The Preparation Of 2-halogen-2,2- Difluoroacetic Acid And Its Derivatives

2-chloro-2,2-difluoroacetic acid, 2-bromo-2,2-difluoroacetic acid and their deritives are important fluorine fine chemicals. Because of containing CF2,they have been widely used in the synthesis of the fluorine-containing medicine intermediates and pesticide intermediates. Unfortunately, there are many issues in the existing methods of producing them. For example, the raw material is expensive and hard to be obtained; the catalyst is much more expensive and highly toxic; the amount of the solvent and the low selectivity of the target product etc.. Therefore, these methods are difficult to bring about industrialized mass production.1,2,2-trichloro-1,1-difluoroethane(R122), as the by-product of the production of2,2-dichloro-1,1,1-trifluoroethane(R123), which was made by Zhejiang Lantian Environmental Protection Hi-Techco., Ltd, was used as the raw material to produce ethyl bromodifluoroacetate by elimination, bromination, oxidation and esterification.And at the same time, 1,1,1,2-tetrachloro-2,2-difluoroethane(R112a), as another by-product, was used to produce 2-chloro-2,2-difluoroacetic acid.This paper mainly discusses the following contents. Firstly, according to the literature, 1,2-dibromo-1,1-dichloro-2,2-difluoroethane was produced by R122.Second, trying and optimizing the reaction conditions of1,2-dibromo-1,1-dichloro-2,2-difluoroethane and sulfur trioxide, including the pretreatment of sulfur trioxide, the choices of the Cat., the adding way of sulfur trioxide, the control of the temperature and the exported way of2-bromo-2,2-difluoroacetyl chloride. As well as R112 a.Avoiding the use of concentrated sulfuric acid and toxic mercury catalyst, thus,the technique is more environmentally friendly and it is easy to be industrialized.