Tag: M.W=100-150

Wandlowski, Th. published the artcileStructural and Thermodynamic Aspects of Phase Transitions in Uracil Adlayers. A Chronocoulometric Study, Recommanded Product: 3-Methylpyrimidine-2,4(1H,3H)-dione, the publication is Langmuir (1996), 12(26), 6604-6615, database is CAplus.

The phase formation of uracil and 5 uracil alkyl derivatives on a Au (111) single crystal electrode from aqueous 0.05 M KClO₄ was studied by using chronocoulometry, cyclic voltammetry, and phase-sensitive ac voltammetry. As a function of the applied electrode potential and/or the adsorbate concentration, uracil (U), 5-methyluracil (5-MU), and 5,6-dimethyluracil (5,6-DMU) exhibit 4 different adsorption regions. These are assigned to a “dilute” phase (I), a 2-dimensional condensed physisorbed film (II), a partial charge transfer/deprotonation region (III), and a chemisorbed film (IV). Substitution of the N (1)- and/or the N (3)-ring N with Me groups prevents the formation of the ordered physisorbed film II. In the case of 1-methyluracil (1-MU) and 3-methyluracil (3-MU), region I is followed immediately by regions III and IV. No indications for the latter 2 regions were found with 1,3-dimethyluracil, where both ring N atoms are blocked simultaneously with Me groups. Quant. thermodn. adsorption parameters (e.g., film pressure, Gibbs surface excess, Gibbs energy of adsorption, and electrosorption valence) were determined on the basis of chronocoulometric measurements for the “dilute” and the 2-dimensional condensed physisorbed film. All of these mols. are oriented parallel to the electrode surface in both ordered regions. The corresponding values of the Gibbs energies of adsorption ΔG_I° and ΔG_II° of the 6 uracil derivatives on Au (111) indicate weak chemisorption. On the basis of structural and energetic data, the formation of the 2D-condensed physisorbed film of U, 5-MU, and 5,6-DMU is interpreted as a replacement of residual interfacial H₂O mols. accompanied by the creation of a 2D network of planar oriented and (via H bonds) interconnected mols. The adsorption and phase formation parameter obtained for the 6 uracil derivatives on Au (111) in regions I and II is complemented by anal. of selected (published) results on Ag (111) and Hg electrodes. No quant. thermodn. data were extracted in regions III and IV.

Langmuir 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 C19H14Cl2, Recommanded Product: 3-Methylpyrimidine-2,4(1H,3H)-dione.

Referemce:
https://pubchem.ncbi.nlm.nih.gov/compound/Pyrimidine,
Pyrimidine – Wikipedia

Brown, D. J. published the artcileSimple pyrimidines. III. Methylation and structure of the aminopyrimidines, Application of N,N-Dimethylpyrimidin-4-amine, the publication is Journal of the Chemical Society (1955), 4035-40, database is CAplus.

