Functional Groups with Double Bonds

For reviews of thiokelones and other compounds with C=S bonds, see Schaumann, in Patai Supplement A The Chemistry of Double-bonded Functional Groups, vol. 2, pt. 2 Wiley New York. 1989. pp. 1269-1367 Ohno. in Oae Organic Chemistry of Sulfur, Plenum New York, 1977. pp. 189-229 Mayer, in Janssen Organosulfur Chemistry Wiley New York, 1967, pp. 219-240 Campaigne, in Palai The Chemistry of the Carbonyl Group, pt. 1 Wiley New York, 1966, pp. 917-959. 

FIGURE 23.1 The reactions of ethylene and menthene with bromine. In both molecules, electrostatic potential maps show similar polarity patterns for the carbon-carbon double bond functional group. Bromine therefore reacts with both in the same way, regardless of the size and complexity of the remainder of the molecule. 

Complex formation involving compounds with double-bonded functional groups... 

The stmctural features that make it possible to classify compoimds into families are called functional groups. A functional group is a group of atoms within a molecule that has a characteristic chemical behavior. Chemically, a given functional group behaves in nearly the same way in every molecule it s a part of. For example, compare ethylene, a plant hormone that causes fmit to ripen, with menthene, a much more complicated molecule found in peppermint oil. Both substances contain a carbon-carbon double-bond functional group, and both therefore react with Br2 in the same way to give a product in which a Br atom... 

A group of flavoenzyme reductases mediate the reduction both nitrate esters and C= C double bonds generally activated with carbonyl or nitro functions. The structures of the substrates vary widely (references in Faber 1997). 

Transition metals can display selectivities for either carbonyls or olefins (Table 20.3). RuCl2(PPh3)3 (24) catalyzes reduction of the C-C double bond function in the presence of a ketone function (Table 20.3, entries 1-3). With this catalyst, reaction rates of the reduction of alkenes are usually higher than for ketones. This is also the case with various iridium catalysts (entries 6-14) and a ruthenium catalyst (entry 15). One of the few transition-metal catalysts that shows good selectivity towards the ketone or aldehyde function is the nickel catalyst (entries 4 and 5). Many other catalysts have never been tested for their selectivity for one particular functional group. 

An alternative method to make PAEs is the acyclic diyne metathesis (ADIMET) shown in Scheme 2. It is the reaction of a dipropynylarene with Mo(CO)6 and 4-chlorophenol or a similarly acidic phenol. The reaction is performed at elevated temperatures (130-150 °C) and works well for almost any hydrocarbon monomer. The reaction mixture probably forms a Schrock-type molybdenum carbyne intermediate as the active catalyst. Table 5 shows PAEs that have been prepared utilizing ADIMET with these in situ catalysts . Functional groups (with the exception of double bonds) are not well tolerated, but dialkyl PPEs are obtained with a high degree of polymerization. The progress in this field has been documented in several reviews (Table 1, entries 2-4). Recently, a second generation of ADIMET catalyst has been developed that allows... 

Hyperbranched polymers (see structure LXII in Sec. 2-16a) are produced from monomers that contain both a polymerizable double bond and an initiating function, such as p-(chloro-methyl)styrene. The product is highly branched with one double bond end group and many... 

The potential for direct toxicity, as manifested by acylating or alkylating groups, or by double bonds in conjunction with a carbonyl function that will thereby act as Michael acceptors, is easily recognized. 

Conjugate addition of hydride. The reagent will not react with isolated double bonds, carbonyl groups. Many functional groups resistant to reaction. 

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