Benzene, alkylation iodination

A series of methyl derivatives of benzene has been studied by the method of spectral analysis in the UV region. The position of an absorption band for n-o-complexes of alkyl-benzenes with iodine as an electron acceptor has been determined. A series of increase of donor force of benzene methyl derivatives have been derived [34]... 

The dipole moment varies according to the solvent it is ca 5.14 x 10 ° Cm (ca 1.55 D) when pure and ca 6.0 x 10 ° Cm (ca 1.8 D) in a nonpolar solvent, such as benzene or cyclohexane (14,15). In solvents to which it can hydrogen bond, the dipole moment may be much higher. The dipole is directed toward the ring from a positive nitrogen atom, whereas the saturated nonaromatic analogue pyrroHdine [123-75-1] has a dipole moment of 5.24 X 10 ° C-m (1.57 D) and is oppositely directed. Pyrrole and its alkyl derivatives are TT-electron rich and form colored charge-transfer complexes with acceptor molecules, eg, iodine and tetracyanoethylene (16). 

Cyanide and thiocyanate anions in aqueous solution can be determined as cyanogen bromide after reaction with bromine [686]. The thiocyanate anion can be quantitatively determined in the presence of cyanide by adding an excess of formaldehyde solution to the sample, which converts the cyanide ion to the unreactive cyanohydrin. The detection limits for the cyanide and thiocyanate anions were less than 0.01 ppm with an electron-capture detector. Iodine in acid solution reacts with acetone to form monoiodoacetone, which can be detected at high sensitivity with an electron-capture detector [687]. The reaction is specific for iodine, iodide being determined after oxidation with iodate. The nitrate anion can be determined in aqueous solution after conversion to nitrobenzene by reaction with benzene in the presence of sulfuric acid [688,689]. The detection limit for the nitrate anion was less than 0.1 ppm. The nitrite anion can be determined after oxidation to nitrate with potassium permanganate. Nitrite can be determined directly by alkylation with an alkaline solution of pentafluorobenzyl bromide [690]. The yield of derivative was about 80t.with a detection limit of 0.46 ng in 0.1 ml of aqueous sample. Pentafluorobenzyl p-toluenesulfonate has been used to derivatize carboxylate and phenolate anions and to simultaneously derivatize bromide, iodide, cyanide, thiocyanate, nitrite, nitrate and sulfide in a two-phase system using tetrapentylammonium cWoride as a phase transfer catalyst [691]. Detection limits wer Hi the ppm range. 

Chlorine heptoxide is more stable than either chlorine monoxide or chlorine dioxide however, the CI2O7 detonates when heated or subjected to shock. It melts at —9l.5°C, boils at 80 0, has a molecular weight of 182 914. Tt is soluble in benzene, slowly attacking the solvent with water to form perchloric acid it also reacts with iodine to form iodine pentoxide and explodes on contact with a flame or by percussion, Reaction with olefins yields the impact-sensitive alkyl perchlorates. 

When the magnesium alkyl compound does not form readily, i. e. in using aryl halides, a crystal of iodine is often added to start the reaction. Other solvents than ether have been used, i. e. anisole, phenyl amyl ether, and dimethyl-aniline. The solvent apparently combines with the compound MgRX forming intermediate products R20.MgRX and R3N.MgRX, and acts as a catalyst, since it has been found that the reactions proceed in benzene or xylene provided a small amount of ether or dimethyl-aniline be added. 

I2 is a very weak electrophile. It is just reactive enough to attack the para position of aniline. Phenol ethers are attacked by iodine only in the presence of silver(I) salts (—> Agl + I3 ). Benzene and alkyl benzenes react with I2 only when the iodine is activated still more strongly by oxidation with iodic or nitric acid. 

Saccharin 218 is obtained by KMn04 oxidation of o-methylbenzenesulfonamide 217 (Scheme 126). Various V-alkylsaccharins 219 (n = 2) and A-alkyl-l,2-benzisothiazolin-3-one A-oxides 219 (n= 1) are conveniently prepared in moderate to good yields by the reaction of A-alkyl(0-methylarene)sulfonamides with (diacetoxyiodo)benzene in the presence of iodine under irradiation with a tungsten or mercury lamp <1999T14885, CHEC-III(4.05.9.1.2)599>. 

Similarly, the enamine salt 15 is obtained by lithiation of 14 (equation 5). In both cases the lower steric hindrance leads to higher stability of the enaminic system33 where the double bond is formed on the less substituted carbon. The Af-metalated enamines 11 and 15 are enolate analogs and their contribution to the respective tautomer mixture of the lithium salts of azomethine derivatives will be discussed below. Normant and coworkers34 also reported complete regioselectivity in alkylations of ketimines that are derived from methyl ketones. The base for this lithiation is an active dialkylamide—the product of reaction of metallic lithium with dialkylamine in benzene/HMPA. Under these conditions ( hyperbasic media ), the imine compound of methyl ketones 14 loses a proton from the methyl group and the lithium salt 15 reacts with various electrophiles or is oxidized with iodine to yield, after hydrolysis, 16 and 17, respectively (equation 5). 

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