Vinylic carbon, and

The term allylic refers to a C=C—C unit The singly bonded carbon is called the allylic carbon, and an allylic substituent is one that is attached to an allylic carbon Conversely doubly bonded carbons are called vinylic carbons, and substituents attached to either one of them are referred to as vinylic substituents... 

Coordination of vinylarenes to an Fe(CO)3 group gives rise to a complex (95) in which the metal is bound to the vinyl carbons and two of the carbons within the six-membered ring (equation ll)107. Crystal structure analysis indicates substantial bond localization in the uncomplexed portion of the ring. This has been interpreted as a loss of aromatic character due to participation of some of the 7r-electrons in coordination to iron. 

The sp carbon of an alkene is called vinylic carbon, and an sp carbon that is adjacent to a vinybc carbon is called an allylic carbon. The two... 

When halogen atoms are attached to a vinylic carbon and also to one allylic to it, an SN2 process converts the vinylic halogen into an allylic one, while the formerly allylic one is replaced, and a new olefin is formed. Another SK2 attack at the new terminal vinylic carbon would result in the replacement of the original vinylic halogen. The vinylic halide can thus be exchanged in two consecutive SN2 reactions. 

In solution, propargyl cations may in principle be generated by electrophilic addition to vinylacetylenes (equation 34). However, by all the evidence, the electrophilic attack by protons occurs more readily at the terminal acetylenic carbon than at the terminal vinyl carbon, and cation 176 is generated instead (de la Mare and Bolton, 1966). 

In spite of numerous failures to prepare vinyl chlorofor-mate and Isopropenyl chloroformate by direct phosgenatlon of either acetaldehyde or acetone, we accepted the challenge to find economical routes to vinylic chloroformates and their derivatives, vinylic carbonates and carbamates. 

Alkenyl chloroformates, especially vinyl and isopropenyl chloroformates, as well as vinylic carbonates and carbamates have found number of valuable applications in various fields. 

Polymerization and copolymerization of vinyl chloroformate (Ref. 133, 134, 135), vinyl carbonates and carbamates (135, 136) using standard radical initiators (e.g. per-oxydicarbonates) to yield high molecular weight polymers and random copolymers is well documented. More recently,... 

Vinyl carbonates and carbamates containing chromophore groups have been prepared and claimed as useful polymerisable photoinitiators for photoreticulable polymers (Ref. 147). 

Polymers and copolymers of vinylic carbonates and carbamates may find interesting applications as aroma and flavours releasing agents. For example, isopropenyl menthyl carbonate has been patented (Ref. 148) as an useful monomer for the manufacture of a smoking composition comprising an admixture of tobacco and a menthol-release agent. Recently, Harwood et. al (Ref. 149) have published a new preparation of enol carbonates including especially isopropenyl menthyl carbonate by selective O-acylation of ketones sodium... 

The materials obtained from polymerization of vinyl carbonates and carbamates are hard (but not brittle) clear thermoplastics with high decomposition temperatures, excellent chemical resistance and varying glass transition temperatures. 

Besides the synthesis of vinylic carbonates and carbamates, Olofson and coworkers reported a simple synthesis of 1-(1,3- butadienyl)carbonates and carbamates (Ref. 162). 

The CNMR confirms the structure two vinyl carbons and a carbonyl. 

The chemical shifts of the carbons in vinyl groups have been reported to be mainly controlled by the 7r-electron density,356-358 and, therefore, it is expected that the chemical shifts for vinyl carbons and the e value can be correlated by a linear relationship. This was demonstrated by Hatada and co-workers.359 The linear relationships clearly indicate that the chemical shift of /3-carbon (SC/3) shifts to a lower field and the shift of a-carbon (SCa) to higher field as the e value of the monomer becomes larger the 7r-electron density of the /3-carbon decreases and that of the a-carbon increases when the e value of the monomer increases. So the results are considered to be convincing proof for the validity of the e value as a measure of polarity. 

The carbonyl group appears to withdraw electrons from the adjacent vinyl carbons and therefore increase the dissociation energy of the Cd—bond. The methyl C—H bond strength in acetaldehyde, CH3CH=0 to CH2 CH=0 + H of 96.4 kcal mol [115] shows resonance stabilization of the methyl radical with the carbonyl of ca. 4.5 kcal-mof relative to the 101 value of ethane. 

Similarly, Fischer carbene complexes are formed when Grubbs systems react with vinyl esters, vinyl carbonates, and vinyl halides. However, these Fischer car-benes are known to decompose to give terminal ruthenium carbide species by elimination of HX (X = OjCR, OjCOR, halide) [83-86]. Notably, the formation of the carbide complexes is less favorable in phosphine-free systems, which enables the Hoveyda [56] and Piers [87] catalysts to promote the cross metathesis of vinyl hahdes and terminal or internal olefins [88]. 

The structure of one derivative 12 (R = Ph, = Me) was proven by an X-ray crystal structure analysis. A picture is shown in Figure 4.1. In this structure, it is interesting to note that both gold-carbon distances, that is, the one to the vinyl carbon and the one to the carbon atom of the NHC, are almost identical. 

Solution to 23a The reaction takes place hy an 8 2 pathway because neither alkyl group will form a relatively stable carbocation (one would be vinylic and the other primary). Iodide ion attacks the carbon of the ethyl group because otherwise it would have to attack a vinylic carbon, and vinylic carbons are not attacked by nucleophiles (Section 9.5). Thus, the major products are ethyl iodide and an enol that immediately rearranges to an aldehyde (Section 7.7). 

We have attempted the copolymerization of 1-menthyl vinylether ([a] d = -61.5°) with various monomers (styrene, phenylmaleimide, maleic anhydride, dime thy Imaleic ester, dimethylpimalic ester, vinyl-carbonate, and indene) and submitted them to hydrolysis by HBr in order to verify the asymmetry introducing reaction in these radical copolymerizations [15]. The optical rotation, ORD and CD were measured before and after eliminating the active menthyl group by hydrolysis. The results are shown in Table I. All copolymers, with the exception of those containing styrene, showed optical rotation before and after hydrolysis We believe that the introduction of asymmetry to the main chain is demonstrated by our results. 

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