Bromotrifluoromethane

Template:Short description Template:Chembox Bromotrifluoromethane, commonly referred to by the code numbers Halon 1301, R13B1, Halon 13B1 or BTM, is an organic halide with the chemical formula C Br F₃. It is used for gaseous fire suppression as a far less toxic alternative to bromochloromethane.<ref name=Ullmann>Template:Ullmann</ref>

Table of physical propertiesEdit

Property	Value
Critical temperature (T_c)	66.9 °C (340.08 K)
Critical pressure (p_c)	3.956 MPa (39.56 bar)
Critical density (ρ_c)	5.13 mol.l⁻¹
Ozone depletion potential (ODP)	10 (CCl₃F = 1)
Global warming potential (GWP)	6900 (CO₂ = 1)

SynthesisEdit

Bromotrifluoromethane is commercially synthesized in a two-step process from chloroform. Chloroform is fluorinated with hydrogen fluoride.<ref>Template:Cite journal</ref>

CHCl3 + 3 HF → CHF3 + 3 HCl

The resulting Fluoroform is then reacted with elemental bromine.

CHF3 + Br2 → CF3Br + HBr

UsesEdit

File:Halon fire suppression warning sign.jpg

Warning sign for fire suppression system

File:Halon 1301 Fire Extinguisher.jpg

Civilian Halon 1301 fire extinguisher, USA, 1980s

Halon 1301 was developed in a joint venture between the U.S. Army and Purdue University in the late 1940's,<ref>"Final Report on Fire Extinguishing Agents for the Period September 1, 1947, to June 30, 1950", Contract No. W44-099eng-507, Purdue Research Foundation, Lafayette, Indiana, July 1950.</ref> and became a DuPont product in 1954. It was introduced as an effective gaseous fire suppression fixed systems agent in the 1960s, and was used around valuable materials, such as aircraft, mainframe computers, and telecommunication switching centers, usually in total flooding systems.<ref>NFPA 12A Standard on Halon 1301 Fire Extinguishing Systems https://www.nfpa.org/codes-and-standards/1/2/a/12a?l=125</ref> It was also widely used in the maritime industry to add a third level of protection should the main and emergency fire pumps become inoperable or ineffective. Halon 1301 was never widely used in portables outside marine, military and spacecraft applications, due to its limited range, and invisible discharge. It does not produce the characteristic white cloud like CO₂ and is difficult to direct when fighting large fires. Halon 1301 is ideal for armored vehicles and spacecraft, because it produces fewer toxic by-products than does Halon 1211, which is critical for combat or space conditions where a compartment may not be able to be ventilated immediately. Halon 1301 is widely used by the U.S. Military<ref>Hodges and McCormick, "Fire Extinguishing Agents for Protection of Occupied Spaces in Military Ground Vehicles," 2010, DTIC ADA517470 https://apps.dtic.mil/sti/citations/ADA517470</ref> and NASA in a 2-3/4 lb portable extinguisher with a sealed, disposable cylinder for quick recharging. Other agents such as CO₂ and FE-36 (HFC-236fa) wet chemical are largely replacing halon 1301 for environmental concerns. Civilian models in 2-3/4, 3, and 4 lb sizes were also made.

It is considered good practice to avoid all unnecessary exposure to Halon 1301, and to limit exposures to concentrations of 7% and below to 15 minutes. Exposure to Halon 1301 in the 5% to 7% range produces little, if any, noticeable effect. At levels between 7% and 10%, mild central nervous system effects such as dizziness and tingling in the extremities have been reported.<ref>NFPA 12A Standard on Halon 1301 Fire Extinguishing Systems, 2004 Edition / Annex D, Hazards to Personnel, section D.2.2</ref> In practice, the operators of many Halon 1301 total flooding systems evacuate the space on impending agent discharge.

Halon systems are among the most effective and commonly used fire protection systems used on commercial aircraft. Halon 1301 is the primary agent used in commercial aviation engine, cargo compartments, and auxiliary power unit fire zones.<ref>United States Environmental Protection Agency | Guidance for the EPA Halon(R) Emission Reduction Rule | Federal Aviation Administration</ref><ref>Boeing Commercial Aeromagazine | Quarter 04, 2011 | Replacing Halon in Fire Protection Systems: a Progress report</ref> Efforts to find a suitable replacement for Halon 1301 have not produced a widely accepted replacement.<ref>Aerospace Manufacturing and Design | Halon Alternatives for Aircraft Propulsion Systems consortium formed | January 27, 2015</ref><ref>FAA | Task Group on Halon Options</ref>

Bromotrifluoromethane was also used as a filling of the bubble chamber in the neutrino detector Gargamelle.

Before the dangers of Halon 1301 as an ozone depleter were known, many industrial chillers used it as an efficient refrigerant gas.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

File:H-1301 mm.png

H-1301 measured by the Advanced Global Atmospheric Gases Experiment (AGAGE) in the lower atmosphere (troposphere) at stations around the world. Abundances are given as pollution free monthly mean mole fractions in parts-per-trillion.

Chemical reagentEdit

It is a precursor to trifluoromethyltrimethylsilane, a popular trifluoromethylating reagent in organic synthesis.<ref>Template:Cite journal</ref>

AlternativesEdit

File:Halon1301.JPG

Halon 1301 hazard sign, with instructions upon gas discharge.

Alternatives for normally occupied areas include (PFC-410 or CEA-410), C₃F₈ (PFC-218 or CEA-308), HCFC Blend A (NAF S-III), HFC-23 (FE 13), HFC-227ea (FM 200), IG-01 (argon), IG-55 (argonite), HFC-125, or HFC-134a. For normally unoccupied areas, the alternatives include carbon dioxide, powdered Aerosol C, CF₃I, HCFC-22, HCFC-124, HFC-125, HFC-134a, gelled halocarbon/dry chemical suspension (PGA), blend of inert gas, high expansion foam systems and powdered aerosol (FS 0140), and IG-541 (Inergen).<ref>Halon 1301 Replacements Template:Webarchive</ref> Perfluorocarbons, i.e., PFCs such as C₃F₈, have very long atmospheric lifetimes and very high global warming potentials. Hydrochlorofluorocarbons, i.e., HCFCs including HCFC containing NAF S-III, contain chlorine and are stratospheric ozone layer depleters, although less so than Halon 1301. Their selection for usage as Halon replacements should consider those factors, and is restricted in some countries.

ReferencesEdit

External linksEdit

Template:Halomethanes Template:Fluorine compounds