Preparation Of 2-choloro-4 5-difluorobenzoic Acid From 4 5-difluorophthalic Anhydride Of 4 5-difluorophthalic Acid - Occidental Chemical Corporation

Chlorodenitration reactions are known. For example, Ponomarenko discloses (J. Gen. Chem USSR (Engl. Tran.) that 3-nitrophthalic anhydride reacts with chlorine at a temperature of 230°-250° C. to form 3-chlorophthalic anhydride. It is likely to be expected that this course of would be prove troublesome if utilized to a nitrobenzoic acid because the single carboxylic acid group decarboxylates extra readily then the phthalic anhydride.

Nitrobenzene is a pale yellow liquid with a distinct almond like odour. The colour of the liquid varies from pale yellow to yellowish brown relying on the purity of the compound. Being a high boiling paint liquid, the probability of poisoning by inhalation of vapour from the cold liquid isn't a lot. Since nitrobenzene is a highly toxic substance, it would produce either acute poisoning by absorption of a large quantity in a short time or chronic poisoning by continued exposure to small quantities. It may be absorbed by inhalation, ingestion or instantly by the intact pores and 5-Trifluorophenethanol skin. Its toxic response is enhanced by subsequent ingestion of ethanol. In trade the key hazard is absorption by way of the skin. Observance of this code of safety will reduce the frequency and severity of hazard.

The error resulting from the Volhard Technique is what our group is most concerned with. By
evaluating the solubility products in equations four and 5 below (Pietrzyk and Frank, 326), one can
easily conclude that silver chloride is extra soluble than silver thiocyanate.
Ksp (AgSCN) = 1.0 x 10-12 (4)
Ksp (AgCl) = 1.Eight x 10-10 (5) As a consequence, equation six below dominates:
AgCl + SCN- ---> AgSCN + Cl- (6) This response above happens to a big extent near the top level within the back-titration of the surplus
silver ion. Because of this, low values are decided in the chloride evaluation. Rigorous calculations have
proven that an overconsumption of 1.6 mL or more of excess 0.1 M thiocyanate will happen (Skoog and
West, 227).