Monoprotonated pyrazine cation

Electrochemical processes involving pyrazine (pz) and monoprotonated pyrazine cation (pzlf adsorbed on a silver surface have been investigated by Surface-Enhanced Raman Scattering (SERS). The investigation of the faradaic and non-faradaic behaviour of pz adsorbed on silver by SERS is a good example of the application of this technique to the study of solid-liquid interfaces. Electrochemical SERS can be used to infer the orientation of the adsorbed molecule. The results presented in this work indicate that pz adsorbs end-on via the lone pair electrons on the nitrogen, and this orientation is not potential dependent. 

Adsorption of Monoprotonated Pyrazine Cation on SUver Electrodes. Pyrazine is a very weak base (pKai = 0.65 (12)), and hence the monoprotonated pz spectrum was obtained in a 1 M HCIO4 + 1 M KBr solution. Figure 8 shows spectra of pzlT adsorbed on a silver electrode at two different potentials. One band at ca. 990 cm is observed for an applied potential of -310 mV vs. SCE. A broad envelope containing two bands (one at ca. 1015 cm and another at ca. 1030 cm, corresponding to the modes number 1 and 12 in Wilson s notation, respectively) appears as the applied potential becomes more positive (see the spectrum at -170 mV presented in Figure 8). The forms of these two normal vibrational modes are presented below (13) ... 

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