Carbonyl functional groups carboxylic acids

Because the halogen in the acyl halide and the RCO2 substituent in the anhydride are good leaving groups and because they activate the adjacent carbonyl function, these carboxylic acid derivatives are useful synthetic intermediates for the preparation of other compounds, a topic to be discussed in Sections 20-2 and 20-3. 

Carboxylic acids are easily converted to a variety of acid derivatives. Each derivative contains the carbonyl group bonded to an oxygen or other electron-withdrawing element. Among these functional groups are acid chlorides, esters, and amides. All of these groups can be converted back to carboxylic acids by acidic or basic hydrolysis. 

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. 

Antoniotti and Dunach have reviewed the stoichiometric and catalytic oxidation of epoxides and their scope in organic synthesis, with particular focus on the Bi/02-catalyzed oxidation developed in their group. Such reactions can lead to either the oxidative cleavage of the epoxy carbon-carbon bond (giving carbonyl compounds or carboxylic acids (Scheme 57, Equation 14) or alternatively the formation of a-functionalized ketones when the C-C bond of the epoxide remains uncleaved (Scheme 57, Equation 15) <2003S2753>. 

The characteristic chemical behavior of carboxylic acids is, of course, determined by their functional group, carboxyl, — COOH. This group is made up of a carbonyl group (C O) and a hydroxyl group (—OH). As we shall see, it is the —OH that actually undergoes nearly every reaction—loss of H, or replacement by another group—but it does so in a way that is possible only because of the effect of the C O. 

Carbonyl group C=0, the functional group characteristic of aldehydes, ketones, atid. together with an OH group, carboxylic acids. 

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. 

Figure 21.8 Methods for oxidizing carbon nanotubes. Oxidation results in surface functional hydroxyl, carbonyl, and/or carboxylic acid groups. (Reproduced with permission from V. H. Grassian, Nanoscience and Nanotechnology Environmental and Health Impacts. Copyright 2008 John Wiley Sons, Inc.)...

A ketone or aldehyde group can also be named as a substituent on a molecule with another functional group as its root. The ketone carbonyl is designated by the prefix OXO-, and the —CHO group is named as a formyl group. Carboxylic acids frequently contain ketone or aldehyde groups named as substituents. 

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