Mastryukov, Vladimir S. published the artcileThe effect of methylation on the structure of uracil, Safety of 3-Methylpyrimidine-2,4(1H,3H)-dione, the publication is Journal of Molecular Structure (1995), 173-86, database is CAplus.
Equilibrium geometries of uracil, 1-methyluracil and 3-methyluracil (in which the Me group is attached to nitrogen), 5-methyluracil (thymine) and 6-methyluracil (in which the Me group is attached to carbon), 1,3-dimethyluracil and 5,6-dimethyluracil have been determined by ab initio Hartree-Fock calculations with the split-valence 4-21G basis set. For the methylated derivatives, calculations are made for different conformations corresponding to different orientations of the Me groups. The conformational energy differences are small, indicating a very low barrier to internal rotation, except for 5- and 6-methyluracils in which there is a preference of 1-2kcalmol-1 for the conformer with the Me C-H bond eclipsing the double bond of the ring. The structural differences between the methylated uracils and the parent mol. are analyzed. Angular deformations within the ring induced by substitution of a Me group for hydrogen follow, to a rough approximation, the trends established earlier for benzene derivatives on the basis of X-ray studies. Deviations occur due to the difference between nitrogen and carbon in the ring, with deformations being more pronounced for N- than for C-substituted uracils. The Me groups, in general, show a distinct tilt away from an adjacent carbonyl group, indicating a repulsive interaction. Mulliken population anal. shows the electroneg. Me group withdraws charge mainly from the atom to which it is attached and, to at least as great an extent, from the adjacent ring atoms. The results are compared with those obtained earlier by the semiempirical MINDO/3 method and also by different exptl. techniques including X-ray, neutron, and electron diffraction. These other studies have given much information on the structure of the compounds, but because of their nature they have not been able to analyze detailed structural variations induced by the Me group substitution.
Journal of Molecular Structure published new progress about 608-34-4. 608-34-4 belongs to pyrimidines, auxiliary class Pyrimidine,Amide, name is 3-Methylpyrimidine-2,4(1H,3H)-dione, and the molecular formula is C5H6N2O2, Safety of 3-Methylpyrimidine-2,4(1H,3H)-dione.
Referemce:
https://pubchem.ncbi.nlm.nih.gov/compound/Pyrimidine,
Pyrimidine – Wikipedia