Geometry uracil

The effect of solvation on uracil and thymine photophysics has been studied by Gustavvson and coworkers, who have studied uracil with four explicit water molecules and PCM to study distorted geometries [92,93,149], The conical intersection connecting Si to the ground state that was found in the gas phase is also present in solution. The barrier connecting the Si minimum to the conical intersection is lower in solution, however, causing much shorter lifetimes. So the nanosecond lifetime which is observed in the gas phase is not observed in solution but a picosecond lifetime is observed. 

Shukla MK, Mishra PC (1999) A gas phase ab initio excited state geometry optimization study of thymine, cytosine and uracil. Chem Phys 240 319... 

When the monosodium salts of uracil and similar pyrimidines react with diphenyl phosphorochloridate, phosphorylation takes place on oxygen unless other suitable nucleophilic centres are present and free.69 The reaction between the sodium salt of a 1,3-dicarbonyl compound and diethyl phosphorochloridothionate yields the Z-vinylphosphorothionate if the tetrabutylammonium salt is employed, the product has E geometry. This phenomenon has been interpreted in terms of the shape of the... 

One of the most prominent hydrogen-bonded systems is DNA. Despite numerous experimental and theoretical investigations on vibrational spectra of nucleic acid bases [7-13], information on inter- and intramolecular interactions in base pairs and DNA oligomers is still limited [14-25]. A recent example is the work on single adenine-uracil (AU) base pairs in the Watson-Crick geometry in solution, which showed an enhancement of vibrational energy... 

An analogous stereoelectronic influence on the rate of the reductive repair process was also observed by Carell et al. [28]. The ring opening of the dimer radical anion also proceeds stepwise, but with the C(5)-C(5 ) bond being broken first. The C(5) and C(5 )-methyl groups of thymine-derived dimers, which were found to be repaired more slowly than the uracil-derived dimers, lead to distortion of the geometry, which results in deceased overlap of the n C(4)-0(4) orbital with the a C(5)-C(5 ) orbital. 

Figure 10-2. Singly occupied molecular orbitals of uracil obtained with the ROKS method for vertical excitation (a) and at 5] optimized geometry (b). H atoms are shown in white, C atoms in light grey, O atoms in dark grey, and N atoms in black...

Figure 16-5. Evolution of the ground and lowest singlet excited states for uracil (U) from the FC geometry along the 1 (tttt HL) MEP. (Reproduced from Ref. [47] with permission from the American...

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