cf. C.A. 49, 14000f. 2- (I) and 4-aminopyrimidine (II) were shown to exist largely in the amino form, by comparison of their basic strength, and ultraviolet and infrared spectra with those of the corresponding nuclear and extranuclear N-Me derivatives The preparation of the nuclear N-Me derivatives involved the methylation of I and II to 1,2-dihydro-2- (III) and 1,4-dihydro-4-imino-1-methylpyrimidine (IV), resp. In alk. solution, III rearranged to 2-methylaminopyrimidine (V), while IV was hydrolyzed to 1,4-dihydro-1-methyl-4-oxopyrimidine (VI). The ultraviolet spectra of the cations of I and II were similar to those of the cations of III and IV, which suggested that a proton was bonded to a nuclear N atom in cations from I and II. This view was suggested by the marked difference between the spectra of the cations of I, II, V, 2-dimethylamino (VII), 4-methylamino- (VIII), and 4-dimethylaminopyrimidine (IX) and that of the neutral mol. of pyrimidine itself. For the neutral molecules of I and II the ultraviolet absorption curves were quantitatively displaced along the wavelength scale from those of the corresponding nuclear N-Me derivatives (III and IV) than from those of the extranuclear N-Me analogs V, VII, VIII, and IX. There is the possibility of some amine-imine tautomerism. The extent of such tautomerism was calculated from the ionization constants of the N-Me series fixed in the amino and imino forms. K_tautometric = [amine]/(imine] = K_a[amino]/K_a[imino]. By using the ionization constants of III, IV, V, VII, VIII, and IX it was found that the amine-imine tautomeric constant in aqueous solution was of the order of 10⁶ for both I and II. In the solid state and in nonaqueous solvents I and II similarly exist largely in the amino form as was shown by their infrared spectra. Both I and II in CCl₄ gave 2 sharp bands at 3540 and 3430 cm.^-1 due to asym. and sym. stretching modes of the unassocd. NH₂ group and 2 broad bands at 3320 and 3170 cm.^-1 due to vibration modes of the intermol. H-bonded NH₂ group. V and VIII give only 1 sharp band at 3460 cm.^-1 and a broad one near 3260 cm.^-1 In the double-bond stretching region, I and II showed a strong band at 1650 cm.^-1 which was due to internal deformation of the NH₂ group, for it disappeared upon deuteriation. In the same region the salts of III and IV absorbed strongly at 1646 cm.^-1 and the deuteriated compounds showed some absorption, which may be due to the C:N stretching mode. V and VIII showed a strong band near 1615 cm.^-1 and were unaffected by deuteriation. I (5 g.), 10 ml. MeI, and 60 ml. MeOH were kept 5 days at room temperature to give 2.9 g. III hydriodide (X), m. 247-8° (decomposition) (from 95% EtOH). X (0.23 g.) cooled to 0°, moistened with H₂O, covered with Et₂O, and then ground with 1 g. powd. KOH and the Et₂O solution separated, dried, and concentrated yielded crude III. Recrystallization of III was carried out by solution in Et₂O, drying, filtering through cotton, concentrating, cooling to room temperature, filtering with a filter stick, and drying in a desiccator over CaCl₂ to yield pure III, yellow needles, m. 102-4°; picrate, m. 198-200° (from EtOH). X (1 g.) heated 10 min. in 12 ml. NaOH solution yielded 71% V, m. 59-60°; picrate, m. 191° (mixed m.p. with III picrate showed a depression). II (5 g.), 5 ml. MeI, and 25 ml. MeOH refluxed 1 hr. gave 10 g. IV hydriodide (XI), m. 205-6° (from EtOH). In another experiment the reactants were left 3 days at room temperature to give XI, m. 163-4°. Recrystallization of this lower-melting form or storage for 3 days gave the higher-melting form. XI picrate, m. 172-3° (from EtOH). XI (0.9 g.) left 10 hrs. at 20-5° with 0.1N NaOH, HCl added to pH 5, the solution evaporated and the residue treated with picric acid yielded 55% VI picrate, m. 164-6°. VI picrate, prepared from authentic base also m. 164-6°. The 2 specimens showed no mixed m.p. depression. An attempt to prepare 1,2,3,4-tetrahydro-2,4-diimino-1,3-dimethylpyrimidine gave only a single monomethylated derivative of indeterminate structure.

Journal of the Chemical Society published new progress about 31401-45-3. 31401-45-3 belongs to pyrimidines, auxiliary class Pyrimidine,Amine, name is N,N-Dimethylpyrimidin-4-amine, and the molecular formula is C6H9N3, Application of N,N-Dimethylpyrimidin-4-amine.

Referemce:
https://pubchem.ncbi.nlm.nih.gov/compound/Pyrimidine,
Pyrimidine – Wikipedia

Herbich, Jerzy published the artcileDual fluorescence of 4-(dialkylamino)pyrimidines. Twisted intramolecular charge transfer state formation favored by hydrogen bond or by coordination to the metal ion, Quality Control of 31401-45-3, the publication is Journal of Physical Chemistry (1989), 93(9), 3439-44, database is CAplus.

4-(N,N-Dimethylamino)pyrimidine did not exhibit any markedly dual luminescence even in highly polar (aprotic) solvents, unless the ortho substituent deviated the NMe₂ group from coplanarity with the ring. Protic solvents or complexation with Zn²⁺ caused the longwave fluorescence to appear distinctly. 4-(N,N-Diethylamino)pyrimidine revealed dual luminescence in sufficiently polar (aprotic) environment. In alc. solutions the intensity of the fluorescence was reduced. Fluorescence properties of this group of compounds fit the twisted intermol. charge transfer model. The importance of nonradiative deactivation increases with the H⁺-donating ability of the solvent.

Journal of Physical Chemistry published new progress about 31401-45-3. 31401-45-3 belongs to pyrimidines, auxiliary class Pyrimidine,Amine, name is N,N-Dimethylpyrimidin-4-amine, and the molecular formula is C6H9N3, Quality Control of 31401-45-3.

Referemce:
https://pubchem.ncbi.nlm.nih.gov/compound/Pyrimidine,
Pyrimidine – Wikipedia

Smets, J. published the artcileFT-IR spectroscopic study of uracil derivatives and their hydrogen-bonded complexes with model proton donors. Part 5. Complexes of uracils with hydrogen chloride in argon matrixes, Recommanded Product: 3-Methylpyrimidine-2,4(1H,3H)-dione, the publication is Journal of Molecular Structure (1994), 318(1-3), 37-53, database is CAplus.

