The Deterioration of Dried Fruit. IV. Spectrophotometric and Polarographic Studies

Abstract

Vol. 70 tween 3000 and 2100 A. than that for the phenylhydrazine part of the molecule. This characteristic is exhibited, however, by several of the DNPH's prepared from apricot sirup, and suggests the possibility that it is common to a group of substances not represented in studies of known compounds. It is well known that alcoholic DNPH solutions change color from yellow to red or from yellow to blue when they are made alkaline. The resultant color has been used as the basis for colorimetric analytical methods in a number of cases. The results of work reported in this paper indicate a correlation between the color of DNPH's in alkaline ethanol solution and the degree of adsorption on magnesium sulfate. Furthermore, wide "phenylhydrazine adsorption" bands seem to be associated with compounds which give a blue color change in alkaline alcohol. These properties may be characteristic of a particular type of DNPH. The formation of a red color in alkaline ethanol is characteristic of simple aldehyde and ketone dinitrophenylhydrazones, while the formation of blue colors is associated with 2,4-dinitrophenylhydrazine derivatives such as bis-hydrazones which form with compounds such as sugar osones, glyoxal, diacetyl and methyl glyoxal.13 It is (13) Neuberg and Strauss, Arch. Biochent., 11, 457 (1946); 7. 211 (1945).not to be assumed that only bis-hydrazones give blue colors in alkaline ethanol solutions, but the fact that the blue color change is associated with bis-hydrazones and osazones is of special interest in view of the fact that apricots contain high concentrations of sugars. The possibility that sugar derivatives may be among these unknowns should not be overlooked.

Practical computation of electronic excitation in solution: vertical excitation model

“…Calculated excitation energies u and solvatochromic shifts Du of the lowest excited states of acetone, acrolein, C153, IM, JM, methanal, MCP, and pyridine in polar and nonpolar solvents will be compared with available reference data [100][101][102][103][104][105][106][107][108][109][110][111] and the rest of this section is devoted to explaining the sources of this data.…”

Electronic excitation energies in solution at equation of motion CCSD level within a state specific polarizable continuum model approach

“…[14][15][16][17][18][19][20][21][22][23] The coupling is realized through a simple strategy which exploits an external macroiteration PCM procedure, 24,25 which requires the calculation of the excited state charge density. This macroiteration procedure is, in general, not the most efficient strategy to introduce the solvent effect because it requires that the calculation on the solute system is performed many times until selfconsistency between the solute charge density and the solvent response is achieved.…”

Computational Spectroscopy by Classical Time‐Dependent Approaches

“…Also, the presence of two characteristic functional groups at the same time has important consequences in the chemistry and photochemistry of acrolein. For these reasons, its UVabsorption spectrum has been extensively studied in different solvents [104][105][106][107][108][109][110] as well as in the gas phase [111][112][113], and a solvatochromic blue shift of the n ! p à transition of the C¼O group has been observed in going from the gas phase to aqueous solution, as previously found also for acetone [114] and predicted for formaldehyde [115].…”