Cyclic addition

The cyanohydrin of methyl perfluoroheptyl ketone was synthesized by a two-step process addition of sodium bisulfite and subsequent treatment with sodium cyanide. When the ketone was reacted with sodium cyanide, cyclic addition products were obtained, instead of the product of cyanohydrin formation. This result was attributed to the solubility characteristic of a long perfluoroalkyl group, which makes the compound less soluble in water and polar organic solvents [54] (equation 40) (Table 14). 

In the reaction of benzonitrile oxide (1,3-dipolar addition) with AyV -thiocarbonyldi-1,2,4-triazole the cyclic addition product has been isolated in 87% yield -170- ... 

Figure 12.10 The imidazole reaction between glyoxal and arginine creates cyclic addition compounds lacking positive charge.

It has been reported by R.Scheiner that phenylazide forms triazoline compounds by 1,3-cyclic addition to unsaturated olefines such as n-butylethylene and norbornen(9 ). These triazolines are decomposed photochemically or thermally to give imine compounds and aziridine as is shown in scheme 1. These facts suggest that phenylazide may react with 3-methyl-1-butene to give triazoline in a similar reaction to that with norbomen. 

A vast range of natural sugars exempMly these cyclic addition products. A typical sugar exists predominantly in the form of a hemiacetal or hemiketal in solution, although this is an equilibrium reaction, and the open chain carbonyl form is always present to a small extent (<1%). The formation of a six-membered cyclic hemiacetal from glucose is achieved by attack of the C-5 hydroxyl onto the protonated carbonyl (conjugate acid). 

R values were calculated from elemental analysis for carbon, hydrogen, and chlorine. It can be seen again that temperature has a very marked effect on composition. Even at 100°, however, about 16 mol% sulfur dioxide is present. There was also produced a small quantity (1 to 10% of the amount of copolymer) of the cyclic addition product, 3-chloro-2,5-dihydrothiophene-l,1-dioxide, m.p. 99-100°. 

Various alkyl-substituted crown ethers have been prepared by cyclic addition across a double bond (e.g. bromination (77S854) or oxymercuration (80CC925)). Similarly, displacement of oligoethylene glycol dichlorides by cyanamide yields V-cyano monoaza crown ethers (81TL4105). 

In the reaction of ethylene with sulfuric acid, several side reactions can lead to yield losses. These involve oxidation, hydrolysis—dehydration, and polymerization, especially at sulfuric acid concentrations >98 wt % the sulfur trioxide can oxidize by cyclic addition processes (99). 

Ring Formation by Organic Cyclic Addition Reactions 889... 

Cyclic addition reactions of 16a with diynes or cyanamide are interpreted as being initiated by an electrophilic attack of the cyanamide or the terminal carbon atom of a C=C bond. Both result in ring expansion and the formation of 2,4-As,As-diphosphapyridine 39 <1998ZNB443> or l,3-A5,A5-diphosphabenzenes 40, respectively (Scheme 10). The diyne reaction is not limited to conjugated systems. 1,5-Hexadiyne and 1,7-octadiyne can be used as well <1997JOM(529)223>. 

During the manufacturing process of styrene-butadiene rubber the polymerisation is stopped at a conversion rate of less than 90%. The residual monomers styrene and butadiene are removed by distillation. The odour-in-tensive compounds 4-phenylcyclohexene (from styrene and cis-butadiene) and 4-vinyl cyclohexene (from cis-butadiene and trans-butadiene) can be formed from the remaining monomers under the conditions of a thermally permitted Ti2s-t- 4s Diels-Alder cyclic addition. During indoor air measurements, carried out in six different office rooms in each case 3 days after new carpets had been laid, concentrations of 4-phenylcyclohexene of 29-45 pg m could be ascertained. It is suspected that the emission of the trimer of 2-methyl-l-propene from a glued carpet is also caused by chemical reaction. 

The cyclic addition of sulphonyl isocyanates to S4N4 has been shown. The monoaddition product (27) is formed without exception and is explained by... 

The Diels-Alder reaction is an addition reaction involving an alkene and a diene. Let s look at a representative Diels-Alder reaction involving 1,3-butadiene and an alkene (dienophile means diene-lover). The reaction involves a cyclic transition state. The product is usually a cyclic addition product. Study the representative reaction given below. Pay close attention to how the new bonds are formed in relation to the reactants. 

In all these cases is reported the importance of the end-chain on the superficial migration of the additive. On the contrary, diffusion of cyclic polymers having no chain ends would be of great interest in the study of polymer surface segregation. In 2006, Tanaka compared time evolution of isotopic interfaces in two bilayers films, one made of cyclic polystyrene (c-hPS/c-dPS) and the linear counterpart (1-ZiPS/l-dPS) [76]. He showed that interdiffusion of the cyclic macromolecules was faster than the linear polymers one. Therefore, it would be very interesting to examine the surface segregation behavior of a binary film composed of a cyclic additive in a linear matrix. 

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