SPECTROSCOPIC STUDIES OF KETO–ENOL EQUILIBRIA: PART 2. ANOMALOUS ULTRAVIOLET ABSORPTION SPECTRA OF SATURATED 1,2-DICYANO ESTERS

1962 ◽  
Vol 40 (12) ◽  
pp. 2272-2277 ◽  
Author(s):  
T. R. Kasturi ◽  
B. N. Mylari ◽  
A. Balasubramanian ◽  
C. N. R. Rao
Keyword(s):  
Absorption Band ◽  
Absorption Spectra ◽  
Spectroscopic Studies ◽  
Anomalous Behavior ◽  
Enol Form ◽  
Ultraviolet Absorption ◽  
Polar Solvents ◽  
Solvent Dependence

1,2-Dicyano esters show an absorption band around 245 mμ in alcoholic solutions which is not found in non-polar and other polar solvents. This anomalous behavior has been found to be due to the unusual solvent dependence of the equilibrium between the keto and enol forms. The intensity of the absorption band in alcoholic solutions decreases with increase in concentration of the 1,2-dicyano ester, indicating association of the enol form. The keto–enol equilibrium is also found to be sensitive to the substituent R of the alcohol ROH.

N.M.R. and absorption spectra of nitrotoluidines

1974 ◽  
Vol 27 (4) ◽  
pp. 915 ◽  
Author(s):  
T Yokoyama
Keyword(s):  
Hydrogen Bonding ◽  
Absorption Band ◽  
Nitro Group ◽  
Absorption Spectra ◽  
Long Range ◽  
Chemical Shifts ◽  
Intramolecular Hydrogen Bonding ◽  
Polar Solvents ◽  
Dimethylamino Group ◽  
Intramolecular Hydrogen

N.m.r. chemical shifts of ring protons and absorption spectra of 4-substituted 2-nitroaniline deriva- tives were investigated. It was ascertained that the rotations of dimethylamino and/or 2-nitro groups are influenced by the resonance interaction of the dimethylamino group with 4-substituents and the C1 → C2 absorption band is displaced bathochromically by resonance saturation with 4-substituents. The long-range coupling of NH with H5 in N-methyl-2-nitro-p-toluidine was found to be absent and it is considered that the intramolecular hydrogen bonding of amino hydrogen with the 2-nitro group is ruptured by ROH and polar solvents.

scholarly journals Curcumin analogues for possible cancer treatment A QSAR and partial ordering study

2021 ◽  
Vol 1 (2) ◽  
pp. 001-016
Author(s):  
Lars Carlsen ◽  
Poul Erik Hansen ◽  
Bahjat A Saeed ◽  
Rita S Elias
Keyword(s):  
Cancer Treatment ◽  
Spectroscopic Studies ◽  
Enol Form ◽  
Partial Ordering ◽  
Therapeutic Effects ◽  
Prostate Cancer Treatment ◽  
Polar Solvents ◽  
Curcumin Analogues ◽  
Structure Activity ◽  
Selection Of

The possible effect of curcumin as a potential natural cancer treatment drug has been intensively discussed. In the present study the probabilities of a series of curcumin analogues to possess potential as antineoplastic, prostate cancer treatment and anticarcinogenic agents has been studied theoretically applying a selection of quantitative structure-activity relation and absorption, distribution, metabolism, and excretion (ADME) approaches. From spectroscopic studies it is evident that these compounds can be found in both enol and diketo forms, the former in general the more predominant in non-polar solvents, whereas in polar solvents, like water an increasing amount of the diketo form can be noted. Hence, the probabilities for both the enols and diketo forms to possess the above-mentioned effects were studied. In most cases the enol form shows the highest probabilities for being effective although the differences are not significant. Thus, it is suggested to look at the sum of effects of the keto and the enol forms in relation to the possible therapeutic effects of the compounds here studied.

Coordination complexes of amino acids: Preparation and properties of some Amino-acidatobis(acetylacetonato)cobalt(III) and Bis(amino-acidato)(acetylacetonato)cobalt(III) complexes

1968 ◽  
Vol 21 (3) ◽  
pp. 679 ◽  
Author(s):  
SH Laurie
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Absorption Band ◽  
Absorption Spectra ◽  
Coordination Complexes ◽  
Optically Active ◽  
Ultraviolet Absorption ◽  
Visible Absorption ◽  
Molecular Weights ◽  
Cotton Effects

Complexes of the type [Co(acac)2(aa)] have been synthesized, in which the amino acid is DL- and L-phenylalanine, L-valine, L-leucine, L-proline, DL-, L-,and D-alanine, and glycine. The complexes were characterized by means of analyses, molecular weights, and their infrared, visible, and ultraviolet absorption spectra. During the syntheses several of the bis(amino-acidato) complexes, [Co(acac)(aa)2], were also formed; the L-phenylalanine and glycine complexes were isolated and characterized. The complexes prepared from the optically active amino acids exhibited Cotton effects in the region of the visible absorption band (lA1g, + 1T1g). These effects have been attributed to induced asymmetry rather than stereoselectivity. Amino acids of the same configuration gave rise to Cotton effects of the same sign, ie. (-)590-[Co(acac)2(L-aa)], (-)6590-[Co(acac)(L-aa)2], and (+)590-[Co(acac),(D-aa)].

