Substituents unsaturated groups

C—H bonds are polarized by attached unsaturated carbon substituents. Such groups "activate" the neighbouring CHj, CHp or CH groups in the following order CR=NR > COR > CN > COOR > CR = NR > Ph > CR=CRj. Two activating substituents reinforce each other. 

Nitro and Other Electron-Withdrawing Substituent. The presence of unsaturated groups such as nitro at conjugative positions should cause strong resonance interaction in the transition state since a nucleophilic reagent is electron-repelling (structures 48-50). At positions of the... 

The Curtius rearrangement is a useful method for the preparation of isocyanates as well as of products derived thereof. The substituent R can be alkyl, cycloalkyl, aryl, a heterocyclic or unsaturated group most functional groups do not interfere. 

Some polarographic work has been performed on sulphones in which, evidently, other functional groups suffered reduction. Thus the vinyl group rather than the sulphone group of methyl vinyl sulphone was reduced polarographically -. The unsaturated group of a, -unsaturated sulphones was also reduced . Halogen substituents have been... 

Unsaturated groups are very interesting for application development because this specific functionality opens up a broad range of possibilities for further (chemical) modification of the polymer structure, and therefore its physical and material properties. The direct microbial incorporation of other functional substituents to the polymer side chains, e.g. epoxy-, hydroxy-, aromatic-, and halogen functional groups, influences the physical and material properties of poly(HAMCL) even further [28,33,35,39-41]. This features many possibilities to produce tailor-made polymers, depending on the essential material properties that are needed for the development of a specific application. 

Unsaturated groups, known as chromophores, are responsible for — tz, and k — 7t absorption mainly in the near UV and visible regions and are of most value for diagnostic purposes and for quantitative analysis. The mx and e values for some typical chromophores are given in Table 9.2. The positions and intensities of the absorption bands are sensitive to substituents close to the chromophore, to conjugation with other chromophores, and to solvent effects. Saturated groups containing heteroatoms which modify the absorption due to a chromophore are called auxochromes and include -OH, -Cl, -OR and -NRr... 

Points of similarity as a function of M in compounds of the types R3MR, R3MX and R3MCH2Rff (R = organic substituent M = Ge, Sn, Pb Rjr = aromatic or a,fi-unsaturated group X = halogen, N<, O—, S— or other atoms having at least one unshared electron pair) are ... 

On the contrary, the arrangement is dominated by electronic effects because of 7r-7r-interactions between the axial 0-Al and the substituents of the ketone. Repulsive interactions that occur with r-systems of unsaturated groups such as phenyl, alkenyl or alkynyl make these groups large... 

This section discusses cycloaddition reactions involving unsaturated bonds (C = C, C = X, C = C) substituted with a trifluoromethyl group or another fluoroalkyl substituent. Unsaturated bonds directly substituted with fluorine atoms are not included. 

The main locoselective features of hydroalumination, which are discussed in some detail in Section 3.11.2.3 are (i) (DsC bonds are attacked in preference to (D=C bonds (ii) terminal HC C and H2C=CH groups are hydroaluminated much more rapidly than internal C C and CH=CH linkages and (iii) electron-releasing substituents on the carbon-carbon unsaturated group increase the rate of hydroalumination (Table 4). Illustrative are the relative initial rates for PhC 3isCE with E = Ph, Me, H,... 

Phosgene is a suitable reagent for converting secondary amides and N-unsubstituted lac-tams to imide chlorides, e.g. (195) and (196) (Scheme 27). The substituents at nitrogen might be saturated aliphatic or aromatic groups, but even unsaturated groups seem to be possible. The reaction,... 

Cardanol, the main component obtained by thermal treatment of cashew nut shell liquid (CNSL), is a phenol derivative having the meta substituent of a C15 unsaturated hydrocarbon chain with one to three double bonds as the major component. The SBP-catalyzed polymerization of cardanol in aqueous acetone produced the oily soluble polymer with Mn of several thousands.38 The carbon—carbon unsaturated group in the side chain of cardanol did not change during the polymerization. The curing by... 

In Section 1.2 we noted that the bonding in CH5+ could be described in terms of three 2c-2e C-H bonds and one 3c-2e C—H—H bond. In Section 1.3 we noted that 3c-2e C—H—M bonds could account for agostic interactions between coordinatively unsaturated metal atoms and substituent alkyl groups, and indeed for metal-alkane a complexes. Similarly, 3c-2e M—C—M bonds... 

Several examples have appeared of diversion of the normal photochemistry of ortho-alkyl aromatic ketones due to apparent interception of the intermediate biradical by an unsaturated group present elsewhere in the molecule.Thus the vinyl aryl ketones (376) are converted to (377) in reasonable yields upon irradiation with ultra-violet light,while irradiation of the ortho-alkynyl acetophenone (378) in methanol yields diastereomers of (379)The latter reaction is thought to proceed by coupling of the initially formed ketyl radical onto the alkyne to give a carbene (380). The photochemistry of the jS-diketone (381) gives a mixture of the benzocyclobutenol (382) and the tetralone (383), and the proportions depend on the identity of the R-substituent in (381). The formation of (383) can be rationalised in terms of interception of the ketyl radical in the initially formed 1,4-biradical by the remote carbonyl group. 

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