n-Propyl bromide

n-Propyl bromide
Identifiers
CAS number 106-94-5 YesY
ChEMBL CHEMBL1230095 N
RTECS number TX4110000
Jmol-3D images Image 1
Properties
Molecular formula C3H7Br
Molar mass 122.99
Appearance Colorless liquid
Density 1.353
Melting point

-109.9 °C, 163 K, -166 °F

Boiling point

71.0 °C, 344 K, 160 °F

Solubility in water 0.25 g/100 mL at 20 °C
Solubility in ethanol fully miscible
Solubility in diethyl ether fully miscible
Refractive index (nD) 1.43414
Viscosity 6.509 cP at 0 °C
5.241 cP at 20 °C
Hazards
R-phrases R11 R60 R63 R36/37/38 R48/20 R67
S-phrases S53 S45
NFPA 704
NFPA 704.svg
0
2
0
Flash point None
Related compounds
Related alkyl halides Ethyl bromide
isopropyl bromide
n-propyl chloride
 N bromide (verify) (what is: YesY/N?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

n-Propyl bromide (also 1-bromopropane or 1-propyl bromide) is a colorless to off-white, non-flammable chemical compound. It has the chemical formula C3H7Br. It is an organic solvent used for the cleaning of metal surfaces, removal of soldering residues from electronic circuit boards, and as an adhesive solvent. It has a characteristic hydrocarbon odor.

Use as a degreasing agent

N-propyl bromide (1-bromopropane) is an example of an untested substance being substituted for possibly less potent materials that were more strictly regulated in the occupational and general environment. For example, NIOSH reported two cases involving workers exposed to 1-BP and diagnosed with clinical manifestations of neurotoxicity. The cases, when coupled with previously reported studies of workers exposed to 1-BP, illustrate potential health risks of 1-BP exposure. Clinicians and public health professionals should be alert to potential health effects among workers exposed to 1-BP, particularly in dry cleaning and other workplaces where 1-BP use might be increasing, and effective control methods to limit exposure to 1-BP should be implemented at worksites.


In the early 1990s, it was discovered that n-propyl bromide had been wrongly classified as a flammable solvent in reference books of the United Kingdom. In the USA, it has been proven to not be a flammable solvent as tested under the standard tests for flammability from the American Society for Testing and Materials (ASTM). Since that time, the use of n-propyl bromide (NPB) has flourished. In most of the modern world, NPB has seen increased use as a solvent for vapor degreasing of metals in industrial processes, defluxing of electronic circuit cards to remove flux, ionics, and particulates, also used as a diluent in the manufacturing of medicinal tablets, an extraction agent for the purification of herbs and natural plant extracts, and in some countries NPB is used in adhesive formulations and as a solvent in aerosol formulations.

In practically all of the uses for NPB the solvent replaces the use of dangerous chlorinated solvents such as trichloroethylene (TCE), perchloroethylene (PCE), Dichloromethane (DCM or methylene chloride), and trans, dichloroethylene (Trans DCE). TCE, PCE, and DCM are rated as "Hazardous Air Pollutants" or HAPs in the United States and many other countries. HAPs have been identified by the US Government as Cancer-Causing products in most instances and therefore are under tighter environmental and personal exposure limits. N-propyl bromide is not a HAP, so many companies are turning to NPB as the best alternative in order to achieve the final goal of cleaning parts or extracting herbs and so forth.

Competition to n-propyl bromide (NPB) is traced back to the manufacturers of chlorinated solvents as well as high-cost "fluorinated solvents" that tend to be promoted as alternatives to cleaning with chlorinated solvents. The fluorinated solvent options are generally safer to use in the manufacturing processes, however they are much less effective. So much so, that they are typically blended with a stronger solvent, such as the flammable trans, dichloroethylene, in order to increase the solubility of various contaminants in the solvent blend.

1-Bromopropane was subjected to 2-year bioassay by the U.S. National Toxicology Program. There was some evidence of carcinogenic activity of 1-bromopropane in male F344/N rats based on the occurrence of rare adenomas of the large intestine and increased incidences of neoplasms of the skin. Increased incidences of malignant mesothelioma and pancreatic islet adenoma may also have been related to 1-bromopropane exposure. There was clear evidence of carcinogenic activity of 1-bromopropane in female F344/N rats based on increased incidences of adenoma of the large intestine. Increased incidences of neoplasms of the skin may also have been related to 1-bromopropane exposure. There was clear evidence of carcinogenic activity of 1-bromopropane in female B6C3F1 mice based on increased incidences of alveolar/bronchiolar neoplasms. There was no evidence of carcinogenic activity of 1-bromopropane in male B6C3F1 mice exposed to concentrations of 62.5, 125, or 250 ppm 1-bromopropane.

Exposure to 1-bromopropane resulted in increased incidences of nonneoplastic lesions in the nose of rats and mice, the larynx of rats and male mice, the trachea of female rats and male and female mice, and the lung of mice. Suppurative inflammatory lesions with Splendore-Hoeppli material were present primarily in the nose and skin of male and female rats exposed to 1-bromopropane.

The flammable characteristics of n-propyl bromide are contained to a narrow concentration in air between approximately 4% and 7% by volume. It is unusual for NPB to ever catch fire because the solvent is "self-extinguishing". Self-extinguishing refers to a chemical property where a solvent that has caught fire will overcome itself and consume or inhibit the available oxygen that is supporting the flame. This is the case with NPB. The vapor above the solvent can be lit to catch fire, however within a few moments the vapor loses the fuel and the fire will snuff itself out. This has been shown in several videos produced by Enviro Tech International Inc where the same test is conducted with other solvents and they all continue to burn, yet when a flame hovers over a solution of NPB, the bromine in the NPB apparently suffocates the oxygen from the vapor over the mixture and the flame disappears.

The atmospheric properties of n-propyl bromide are short-lived and its a hydrocarbon, so by default NPB has been classified as a Volatile Organic Compound by the US Environmental Protection Agency. Recent studies by Whitten and Yarwood published in the Journal of the Air & Waste Management Association state that NPB is actually a VOC inhibitor, of sorts.[1] The details of this argument are left to the reader to pursue, but these peer-reviewed and published results are not the first case to show that NPB should be delisted as a VOC. The US EPA has not moved forward on the idea of delisting NPB as a VOC.

The application of NPB should probably be confined to industrial uses where the users will be properly outfitted with safety glasses, gloves, and in some cases, half-face respirators, at their leisure. All chemicals, and solvents, should be handled with the utmost care. The use of NPB is no different in that regard.

References

  1. ^ Whitten and Yarwood, Journal of the Air & Waste Management Association, Vol 58, July 2008, pp 891-901
  • EPA’s Proposed Regulation of n-Propyl Bromide [1]
  • USEPA SNAP Approval of n propyl bromide [2]
  • NTP Toxicology and Carcinogenesis Studies of 1-Bromopropane (CAS No. 106-94-5) in F344/N Rats and B6C3F1 Mice (Inhalation studies)

http://ntp.niehs.nih.gov/INDEXF0D9_2.HTM?objectid=4E0C03A9-F1F6-975E-79F1E370B9027815

  • Neurologic Illness Associated with Occupational Exposure to the Solvent 1-Bromopropane --- New Jersey and Pennsylvania, 2007--2008

http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5748a2.htm


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