Benzotrifluoride, nitration

If the benzotrifluoride contains an ammo group N-nitration in acenc acid and acetic anhydride furnishes the tnfluoromethyl nitroaminobenzene [22] C-nitration... 

Trifluoromethyl)benzene (benzotrifluoride, 15) was the first organic fluoride to incorporate a trifluoromethyl group. By a standard nitration process, it formed l-nitro-3-(trifluoromethyl)-benzene (16) which was reduced to the 1-amino derivative, 17. This we a-directive influence on electrophilic aromatic substitution contrasted with that for fluorobenzene, which gave 4-and 2-nitro products. 

Swarts778 in 1922 this amine is prepared by nitrating benzotrifluoride and reducing the nitro compound in methanol catalytically with Raney nickel.779,780 The yield of trifluoroacetic acid amounts to 90-95% if suitable technique is used — apparatus is described in detail by Wachter.781... 

Our investigations with Kuhn ( ) have shown that aromatic compounds, including deactivated ones such as halobenzenes and benzotrifluoride, can be nitrated with ease using nitryl halides and a suitable Friedel-Crafts catalyst. 

When the N2O5 nitration is carried out in liquid anhydrous HF as solvent (which does not appear to react with N2O5 at a temperature below 0°) using a catalyst such as BF-j, SbF, PF5, AsF, SiFij, NbF, WFg, etc, a quantitative formation of the corresponding nitronium salts takes place. As HF also acts as a good ionizing solvent, an extremely active nitration medium is obtained. Nitrobenzene and benzotrifluoride are nitrated with yields of over 90% at temperatures between -20 and 0°. 

The reaction of benzotrichloride with anhydrous HF at 120 °C in a nickel or stainless-steel reactor produces benzotrifluoride, from which 3-trifluoromethyl-aniline is obtained by selective nitration and subsequent catalytic reduction of the 3-trifIuoromethylnitrobenzene. 

The rates of electrophilic substitution on other even aromatic systems, and the effects of substituents, can be deduced in the usual way. Thus since -1- / substituents destabilize odd AH cations while — / substituents stabilize them, substitution should tend to take place in such a way as to ensure that + / substituents are at inactive positions in the arenonium intermediate and - / substituents at active positions. For example, in benzene, where the positions ortho and para to the point of substitution are active in the intermediate benzonium ion (89), +/ substituents (e.g., CF3) are best placed in the meta position, while — / substituents (e.g., CH3) should be ortho or para. Benzotrifluoride (PhCF3) consequently substitutes mainly meta, nitration, for example, giving (90), while toluene (PhCH3) substitutes mainly ortho and para, giving, e.g., (91) and (92) on nitration. 

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