Hydrogen bonding ethanolamine

A bifunctional reagent such as ethanolamine can favor ortho substitution of azines due to hydrogen bonding as in 62. With a bifunctional nucleophile such as ethylene glycol anion, facilitation of... 

A hydrogen-bonded cyclic transition state can be postulated for a nucleophile like ethanolamine or ethylene glycol anion whose hydrogen bonding to an azine-nitrogen in aprotic solvents can facilitate reaction via a cyclic transition state such as 78, cf. Section II, F. Ethanolamine is uniquely reactive with 2-chloronitrobenzene by virtue of a cyclic solvate (17) of the leaving group, a postulate in line with kinetic evidence. 

Figure B10.1. The frontier orbitals of an —NH2 group and an —OH group. The stronger hydrogen-bonding interaction (b) determines the most stable conformation of ethanolamine.

To act as an SDA, a molecule must fulfil certain other prerequisites besides stability [5-7]. A critical factor is its solubility in the solvent used (usually water). The potential SDA must possess at least a limited solubility to take part in the reaction. However, if the solubility is too high or if the SDA forms strong hydrogen bonds with water, then its tendency to co-crystallize with the silica will be low and it will prefer to stay in solution. For this reason, alcohols are only weak SDAs, for instance. The fact that ethylene glycol and ethanolamine are grouped with other SDAs for the synthesis of silica sodalite in Fig. Id seems to contradict this conclusion. However, these molecules act as SDAs only in solvothermal synthesis, in which the SDA simultaneously acts as the solvent. 

Hydrogen bonding in (Continued diamine, diol mixtures, 138 ethanolamine, 282 nucleic acids, 137-138 proteins, 137-138 water dimer, 138 water trimer, 139... 

---