Boron nitride is a polymeric white solid. It is isoelectonic with graphite. It has been prepared in four allotropic forms. The most common is the hexagonal form which has graphite like structure consisting of layers fused six membered (BN)₃ rings.

(1)    Highly pure hexagonal boron nitride can be prepared by reaction of ammonia with BCI₃ or BF₃

                                                Pyrolyisi
2BCI₃ + 6NH₃   →  2B(NH₂)₃     →  2(BN)₃
                           -6HCI           750⁰C

(2)    It is also prepared by reaction of diboron trioxide (B₂O₃) with NH₃ at 1200⁰ C.

B₂O₃ + 2NH₃  →   2(BN)_x + 3H₂O

(3)    In laboratory, it can be prepared by fusion of borax with NH₄ or by fusion of urea and boric acid.
Strucutre: The polymeric solid has a graphite-like structure containing alternate boron and nitrogen atoms. The remaining two electrons on nitrogen are used for forming π-bonds by donation form N to B atoms. Alternate sheets are located such that boron atoms are directly over nitrogen atoms. This structure gives rise to easily sliding of planes relative to each other lending boron nitride lubricant

properties, comparable to those of graphite. Unilike graphite, it is a colorless electrical insulator, as there is a large energy gap between filled and vacancy π-bonds.

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