Fluorescence of acetone

The acetone-sensitized photodehydrochlorination of 1,4-dichlorobutane is not suppressed by triplet quenchers (20), but the fluorescence of the sensitizer is quenched by the alkyl chloride (13). These observations imply the operation of a mechanism involving collisional deactivation, by the substrate, of the acetone excited singlet state (13,21). This type of mechanism has received strong support from another study in which the fluorescence of acetone and 2-butanone was found to be quenched by several alkyl and benzyl chlorides (24). The detailed mechanism for alkanone sensitization proposed on the basis of the latter work invokes a charge-transfer (singlet ketone)-substrate exciplex (24) and is similar to one of the mechanisms that has been suggested (15) for sensitization by ketone triplets (cf. Equations 4 and 5). 

Dialkyl ketones can undergo radiative deactivation (fluorescence) from the singlet in solution. For example, the quantum yield of fluorescence of acetone at 25°C is 0.01.30 However, the addition of maleic anhydride quenches this fluorescence, and the photocycloaddition product is obtained. Thus, it appears that, in this case, the photocycloaddition reaction can compete with fluorescence for the n,n singlet.32 Such is not the case with ordinary olefins. For example, the fluorescence of acetone was completely unaffected by the addition of 2-pentene,30 and the photocycloaddition reaction is inefficient.32... 

Experimental data show that, at temperatures from about 100 to about 200 °C, co 1 at wavelengths from 2500 to 3200 A50,51. The value cannot be exactly unity toward the long wave end of this region because there is a small fluorescence of acetone even at these temperatures52. The exact point at which fluorescence ceases to be excited is indeterminate and should be slightly temperature dependent. There is no fluorescence at 2537 A. The quantum yield of fluorescence seems never to have been determined with high precision, partly because it is low and the intensity very weak. The value is certainly less than 0.01 under the experimental conditions cited. Hence within the experimental error one may state... 

However, Noyes and co-workers, in a series of publications,52.s3.9e.97 have reported studies on the fluorescence of acetone that, by showing the complexity of the steps between light absorption and decomposition of the acetone molecule, revealed that complications were to be expected when oxygen was added to the system. 

Electronic Spectrum. Acetone is the simplest ketone and thus has been one of the most thoroughly studied molecules. The it n absorption spectrum extends from 350 nm and reaches a maximum near 270 nm (125,175). There is some structure observable below 295 nm, but no vibrational and rotational analysis has been possible. The fluorescence emission spectrum starts at about 380 nm and continues to longer wavelengths (149). The overlap between the absorption and the fluorescence spectra is very poor, and the 0-0 band has been estimated to be at - 330 nm (87 kcal/mol). The absorption spectra, emission spectra, and quantum yields of fluorescence of acetone and its symmetrically methylated derivatives in the gas phase havbe been summarized recently (101). The total fluorescence quantum yield from vibrationally relaxed acetone has been measured to be 2.1 x 10 j (105,106), and the measurements for other ketones and aldehydes are based on this fluorescence standard. The phosphorescence quantum yield is -0.019 at 313 nm (105). 

Rebbert and Ausloos reported that -butyraldehyde quenches the phosphorescence, but exerts no influence on the fluorescence, of acetone (excited by radiation of 3130 A wavelength). Borkowski and Ausloos reported that strong phosphorescence can be observed on irradiating n-butyraldehyde in the presence of biacetyl. The phosphorescence yield increases with increasing aldehyde concentration, and... 

A suspension of a cell line (usually T lymphocyte lines such as HG, HUT-78, or CEM) infected with HIV is spotted on microscope slides, air dried, and fixed in acetone. Addition of uninfected cells to the suspension provides a means for detecting nonspecific reactions in the same smear. Typical localized fluorescence of infected cells is seen after reaction with positive sera. Little or no fluorescence is seen with negative sera. 

