Ashutosh Jogalekar in The Curious Wavefunction:
A few years ago, a committee organized by the International Union of Pure and Applied Chemistry (IUPAC) – the international body of chemists that defines chemical terms and guides the lexicon of the field – met to debate and finalize the precise definition of a hydrogen bond.
Defining a hydrogen bond in the year 2011? Hydrogen bonds have been known for at least seventy years now. It was in the 1940s that Linus Pauling defined them as foundational elements of protein structure; the glue that holds molecules including life-giving biological molecules like proteins and DNA together. Water molecules form hydrogen bonds with each other, and this feature accounts for water's unique properties. Whether it's sculpting the shape and form of DNA, governing the properties of materials or orchestrating the delicate dance of biochemistry performed by enzymes, these interactions are essential. Simply put, without hydrogen bonds, not just modern civilization but life itself would cease to exist. No wonder that they have been extensively studied in hundreds of thousands of molecular structures since Pauling highlighted them in the 1940s. Today no chemistry textbook would be legitimate without a section on hydrogen bonding. The concept of a hydrogen bond has become as familiar and important to a chemist as the concept of an electromagnetic wave or pressure is to a physicist.
What the devil, then, were chemists doing defining them in 2011?