Infrared Spectrum and Force Constants of the Nitrite Ion

The infrared spectra of the following compounds have been investigated: microcrystalline NaNO₂, KNO₂, and AgNO₂; and aqueous solutions of NaNO₂ and KNO₂. The spectra of N¹⁵‐labeled compounds have also been obtained. The spectrum of the high‐temperature modification of NaNO₂, which exists above 160°, has been observed. The fundamental frequencies for NO₂^— (in crystalline NaNO₂) are: ${\nu }_1({\mathrm{a}}_1\text{)=1328±2\hspace{0.17em}}{\mathrm{cm}}^{\text{−1}}\mathrm{\hspace{0.17em}(}{\mathrm{N}}^{14}\text{),1303±2\hspace{0.17em}(}{\mathrm{N}}^{15}{\mathrm{);\nu }}_2({\mathrm{a}}_1\text{)=828.2±0.4\hspace{0.17em}(}{\mathrm{N}}^{14}\text{),823.6±0.4\hspace{0.17em}(}{\mathrm{N}}^{15}{\mathrm{);\nu }}_3({\mathrm{b}}_1\text{)=1261±3\hspace{0.17em}(}{\mathrm{N}}^{14})$ . These are used to calculate the following force constants, in units of millidynes/A: $f_d{\text{=7.69±0.10,f}}_{\alpha }{\mathrm{/d}}^2{\text{=1.75±0.04,f}}_{\mathrm{dd}}{\text{=1.94±0.13,f}}_{\mathrm{d\alpha }}\text{/d=0.505±0.113}$ .