Chemistry · Ch 9 — Elements of Group 13, 14 and 15
Orthoboric acid / boric acid (H3BO3)
Orthoboric acid / boric acid (H3BO3)
Orthoboric acid, also called boric acid, H3BO3, has a central boron atom bonded to three -OH groups, giving each individual molecule a trigonal planar B(OH)3 shape. In the solid state, however, these planar units do not exist in isolation: they stack into extended, layered sheets, with adjacent B(OH)3 units in the same layer held together by hydrogen bonds between the -OH groups of neighbouring molecules (see the Orthoboric-acid-structure figure note). This hydrogen-bonded, layered arrangement is wha …
What this figure shows. Solid orthoboric acid is drawn as flat, trigonal-planar B(OH)3 units, each with boron at the centre bonded to three -OH groups, and each -OH group of one unit hydrogen-bonded to an -OH group of a neighbouring unit. Repeating this hydrogen-bonding pattern across many B(OH)3 units builds an extended two-dimensional sheet, and the diagram shows several such sheets stacked to form the layered crystal structure described in the running text, with only weak forces holding successive layers together, similar in spirit to graphite's layered structure and giving solid boric acid its characte …