Solvent Dependence of Photoinduced Intramolecular Electron Transfer: Criteria for the Design of Systems with Rapid, Solvent-Independent Charge Separation
✍ Scribed by Drs. Jan Kroon; Prof. Dr. Jan W. Verhoeven; Prof. Dr. Michael N. Paddon-Row; Dr. Anna M. Oliver
- Publisher
- John Wiley and Sons
- Year
- 1991
- Tongue
- English
- Weight
- 561 KB
- Volume
- 30
- Category
- Article
- ISSN
- 0044-8249
No coin nor oath required. For personal study only.
✦ Synopsis
consisting of proton transfer from the substrate to base in a rapid and reversible reaction, whose position of equilibrium is governed by the hydroxide ion concentration, followed by an "uncatalyzed" rate-determining protonation at carbon by water. The hydroxide-ion catalytic coefficient for such a process is equal to the equilibrium constant for the first step times the rate constant for the second: k,", = Kk. This equilibrium constant is also equal to the acidity constant of the ynamine ionizing as an acid divided by the autoprotolysis constant of water, K = KJK,. Use of k = l o L 1 sK1 as an upper limit for this rate combined with the experimentally determined value of kHOe = 6.5 x lo6 M-'s-' for phenylaminoacetylene then gives pK, I 18.0 as an upper limit for the acid dissociation of this ynamine [Eq. (i)]. This
K.
PhCECNH, PhC=CNHe + H0 (i) makes phenylaminoacetylene at least 17 pK units more acidic than ammonia (pK, = 35['51) and provides another example of the dramatic acidifying effect of the acetylenic group.