Emergencies hydrogen fluoride

DichlorobenzotrifIuoride. This dichloro compound is produced from 2,4-dichloroben2otrichloride and hydrogen fluoride. One commercial appHcation is the manufacture of the pre-emergent herbicide, dinitramine [29091 -05-2]. 

The crystal structure of many compounds is dominated by the effect of H bonds, and numerous examples will emerge in ensuing chapters. Ice (p. 624) is perhaps the classic example, but the layer lattice structure of B(OH)3 (p. 203) and the striking difference between the a- and 6-forms of oxalic and other dicarboxylic acids is notable (Fig. 3.9). The more subtle distortions that lead to ferroelectric phenomena in KH2PO4 and other crystals have already been noted (p. 57). Hydrogen bonds between fluorine atoms result in the formation of infinite zigzag chains in crystalline hydrogen fluoride... 

The popular acids for deprotection by acidolysis are hydrogen fluoride for benzyl-based protectors and trifluoroacetic acid for rerr-butyl-based protectors. The use of hydrogen fluoride for deprotection emerged from the observation that it is a good solvent for dissolving enzymes (because of the N-to-0 acyl shift see Section 6.6), and that the enzymatic activity is recovered (O-to-N acyl shift) in saline solution. Two different approaches are employed for removal of benzyl-based... 

Stewart, N. E. and J. W. McVey. 1994. Design Concepts for a Hydrogen Fluoride Emergency De-Inventory System. Process Safety Progress 13(2) 105-107. 

The preference for the edge-protonated structure emerges from interesting microwave spectroscopy experiments conducted on the cyclopropane-hydrogen fluoride and cyclopropane-hydrogen chloride complexes which reveal a structure like that shown in Figure 54. 

Fluorine and hydrogen fluoride are extremely dangerous and should only be used in purpose-built apparatus gloves and face shields should be used when working with hydrofluoric acid and accidental exposure should be treated as a hospital emergency. 

It is advisable to be prepared for emergencies whenever hydrogen fluoride is to be employed. Since physicians are not generally familiar with the treatment of hydrogen fluoride bums, it is further suggested that the operator avail himself of the most recent information on this subject. 

There are also five Chemical Emergency Preparedness and Prevention Advisories listed at http //www.epa.gov/emergencies/publications.htm. These advisories cover such timely topics as Solid Ammonium Nitrate Storage, Handling and Management , as well as advisories on Hydrogen Fluoride, Advisories Ammonia, and others. 

The Chemical Emergency Preparedness and Prevention Office has estimated the zone of vulnerability under worst-case scenario conditions for facilities containing different hazardous substances. They conclude that for a facility containing toxic substances, the median distance from the facility to the outer edge of its vulnerable zone is 1.6 miles. Flammable substances have a worst-case scenario vulnerability zone whose median distance reaches 0.4 miles from the facility. However, many facilities reported vulnerability zones extending 14 miles from the facility (primarily for urban area releases of chlorine stored in 90-ton rail tank cars) and 25 miles (for rural releases of chlorine stored in 90-ton rail tank cars). Other chemicals for which the reported vulnerability zone equaled or exceeded 25 miles include anhydrous ammonia, hydrogen fluoride, sulfur dioxide, chlorine dioxide, oleum (fuming sulfuric acid). 

Personnel working with hydrogen fluoride should wear safety glasses plus a face shield, acid resistant gauntlet-type gloves, and acid resistant jacket, pants, and boots. For emergency use, a positive pressure air-line respirator or SCBA, and acid suits should be available. 

One example of such disasters, based on the EPA Office of Solid Waste and Emergency Response, July 1993 (EPA-560-K-93-001 Series 8, No. 3), is the release of 30,(X)0 to 50,000 pounds of hydrogen fluoride (HE) and isobutane at a Texas... 

Difluoroethane is reacted to form vinyl fluoride and hydrogen fluoride. A natural gas fired process heater supplies molten salt used to maintain the reactor temperature. The gaseous reaction products are separated and the hydrogen fluoride and difluoroethane are recycled back to the DFE process. The crude vinyl fluoride is purified and stored until shipped by railcar or truck tanker. Acidic vent gases from this process are controlled by the emergency scrubber of the DFE process. 

In a survey of different carboxylic acids, citric acid has emerged as the best candidate to reach optimum enantioselectivity. The protonation of various silyl enolates 76 in the presence of (DHQ)2AQN 78 (10 mol%) afforded the corresponding ketones 77 with fair levels of enantioinduction up to 75% (for example see 76a,c,e->77a,c,e Scheme 3.41). Although this simplified process exhibits somewhat lower performances than that using a latent source of hydrogen fluoride [33], it shows clear advantages in view of implementation simplicity and cost (Scheme 3.41). 

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