NMERI 99/8/33350
`
`TROPODEGRADABLE BROMOCARBON EXTINGUISHANTS
`
`Joseph Lifke, April Martinez, and Robert E. Tapscott, J. Douglas Mather
`
`Center for Global Environmental Technologies
`NEW MEXICO ENGINEERING RESEARCH INSTITUTE
`The University of New Mexico
`901 University Boulevard SE
`Albuquerque, New Mexico 87106-4339
`
`Final Report, 3/98 – 9/99
`
`May, 2001
`
`
`
`Sponsored by:
`The Department of Defense
`Strategic Environmental Research and Development Program
`
`The views and conclusions contained in this document are those of the authors and should not be
`interpreted as representing the official policies, either expressed or implied, of the Strategic
`Environmental Research and Development Program or any other part of the U.S. Government.
`
`
`
`Page 1 of 68
`
`Arkema Exhibit 1144
`
`

`
`NOTICE
`
`Mention of trade names or commercial products does not constitute endorsement or
`recommendation for use. Because of the frequency of usage, Trademarks ® or ™ are not
`indicated.
`
`This report has been reviewed by the Public Affairs (PA) Officer and is releasable to the
`National Technical Information Service (NTIS). At NTIS it will be available to the general
`public, including foreign nationals. This report may also be viewed and downloaded from the
`NIST NGP internet site: http://www.bfrl.nist.gov/866/NGP/publications.htm.
`
`_____________________________
`Ron Sheinson
`Contracting Officer’s Technical Representative
`
`_____________________________
`Richard Gann
`Technical Program Manager
`
`
`
`Please do not request copies of this report from NIST. Additional copies may be purchased
`from:
`
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`5285 PORT ROYAL ROAD
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`
`Federal government agencies and their contractors registered with Defense Technical
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`
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`
`
`Form Approved
`OMB No. 0704-0188
`Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and
`maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including
`suggestions for reducing this burden, to Washington Headquarters Services, Directorate for information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302,
`and to the Office of Management and Budget, Paperwork Reduction Project (0704-0188), Washington, DC 20503.
`3. REPORT TYPE AND DATES COVERED
`1. AGENCY USE ONLY (Leave blank)
`2. REPORT DATE
`
`5/2001
`Final Report, 3/98 – 9/99
`
`4. TITLE AND SUBTITLE
`5. FUNDING NUMBERS
`
`TROPOEGRADABLE BROMOCARBON
`
`
`EXTNGUISHANTS
` DASW01-00-P3345
`
`REPORT DOCUMENTATION PAGE
`
`6. AUTHOR(S)
`
`J. Douglas Mather, Robert E. Tapscott, Joseph Lifke,
`April Martinez
`
`
`7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)
` New Mexico Engineering Research Institute
`
`The University of New Mexico
` Albuquerque, New Mexico 87106-4339
`9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES)
`
`Department of Defense – Strategic Environmental Research and
`Development Program
`
`
`
`8. PERFORMING ORGANIZATION
`REPORT NUMBER
` NMERI 99/8/33350
`
`10. SPONSORING/MONITORING
`AGENCY REPORT NUMBER
`
`
`
`
`11 SUPPLEMENTARY NOTES
`
`
`
`
`
`12b. DISTRIBUTION CODE
`
`12a. DISTRIBUTION/AVAILABILITY STATEMENT
`
`13. ABSTRACT (Maximum 200 words)
`Current commercially available Halon 1301 replacement compounds (other than CF3I) lack the fire suppression
`effectiveness of halon primarily because they do not contain bromine in their molecular structure. Bromine is thought to catalyze
`radical recombination reactions which deprive the combustion process of the •OH and •H radical species which promote the
`combustion of fuel molecules in the gas phase. This project was conceived to develop new fire suppressants incorporating bromine
`by basing the compounds on chemical families with expected or demonstrated short atmospheric lifetimes. These compounds are
`said to be tropodegradable bromocarbons. The targeted chemical families in order of importance were partially fluorinated alkenes,
`ethers, and amines. The alkenes have now been shown to have very short lifetimes on the order of days. This project identified
`several low boiling brominated and partially fluorinated alkenes, ethers, and amines with potential of meeting the toxicity, fire
`suppression, and environmental criteria currently identified under the EPA’s SNAP program for halon replacements. Several of
`these tropodegradable compounds were subsequently acquired and their cup-burner flame suppression performance evaluated with
`promising results. Several of the bromofluoro alkenes have now also been evaluated in an acute inhalation toxicity test which
`yielded extremely promising results for this chemical family. This is an interim report covering the first phase of an ongoing effort.
