OLEFIN GROUP

PPha, pyridine) organic groups (olefines, aromatic derivatives) and also form other derivatives, e.g. halides, hydrides, sulphides, metal cluster compounds Compounds containing clusters of metal atoms linked together by covalent (or co-ordinate) bands, metaldehyde, (C2H40) ( = 4 or 6). A solid crystalline substance, sublimes without melting at I12 1I5" C stable when pure it is readily formed when elhanal is left in the presence of a catalyst at low temperatures, but has unpredictable stability and will revert to the monomer, ft is used for slug control and as a fuel. 

When sp hybridised carbon atoms (carbonyl groups, olefinic fragments, aromatic rings) are present in an aliphatic carbon chain they cause a downfield shift of 1-2 ppm when present at They have less than half of this effect when present at Cp... 

Since the discovery of ruthenium and molybdenum carbene complexes that efficiently catalyze olefin metathesis under mild reaction conditions and that are compatible with a broad range of functional groups, olefin metathesis has increasingly been used for the preparation of alkenes on insoluble supports. In particular, the ruthenium complexes Cl2(PCy3)2Ru=CHR, developed by Grubbs, show sufficient catalytic activity even in the presence of air and water [781] and are well suited for solid-phase synthesis. 

For molecular properties of the TAG polymorphs, local molecular structural information such as methyl-end group, olefinic conformation, and chain-chain interaction are unveiled by infrared (IR) spectroscopy, especially Fourier-transformed infrared spectroscopy (FT-IR) (23, 24). Compared with a pioneering work by Chapman (25), great progress has been achieved by using various FT-IR techniques, such as polarized transmission FT-IR, reflection absorption spectroscopy (RAS), and attenuated total reflection (ATR) (26-28). 

In the case of a cis-alkyl group, olefin coordination from the side of the carbon atom is energetically favored (reaction (27)). Ethylene adsorption from the side of the atom (reactions (28), (29)) requires a higher activation energy. The... 

While conventional metathesis catalysts are ineffective for the metathesis of olefins with primary or tertiary amino groups, olefins with quarternary ammonia groups are converted to a,co-bifunctional olefins. ... 

Compounds containing Ad and 5d electron elements are generally more stable than those of 3d electron metals. The former compounds are characterized by greater thermal stability and by greater resistance to water and oxidizing agents. Many platinum group olefin complexes are air stable in the presence of water. This is a result of the character of the metal-olefin bond. 

Manganese group olefin compounds have electronic configuration (Table 6.14). Cationic complexes such as [Mn(CO)5 (olefin)] are not formed from the unstable Mn(CO)g but from the chlorocarbonyl compound Mn(CO)5Cl and olefin in the presence of AICI3, or by protonation reaction of <7-allyl compounds ... 

The addition of diazoethane to benzylidenemalonic esters and a-cyano-acrylic esters gives 5-methyl-l-pyrazoIines (90), " Pyrolysis of these compounds is similar to that of the derivatives without a 5-methyl group, olefin formation occurring with migration of a 4-substituent to the 5-position. 

These compounds show a strong relationship to all kinds of olefins and also to carbonyl groups. Olefins are in the vast majority of cases the precursors for epoxides, while on the other hand these three-membered cyclic ethers are at the oxidation level of aldehydes or ketones and can easily undergo rearrangements leading to these carbonyl compounds. 

The NMR spectrum of a polystyrene macromonomer, 19, prepared by chain transfer with allylic sulfide 17, is shown in Figure 4. The end group olefinic protons appear at 6 -5.1 and 4.7 ppm and the t-butyl end group at 6 -1.2 ppm. (The sharp signals at 5 2.0 and 2.2 ppm are due to ds-acetone and water respectively, present in the solvent). 

---