Knowledge Bank

Low temperature infrared spectra have been obtained for the products of the reaction of salt molecules with halogen and hydrogen halide molecules isolated in argon matrices. The reaction of an alkali chloride salt with hydrogen chloride leads to a single, extremely intense hand near $700cm-1$, whose position varies slightly with the alkali metal, Thermo-dynamic considerations have led to the assignment of this band to the asymmetric stretch of the linear, centrosymmetric $HCl2-$ anion in the ion pair $M+$ $HCl2-$. Comparison to the microwave discharge studies of Noble and Pimentel, and the photolysis work of Milligan and Jacox has led to the conclusion that the species observed by both sets of workers is the isolated $HC2-$ anion, as assigned by Milligan and Jacox. Similar studies of salt-halogen reactions have led to the production of the $X3-$ species in the Ion pair $M+X3-$. The asymmetric stretch has been observed in the infrared spectra between 340 and $375cm-1$ , while the symmetric stretch has been detected In Raman studies of these systems, and lies between 235 and $275cm-1$.