Spectrofluorometric studies. IV. Photochemistry of monofluorobenzene

Abstract

The photochemistry of monofluorobenzene in the vapor phase has been examined over a range of wavelengths extending from 2350 to 2710 Á. The sensitized emission of biacetyl was used to determine triplet-state yields for exciting wavelength of 2470, 2550, 2590, and 2670 Á. The effect of cyclohexane on the fluorescence yield and on the sensitized emission yield has been examined.

Spectrofluorometric studies. IX. Fluorescent and triplet yields of the tetrafluorobenzenes excited in the 2600 Å region

“…Once again, neither the fluorescent yield nor the triplet yield is quenched by the addition of c-B-2 ( Table 2). The basic photochemistry of the three isomers of TFB appears to fit into the pattern of the photochemistry of the other fluorinated benzenes reported previously (10,(13)(14)(15) and thus the kinetic schemes given in the above references are likely valid for the isomers of TFB. The relatively low sum of the fluorescent yield plus the triplet yield for 1,2,3,4-and 1,2,3,5-TFB and hence the relatively large quantum deficit [l -( a , + a,)] at all the exciting wavelengths examined suggests that either intramolecular rearrangement (16) or 1,2,4,5-TFB radiationless transitions are important processes The excitation wavelengths used were 2520 and in these molecules.…”

“…All emission measurements were performed on a modified Aminco-Bowman spectrofluorometer. Details concerning the modification and processing of raw data have been discussed in earlier publications (9,10). The reported quantum yields are based on the singlet and triplet yields of benzene given by Noyes et al (11,12).…”

Spectrofluorometric studies. VIII. The effect of CO2 and CHCl3 on the photochemistry of monofluorobenzene

“…), obtained from the American Instrument Company, Inc., was employed for emission and absorption measurements. Experimental details concerning light source, absorption measurements, and correction factors have been given previously (15,8).…”

“…If this precaution is not taken, the FB molecules in high vibrational levels of the triplet 1 state can, on collision, create BiA molecules with enough energy to dissociate (7). In a previous study of the photochemistry of FB (8), this precaution was not taken and hence we believe the triplet yields given in ref. 8 to be artificially low.…”

“…In a previous study of the photochemistry of FB (8), this precaution was not taken and hence we believe the triplet yields given in ref. 8 to be artificially low. The vibrational quenchers employed were CHCI, and CO,.…”