With carbonyl group ionic

The substrate itself also activates the reagent 4. Alkoxy group at a-position of ketone will form a chelate intermediate that activates the f)is(iodozindo)methane to react with carbonyl group of ketone. Such substrates with 4 undergo methylenation in the absence of any additive. As shown in Scheme 8.15, a substrate that has a-benzyloxyketone and simple ketone groups in the same molecule can be converted into the chemoselective methylenated product. In the methylenation reaction, activations of bis(iodozindo)methane (4) have been done with titanium salt, a-alkoxy group of ketone, THT, or ionic liquid. This means that the readivity of 4 can be tuned to perform a seledive methylenation. In Scheme 8.16, a keto alkanal and a keto ester were examined for the chemoseledive methylenation [18,23,27]. 

It might be noted that most (not all) alkenes are polymerizable by the chain mechanism involving free-radical intermediates, whereas the carbonyl group is generally not polymerized by the free-radical mechanism. Carbonyl groups and some carbon-carbon double bonds are polymerized by ionic mechanisms. Monomers display far more specificity where the ionic mechanism is involved than with the free-radical mechanism. For example, acrylamide will polymerize through an anionic intermediate but not a cationic one, A -vinyl pyrrolidones by cationic but not anionic intermediates, and halogenated olefins by neither ionic species. In all of these cases free-radical polymerization is possible. 

These cements set in 3-5 to 56 minutes (at 37 °C). Infrared spectroscopy showed that as the cement set there was loss of acid carbonyl groups and OH groups associated with calcium hydroxide, and simultaneously formation of ionic carboxylate groups and hydrogen-bonded OH groups. 

At the first step, the insertion of MMA to the lanthanide-alkyl bond gave the enolate complex. The Michael addition of MMA to the enolate complex via the 8-membered transition state results in stereoselective C-C bond formation, giving a new chelating enolate complex with two MMA units one of them is enolate and the other is coordinated to Sm via its carbonyl group. The successive insertion of MMA afforded a syndiotactic polymer. The activity of the polymerization increased with an increase in the ionic radius of the metal (Sm > Y > Yb > Lu). Furthermore, these complexes become precursors for the block co-polymerization of ethylene with polar monomers such as MMA and lactones [215, 217]. 

These reactions have an analogy in the Sn2 reactions of a-haloketones such as phenacyl bromides.175 The rate-enhancing effect of x-carbonyl groups on SN2 processes at carbon is well known, and has been attributed to conjugation of the p-orbital on carbon in the SN2 transition state with the carbonyl re-bond,164 175 177 stabilisation of ionic character at the central carbon as outlined by Pross,164,178 as well as electrostatic attraction to the carbonyl carbon.176 Although there... 

Hydroxy- and 4-hydroxypyridines are in tautomeric equilibrium with isomers bearing a carbonyl group (Scheme 2.22). These are called 2- and 4-pyridones, respectively. The pyridone forms are favoured in ionic solvents and also in the solid state. 

Even though radicals can be nucleophilic or electrophilic, the chemistry of radicals is not naturally intertwined with the carbonyl group and related functionalites in the same way that the chemistry of ionic reactions is. This notation does not now account for the frequent need for radicals and alkenes to be electronically paired for a successful reaction. This is in part because I could not envision a simple, unambiguous notation device and more importantly because such a device could be artificial and misleading in the realm of radical cyclizations where arrangement of the double bond and the radical site in the molecule is often much more important than any electronic pairing. 

---