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Rates of detritiation in trifluoroacetic acid have been measured for the five non-equivalent positions in the nonaiternant hydrocarbon fluoranthene. Rates a t 70.0" times 1 07k (sec.-l) for detritiation at each position are as follows: 1 -,

R. H I A~, CHRISTINE MCCOLEMAN, and G. R. HOWE. Can. J. Chem. 53,559 (1975). Triphenylstibine reduced r-Bu02H to r-BuOH almost as fast as Ph3P does, while triphenylarsine reacts only 1/60as fast. Both reductions are first-order ineach component; in ethanol k, for Ph3Sb and Ph3As are 106.7e-9.71RT and 109.1e-15.7RT; respectively. The reductions are not very sensitive to choice of solvent, but are strongly catalyzed by compounds of molybdenum and vanadium.The relative rate order PH3P 3 Ph3Sb > Ph3As is ascribed to two conflicting trends,availability of d-orbitals for T-bonding with peroxidic oxygen, and the Group VB to oxygen bond strength.R. HIATT, CHRISTINE MCCOLEMAN et G. R. HOWE. Can. J. Chem. 53,559 (1975). La triphenylstibine rkduit le r-Bu02H en r-BuOH presqu'aussi rapidement que le fait Ph3P; par ailleurs la triphenylarsine rtagif environ 60 fois moins rapidement. Chacune des reductions est du premier ordre en chacun des rkactifs; dans I'ethanol, les valeurs de k, pour Ph3Sb et Ph3As sont respectivement de 106.7e-9.71RT et l@.le-l5.7/RT. Les reductions ne sont pas sensibles a u choix du solvant mais sont fortement catalysees pardes composis du molybdkne et du vanadium.L'ordre relatif des vitesses Ph3P 3 Ph3Sb >Ph3As est attribue h deux tendances contradictoires soit la disponibilite d'orbitales pour former des liens T avec I'oxygkne du peroxyde et l a force de la liaison de I'oxygkne avec les eltments du groupe VB.[Traduit par le journal]

Hewlett-Packard No. 2801A quartz digital thermometer. Temperatures are believed accurate to +0.04°.Kinetic measurements for all of the thenils, with the exception of 3,3'-benzo[b] thenil, 2,2'-benzo[b]thenil, and 5,5'-di(2"thienyl)-2,2'-thenil, were carried out in the same manner.A sample of the thenil, in the range of 2.5-3.0 mmol, was weighed to 0.1 mg and placed in a 250-ml Teflon screw cap bottle, along with a magnetic stirring bar. The thenil was dissolved in 100.0 ml of equilibrated dioxane with stirring. The solution was continuously stirred during the kinetic run by means of a submersible magnetic stirrer mounted directly beneath the reaction vessel. A 50.00-ml quantity of 0.1 N temperature equilibrated potassium hydroxide solution was pipetted into the thenil solution with vigorous stirring. The vessel was sealed with a screw cap arrangement that permitted the insertion and withdrawal of a pipette. A 10.00-ml aliquot of the thenil solution was immediately withdrawn. The aliquot was quenched in a 10-ml sample of ice cold acetone and the clock was started.The sample was titrated to either a phenolphthalein (pH 8.3) or thymol blue (pH 8.0) end point with 0.01 N hydrochloric acid. At various intervals, depending on the rate of potassium hydroxide disappearance, 10-ml aliquots were withdrawn and titrated in the same manner.Simultaneously with the kinetic runs, a blank sample was determined under the same conditions described above, except that the thenil was omitted. In this manner it was possible to correct for any acidic impurity present in the thenil and also for any reaction of the base with the solvent. During the 80°runs and to a lesser extent at 70°, a small correction (by never more than 3%) was found to be necessary.At other temperature, the correction was too small to be measured.

Die Geschwindigkeit der Detritiierung von 3‐, 4‐, 8‐, 9‐Brom‐[2‐T]‐ und ‐[3‐T]‐ fluoranthen, von 3‐Brom‐[8‐T]fluoranthen und von 1‐, 4‐, 6‐, 7‐, 8‐, 9‐ und 10‐Nitro‐[3‐T]fluoranthen und zum Vergleich von [2‐T]‐, [3‐T]‐ und [8‐T]Fluoranthen in Trifluoressigsäure wird bei 70°C und z.T. bei 128,25°C gemessen.

The principles underlying the calculations of activation energies for electrophilic aromatic substitution are examined. Hijckel and self-consistent-field methods have been used to calculate localisation energies and electron distributions for the ground state and for transition states for ortho-, me&-, and para-substitution in some monosubstituted benzenes. The localisation energies fail to predict correctly the observed results by either method. Correlation with uf values is better with the Huckel than the SCF method, but this is considered fortuitous.

Suwnmary All-valence-electron CND0/2 calculations cor-upon the rate of electrophilic hydrogen exchange relative to rectly predict the directional and reactivity effects of a single position in benzene, "plus" indicating an increase in substituents upon electrophilic aromatic substitution, rate, "minus" a decrease. The predictions agree with the and indicate that alternation of charge-density in the experimental results1,* in every case e.g. the chloro-group is ring system is a feature of both 0-and .rr-type molecular deactivating but is ortho-para directing. orbitals.

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