The hydrogen bond is the most important of all directional intermolecular interactions. It is operative in determining molecular conformation, molecular aggregation, and the function of a vast number of chemical systems ranging from inorganic to biological. Research into hydrogen bonds experienced a stagnant period in the 1980s, but re-opened around 1990, and has been in rapid development since then. In terms of modern concepts, the hydrogen bond is understood as a very broad phenomenon, and it is accepted that there are open borders to other effects. There are dozens of different types of X-H.A hydrogen bonds that occur commonly in the condensed phases, and in addition there are innumerable less common ones. Dissociation energies span more than two orders of magnitude (about 0.2-40 kcal mol(-1)). Within this range, the nature of the interaction is not constant, but its electrostatic, covalent, and dispersion contributions vary in their relative weights. The hydrogen bond has broad transition regions that merge continuously with the covalent bond, the van der Waals interaction, the ionic interaction, and also the cation-pi interaction. All hydrogen bonds can be considered as incipient proton transfer reactions, and for strong hydrogen bonds, this reaction can be in a very advanced state. In this review, a coherent survey is given on all these matters.

The hydrogen bond in the solid state.

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Aryl-aryl bond formation one century after the discovery of the Ullmann reaction.

https://www.erowid.org/archive/rhodium/pdf/suzuki.cross-coupling.review.1995-1998.pdf

Recent advances in the cross-coupling reactions of organoboron derivatives with organic electrophiles, 1995–1998

Recent applications of the Suzuki–Miyaura cross-coupling reaction in organic synthesis

Hydrogen bonds are like human beings in the sense that they exhibit typical grouplike behavior. As an individual they are feeble, easy to break, and sometimes hard to detect. However, when acting together they become much stronger and lean on each other. This phenomenon, which in scientific terms is called cooperativity, is based on the fact that 1+1 is more than 2. By using this principle, chemists have developed a wide variety of chemically stable structures that are based on the reversible formation of multiple hydrogen bonds. More than 20 years of fundamental studies on these phenomena have gradually developed into a new discipline within the field of organic synthesis, and is nowadays called noncovalent synthesis. This review describes noncovalent synthesis based on the reversible formation of multiple hydrogen bonds. Starting with a thorough description of what the hydrogen bond really is, it guides the reader through a variety of bimolecular and higher order assemblies and exemplifies the general principles that determine their stability. Special focus is given to reversible capsules based on hydrogen-bonding interactions that exhibit interesting encapsulation phenomena. Furthermore, the role of hydrogen-bond formation in self-replicating processes is actively discussed, and finally the review briefly summarizes the development of novel materials (nanotubes, liquid crystals, polymers, etc.) and principles (dynamic libraries) that recently have emanated from this intriguing field of research.

Noncovalent synthesis using hydrogen bonding

Publisher Summary This chapter discusses the hydrogen bonding, which has been recognized as the single most important intermolecular interaction, The chapter presents the hypothesis that there are three kinds of hydrogen bond: weak, strong, and very strong. These are determined by the shape of the potential energy well and the respective positions of hydrogen and deuterium within the well, which can be used to provide information about the well that applies in a particular example. The role of hydrogen bonding in catalysis has been discussed, although mainly in terms of the salicylate ion as a leaving group. With its strong intramolecular hydrogen bond playing an essential part in the reaction mechanism, it seems likely that this will herald other systems where the role of a strong hydrogen bond may serve as the key step in a catalytic process.

Hydrogen Bonding and Chemical Reactivity

Publisher Summary This chapter reviews that acid and base catalysis of a chemical reaction involves the assistance by acid or base of a particular proton-transfer step in the reaction. Many enzyme catalyzed reactions involve proton transfer from an oxygen or nitrogen centre at some stage in the mechanism and often the role of the enzyme is to facilitate a proton transfer by acid or base catalysis. Proton transfer at one site in the substrate assists formation and/or rupture of chemical bonds at another site in the substrate. It discusses that an increasing number of categories of proton transfer of oxygen and nitrogen acids are being discovered that do not fit this simple picture and many of these more complex proton transfers have been proposed as components of multi-step mechanisms. In a sense, the more complex proton transfers are of greater chemical interest than processes controlled by the rate of encounter between reactant molecules. The chapter highlights that the presence of an intramolecular hydrogen bond in an acid considerably modifies the acid–base behavior and rates of proton transfer are different from the diffusion-limited values.

Mechanisms of Proton Transfer between Oxygen and Nitrogen Acids and Bases in Aqueous Solution

Glowing jellyfish, luminescence and a molecule called coelenterazine.

2-Amino-3-benzoyl-5-bromopyrazine 6 is prepared from 2-chloropyrazine in 4 steps and its transition metal-catalysed Suzuki coupling to arylboronic acids is explored as a route to the pyrazine ring system found in the luminescent chromophore coelenterazine 2.

Frank Hibbert

Papers

Hydrogen Bonding and Chemical Reactivity

Mechanisms of Proton Transfer between Oxygen and Nitrogen Acids and Bases in Aqueous Solution

Glowing jellyfish, luminescence and a molecule called coelenterazine.

Hydrogen Bonding and Chemical Reactivity

A Suzuki Coupling Approach to Pyrazines Related to Coelenterazine