Fluorescence quenching has proven to be a powerful means to determine location of tryptophans. Small organic molecules, such as acetone, acrylamide, and amino acids, have been used to quench fluorescence of tryptophans which are exposed to the solvent.(50 51) These molecules apparently quench by close interaction and so provide a tool to determine the surface accessibility7 of tryptophan in a protein. 

Over 50 different pyridazin-3-ones were evaluated for biological activity in a wheat (Triticum aestivum L.) test system described previously (1). Briefly, seeds were germinated in 9-cm petri dishes on three layers of filter paper. Pyridazinones were dissolved in acetone and the filter papers were impregnated with 1 ml of acetone solution. After the soluent evaporated, 10 ml of distilled water were added to form an inhibitor concentration of 100 yM. Seeds were planted directly on the moist papers and germinated for 4 days in a controlled environment chamber on a 16-hr photoperiod with 27+lC day temperature and 21+lC night temperature. Light intensity from both fluorescent and incandescent bulbs was 28 klux at dish level. Lipids were extracted and recovered from 1 g of lyophilized shoot tissue, separated into membrane and non-membrane lipids, and analyzed by gas chromatography as described (1). 

Bicyclopropylidene (1) readily reacted with photochemically generated singlet oxygen at 30-35°C to give spiro[2.3lhexan-4-one (203) and 7-oxadi-spiro [2.0.2.1]heptane (202) [104,1411. Bicyclopropylidene epoxide 202 can also be prepared by epoxidation of 1 with m-chloroperbenzoic acid in the presence of Na2C03 [141] or with KHSOs/acetone [74]. Bicyclopropylidene (1) was found to quench the fluorescence of 9,10-dicyanoanthracene [81]. 

Quenching of Singlets of Carbonyl-Containing Compounds, a. Acetone. Recent reports have shown that singlet complications are not restricted to hydrocarbons for example, the photodecomposition of 1,4-dichlorobutane (52) to free radicals is sensitized by the (n, n) singlet state of acetone.216 Besides the observations that 52 quenches acetone fluorescence and that... 

The fluorescence and phosphorescence of trifluoroacetone vapor has been studied by Ausloos and Murad60 who state that the behavior is similar to that of acetone and may be explained by a similar mechanism. In this process, the acetone molecules (A) on absorption of radiation, are converted into vibrationally excited molecules in the upper singlet... 

Table V. Fluorescence Spectra of Acetone-Soluble Fractions...

Another base-catalyzed reaction is the addition of enolate anions derived from ketones to the 4 position of the pyridine nucleotides (Eq. 15-19). The adducts undergo ring closure and in the presence of oxygen are converted slowly to fluorescent materials. While forming the basis for a useful analytical method for determination of NAD+ (using 2-butanone), these reactions also have created a troublesome enzyme inhibitor from traces of acetone present in commercial NADH.132... 

Time Resolved Spectra. We have studied the time evolution of the fluorescence of BA in acetone as shown in Figure 29. The results are in qualitative agreement with the simulated time-dependent spectra using the simulated p(z,t) and Eq. (38) (see Figure 30). This strongly supports the validity of the adiabatic GLE model for the charge transfer of S, BA. 

Method. The organothiophosphorus insecticides are separated on silica gel with hexane-acetone (2 1 or 3 1). The plate is dried in air and sprayed with a solution of calcein-palladium chloride (0.0005 M palladium chloride in 0.1 M hydrochloric acid mixed with an equal volume of 10-3 Af calcein, adjusted to pH 7.2 with phosphate buffer and diluted with water to obtain a 2.0 10 4Af solution of palladium equilibrated overnight) which is diluted 1 1 with a 50% solution of acetone—water. When the plate is translucent it is dried in air and stored for 18—24 h in a closed chromatographic tank containing a beaker of a saturated solution of calcium nitrate tetrahydrate. This procedure permits the full fluorescence to develop under controlled humidity. The plate is then observed under a UV light at 365 nm, or scanned quantitatively at 365 nm (excitation) and 518 nm (emission). 

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