Pulse radiolysis of aqueous cyanide solutions. Kinetics of the transient OH and H adducts and subsequent rearrangements. [pH range 1. 9-15]

Journal Article · Thu Jul 01 00:00:00 EDT 1976 · J. Phys. Chem.; (United States)

OSTI ID:7341311

Buechler, H; Buehler, R E; Cooper, R

OH radical reactions with aqueous cyanide were studied by pulse radiolysis over the pH range 1.9-15. The reaction is characterized by three pH ranges: In acid solution (up to pK (HCN/CN/sup -/) = 9.3), OH adds to HCN with k = (6 +- 2) x 10/sup 7/ M/sup -1/ s/sup -1/, forming HO--CH=N. This radical disappears by second-order kinetics with 2k = (2.8 +- 0.5) x 10/sup 9/ M/sup -1/ s/sup -1/. In alkaline solutions (pH 9.3 to pK (OH/O/sup -/) = 11.9) the OH radical adds to CN/sup -/ with k = (7.1 +- 0.5) x 10/sup 9/ M/sup -1/ s/sup -1/. Subsequently a fast protonation equilibrium occurs HO--C=N/sup -/ + H/sup +/ reversible HO--C=NH (pK = 10.2 +- 0.5), the product decaying by an H-atom transfer to the radical .CONH/sub 2/ with k = (4.0 +- 1.0) x 10/sup 7/ s/sup -1/. This latter radical disappears with 2k = (6.2 +- 1.0) x 10/sup 9/ M/sup -1/ s/sup -1/. In very alkaline solutions (pH > pK (OH/O/sup -/) = 11.9) the O/sup -/ addition to CN/sup -/ (k = 2.6 x 10/sup 8/ M/sup -1/ s/sup -2/) and the consecutive protonation and rearrangement to form .CONH/sup -/ are identical with the results published by Behar. Computer simulation techniques were used to determine the resolved spectra, extinction coefficients, and rate constants from the experimentally observed absorptions. The amount of contribution from remaining H-atom reactions has been analyzed separately. The H addition to HCN (k = 3.6 x 10/sup 7/ M/sup -1/ s/sup -1/) leads to the CH/sub 2/=N. radical showing an absorption band with lambda/sub max/ 275 nm. This radical disappears by a second-order process with 2k = (2.6 +- 0.8) x 10/sup 9/ M/sup -1/ s/sup -1/. The results for the OH reactions have been corrected for the contribution from the small amount of H-atom reactions throughout the mechanism.

• Research Organization: Swiss Federal Inst. of Tech., Zurich
• OSTI ID: 7341311
• Journal Information: J. Phys. Chem.; (United States), Vol. 80:14
• Country of Publication: United States
• Language: English

Related Subjects

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY
CYANIDES
CHEMICAL RADIATION EFFECTS
ABSORPTION SPECTRA
AQUEOUS SOLUTIONS
CHEMICAL REACTION KINETICS
HYDROGEN
HYDROXYL RADICALS
INTERMEDIATE STRUCTURE
PH VALUE
PULSED IRRADIATION
RADIOLYSIS
CHEMICAL REACTIONS
CHEMISTRY
CRYOGENIC FLUIDS
DECOMPOSITION
DISPERSIONS
ELEMENTS
FLUIDS
IRRADIATION
KINETICS
MIXTURES
NONMETALS
RADIATION CHEMISTRY
RADIATION EFFECTS
RADICALS
REACTION KINETICS
SOLUTIONS
SPECTRA
400600* - Radiation Chemistry