Substituted phenyl groups

For aldehydes with one or more phenyl groups substituted on the a-carbon the scheme (29) is complicated by carbanion formation (31) ... 

The nitration of 27 using nitric acid in acetic anhydride at -5°C gives the 4-nitropyrazole (39%) without phenyl group substitution. This product can be nitrated further to 3-methyl-4-nitro-5-(3-nitrophenyl)-1-phenylpyrazole (7%) and 3-methyl-4-nitro-5-(3-nitrophenyl)-l-(4-nitro-phenyDpyrazole (50%) using nitric acid sulfuric acid (Fig. 7). 

Show the intermediate that would result if the growing chain added to the other end of the styrene double bond. Explain why the final polymer has phenyl groups substituted on alternate carbon atoms rather than randomly distributed. 

The analysis of the effect that the different substituents may have on the rate coefficients in this case is particularly hard to perform by using simple inductive effects, as described for instance by the Hammett substituent constants. Note that, despite the fact that most of the 28 carbenium ions exhibit para substitution, the general structure on top of Chart 6, shows a complex substitution pattern at the carbocation centre. In order to asses the effect of multiple substitution at this site, we first considered those compounds that have two fixed hydrogen atoms at the -position of the phenyl group, which according to Hammett classification have crp(H) = 0.0, and the third phenyl group substituted at -position with H (compound 96 in Chart 6) OCH3 (compound 97 in... 

Coulson free valences (F) (see Table III) calculated from the Hiickel model indicate that, when there are phenyl groups substituted at positions 1 and 4 and methyl groups at positions 5 and 7, electrophilic substitution will take place at the ortho and para positions of the phenyl groups as well as at position 6 of the dihydrodiazepinium ring.34 Similar results are suggested for 5,7-phenyl-disubstituted dihydrodiazepinium salts, with substitution occurring preferentially at position 6. Bromination and nitration of the 5,7-dimethyl-l, 4-diphenyldihydrodiazepinium cation does indeed take place at the predicted sites. Bromination of 5,7-di-... 

Wood, M.G. Pastor, S.D. Lau, J. DiFazio, M. Suhadoolnik, J. Benzotriazoles containing phenyl groups substituted by heteroatoms and compositions stabilized therewith, U.S. Patent... 

The A -aryl oxazolidinone-bearing ketone catalysts 5 are readily prepared in large quantities from glucose and inexpensive anilines in four steps. Phenyl groups substituted with methylsulfonyl (5a) or alkyls (5b, 5c) consistently provide high enantioselectivity for a variety of cw-olefms and certain terminal olefins. cw-P-Methylstyrenes can be epoxidized with... 

A phosphine-Schiff base ligand (17) has been used for copper-catalysed asymmetric conjugate addition of diethylzinc to various ( )-alkenyl aryl ketones where the aryl ring is either a phenyl group substituted by nitro, chloro, or methoxy groups or not substituted or a naphthyl group. When the conjugate addition has been performed in ethyl acetate... 

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