U641649.pdf (31.34 MB)
Spectroscopic studies of solvent perturbation.
thesisposted on 2015-11-19, 08:46 authored by Antonio Stephen. Pena-Nuñez
The work in this thesis comprises a series of investigations into solvation phenonena. Any such studies concerning aqueous/non-aqueous solvation must address the role of water as a prime solvent capable of hydrogen bonding. Existing structural models for liquid water and aqueous solutions are discussed. The first and second overtone regions (near infrared) are investigated for water/amide systens, the latter region proving to be more informative. The loss of water (OH) free groups is determined fron the spectra with the use of computer graphics which shows that the originally labelled "(OH) free" peak is, in fact, only c. 40% free, the renainder being weakly hydrogen bonded species. These results are then compared with a theoretical approach using the Law of Mass Action. A good correlation is found between experimental and theoretical results, which consequently leads to an accurate classification of the basicities of the amides studied. A thermodynamic approach to these systems was formulated in order to attorpt to assign basicities in a more mathematically rigorous fashion. The solvation of di-tert-butyl nitroxide was extensively investigated using several spectroscopic techniques, e.g. IR, resonance Raman, electronic, in order to ascertain exactly the solvation of the molecule in water, i.e. di H-bonded or mono, etc. This investigation was undertaken in order to help resolve uncertainties in assessing the molecular enviroiment when the molecule is used as an ESR spin label for important biomolecules. It is suggested that the results indicate strongly that DTBN is di H-bonded in water and mono H-bonded in alcohols. The solvation of cyanamethane was investigated using mainly IR but also and C spectroscopic methods. This was prorpted by the unusual high frequency Vmax shift for (CEN) in protic media and the lew frequency Vmax shift encountered in dipolar aprotic media. An attempt was made to explain these phenonena in terms of "end on" H bonding for protic media and "reinforced dipolar interaction" for dipolar aprotic solvents. The solvation of cyanide ion was investigated using IR spectroscopy. This was done to ascertain the nature of peaks sonetimes attributed to "ion-aggregates" or "ion-pairs", in order to see if such peaks might not be in fact due to solvated states resulting fron residual water impurity present in the dipolar media or salt itself. Also an attempt was made to explain Vmax shifts in terms of the character of the "lone-pairs" of electrons used for H-bonding at the carbon or nitrogen.
Date of award1984-01-01
Awarding institutionUniversity of Leicester