Chemistry Question #484

chris, a 20 year old male from Saint John asks on December 25, 2001,

Boron trifluoride (BF3) is non-polar, yet is much more soluble in a polar tetrhydrofuran (THF) than in non-polar solvents. Can you explain why BF3 is non-polar; and rationalize this apparent exception to the "like dissolve like" rule and illustrate your explanation by showing the interaction between BF3 and THF. Thanks alot for your time.

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The answer

Reg Mitchell answered on December 27, 2001

BF3 reacts with any ether to form a new compound BF3.Et2O where the B has a negative charge and the O a positive one; likewise THF+_BF3-. This has a much higher boiling point than either and is soluble in polar organic solvents.

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