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  1. #1
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    Trimethyl aluminium


    Read this in this months fridge mag, trimethyl aluminium is whats made when the methyl chloride in fake R134a reacts with aluminium in compressor etc, it goes bang when when it meets air. Three engineers have been killed so far due to stuff going pop while being fixed. These were reefer unit but some car ac systems have been affected as well. The methyl chloride will eat hoses etc too and turns oil into goo....

    Be careful where you get your gas!


    Mostly found in Oxfordshire, UK :)

  2. #2
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    Re: Trimethyl aluminium

    ref from wikipedia
    Trimethylaluminium

    From Wikipedia, the free encyclopedia
    (Redirected from Trimethyl aluminium)
    Jump to: navigation, search
    IUPAC name[hide]
    trimethylalumane
    Other names[hide]
    Trimethylaluminium; aluminium trimethyl
    CAS number 75-24-1 Y
    PubChem 16682925
    ChemSpider 10606585 Y
    Jmol-3D images Image 1
    • C[Al](C)C
    • InChI=1S/3CH3.Al/h3*1H3; Y
      Key: JLTRXTDYQLMHGR-UHFFFAOYSA-N Y

      InChI=1/3CH3.Al/h3*1H3;/rC3H9Al/c1-4(2)3/h1-3H3
      Key: JLTRXTDYQLMHGR-MZZUXTGEAJ
    Molecular formula C6H18Al2
    Molar mass 144.18 g/mol
    Appearance Colorless liquid
    Density 0.752 g/mL
    Melting point 15 C
    Boiling point 125 C
    Main hazards Pyrophoric
    NFPA 704
    4
    3
    3
    W
    Y (verify) (what is: Y/N?)
    Except where noted otherwise, data are given for materials in their standard state (at 25 C, 100 kPa)
    Infobox references
    Trimethylaluminium is the chemical compound with the formula Al2(CH3)6, abbreviated as Al2Me6, (AlMe3)2 or the abbreviation TMA. This pyrophoric, colorless liquid is an industrially important organoaluminium compound. It evolves white smoke (aluminium oxides) when the vapor is released into the air.
    [edit] Structure and bonding

    Al2Me6 exists as a dimer, analogous in structure and bonding to diborane. As with diborane, the metalloids are connected by a 3-center-2-electron bond: the shared methyl groups bridge between the two aluminium atoms. The Al-C(terminal) and Al-C(bridging) distances are 1.97 and 2.14 , respectively.[1] The carbon atoms of the bridging methyl groups are each surrounded by five neighbors: three hydrogen atoms and two aluminium atoms. The methyl groups interchange readily intramolecularly and intermolecularly.
    3-Centered-2-electron bonds are an utterance of "electron-deficient" molecules and tend to reactions with Lewis bases that would give products consisting of 2-centered-2-electron bonds. For example upon treatment with amines gives adducts R3N-AlMe3. Another reaction that gives products that follow the octet rule is the reaction of Al2Me6 with aluminium trichloride to give (AlMe2Cl)2.
    The species AlMe3, which would feature an aluminium atom bonded to three methyl groups is unknown. VSEPR Theory predicts that such a molecule would have idealized threefold symmetry, as observed in BMe3.
    [edit] Synthesis and applications

    TMA is prepared via a two-step process that can be summarized as follows:
    2 Al + 6 CH3Cl + 6 Na → Al2(CH3)6 + 6 NaClTMA is mainly used for the production of methylaluminoxane, an activator for Ziegler-Natta catalysts for olefin polymerisation. TMA is also employed as a methylation agent. Tebbe's reagent, which is used for the methylenation of esters and ketones, is prepared from TMA. TMA is often released from sounding rockets as a tracer in studies of upper atmospheric wind patterns.
    TMA is also used in semiconductor fabrication to grow thin film, high-k dielectrics such as Al2O3 via the processes of Chemical Vapor Deposition or Atomic Layer Deposition.
    TMA forms a complex with the tertiary amine DABCO, which is safer to handle than TMA itself.[2]
    In combination with Cp2ZrCl2 (zirconocene dichloride), the (CH3)2Al-CH3 adds "across" alkynes to give vinyl aluminium species that are useful in organic synthesis in a reaction known as carboalumination.[3]
    [edit] Semiconductor grade TMA

    TMA is the preferred metalorganic source for metalorganic vapour phase epitaxy (MOVPE) of aluminium-containing compound semiconductors, such as AlAs, AlN, AlP, AlSb, AlGaAs, AlInGaAs, AlInGaP, AlGaN, AlInGaN, AlInGaNP etc. Criteria for TMA quality focus on (a) elemental impurites, (b) oxygenated and organic impurities.
    [edit] References


    [edit] External links


  3. #3
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    Re: Trimethyl aluminium

    Found a link to the article,

    http://www.acr-news.com/news/news.asp?id=2641&src=tw

    It go bang!
    Mostly found in Oxfordshire, UK :)

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    Re: Trimethyl aluminium

    A few questions:
    1. How does a service technician determine beforehand whether an unknown system is safe to work on?
    2. What are safe working procedures to remove the hazardous material, & make the system safe?
    3. If a system is determined to be contaminated, what happens - is it scrapped?
    4. If scrapped, should it be made safe first?
    Innovator, IP trader - Rarefied Technologies
    The impossible in real time - miracles may take slightly longer... :)

  5. #5
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    nevgee is offline Veteran Poster I am starting to push the Mods: of RE
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    Re: Trimethyl aluminium

    I read that the real danger is due to the fact that trimethyl aluminium combusts instantaneously (explosively) on contact with air.

    Apparently it is a liquid and generally sits in the crankcase with the oil! If no oxygen gets to the substance everything would appear to remain safe but for the fact this stuff creates havac if mixed with POe oil and generally becomes a seriously aggressive kid on the block by destroying everything it touches, especially seals.
    Sounds very much like a substitute for Alien spit.

    That makes a suspected contaminated system one really hot potato to handle. safe bet would be to call the Bomb squad and walk (run) away.

    It has been suggested a practical way to remove the substance would be to pierce the base of the crankcase and use OFN to blow (no pun intended) the contaminated oil out into a container of water. Sounds simple enough but I wouldn't particularly wish to be the one to try it.

    Upside is that you do not need to have an "F" Gas qualification to handle Methyl Chloride or its bi products. So leave it to the cowboys to deal with.
    Reality is an elusion created by alcohol deficiency. Quaff and enjoy. [Yorkshire, UK]

  6. #6
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    Re: Trimethyl aluminium

    This is no joke.
    i think the big question is:HOW DO U DETERMINE IF THE SYSTEM U HAVE TO WORK ON ARE CONTAMINATED?
    Hope this will teach the gas buyers to make sure that they buy quality gas and not just the cheapies from China.
    THE BEST WAY OF LEARNING IS TO DO IT YOURSELF!!!

  7. #7
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    Re: Trimethyl aluminium

    Cambridge Refrigeration Technology is working on finding solutions to the problem. Their latest report can be found here:

    http://www.ttclub.com/fileadmin/uplo...efrigerant.pdf

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