The Absorption Spectrum and Photochemical Decomposition of Hydriodic Acid

Adipic Acid Production via Metal-Free Selective Hydrogenolysis of Biomass-Derived Tetrahydrofuran-2,5-Dicarboxylic Acid

“…FA is unreactive without HI (Table , entry 6), providing further evidence of H 2 ’s inability to directly participate in the reaction without HI. The formation of SA from FA in the presence of HI suggests that HI can indeed facilitate hydrogenation of the CC bond, via one of two pathways: (1) HI is added across the CC bond to make 2-iodobutanedioic acid followed by a displacement reaction with HI to form SA and I 2 ; and (2) HI first decomposes into I 2 and H 2 , which is then used to hydrogenate the CC bond . In contrast, HI cannot drive the cascade reaction from THFDCA to AA in the absence of H 2 .…”

“…The presence of HI is necessary to activate H 2 , because no hydrogenolysis is observed regardless of reactants. HI is known to decompose into H 2 and I 2 both photochemically as well as thermochemically. − Moreover, I 2 can be converted to negatively charged, higher-order iodide species such as the triiodide (I 3 – ) via the exergonic addition of iodide to iodine (I 2 + I – → I 3 – ) in a variety of solvents. − Such reactions of I – demonstrate its ability to act as reducing agent through either direct electron transfer or the production of H 2 , e.g., R–OH + 2 HI → R-H + H 2 O + I 2 (Scheme a, bottom pathway). , Degradation of iodide was observed in our system by analyzing postreaction solutions by ultraviolet–visible spectroscopy (UV–vis), which show strong absorption bands at ∼350 and 290 nm (Figure S3a). These bands have been assigned to the excitation of an electron from the π and σ molecular orbitals of triiodide, respectively, to the σ* orbital in triiodide. , Furthermore, the intensity of these bands increases over the course of reaction (4 h), which reflects the gradual conversion of iodide and the formation of triiodide (Figure S3b).…”

“…The formation of SA from FA in the presence of HI suggests that HI can indeed facilitate hydrogenation of the CC bond, via one of two pathways: (1) HI is added across the CC bond to make 2-iodobutanedioic acid followed by a displacement reaction with HI to form SA and I 2 ; and (2) HI first decomposes into I 2 and H 2 , which is then used to hydrogenate the CC bond. 59 In contrast, HI cannot drive the cascade reaction from THFDCA to AA in the absence of H 2 . Although H 2 is not required for MA hydrogenolysis, enhanced conversion of MA was observed when HI and external H 2 were cofed in comparison with that when only HI was employed (see below).…”

“…The presence of HI is necessary to activate H 2 , because no hydrogenolysis is observed regardless of reactants. HI is known to decompose into H 2 and I 2 both photochemically 59 as well as thermochemically. 60−62 Moreover, I 2 can be converted to negatively charged, higher-order iodide species such as the triiodide (I 3…”

1 potential, 2 potentials, 3 potentials–4: Untangling the UV photodissociation spectra of HI and DI

“…Research on this problem began in earnest in the 1930's with a series of measurements of the UV photodissociation continuum over an increasingly wide range of frequencies. [2][3][4] Rollefson and Booher suggested that the A-band spectrum might be due to transitions into two different final electronic states with asymptotes separated by the I( 2 P 3/2 )→ I( 2 P 1/2 ) atomic spin orbit splitting, 2 but the available experimental data could not prove this, and in the first empirical inversion analysis applied to this system, Goodeve and Taylor 4 interpreted their spectrum in terms of transitions onto a single repulsive final state potential energy curve.…”