`
`
`15. NUMBER OF PAGES
`
`16. PRICE CODE
`
`20. LIMITATION OF ABSTRACT
`
`
`
`Unclassified
`Standard Form 298 (Rev. 2-89)
`Prescribed by ANSI Std 239-18
`
`14. SUBJECT TERMS
` Bromofluoro-alkene; Bromofluoro-ether, Bromofluoro-amine, Halon 1301,
`
`Fire Extinguishant, tropodegradable, cup-burner, atmospheric lifetime
`19. SECURITY CLASSIFICATION
`18. SECURITY CLASSIFICATION
`17. SECURITY
`OF ABSTRACT
`OF THIS PAGE
`CLASSIFICATION OF
` Unclassified
` Unclassified
`REPORT
` UNCLASSIFIED
`NSN 7540-280-5500
`
`
` i
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`Page 3 of 68
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` UNCLASSIFIED
`SECURITY CLASSIFICATION OF THIS PAGE
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`UNCLASSIFIED
`SECURITY CLASSIFICATION OF THIS PAGE
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`PREFACE
`
`This report was prepared by the Center for Global Environmental Technologies (CGET)
`at the New Mexico Engineering Research Institute (NMERI), The University of New Mexico,
`Albuquerque, New Mexico, for the Department of Defense Strategic Environmental Research
`and Development Program Next Generation Fire Suppression Program under Contract
`DASW01-00-P3345. The corresponding University of New Mexico Contract Number is 8-
`33350.
`
`The Start Date was March 1, 1998, and the End Date was September 30, 1999. The NGP
`Contracting Officer’s Technical Representative is Dr. Ronald Sheinson and the NMERI
`Principal Investigator is Dr. J. Douglas Mather and the Co-Principal Investigator is Dr. Robert E.
`Tapscott.
`
`
`
`NMERI 99/8/33350
`
`
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`EXECUTIVE SUMMARY
`
`The objective of the Tropodegradable Bromocarbon Extinguishants project is to identify
`new chemical compounds with the potential to replace Halon 1301 in total flood fire
`extinguishment and explosion inertion applications.
`
`Development of replacement chemicals for existing halons is mandated by international
`treaty, based on the now widely accepted link between atmospheric bromine levels and
`stratospheric ozone depletion.
`
`Under the Montreal Protocol, an international treaty enacted in 1987 and amended in
`1990, 1992, and 1995, the production of halon fire and explosion protection agents was phased
`out in the United States and other industrialized nations at the end of 1993. One of these agents,
`Halon 1301, is used throughout the US DoD in total flood applications. To date, no
`environmentally acceptable substitute equivalent to Halon 1301 in toxicity, effectiveness, and
`dimensionality has been identified. Most of the replacements now being commercialized or
`proposed for commercialization are saturated fluorine-containing halocarbons:
`hydrofluorocarbons (HFC), hydrochlorofluorocarbons (HCFC), and perfluorocarbons (PFC or
`FC) and fluoroiodocarbons (FIC). Except for CF3I these replacement chemicals are less
`effective than Halon 1301 in most scenarios and/or and have one or more adverse global
`environmental impacts (ozone depletion, global warming, long atmospheric lifetime). It is
`unlikely that new, exceptionally effective, and environmentally acceptable halon replacements
`will be identified among the normal saturated fluorine-containing halocarbons. Earlier DoD
`funded projects determined that brominated halocarbons with chemical features leading to very
`short atmospheric lifetimes (“tropodegradable” bromocarbons) are very promising compounds
`for evaluation as halon replacements. This projects goal was to identify, acquire and
`characterize the flame extinguishment performance of tropodegradable bromocarbons with the
`potential of meeting all toxicity, environmental, and performance requirements of a Halon 1301
`replacement.