FT-IR spectra are reported for uracils complexed with hydrogen chloride in Ar matrixes. The spectral characteristics demonstrate that uracils form a C₄:O···H-Cl hydrogen bond of intermediate strength in Ar matrixes. The large shift of the proton donor mode ν_s finds support in the vibration correlation diagram for O-base.HCl complexes. For some of the bases a small amount of the C₂:O···HCl species is identified in matrixes containing an excess of HCl. H-bonding of the C:S group plays only a minor role in thiouracils. For all the bases studied here, N-H···Cl-H structures are also identified from the shifts of the uracil N-H modes. The results allow the discussion of particular bonding trends for the basic groups in uracils, these trends being largely consistent with earlier reported results for complexes of uracils with other proton donors.

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 C14H10O4, Recommanded Product: 3-Methylpyrimidine-2,4(1H,3H)-dione.

Referemce:
https://pubchem.ncbi.nlm.nih.gov/compound/Pyrimidine,
Pyrimidine – Wikipedia

Chen, Yunan published the artcileAn experimental investigation of sewage sludge gasification in near and super-critical water using a batch reactor, Computed Properties of 31401-45-3, the publication is International Journal of Hydrogen Energy (2013), 38(29), 12912-12920, database is CAplus.

The gasification of sewage sludge in near and super-critical water was investigated in a batch reactor. Results showed that the formation of gaseous products could be intensively affected by temperature In order to understand the effect of temperature on the development of reaction process and the formation of gaseous products better, the detailed characteristics of solid and liquid products were analyzed by SEM, N₂ adsorption-desorption technique, FTIR, TOC, Ammonia-nitrogen anal. and SPE-GC/MS. The changes in the yield distribution of products and the characteristics of solid and liquid products indicated that organic matters in sewage sludge were almost completely dissolved and hydrolyzed in water at 425 °C. The dissolution and hydrolysis products were gasified by reforming and other reactions. The polymerization and dehydrogenation also occurred in dissolution and hydrolysis products, and the Diels-Alder reaction mechanism could be used to explain the phenomenon.

International Journal of Hydrogen Energy published new progress about 31401-45-3. 31401-45-3 belongs to pyrimidines, auxiliary class Pyrimidine,Amine, name is N,N-Dimethylpyrimidin-4-amine, and the molecular formula is C6H9N3, Computed Properties of 31401-45-3.

Referemce:
https://pubchem.ncbi.nlm.nih.gov/compound/Pyrimidine,
Pyrimidine – Wikipedia

Li, Wu-Hu published the artcileIn-Situ Infrared Spectroscopic and Scanning Tunneling Microscopy Investigations of the Chemisorption Phases of Uracil, Thymine, and 3-Methyl Uracil on Au(111) Electrodes, Category: pyrimidines, the publication is Langmuir (1999), 15(14), 4875-4883, database is CAplus.

The complementary techniques of in-situ IR spectroscopy and scanning tunneling microscopy (STM) have been used in this study to build detailed structural models for the chemisorbed forms of uracil, thymine, and 3-Me uracil on Au(111) electrodes. The IR spectra, in water and D₂O electrolytes, show that both uracil and thymine adopt similar coordination forms with the surface with both exocyclic oxygen atoms and a deprotonated N3 facing in toward the surface in a vertically oriented chemisorbate. 3-Me uracil cannot exhibit such a surface coordination and its IR signature in the carbonyl stretching region is quite different. This is interpreted as the chemisorbate interacting through its deprotonated N1 and C2=O. STM has been used to characterize and compare the mol. ordering of the three resp. adsorbates. Uracil exhibits the highest coverage structure c(3x√3), while thymine exhibits smaller ordered domains which are expanded in one direction to allow for the spatial requirements of the Me group on thymine. The domain size for the thymine chemisorbate could be improved by temperature annealing the electrode in-situ and a “pseudo c(√3×4)” structure was observed Both the uracil and thymine chemisorbate structures feature chains of mols., stacked like “rolls of coins”, close enough for-stacking to occur. The structure of thymine overlayers differs from uracil, since there are a number of different possible orientations of adjacent mol. rows, which results in a high frequency of stacking faults. These differences are discussed. 3-Me uracil is quite different, exhibiting a rather low coverage, albeit a highly ordered structure (5×2√3) which cannot allow-stacking. On the basis of these observations, the factors governing the formation of the resp. chemisorbed phases are discussed.

Langmuir 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, Category: pyrimidines.

