Addition reactions to carbonyl groups

A number of groups have criticized the ideas of Dauben and Noyce, especially the concept of PDC. Kamernitzsky and Akhrem, " in a thorough survey of the stereochemistry of addition reactions to carbonyl groups, accepted the existence of SAC but not of PDC. They point out that the reactions involve low energies of activation (10-13 kcal/mole) and suggest that differences in stereochemistry involve differences in entropies of activation. The effect favoring the equatorial alcohols is attributed to an electrostatic or polar factor (see also ref. 189) which may be determined by a difference in the electrostatic fields on the upper and lower sides of the carbonyl double bond, connected, for example, with the uncompensated dipole moments of the C—H bonds. The way this polar effect is supposed to influence the attack of the hydride is not made clear. 

The balance between anion activation and cation inhibition of addition reactions to carbonyl groups is exemplified by the reaction of acetonitrile anion with benzaldehyde (Scheme 7). When the cation is Li+, addition of [2.1.1]cryptand (15b) markedly decreases the reaction rate suggesting cation inhibition is dominant. When M = K+, addition of [2.2.2]cryptand (15d) increases the rate by, presumably, a predominant anion activation. Finally when M = Na+, the two effects cancel out and the reaction rate is unaffected by [2.2.1]cryptand (15c) addition (80PAC2303,81TL1685). 

Acetalization (see Addition reactions to carbonyl groups, Protection of aldehydes and ketones)... 

Magnesium, 235 Samarium(II) iodide, 270 Titanium(IV) chloride, 304 Addition reactions to carbonyl groups—Addition of functionalized CARBON NUCLEOPHILES (see also Aldol reaction and other specific condensation reactions, Meth-ylenation, Peterson Olefination, Refor-matsky reaction, Wittig reaction, Wittig-Horner reaction)... 

Aluminum chloride, 15 Arenediazonium tetrafluoroborates, 19 Rhodium(II) carboxylates, 266 Tris(dimethylamino)sulfonium difluoro-trimethylsilicate, 336 Asymmetric reactions Addition reactions to carbonyl groups Bis(2,4-dimethyl-3-pentyl) tartrate, 36 (S)-( + )-2-Methoxymethylpyrrolidine, 180... 

The lone pairs may act as nucleophiles in substitution reactions of alkyl halides and sulfonates, in the solvolysis of epoxides, and in addition reactions to carbonyl groups. These reactions often proceed with acid or base catalysis. 

Some selected addition reactions to carbonyl groups are quoted here the list is not exhaustive. 

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