`
`The history of halon replacement development reflects concurrent progress in fire science
`and basic environmental and atmospheric research areas. Halon development history has the
`
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`appearance of a sequential process involving research-based agent discovery, environmental
`research resulting in tighter acceptance and selection criteria followed by rejection of developed
`alternatives, and a resumption of applied research focused on fire suppression agents. At this
`point environmental property requirements and to a lesser extent toxicological performance
`targets for halon replacements have become more clearly refined and reliably serve as guides in
`compound selection and evaluation.
`
`The targeted compounds in this project all contain bromine and are fluorinated to render
`them non-flammable. Their expected short atmospheric lifetimes translate directly into very low
`ozone depletion and global warming potentials. The chemical families of interest include the
`bromofluoro alkenes, ethers, and amines.
`
`In this project, bromofluoroalkenes were the primary focus of compound selection,
`acquisition and testing efforts due to their promising toxicity, flame suppression, short
`atmospheric lifetime, and acceptable physical properties. The bromofluoro-alkene chemical
`family is probably the most studies of all candidate families. Should the remaining chemical
`families advance to the same level of study they may also prove to be just or more promising as
`sources of halon replacements.
`
`Data from the RTECS database as well as acute inhalation toxicity and subsequent
`AMES test data for several of the bromofluoro alkenes of interest here is very promising. Flame
`extinguishment testing of several bromofluoro alkenes have yielded cup-burner values
`comparable to those of halon 1301 and 1211. Finally, synthetic methods, in some cases, are
`expected to enable relatively low cost manufacture of selected bromofluoroalkenes and give
`hope to the potential for low cost industrial preparation of others.
`
`This project continued previous efforts to identify tropodegradable bromofluoro organic
`compounds with optimal boiling point and flame extinguishment properties. Through
`collaboration with the Advanced Agent Working Group (AAWG) and a U.S. Air Force Halon
`1211 replacement project eight bromofluoro-alkenes were evaluated for acute inhalation toxicity
`resulting in the identification of five promising compounds.
`
`
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`
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`Section
`
`TABLE OF CONTENTS
`
`Page
`
`SECTION I. PROJECT SUMMARY..............................................................................................1
`
`A. BACKGROUND ..................................................................................................1
`B. PROJECT TASKS................................................................................................5
`Task 1. Compound selection................................................................................5
`Task 2. Acquisition - Synthesis and Characterization ..........................................6
`Task 3. Cup-Burner Testing..................................................................................6
`C. TECHNICAL PROBLEMS..................................................................................7
`D. GENERAL METHODOLOGY............................................................................7
`E. TECHNICAL RESULTS......................................................................................8
`F.
`IMPORTANT FINDINGS..................................................................................10
`G. SIGNIFICANT HARDWARE DEVELOPMENT.............................................10
`H. SPECIAL COMMENTS.....................................................................................11
`I.
`IMPLICATIONS FOR FURTHER RESEARCH...............................................11
`
`SECTION II. BIBLIOGRAPHY ...................................................................................................13
`
`A. PAPERS PRESENTED ......................................................................................13
`
`SECTION III PROJECT DESCRIPTION.....................................................................................14
`
`A. COMPOUND SELECTION...............................................................................14
`1. Alkene toxicity information reviewed .......................................................16
`2. Amine Toxicity Information Reviewed.....................................................21
`3.
`Ether Toxicity Information Reviewed .......................................................21
`4. Atmospheric lifetime estimates for alkenes...............................................24
`5. Atmospheric lifetime estimates for ethers .................................................27
`6. Atmospheric lifetime estimates for amines................................................30
`7.
`Physical property estimates – boiling point effects ...................................31
`B. COMPOUND SYNTHESIS AND ACQUISITION...........................................33
`
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`1. Bromofluoro-alkenes .................................................................................34
`2. Bromofluoro-ethers....................................................................................35
`3. Bromofluoro-amines..................................................................................36
`C. SYNTHESES PERFORMED OR ATTEMPTED..............................................37
`1.