Referemce:
https://pubchem.ncbi.nlm.nih.gov/compound/Pyrimidine,
Pyrimidine – Wikipedia

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

Gambacorta, Augusto published the artcileHSAB driven chemoselectivity in alkylation of uracil derivatives. A high yielding preparation of 3-alkylated and unsymmetrically 1,3-dialkylated uracils, Name: 3-Methylpyrimidine-2,4(1H,3H)-dione, the publication is Tetrahedron (1999), 55(43), 12615-12628, database is CAplus.

A qual. hardness scale (N¹<N³<O⁴) has been found for the conjugated bases of 2-methoxy-4(3H)-pyrimidinone and its 5- and 6-Me derivatives and applied to high yielding chemoselective N³ methylation, ethylation and benzylation reactions. Removal of the 2-methoxy group followed by a second alkylation affords unsym. 1,3-disubstituted uracils.

Tetrahedron 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, Name: 3-Methylpyrimidine-2,4(1H,3H)-dione.

Referemce:
https://pubchem.ncbi.nlm.nih.gov/compound/Pyrimidine,
Pyrimidine – Wikipedia

Mueller, Andreas published the artcileProbing the Watson-Crick, Wobble, and Sugar-Edge Hydrogen Bond Sites of Uracil and Thymine, Computed Properties of 608-34-4, the publication is Journal of Physical Chemistry A (2005), 109(23), 5055-5063, database is CAplus and MEDLINE.

The nucleobases uracil (U) and thymine (T) offer three hydrogen-bonding sites for double H-bond formation via neighboring N-H and C:O groups, giving rise to the Watson-Crick, wobble and sugar-edge hydrogen bond isomers. The hydrogen bond properties of all three sites by forming hydrogen bonded dimers of U, 1-methyluracil (1MU), 3-methyluracil (3MU), and T with 2-pyridone (2PY) are probed. The mass- and isomer-specific S₁ ← S₀ vibronic spectra of 2PY·U, 2PY·3MU, 2PY·1MU, and 2PY·T were measured using UV laser resonant two-photon ionization (R2PI). The spectra of the Watson-Crick and wobble isomers of 2PY·1MU were separated using UV-UV spectral hole-burning. The different isomers are identified by combining three different diagnostic tools: (1) Selective methylation of the uracil N3-H group, which allows formation of the sugar-edge isomer only, and methylation of the N1-H group, which leads to formation of the Watson-Crick and wobble isomers. (2) The exptl. S₁ ← S₀ origins exhibit large spectral blue shifts relative to the 2PY monomer. Ab initio CIS calculations of the spectral shifts of the different hydrogen-bonded dimers show a linear correlation with experiment This correlation allows the identification of the R2PI spectra of the weakly populated Watson-Crick and wobble isomers of both 2PY·U and 2PY·T. (3) PW91 d. functional calculation of the ground-state binding and dissociation energies D_e and D₀ are in agreement with the assignment of the dominant hydrogen bond isomers of 2PY·U, 2PY·3MU and 2PY·T as the sugar-edge form. For 2PY·U, 2PY·T and 2PY·1MU the measured wobble:Watson-Crick:sugar-edge isomer ratios are in good agreement with the calculated ratios, based on the ab initio dissociation energies and gas-phase statistical mechanics. The Watson-Crick and wobble isomers are thereby determined to be several kcal/mol less strongly bound than the sugar-edge isomers. The 36 observed intermol. frequencies of the nine different H-bonded isomers give detailed insight into the intermol. force field.

Journal of Physical Chemistry A 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, Computed Properties of 608-34-4.

Referemce:
https://pubchem.ncbi.nlm.nih.gov/compound/Pyrimidine,
Pyrimidine – Wikipedia

Gebauer, Sabine published the artcileHigh performance liquid chromatography on calixarene-bonded silica gels. II. Separations of regio- and stereoisomers on p-tert-butylcalix[n]arene phases, Recommanded Product: 3-Methylpyrimidine-2,4(1H,3H)-dione, the publication is Journal of Chromatographic Science (1998), 36(8), 383-387, database is CAplus.

The chromatog. behavior of new calix[n]arene-bonded (n = 4, 6, 8) silica gels are described. Cavities of different size and shape are formed depending on the number of aromatic moieties. The differences in ring size were used to study chromatog. selectivities towards analytes of various substance classes, including disubstituted aromatics, uracil derivatives, and estradiol epimers. The authors’ results indicate that these calixarene-bonded phases show a high resolution power for regio- and stereoisomers.

Journal of Chromatographic Science 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, Recommanded Product: 3-Methylpyrimidine-2,4(1H,3H)-dione.

Referemce:
https://pubchem.ncbi.nlm.nih.gov/compound/Pyrimidine,
Pyrimidine – Wikipedia