The third is also in the para position; for if benzaldehyde be condensed with aniline, condensation occurs in the para position, for the compound formed may be converted into para-dioxybenzophenone, C6H5CHO -)C6H5CH(C6H4NH2)2 - >C6H5CH(C6H40H)2 -->CO(C6H40H)2 but if para-nitrobenzaldehyde be used in the above reaction and the resulting nitro compound N02 C6H4 CH(C6H4NH2)2 be reduced, then pararosaniline is the final product, and consequently the third amino group occupies the para position.
Para-nitrobenzaldehyde crystallizes in prisms melting at 107° C. and is prepared by the action of chromium oxychloride on para-nitrotoluene, or by oxidizing para-nitrocinnamic acid.
By the reduction of ortho-nitrobenzaldehyde with ferrous sulphate and ammonia, ortho-aminobenzaldehyde is obtained.
Koerner (Ber., 1884, 17, p. 203) by condensing ortho-nitrobenzaldehyde with aniline, the resulting ortho-nitro-para-diamino-triphenylmethane being reduced to the corresponding orthoamino compound, which on oxidation yields chrysaniline.
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