron-attracting) than carbon, the carbonyl carbon becomes susceptible to nucleophilic attack. Hydroxylamine, derived from its hydrochloride salt, can act as a nucleophilic reagent. 

The infrared spectrum of the product was similar to that for the starting polymer with additional peaks due to carboxylic acid and ketone carbonyl functional groups. Figure 1 shows the infrared spectra of the starting poly (IB-PMS) copolymer... 

Organic compounds containing a carbonyl functional group, J C=0, such as aldehydes, ketones, esters, and carboxylic acids, exhibit a low order of toxicity. The lower aldehydes, such as formaldehyde, acetaldehyde, and acrolein, are severe irritants to the eyes and respiratory tract. Acrolein is a severe lachry-mator. Lower carboxylic acids are corrosive substances. Formic acid is a poison, but the toxic effects arise as a result of lowering of the blood pH below normal levels and have little to do with the carbonyl group in the molecule. 

A number of naturally occurring aldehydes and ketones play important roles within living systems. The carbonyl functional group is fairly common in biological compounds. For example, progesterone and testosterone, female and male sex hormones, respectively, are both ketones. 

Ketones Organic compounds containing a C=0 (carbonyl) functional group between two carbon atoms as In RCOR. ... 

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