Photolysis of ethyl-iodide in lithium chloride glassy aqueous solutions with light, λ = 254 nm at 77 K
✍ Scribed by E. M. Burbo; V. S. Gurman
- Publisher
- John Wiley and Sons
- Year
- 1981
- Tongue
- English
- Weight
- 534 KB
- Volume
- 13
- Category
- Article
- ISSN
- 0538-8066
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✦ Synopsis
The photolysis of C2H51 in a glassy salt matrix (5M, 7.5M, 10M) of aqueous LiCl a t 77 K with light of X = 254 nm has been conducted, product analysis being by ESR and UV spectroscopy. The electrolytic medium causes the ionization of product HI, and I-concentrations can be continuously determined. During photolysis [I-] is less than the amount of CzH5I decomposed. But after photolysis thaw-freeze cycling is accompanied by progressive growth in [I-] until the yield matches the C2H51 loss, the quantum yields being 0.26,0.20, and 0.17 for the three LiCl solutions, respectively. The quantum yield of unionized HI is unchanged, however, a t around 0.36, the overall change being due to a fall in the extent to which the HI is ionized in the direct photolysis (4 = 0.22,0.16, and 0.11). It is proposed that this is a consequence of the density increase of matrix packing as the LiCl concentration is increased so that fewer HI are in contact with the aqueous medium and cage recombination is favored.
The results establish that the primary reaction is essentially exclusive:
(1)
CzHsI + h v -C2H4 + HI and that substantial aggregates of C2H51 exist within which HI are caged and cannot be ionized. The direct reaction C2H5I + hv + CzHj +'I' occurs only to a trivial extent, 4 = C2H5 arising virtually totally via C2H4 + H' -C2Hj