Those lattice energies are huge which provides an incredible driving force for their formation. To put those numbers into perspective, the heat of formation of aluminum oxide, Al2O3, which drives the thermite reaction is -1,669.8 kJ/mol. The ones quoted below are much higher because of the small size of the the ions. All neatly mathematically summarized in an equation too complex to write here, but is simply. See https://chem.libretexts.org/Bookshelves/General_Chemistry/Map%3A_Principles_of_Modern_Chemistry_(Oxtoby_et_al.)/UNIT_6%3A_MATERIALS/21%3A_Structure_and_Bonding_in_Solids/21.5%3A_Lattice_Energies_of_Crystals equation 21.5.3
On Jul 9, 2020, at 1:16 PM, Jack Reidy <jreidy2**At_Symbol_Here**STANFORD.EDU> wrote:All,
I forwarded this to our Chemistry Department and received an interesting reply from Prof. Bob Waymouth, chair of the department safety committee, about an alternative explanation for the explosion. In the original email he attached an article, which can be found at this link (http://pubsapp.acs.org.stanford.idm.oclc.org/cen/safety/19970317.html?). The text of the email he sent is below:
Thanks for forwarding. The use of reducing metals (Li, Mg, Al) with fluorinated organic compounds is hazardous and as pointed out by authors, there are several examples of explosions. We had previous experience with Grignards of compounds containing trifluoromethyl groups. (See C&E News Letter from 1997). We had attributed the explosion hazard to be due to the high lattice energies of the metal fluorides. I think this a a more likely interpretation than that of the authors, but they do describe previous explosions with Al reducing agents and perflourinated compounds.
=46rom my quick CRC look (you should check these numbers)
MgF2. Lattice energy -2922 kJ/mol
AlF3 Lattice energy - 5924 kJ/mol
From: ACS Division of Chemical Health and Safety <DCHAS-L**At_Symbol_Here**Princeton.EDU> On Behalf Of DCHAS Membership Chair
Sent: Thursday, July 9, 2020 4:49 AM
Subject: [DCHAS-L] Serious Explosion during Large-Scale Preparation of an Amine by Alane (AlH3) Reduction of a Nitrile Bearing a CF3 Group
Serious Explosion during Large-Scale Preparation of an Amine by Alane (AlH3) Reduction of a Nitrile Bearing a CF3 Group
Here, we wish to report a serious explosion during large-scale preparation of an amine by alane (AlH3) reduction of a nitrile bearing a CF3 group. The accident took place during the reduction of a 1 mol batch of 1-methyl-3-(trifluoromethyl)-1H-pyrazole-5-carbonitrile. At the stage of decomposition of the reaction mixture after reduction with MeOH, the reactor was destroyed by detonation; one researcher was seriously harmed by shatters and burnt by flames. This Case Study describes this incident in detail and discusses how we can prevent similar incidents.
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