Some compounds of boron
Some other important compounds of boron are borax, orthoboric acid and boron hydrides. Let us know something about these compounds.
Borax is an important boron compound. It has a white crystalline solid structure with formula of Na2B4 O7.10H2O. The actual formula for borax is Na2[B4 O5(OH)4].8H2O
We get an alkaline solution when borax is dissolved in water. This alkaline solution is nothing but orthoboric acid. When borax is heated it results in losing its water and further results into swelling of molecule. It turns into glass-like structure on further heating which forms borax bead. On initial heating we get sodium metaborate and if we heat it again then we get sodium anhydride. You must keep one thing in mind that metaborate of transition metals have their own characteristic colour and so borax bead test can be used to identify them in lab. For example, when borax is heated in the presence of CoO on a platinum wire, blue colour bead is formed.
Orthoboric acid: The chemical formula of orthoboric acid is H3BO3. It is a white crystalline solid as well is soapy in touch. It is sparingly soluble in water but it properly dissolves in hot water. Boric acid acts as Lewis acid by accepting electrons from the hydroxyl ion.
Diborane: The molecular formula of diborane is B2H6.When boron trifluoride is treated with LiAlH4 in diethyl ether then we get diborane. Diborane is colourless and is also very toxic with the boiling point of 180K. Diborane is very spontaneous in nature therefore, it catches fire very easily and releases an enormous amount of energy.
On reaction with Lewis bases it undergoes cleavage reaction which gives boron adducts.
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