Activated vinyl group

Cellulose Ethers. Cellulose ethers are formed when cellulose, in the presence of alkali or as alkali cellulose, is treated with alkyl or arylalkyl halides. Two types of reaction are employed in the preparation of cellulose ethers. The most common is nucleophilic substitution. Methylation of alkali cellulose with a methyl halide is an example of this type. The other type of etherification reaction is Michael addition. This reaction proceeds by way of an alkali-catalyzed addition of an activated vinyl group to the cellulose. The reaction of acrylonitrile with alkali cellulose is a typical example. The general reaction is outlined in Scheme 4. 

One of the important methods for annulating a pyridine ring to a pyrimidine nucleus is the reaction of pyrimidin-4-amines with a three-carbon unit having reactive centers at positions 1 and 3. These units in most cases have oxo or related functions, such as esters, nitriles, or activated vinyl groups. 

Difunctional reagents containing two active vinyl groups are capable of reacting with reduced keratin hbers and forming cross-links. Divinyl sulfone has been used for this purpose [91],... 

Non-autoxidative polymerization includes UV curing or thermally induced curing with the use of free-radical initiators, such as benzoyl peroxide or potassium persulfate. Similar to autoxidation, both bulk and surface curing may occur. Surfactants based on activated vinyl groups, such as acrylate and methacrylate esters, are typical examples of this class. Some examples of... 

A final mechanism worth noting is the reverse Michael reaction, in which an activated vinyl group is added to the polysaccharide through a 0-(2-cyanoethyl) derivative [Figure 4] (5). While other etherification reaction mechanisms have been investigated, they have limited qtplication. 

Fig. 5. Mechanism of activity of microbicides with an activated vinyl group.

There are two toxophoric groups in the acrolein molecule, the activated vinyl group and the aldehyde group both groups are able to react with nucleophilic cell entities. Due to this fact acrolein is highly reactive and highly effective and may be defined as a biocide rather than a microbicide. 

Figure 8 Mode of action of mierobieides bearing an activated vinyl group.

Constmction of multilayers requires that the monolayer surface be modified to a hydroxylated one. Such surfaces can be prepared by a chemical reaction and the conversion of a nonpolar terminal group to a hydroxyl group. Examples of such reactions are the LiAlH reduction of a surface ester group (165), the hydroboration—oxidation of a terminal vinyl group (127,163), and the conversion of a surface bromide using silver chemistry (200). Once a subsequent monolayer is adsorbed on the "activated" monolayer, multilayer films may be built by repetition of this process (Fig. 8). 

The close structural similarities between polychloroprene and the natural rubber molecule will be noted. However, whilst the methyl group activates the double bond in the polyisoprene molecule the chlorine atom has the opposite effect in polychloroprene. Thus the polymer is less liable to oxygen and ozone attack. At the same time the a-methylene groups are also deactivated so that accelerated sulphur vulcanisation is not a feasible proposition and alternative curing systems, often involving the pendant vinyl groups arising from 1,2-polymerisation modes, are necessary. 

Graft Copolymerization of Vinyl Monomers Onto Macromolecules Having Active Pendant Group via Ceric Ion Redox or Photo-Induced Charge-Transfer Initiation... 

For the construction of the I ring, the vinylic group introduced to activate the y-hydroxy epoxide moiety of 28 towards cyclization is an acrylic ester residue, which concomitantly allows cyclization on the allylic position, with formation of the tricyclic compound 29 containing the IJK fragment of the natural product, and fur-... 

Since the double bonds in the macromolecules of the copolymer have a much lower activity than that of the vinyl groups in the ISP molecule, crosslinkage occurs in this case at later stages of reaction, i.e., when the monomer conversion exceeds 50%. 

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