Aldehydes and Ketones The Carbonyl Group

Congratulations You have finally gotten to the first of several chapters that examine the chemistry of carbonyl compounds the most important ones in organic chemistry. Why are they so important They are extremely versatile in carbon-carbon bond formation, and, therefore, synthesis. Carbonyl compounds contain an electrophilic carbonyl carbon (which you already know about from Chapter 8) as well as a potentially nucleophilic carbon next to it (which you will learn about shortly). This double-barreled functional capability is unique among the simple compound classes. 

The importance of carbonyl compounds extends to biological chemistry as well, where the carbonyl group plays a central role in biochemical synthesis of naturally occurring molecules. 

Most of the material in these sections is of a relatively routine nature, so only a few points of special interest, or with special implications, will be mentioned. 

Nomenclature of carbonyl compounds presents a bit of a problem in that several alternative names may be possible for almost any compound. 

The number of methods that exist to synthesize carbonyl compounds is impressive to the point of being intimidating. But don t be put off by this situation. Each reaction is presented in an appropriate, logical context. This section mainly reiterates carbonyl syntheses that you ve seen before, perhaps just with a few new examples to help reinforce those original presentations. 

After explaining how to name aldehydes and ketones, we look at their structures and physical properties. Like alcohols, the carbonyl group possesses an oxygen atom with two lone pairs, a structural feature that enables it to function as a weak Lewis base. Moreover, the carbon-oxygen double bond is also highly polarized, making the carbonyl carbon quite electrophilic. In the remainder of this chapter, we show how these properties shape the chemistry of this versatile functional group. 

The biochemistry of the reproductive process inciudes a mechanism by which sperm are seiected for fertiiization by their ability to smell a nearby egg. The aldehyde bourgeonal, shown here, activates this ability, whereas the straight-chain 11-carbon aldehyde, undecanal, shuts it down. 

The photo shows the process of conception, magnified 3,500 times. 

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Carboxylic acids contain a carbonyl group, but it does not undergo the type of addition reactions that occur with the aldehydes and ketones. The carbonyl group in carboxylic acids, esters, amides or acyl chlorides has the electronegative atoms O, N or Cl next to the C=0, and these stop it from acting as a proper C=0 group should (Figure 7.2.15). 

Here, too, as in aldehydes and ketones, the carbonyl group performs two functions (a) it provides a site for nucleophilic attack, and (b) it increases the acidity of hydrogens attached to the alpha carbon. 

Aldehydes and Ketones The Carbonyl Group Solutions to Problems... 

For conjugated aldehydes and ketones the carbonyl group is also partly reduced. Isolated double bonds are unreactive. 

Geminal Difluorination of Aldehydes and Ketones. The carbonyl group of aldehydes and ketones can be converted to a... 

Aldehydes and ketones The carbonyl group has a carbon atom attached by a double bond to an oxygen atom. If one of the two substituents attached to the carbonyl group is an H atom, the compound is an aldehyde, otherwise it is a ketone. In lUPAC nomenclature, the suffix -al is used for aldehydes and -one for ketones. 

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