`2-Bromo-3,3,3-trifluoropropene, CH2=CBrCF3 ........................................37
`2.
`1-Bromo-2-trifluoromethyl propene, ((CF3)2C=CHBr) ...........................38
`3.
`Fluorobromoalkyl-amines..........................................................................38
`D. COMMERCIAL AND ACADEMIC SOURCES...............................................38
`1. Compounds acquired .................................................................................39
`E. CUP-BURNER TESTING..................................................................................41
`
`SECTION IV. TECHNICAL PROBLEMS...................................................................................45
`
`SECTION V. RECOMMENDATIONS ........................................................................................46
`
`SECTION VI. CONCLUSION......................................................................................................47
`
`REFERENCES ..............................................................................................................................48
`
`APPENDIX A Glossary.................................................................................................................52
`
`
`
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`
`
`Figure
`
`LIST OF FIGURES
`
`Page
`
`NMERI cup-burner utilizing mass loss flow rate characterization ............................................42
`NMERI cup-burner with premixed agent/air source. .................................................................43
`
`
`
` viii
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`
`
`Table
`
`LIST OF TABLES
`
`Page
`
`Tropdegradable Compound Cup-Burner Values ..........................................................................2
`Tropospheric Removal Mechanisms ............................................................................................4
`Targeted Halon 1301 Replacement Criteria .................................................................................6
`Tropodegradable Brominated Halocarbon Cup-burner Values....................................................9
`Tropodegradable Bromofluoro-Amines .....................................................................................10
`Acute Inhalation Data for Tropodegradable Alkenes.................................................................12
`List of 26 Halon 1301 Replacement Candidates ........................................................................15
`General Toxicity and Cardiac Sensitization Rules .....................................................................16
`ALC Values for Halogenated Amines........................................................................................17
`Selected Inhalation LC50 Toxicity Information. .........................................................................18
`Selected RTECS Alkene LCLO Inhalation Toxicity Information. ..............................................19
`Acute Inhalation Toxicity of HFAs. ...........................................................................................21
`Toxicity of Ethers .......................................................................................................................22
`Toxicity of HFEs. .......................................................................................................................23
`HFE Toxicity evaluation.............................................................................................................23
`Atmospheric Lifetimes and ODP Values for Common HCFCs and CFCs. ...............................24
`Estimated hydrogen atom abstraction rate constants and alkene atmospheric lifetimes............26
`Partial List of Tropodegradable Alkenes....................................................................................27
`Tropodegradable Ethers..............................................................................................................29
`Three Carbon Tropodegradable Amines– NR1R2R3...................................................................31
`Four Carbon Tropodegradable Amines– NR1R2R3 ..................................................................31
`Estimated Maximum Boiling Point That Can Achieve a Given Concentration.........................33
`Amines Prepared by Bromobis-(trifluoromethyl)amine Addition to Alkenes. ..........................37
`Brominated Tropodegradable Alkenes Acquired .......................................................................39
`Tropodegradable Bromofluoro-amines Acquired.......................................................................40
`Compound Suppliers...................................................................................................................40
