Substituents Located on the Other Ring

Preparation by reaction of m-anisoyl chloride with o-di-chlorobenzene in the presence of excess aluminium chloride first at 20°, then at reflux for 2 h (41%) [119,899]. 

Obtained (by-product) by reaction of 3,5-dinitrobenzoyl chloride with anisole in 

Preparation by Friedel-Crafts acylation of bromobenzene with m-nitrobenzoyl chloride, reduction of the obtained 4-bromo-3 -nitrobenzophenone and diazotization of the resulting 3-amino-4 -bromobenzophenone, followed by hydrolysis of the diazonium salt [900]. 

Preparation by demethylation of 4-bromo-3 -methoxybenzophenone with aluminium chloride in refluxing chlorobenzene [900]. 

Also obtained (poor yield) by reaction of o-chlorobenzoyl chloride with phenyl borate in the presence of aluminium chloride in tetrachloroethane at 100° (3%) [55], 

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Substituents Located on the Other Ring (2,4-Dihydroxyphenyl)(2,4,6-trinitrophenyl)methanone... 

The greater stability of an equatorial methyl group, compared with an axial one, is another example of a steric effect (Section 3.2). An axial substituent is said to be crowded because of 1,3-diaxial repulsions between itself and the other two axial substituents located on the same side of the ring. 

On the other hand, the situation is more complex for the 3-substituted derivatives. In such compounds the substituent can be considered electronically to be located either meta or para to the selenium ring atom (cf. resonance formulas 8 and 9 for a -I -M substituted derivative). However, the substituent-caused shifts in the 3-substituted derivatives indicate that the heteroatom and the substituents are para and not meta related. 77Se chemical shifts are more sensitive than the 13C shifts to changes in electron... 

Benzene molecules bearing alkyl substituents are called alkylbenzenes. The simplest of these is methylbenzene (common name, toluene), shown in Figure 27-1 Ic. The dimethyl-benzenes are called xylenes. Three different compounds (Table 27-6) have the formula CgH4(CH3)2 (see margin). These three xylenes are constitutional isomers. In naming these (as well as other disubstituted benzenes), we use prefixes ortho- (abbreviated o-), meta- m-), or para- (p-) to refer to relative positions of substituents on the benzene ring. The ortho- prefix refers to two substituents located on adjacent carbon atoms for example, 1,2-dimethylbenzene is o-xylene. The meta- prefix identifies substituents on C atoms 1 and 3, so 1,3-dimethylbenzene is 7w-xylene. The para- prefix refers to substituents on C atoms 1 and 4, so 1,4-dimethylbenzene is p-xylene. 

In addition to the completely symmetrical pavine alkaloids, Stermitz et al. (518) found other pavine alkaloids of mrmitagine type (Tables X and XI) in Argemone munita, spp. rotundata. The location of the substituents of the two aromatic rings was determined on the one hand by the classic chemical method, i.e., isolation of hemipinic (Ilb) and meta-hemipinic (lla) acids after alkaline oxidation of 0,0-dimethylmunitagine and, on the other, by NMR analysis oxidative degradation of argemonine resulted only in metahemipinic acid (Ha) and its methylimide (III), respectively. 

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