Other carbonyl-containing compounds

What structural features are responsible for the reactivity order of carboxylic acid derivatives Like the other carbonyl containing compounds that we ve studied they all have a planar arrangement of bonds to the carbonyl group Thus all are about the same in offering relatively unhindered access to the approach of a nucleophile They differ m the degree to which the atom attached to the carbonyl group can stabilize the carbonyl group by electron donation... 

Performing the titration to a potentiometric end point, rather than to a colored end point, has been shown to be the more accurate method. Since other carbonyl containing compounds also react to form the oxime and release hydrochloric acid, this test is not specific for benzaldehyde. 

The anhydrides are similar to other carbonyl containing compounds in that, adjacent aliphatic groups are weakly deshielded while the ortho aromatic protons are strongly deshielded. Their HNMR spectra are similar to those of the carboxylic acids. Be-cause the anhydrides hydrolyze easily to form the corresponding carboxylic acid, the chemical shift range from 10-12 ppm should be checked carefully to determine the presence of the car-boxylic acid -OH group which would indicate that hydrolysis has occurred and to what extent such decomposition products are present in solution. 

Although similar in chemical shifts to the other carbonyl containing compounds, the Primary Amides can be distinguished by the presence of one or two very broad bands at low field (5.5-8.9 ppm) arising from the resonance of the two -NH2 protons. These bands are exchangeable and will not be observed if D20 or TFA are used as the solvent. Due to the partial double bond character of the amide—C(=0)—NH2 bond, the two NH protons may be non-equivalent resulting in two distinct but overlapping resonance bands. 

The Imides are nitrogen containing analogs of the Anhydrides. They contain the -C(=0)-NH-C(=0)-Iinkage and are usually cyclic in structure. As with the other carbonyl containing compounds, the protons of aliphatic groups alpha to the C(=0) group are weakly deshielded. The Imide NH proton resonates at low field (8-12 ppm) and is usually a very broad absorption band. 

IV. From Other Carbonyl-Containing Compounds with Perfluoroalkyl Groups. 316... 

The value of 1 in 20 for the collision yield for acetyl chloride is at variance with the conclusion that the reaction of this halide occurs at the same zero activation energy as does methyl iodide [33]. A few other carbonyl-containing compounds have been studied by Walker and Warhurst [71], viz. 

The most important infrared absorption of carboxylic acids and their derivatives is the result of the C=0 stretching vibration. Infrared spectroscopic data for these derivatives and the other carbonyl-containing compounds are summarized in Table 12.7. 

However, as anticipated on the basis of the reactions of other carbonyl-containing compounds, carboxylic acids (RCO2H) and the other derivatives (i.e., esters, anhydrides, and acid halides) can be reduced to the corresponding alcohols in a variety of ways, and, under carefully controlled conditions, it is often possible to stop the reduction at the aldehyde (RCHO) stage. 

We can write the mechanism for this reaction rather easily, because its important steps are quite analogous to reactions of other carbonyl-containing compounds (Fig. 17.20). As in the reaction of... 

Aliphatic esters Although the infrared spectra of aliphatic esters allows them to be distinguished from other carbonyl-containing compounds, it is often difficult to differentiate between esters which are similar in chemical structure. It is not sufficient to compare the spectrum of an unknown with that of a reference and thus to conclude, because the spectra are similar, even after careful attention to the positions and relative intensities of bands, that an identification has been positively made. It is often necessary to carry out hydrolysis of the sample and to examine the alcohol and acid fragments separately, or, alternatively, another spectroscopic technique may be used to identify the ester directly. 

III. An example of the interpretation of other carbonyl-containing compounds utilizing the above parameters... 

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