NON-AQUEOUS TITRATIONS AS A TOOL IN THE STUDY OF MOLECULAR RECOGNITION PHENOMENA. USES IN DISTINGUISHING HYDROGEN BONDING FROM PROTON TRANSFER, THE MEASUREMENT OF COMPLEX INDUCED pKa SHIFTS, AND THE ABILITY TO DISTINGUISH THE CATALYTIC ROLES OF GENERAL ACIDS AND BASES
✍ Scribed by Christine L. Hannon; Dwayne A. Bell; Anne M. Kelly-Rowley; Larry A. Cabell; Eric V. Anslyn
- Publisher
- John Wiley and Sons
- Year
- 1997
- Tongue
- English
- Weight
- 120 KB
- Volume
- 10
- Category
- Article
- ISSN
- 0894-3230
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✦ Synopsis
Whenever hydrogen bonding is involved in molecular recognition, the possibility of a proton transfer from the donor to the acceptor arises. In most cases the pK a of the donor is far enough above the pK a of the conjugate acid of the acceptor for it to be clear that no proton transfer will occur. However, as the difference between the donor and acceptor pK a s decreases, it can become difficult to predict whether a proton transfer will occur. Since most hydrogen bond-driven molecular recognition is studied in low dielectric solvents, non-aqueous titrations can be used to measure the pK a s and therefore predict proton transfers. In this paper three studies which involved non-aqueous titrations are summarized. The first deals with distinguishing simple proton transfer from host-guest complex formation. The second involves measuring pK a shifts upon host-guest complex formation. The last is a study of the catalysis of a phosphoryl transfer. In all three scenarios the non-aqueous titration method gave results which would have been difficult to obtain by other means, and which proved crucial for a complete understanding of the molecular recognition process.