Spectroscopic studies on some chromones

1970 ◽  
Vol 48 (24) ◽  
pp. 3928-3936 ◽  
Author(s):  
James B. Gallivan
Keyword(s):  
Absorption Spectra ◽  
Room Temperature ◽  
Broad Band ◽  
Spectroscopic Studies ◽  
Luminescence Spectra ◽  
Multiple Bonds ◽  
Polar Solvents ◽  
Singlet States ◽  
Orbital Character ◽  
Phosphorescence Spectra

Absorption and luminescence spectra were measured for chromone, 4-chromanone, and four photoproducts formed by the addition of extramolecular multiple bonds to photo-excited chromone. Absorption spectra in polar and non-polar solvents at room temperature revealed a low lying n → π* singlet transition in all of these systems. The cycloaddition products and 4-chromanone showed a weak fluorescence in polar solvents which was not observed in non-polar solvents, suggesting a solvent reordering, or at least increased mixing of low lying n,π* and π,π* singlet states. No fluorescence could be detected from chromone in either type of solvent. At 77 °K in polar solvents, all of these systems displayed a concentration independent, intense phosphorescence of intermediate lifetime (25 to 200 ms). The lifetime data, combined with the vibrational analyses of the phosphorescence spectra, phosphorescence polarization results, and oxygen induced singlet–triplet absorption spectra support the concept of a lowest energy triplet state of mixed orbital character. More detailed studies on chromone demonstrated a concentration dependent phosphorescence in non-polar solvents, with the "normal" chromone phosphorescence dominant below 10−4 M. At higher concentrations a lower energy, broad band phosphorescence was observed, which in spite of physical aggregation in the ground state, can be ascribed to a chromone exciplex.

STERIC INHIBITION OF RESONANCE: IV. FURTHER SPECTROSCOPIC STUDIES OF 9-NITROANTHRACENE AND 9,10-DINITROANTHRACENE

1959 ◽  
Vol 37 (6) ◽  
pp. 1009-1011 ◽  
Author(s):  
James Trotter
Keyword(s):  
Absorption Spectra ◽  
Spectroscopic Studies ◽  
Ultraviolet Absorption ◽  
Stretching Vibrations ◽  
Steric Inhibition Of Resonance

The frequencies of the NO2 symmetrical stretching vibrations, and the ultraviolet absorption spectra, of solutions of 9-nitroanthracene and 9,10-dinitroanthracene have been measured and correlated with the deviations from coplanarity and resultant resonance inhibition.

Electronic absorption spectra of substituted phthalocyanines in solution and as films

2003 ◽  
Vol 07 (08) ◽  
pp. 551-557 ◽  
Author(s):  
Hiroshi Ogata ◽  
Ryuji Higashi ◽  
Nagao Kobayashi
Keyword(s):  
Absorption Band ◽  
Absorption Spectra ◽  
Electronic Absorption ◽  
Electronic Absorption Spectra ◽  
Film Formation ◽  
Polar Solvents

The electronic absorption spectra of several phthalocyanines substituted at the so-called α-, β- and α and β-positions of the macrocycle have been recorded in solution and as films (α = 1,4,8,11,15,18,22, and 25 positions or 1,8 (or 11),15 (or 18), and 22 (or 25) positions, and β = 2,3,9,10,16,17,23, and 24 positions or 2,9 (or 10),16 (or 17), and 23 (or 24) positions). Phthalocyanines substituted with bulky groups at the α-positions prevent cofacial aggregation so that their Q-absorption band remains at a similar wavelength both in solution and films, although the film spectra are generally broader. Phthalocyanines substituted at the β-positions are apt to aggregate cofacially in polar solvents but in films they may show broad Q-bands which spread out to both shorter and longer wavelengths of the solution Q-band, depending on the bulkiness of the substituents. The film spectra of hexadeca-substituted phthalocyanines exhibit Q-bands at a similar wavelength as in solution, with insignificant broadening of the Q-band on film formation. However, the Soret bands for most of the substituted phthalocyanines are shifted and broadened to longer wavelength in the films.

ULTRAVIOLET ABSORPTION SPECTRA OF ARYL SUBSTITUTED UREAS

1953 ◽  
Vol 31 (10) ◽  
pp. 896-908 ◽  
Author(s):  
J. P. Picard ◽  
A. F. McKay
Keyword(s):  
Absorption Band ◽  
Absorption Spectra ◽  
Inductive Effect ◽  
Progressive Increase ◽  
Ultraviolet Absorption

Absorption spectra of a number of substituted aryl-and sym-diarylureas have been determined in ethanol. As conjugation in the chromophores increased, a gradual displacement of the maxima of the conjugative absorption band towards the visible occurred. This displacement was accompanied by a progressive increase in intensity of absorption. The effect on the absorption spectra of replacing hydrogen of the aryl substituents by alkoxy, methyl, or halogeno groups is discussed. A relationship between the inductive effect of these groups and their influence on the absorption spectra is indicated.

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