Vogels "Textbook of Practical Organic Chemistry", 3
rd edition, p. 678, IV,109. 2,4-dinitrophenol is prepared from 2,4-dinitrochlorobenzene by alkaline hydrolysis with sodium carbonate. For preparation of 2,4-dinitrochlorobenzene (along with a small amount of 2,6-dinitrochlorobenzene you might have a look at T.L. Davis, "The Chemistry of Powder and Explosives" or at the following excerpt from this book..
Preparation of dinitrochlorobenzene:
100g of chlorobenzene is added drop by drop to a mixture of 160g of nitric acid (d. 1.50) and 340g of sulfuric acid (d. 1.84) while the mixture is stirred mechanically. The temperature rises because of the heat of the reaction, but is not allowed to go above 50-55°C. After all the chlorobenzene has been added, the temperature is raised slowly to 95°C and is kept there for 2 hours longer while the stirring is continued. The upper layer of light yellow liquid solidifies when cold. It is removed, broken up under water, and rinsed. The spent acid, on dilution with water, precipitates an additional quantity of dinitrochlorobenzene.
All the product is brought together, washed with cold water, then several times with hot water while it is melted, and finally once more with cold water under which it is crushed. Then it is drained and allowed to dry at ordinary temperature. The product, melting at about 50°C, consists largely of 2,4-dinitrochlorobenzene, m.p. 53,4°C, along with a small quantity of 2,6-dinitro compound, m.p. 87-88°C.....
(uninteresting text, concerning the manufacture of explosives)...........Dinitrochlorobenzene causes severe itching of the skin, both by contact with the solid material and by exposure to its vapours
(this is very true, when I once prepared this compound I was scratching my hands like a mad monkey, so be careful) No yield is given in the procedure, but as far I can remember it was in the 70-80 % range for the mixture of isomers.
Italics mine