`Cup-burner Flame Extinguishment and Application Temperature Limits.................................44
`NMERI Cup-Burner Flame Extinguishment and Application Temperature Limits ..................44
`
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`Page 12 of 68Page 12 of 68
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` x
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`LIST OF ABBREVIATIONS
`
`Advanced Agent Working Group
`AAWG
`Approximate Lethal Concentration
`ALC
`Dose that is anesthetic to 50 percent of an animal test population
`AD50
`Chemical Abstracts Service (American Chemical Society)
`CAS
`CGET Chemical Options Database
`CCOD
`Center for Global Environmental Technologies
`CGET
`cardiac sensitization - no observable adverse effect level
`CSNOAEL
`Department of Defense
`DoD
`Defense Technical Information Center
`DTIC
`U.S. Environmental Protection Agency
`EPA
`(per)fluorocarbon
`FC
`flame extinguishment concentration
`FEC
`fluoroiodocarbon
`FIC
`Global Warming Potential
`GWP
`hydrochlorofluorocarbon
`HCFC
`hydrochorofluoropolyether
`HCFPE
`hydrofluorocarbon
`HFC
`hydrofluoroether
`HFE
`hydrofluoropolyether
`HFPE
`infrared
`IR
`International Union of Pure and Applied Chemistry
`IUPAC
`lowest concentration causing death
`LCLO
`concentration required to cause death in 50 percent of an animal test population
`LC50
`dose required to cause death in 50 percent of an animal test population
`LD50
`Lowest Observable Adverse Effect Level
`LOAEL
`MEDLARS Medical Literature Analysis and Retrieval System
`MSDS
`Material Safety Data Sheet
`NIOSH
`National Institute for Occupational Safety and Health
`NGP
`Next Generation Program
`
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`NOAEL
`ODP
`PFC
`QSAR
`QSPR
`RTECS
`SERDP
`SNAP
`TSCA
`USAF
`UV
`WPAFB
`
`LIST OF ABBREVIATIONS (concluded)
`
`No Observed Adverse Effect Level
`Ozone Depletion Potential
`perfluorocarbon
`Quantitative Structure-Activity Relationship
`Quantitative Structure-Property Relationship
`Registry of Toxic Effects of Chemical Substances
`Strategic Environmental Research and Development Program
`Significant New Alternatives Policy
`Toxic Substance Control Act
`United States Air Force
`ultraviolet
`Wright-Patterson Air Force Base
`
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`
`A
`B
`g
`H
`K
`lb
`M
`mL
`p
`ppm
`s
`T
`vol.%
`wt.%
`•
`
`LIST OF UNITS AND SYMBOLS
`
`constant in vapor pressure equation
`coefficient in vapor pressure equation
`gram
`hour
`Kelvin
`pound
`minute
`milliliter
`pressure
`parts per million
`second
`temperature
`percent by volume
`percent by weight
`denotes a free radical, e.g., •OH, the hydroxyl free radical
`
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`
`A.
`
`BACKGROUND
`
`SECTION I. PROJECT SUMMARY
`
`Under the Montreal Protocol the production of the fire and explosion protection agents
`Halon 1301, Halon 1211, and Halon 2402 was phased out in the U.S. at the end of 1993.* To
`date, no environmentally acceptable halon substitute comparable to the existing halons in
`toxicity, effectiveness, and dimensionality has been identified.
`
`Halocarbons as replacements for halons have been well studied, and exceptionally
`effective, halon replacements have not been identified among the normal saturated halocarbons
`(excluding iodides and other halocarbons with chemical features leading to short atmospheric
`lifetimes).† The hydrochlorofluorocarbons (HCFC), perfluorocarbons (PFC or FC), and
`hydrofluorocarbons (HFC) are all less effective than the present halons in most scenarios.
`Moreover, all of these have some adverse global environmental impact (ozone depletion, global
`warming, and/or long atmospheric lifetime). PFCs and HCFCs are already subject to some
`restrictions, and such restrictions may eventually extend to HFCs.
`
`There is, therefore, reason to look at compounds other than the normal saturated
`halocarbons. Nonhalocarbon candidates and halocarbons with chemical features leading to very
`short atmospheric lifetimes (“tropodegradable” halocarbons) are known as “advanced agents”
`have been assessed in detail [1, 2]. These compounds represent an opportunity to retain bromine
`in the chemical structure of the fire suppressant without risking significant impact on
`stratospheric ozone levels.
`
`Prior to this project very few tropodegradable bromocarbons had been acquired and
`evaluated for cup-burner performance. Those compounds for which data existed, Table 1,
`provided limited evidence of the potential of this group of chemicals to be halon replacements.
`
`*Only Halon 1211 and Halon 1301 have had significant use in the U.S. The primary use of
`Halon 2402 has been in the former Soviet Union and in a few eastern European countries.
`†Appendix A contains a glossary of chemical, toxicological, and other terms.
