Hypsochromic

The auto-association of A-4-thiazoline-2-thione is clearly indicated b the hypsOchromic shift (5 nm) of the 315-nm band when the spectrum is first recorded at 50°C and then at —25°C (10 M in cyclohexane). In the same temperature range the spectrum of 3-methyl-A-4-thiazoline-2-thione remains unchanged (61). 

Electron-donating or -withdrawing properties of a substituent on the 4 and 5 positions have also been used in order to modulate the basicity in the hope to observe either hypsochromic or bathochromic shift (110). 

The meso carbon atom should present a carbenium structure with a low TT electron density in the ground state, in the excited state this carbon possesses the carbeniate structure (C ) with a high tt electron density (119). An electron-donating group in such a position should stabilize the ground state and rise the excited state to the highest level hypsochromic shift results as a whole. 

Knott s rule concerns the importance of the place of the nitrogen atom replacing a methine carbon in the conjugated chain when the atom is separated from the active auxochromic atoms by an odd number of conjugated atoms, the shift is bathochromic. It is hypsochromic when there is an even number, Tne importance of the shift could establish a measure of M effect of various heterocyclic nuclei (79. 124). Many papers have been published, and examples have been given to verify these rules (79-84). 

Most cyanines show prominent, hypsochromic vibrational shoulders at shorter wavelength associated with the long-wavelength electronic transition (Fig. 2). These vibrational shoulders include one or two vibrational quanta (0 — 1 0 — 2 ), in addition to the absorption energy at Intensity... 

The shade may be varied by choosing amines. For aromatic amines, the steric effect of substituents in the ortho position reduces the conjugation of the anibno group with the anthraquinone moiety, and the result is a hypsochromic shift and brighter shade. Thus Cl Acid Blue 129 (120) has a more reddish and brighter shade than Cl Acid Blue 25 (118). Cycloalkylamines have a similat effect on the shade. Cl Acid Blue 62 [5617-28-7] (125) Cl 62045) is an example. 

A large body of information is available on the UV spectra of pyrazine derivatives (B-61MI21400, B-66MI21400). Pyrazine in cyclohexane shows two maxima at 260 nm (log e 3.75) and 328 nm (log e 3.02), corresponding to ir->ir and n ir transitions respectively (72AHC(14)99). Auxochromes show similar hypsochromic and bathochromic shifts to those observed with the corresponding benzenoid derivatives. 

Their physical properties closely resemble those of pterin, which has a basic pKt, of 2.20 and an acidic one of 7.86 associated with N-1 protonation and a hypsochromic shift of the long-wavelength absorption band in the UV spectrum, and N-3 deprotonation effecting a bathochromic shift respectively (Table 4). The xanthopterin (4) and isoxanthopterin types... 

Table 30 reports u C=0) for a variety of azolinones containing ring double bonds. The hypsochromic effect of an oxygen atom or CRa group versus the bathochromic effect of NR, S or C=C can readily be traced. 

Substituents in positions 3 and 4 produce bathochromic shifts whereas substituents in position 5 produce hypsochromic shifts, which become more pronounced as the bulk of... 

Hypoxanthine, 2-trifluoromethyl-synthesis, 5, 587 Hypoxanthine, trimethylsilyl-glycosylation, 5, 536 Hypoxanthinium nitrate, 1,3,7-trimethyl-thiation, 5, 540 Hypsochromic shift, 1, 344... 

The mechanism of interaction with DNA is suggested. Ethidium bromide (EB) displacement assay was performed. We determine the binding constant of Tb-E to DNA to be in the order of Ig K = 6.47 0.4. The bathochromic and hypsochromic effects in the absorption spectra of investigated complex were observed and the interaction is assumed to be mainly of the mono-intercalating type. 

Therefore it is possible to determine absorption spectra directly on the TLC plate by comparison with a substance-free portion of the layer. The wavelengths usually correspond to the spectra of the same substances in solution. However, adsorbents (silanols, amino and polyamide groups) and solvent traces (pH differences) can cause either bathochromic (ketones, aldehydes [60, 61], dyestuffs [62]) or hypsochromic (phenols, aniline derivatives [63]) shifts (Fig. 23). 

Dimroth et al. introduced 8 as a solvatochromic probe of solvent polarity having absorption in the visible region it shows the largest solvatochromic shift of any substance yet reported. Ey (30) is calculated with Eq. (8-76), like Z. (The peculiar symbolism arose because compound 8 happened to be No. 30 on the list of substances studied by Dimroth et al.) The shift is hypsochromic as solvent polarity is increased. Table 8-16 gives some Ey (30) values. - (30) is linearly... 

A hypsochromic shift of 20-50 cm is observed in the double-bond stretching region, when the enamines are converted to the corresponding iminium salts by the electrophilic addition of a proton at the /3-carbon atom. The shift is accompanied by an enhancement in the intensity of the band. Leonard and co-workers (68,71-74) have used this absorption shift as a diagnostic tool for the determination of the position of the double bond... 

He found that the UV maximum exhibits a hypsochromic shift in an alkaline medium. In the IR spectra he found maxima in the carbonyl... 

In the UV spectrum of the protonation products there is a hypsochromic shift of the absorption maximum of enyne system compared to the bases (74DIS) this agrees with the data of the protonation of simple enamines and dienic amines (69MI1). 

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