ABSTRACT
For generations, chemistry students have been taught to regard water as an inappropriate solvent for carrying out organic reactions. However, this has not always been the case. The synthesis of urea by Friedrich Wöhler in 1828,1 generally regarded as the birth of synthetic chemistry,2 was carried out in water by heating an aqueous solution of ammonium cyanate. Use of aqueous reactions continued into the
4.1 Introduction .................................................................................................. 103 4.1.1 Historical Use of Water as a Solvent ................................................ 103 4.1.2 Water as a Green Solvent .................................................................. 104 4.1.3 Overcoming Solubility and Reactivity Issues with Aqueous
Phase Chemistry ............................................................................... 105 4.1.4 Ongoing Challenges with Aqueous Reactivity ................................. 106
4.2 Studies on the Origin of Enhanced Reactivity under Aqueous Conditions .... 107 4.2.1 Polarity Effects ................................................................................. 107 4.2.2 The Hydrophobic Effect ................................................................... 108 4.2.3 Hydrogen Bonding ............................................................................ 109 4.2.4 Heterogeneous Systems .................................................................... 110
4.3 Aqueous Chemistry in the Undergraduate Organic Laboratory .................. 111 4.3.1 Transition Metal-Catalyzed Reactions ............................................. 111 4.3.2 Pericyclic Reactions .......................................................................... 113 4.3.3 Reduction and Oxidation Reactions ................................................. 114 4.3.4 Nucleophilic Additions and Substitutions ........................................ 116 4.3.5 Electrophilic Additions and Substitutions ........................................ 120 4.3.6 Radical Reactions ............................................................................. 121
4.4 Lecture Case Studies in Aqueous Chemistry ............................................... 122 4.4.1 Rhodium-Catalyzed Hydroformylation ............................................ 122 4.4.2 Other Aqueous Biphasic Applications ..............................................124 4.4.3 Synthesis of Right’t™ Azo Pigments .............................................. 125
4.5 Conclusion .................................................................................................... 126 References .............................................................................................................. 127
early part of the twentieth century, and many of the named reactions known today owe their discoveries to reactions performed in water. Some examples include the Baeyer-Villiger oxidation,3 the Curtius rearrangement,4 the Hofmann degradation,5 the Sandmeyer reaction,6 and the Wolff-Kishner reduction.7
