ORGANIC CHEMISTRY - CHAPTER 17: ALDEHYDES AND KETONES

New Reaction

Important Concepts

1. The carbonyl group is the functional group of the aldehydes (alkanals) and ketones (alkanones). It has precedence over the hydroxy, alkenyl, and alkynyl groups in the naming of molecules.

2. The carbon – oxygen double bond and its two attached nuclei in aldehydes and ketones form a plane. The C=O unit is polarized,with a partial negative charge on oxygen and a partial positive charge on carbon.

3. The ¹H NMR spectra of aldehydes exhibit a peak at δ ≈ 9.8 ppm. In ¹³C NMR, the carbonyl carbon absorbs at ~200 ppm. Aldehydes and ketones have strong infrared bands in the region 1690 – 1750 cm^-1; this absorption is due to the stretching of the C=O bond. Because of the avail-ability of low-energy n → π* transitions, the electronic spectra of aldehydes and ketones have relatively long wavelength bands. This class of compounds displays characteristic mass spectral fragmentations around the carbonyl function.

4. The carbon – oxygen double bond undergoes ionic additions.The catalysts for these processes are acids and bases.

5. The reactivity of the carbonyl group increases with increasing electrophilic character of the carbonyl carbon. Therefore, aldehydes are more reactive than ketones.

6. Primary amines undergo condensation reactions with aldehydes and ketones to imines; secondary amines condense to enamines.

7. The combination of Friedel-Crafts acylation and Wolff-Kishner or Clemmensen reduction allows synthesis of alkylbenzenes free of the limitations of Friedel-Crafts alkylation.

8. The Wittig reaction is an important carbon – carbon bond-forming reaction that produces alkenes directly from aldehydes and ketones.

9. The reaction of peroxycarboxylic acids with the carbonyl group of ketones produces esters.

From "Organic Chemistry" Textbook of VOLLHARDT & SCHORE