Nitro-derivatives of abietic acid

It is known that the solid residue of distillation of essential oils (turpentine) of coniferous tress—rosin or colophony—is composed mainly of abietic acid  

Nitration of abietic acid was reported in 1904 [66]. Johansson [67] was the first to describe a crystalline nitro-derivative which he considered to be dinitro-abietic acid of the formula CI9H27(N02)2C00H, m.p. 178-184°C (see also [68]). Later reports by Dubourg [69], Goldblatt et al. [70] described the nitration in nitric acid (d = 1.42) in presence of acetic add to form dinitroabietic add C,8H2j(N02)2C00H of m.p. 171°C (yield 33%). 

Fieser and Campbell [71] nitrated dehydroabietic acid with nitric-sulphuric add mixtures and obtained a product CI9H2J(N02)2C00H, decomposition 178-185°C, identical with this described by Johansson. This was 6,8-dinitro-dehydroabietic add. It seems to be identical with one of the non-identified products with three ( ) NO2 groups of Dubourg [69]. 

A trinitroabietic acid, C15HI6(N02)3C00H, m. p. 156-158°C, was also obtained by Dubourg. He also prepared polynitroabietic add by nitration of abietic acid with hot anhydrous nitric add. 

An ethyl ester of dinitroabietic acid (m.p. 157.5-158°C) was also described by Goldblatt et al. [70]. 

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Nitro-derivatives of abietic acid did not find any practical application, although a few patents were issued [72]. 

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