`
`
`
`1
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`Table 1. Tropdegradable Compound Cup-Burner Values
`
`Compound name
`
`Compound formula
`
`aCup-Burner,
`%
`
`4.5
`CHBr=CHCF3
`1-bromo-3,3,3-trifluoropropene
`b4.5
`CH2=CHCBrF2
`3-bromo-3,3-difluoropropene
`2.6
`CH2=CBrCF3
`2-bromo-3,3,3-trifluoropropene
`3.5
`CH2=CHCF2CBrF2
`4-bromo-3,3,4,4-tetrafluorobutene
`4.5
`CH2=CHCClFCBrF2
`4-bromo-3-chloro-3,4,4-trifluorobutene
`4.3
`1-bromo-2,3,5,6-tetrafluoro-4-(trifluoromethyl)benzene C6BrF4CF3
`4.1
`3-bromo-1,1,1-trifluoro-2-propanol
`CF3CHOHCH2Br
`4.9
`3,3-dibromo-1,1,1-trifluoro-2-propanol
`CF3CHOHCHBr2
`an-heptane fuel using the NMERI Cup-Burner and mixing of separate air/agent flows.
`bA value of 8.5% was reported earlier based on insufficient compound.
`
`Short atmospheric lifetimes of tropodegradable result from one or more of the following:
`(1) reaction with atmospheric hydroxyl free radicals; (2) photolysis; (3) reaction with
`tropospheric ozone; and (4) physical removal (rain-out) [2]. A number of tropodegradable or
`potentially tropodegradable halocarbons (e.g., alkenes, aromatics, polar-substituted halocarbons)
`have been identified as promising candidates for both Halon 1301 and Halon 1301 replacement.
`
`For the compounds of interest here, the atmospheric hydroxyl free radicals (•OH)
`abstract a hydrogen atom and/or add to an unsaturated molecule to give polar products. It has
`been found that the activation energy for hydrogen atom abstraction decreases (as expected) with
`decreasing dissociation energy of the C-H bond. Replacement of either a fluorine atom or a
`hydrogen atom by an oxygen or nitrogen atom alpha to a CH group decreases the bond
`dissociation energy and increases the reaction rate. Beta substitution generally has a much lower
`substituent effect on bond dissociation energies. We have calculated (in agreement with some
`experimental data) that rate constants for reaction with hydroxyl free radicals increase by a factor
`of approximately 200 for addition of an ether linkage adjacent to a hydrogen atom. This gives
`atmospheric lifetimes as short as 0.3 years for some hydrofluoroethers (HFEs). Replacement of
`a fluorine with a bromine will reduce the atmospheric lifetime by about a factor of 10. Thus
`brominated HFEs should have atmospheric lifetimes as short as 11 days. Experimental
`
`
`
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`characterization of OH radical addition to alkene double bonds indicate the trans-2-butene
`derivatives are likely to have the highest rates of OH addition to the double bond.
`
`Unfortunately, no reliable data exist for amines containing fluorine substitution. The
`atmospheric environmental parameters of some HFAs have been reported [3]. The reported
`lifetime for (CF3)2NCH3 of 0.28 years is of particular interest since replacement of one of the
`fluorine atoms by bromine is likely to reduce this to about 0.028 years due to enhanced
`photolysis[4]. A very small amount of data indicates that for bromine-containing compounds,
`each 10 years increase in atmospheric lifetime increases the ODP by approximately 2. Thus, for
`an atmospheric lifetime of 0.028, (CBrF2)(CF3)NCH3 would have an ODP of 0.006.
`
`Addition of •OH free radicals to unsaturated chemicals is a highly effective removal
`process. For alkenes, the hydroxyl radical adds to give a highly energetic product radical. The
`energetic product can then either revert back to products, or it can be stabilized by collision with
`another molecule which can carry off the excess energy. The reverse reaction is probably not
`important below 100°C. Hydroxyl free radicals can also add to a triple bond and to aromatics.
`
`In general, halocarbons require one of the groups carbonyl, conjugated double bonds,
`double bond conjugated to aromatic, polynuclear aromatic, nitro aromatic, or bromine/iodine to
`be present for there to be significant absorption and photodissociation in the troposphere. All of
`the proposed compounds contain bromine; otherwise, only carbonyls are of major interest in the
`proposed research as far as photolysis is concerned.
`
`The only chemicals exhibiting rapid reaction with tropospheric ozone are the alkenes.
