ABSTRACT
Tautomerism of the cytosine molecule is discussed in connection with recent experimental matrix-isolation infrared spectroscopic measurements and recent ab initio calculations of relative stabilities of tautomers and of IR spectra for different tautomeric forms of the compound. Experimental IR spectra in the N-H and O-H stretching regions and in the C = O stretching region are presented for cytosine and for its several derivatives considered as model compounds. This experimental evidence, as well as the quantum-mechanical calculations (including both electron correlation and zero-point vibrational contributions), clearly indicate that two tautomers of cytosine, i.e. the amino-hydroxy and amino-oxo forms with the hydrogen atom at the N(1) position, exist in equilibrium when the cytosine molecule is isolated in an inert environment. The effect of the environment on the relative stabilities of several tautomers is also discussed briefly.
Subject(s)
Cytosine , Cytosine/analogs & derivatives , Cytosine/analysis , Spectrophotometry, Infrared , Stereoisomerism , ThermodynamicsABSTRACT
Design characteristics and performance are described for a low-temperature multiple-reflection cell used with a laser diode spectrometer. The optical pathlength can be varied from 0.04 km to 1.5 km in the temperature controlled cell from 160 K to 300 K. Examples are presented to illustrate pressure broadening in the 16 mum N(2)O band and to indicate some high resolution absorption measurements of rotational manifolds in the nu(4) band of SF(6) and an application to the analysis of the Q-branch of the 2nu(4)-nu(4) hot band transition in SF(6).
