SELECT * FROM question_mgmt as q WHERE id=3171 AND status=1 SELECT id,question_no,question,chapter FROM question_mgmt as q WHERE courseId=2 AND subId=9 AND chapterId=52 and ex_no='1' AND status=1 ORDER BY CAST(question_no AS UNSIGNED)
Explain structures of diborane and boric acid.
(a) Diborane B2H6 is an electron-deficient compound. B2H6 has only 12 electrons - 6 e- from 6 H atoms and 3 e-each from 2 B atoms. Thus, after combining with 3 H atoms, none of the boron atoms has any electrons left. X-ray diffraction studies have shown the structure of diborane as:
2 boron and 4 terminal hydrogen atoms (Ht) lie in one plane, while the other two bridging hydrogen atoms (Hb) lie in a plane perpendicular to the plane of boron atoms. Again, of the two bridging hydrogen atoms, one H atom lies above the plane and the other lies below the plane. The terminal bonds are regular two-centre two-electron (2c - 2e-) bonds, while the two bridging (B-H-B) bonds are three-centre two-electron (3c - 2e-) bonds.
(b) Boric acid Boric acid has a layered structure. Each planar BO3 unit is linked to one another through H atoms. The H atoms form a covalent bond with a BO3 unit, while a hydrogen bond is formed with another BO3 unit. In the given figure, the dotted lines represent hydrogen bonds.
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