`Removal by tropospheric ozone is expected to be significant for these compounds. The
`mechanisms of these reactions are not well understood, and the potential for reaction of highly
`fluorinated alkenes with tropospheric ozone is uncertain. For a globally averaged tropospheric
`ozone concentration of [O3] = 5.0 x 1011 molecules/cm3 and using a maximum repeated rate
`constant of 2 x 10-16 cm3/molecule-s reported in the literature, one calculates a first-order
`reaction rate constant of k1 = (kO3)[O3] = 1 x 10-4. This allows a calculation for alkenes for the
`atmospheric lifetime of t1/e = 1/k1 = 104 seconds or less than one day. Thus, removal by
`tropospheric ozone could be significant for alkenes. Generally, estimates of the atmospheric
`
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`lifetime of alkenes focus entirely on the hydroxyl radical reaction rate constant and ignore the
`ozonolosis reaction.
`
` lists the various removal mechanisms and the families that are likely to have
`Table 2
`significantly decreased tropospheric lifetimes due to each mechanism.
`
`Table 2. Tropospheric Removal Mechanisms
`
`Primary removal mechanism
`
`Example families
`
`Photodegradation
`Reaction with Hydroxyl
`
`Physical Removal
`Reaction with Tropospheric Ozone
`
`Iodides, Carbonyls, Bromides
`Alkenes, Aromatics, Hydrogen-
`Containing Amines, Hydrogen-Containing
`Ethers, Carbonyls
`Ketones, Alcohols, Esters
`Alkenes
`
`The successful development of a halon replacement is predicated on the identification of
`all critical parameters needed for eventual SNAP approval as well as those parameters central to
`the intended fire and explosion inertion and suppression application(s). The compound selection
`criteria employed in this project reflect current toxicity and environmental concerns and overall
`were the result of an evolving understanding of desired halon replacement properties.
`
`This project identified and acquired several tropodegradable compounds (primarily
`alkenes) estimated to satisfy the requirements of a Halon 1301 replacement. The compound
`properties reviewed or estimated included toxicity, boiling point, fire extinguishment
`performance, and tropospheric lifetime.
`
`Commercial chemical companies and institutes of chemical science in Russia and the US
`were provided with lists of the compounds of interest and quotes for synthesis were requested.
`Commercially available and synthesizable compounds were obtained and evaluated.
`Extinguishment tests run on the acquired compounds employed the NMERI cup-burner.
`
`
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`4
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`B.
`
`PROJECT TASKS
`
`In order to advance the study of tropodegradable bromocarbon extinguishants as possible
`Halon 1301 replacements three tasks were identified and undertaken. The development of lists
`of potential tropodegradable bromocarbons preceded this effort as has the identification of
`chemical syntheses and some commercial sources of compounds. Earlier studies compiled
`toxicity information, atmospheric lifetime estimates, and preliminary lists of potential
`compounds of interest [1, 2]. Despite these assets few tropodegradable compounds had actually
`been acquired and had their flame extinguishment properties evaluated. The lack of actual flame
`extinguishment data (and toxicity test data) greatly slowed earlier efforts in the area of halon
`replacement research.
`
`Three basic tasks identified to advance research in this area are identified briefly below.
`
`Task 1. Compound selection.
`
`Of critical importance in the selection of candidate compounds is an adequate
`understanding of chemical compositional and structural factors contributing to compound
`toxicity and extinguishment capability. Target compounds were evaluated and promising
`candidates identified. The compound properties reviewed or estimated included toxicity, boiling
`point, fire extinguishment performance, and tropospheric lifetime. Toxicity estimates are based
`on toxicity literature, toxicology databases and anesthesiology reports. Promising
`tropodegradable compounds were selected based on either known or predicted properties and
`subsequently procured or synthesized. Toxicity and anesthesiology literature review coupled
`with results from Quantitative Structure-Activity Relationships (QSAR) and Quantitative
`Structure-Property Relationships (QSPR) computational evaluations of chemical properties were
`employed to identify tropodegradable compounds with promise as Halon 1301 replacements. In
`all cases, the compounds selected are predicted to have low tropospheric lifetimes (on the order
`of days), low toxicities (LC50 comparable to that of Halon 1301), fire extingui