A Dimorphic Form of d-Catechin

Abstract

NOTES 145In the last communi~ati~n~ was described how the quantum yield may be increased by the addition of NO to the photodecomposing CHJ, the NO reacting with the CH, radical and so preventing the reverse reactions. The quantum yield (1.6) was obtained by comparing the velocity of photodecomposition with that of the photooxidation of CHJ studied by Bates and S p e n~e ,~ where they obtained a quantum yield of about two. With nitric oxide a kinetic equation was obtained which seemed to account for the results pretty well, except that the quantum yield, 1.6, was too large, and should actually have been about unity. This discrepancy was too great to be accounted for by experimental errors. Blaedel, Ogg and Leighton' have recently considered these discrepancies, and have indicated that the quantum yield of Bates and Spence should be 1.0 instead of 2.3, when account is taken of the temperature coefficient of the chloroacetic acid actinometer which Bates and Spence used.The present writers have now carried out a more direct measurement of the quantum yield of the process CHJ + NO + b = I + CH,NO.Apparatus and Procedure.-The photochemical set-up was similar to that previously described.' The reaction cell was of clear quartz, about 4 cm. in diameter, and 7 cm. long, and connected to the rest of the glass apparatus by a quartz-glass seal. The nearest greased tap was 80 cm. from the cell. The source of radiation was a Hanovia mercury arc (medium pressure). Great dissculty was experienced in getting SLI & cient intensity of the 2537 A. resonance radiation, even with the cooled arc. Filters were used to isolate the whole region 2500-2700 A.? which gave more readable results. This, however, involved the use of an average or weighted mean quantum, which we obtained by using the radiation in the uranyl oxalate actinometer described by Leighton and Forbes8; the quantum yield of the decomposition being 0.6 in this region. The Moll large surface thermopile which was used in conjunction with a Moll galvanometer, was Calibrated with the aid of a Hefner lamp as previously TABLE I Temperature, 15-20" C. Mean galvanometer ddections corresponding to absorbed light: -0.2-0.6 cm. Thiosulfate titrations: . -0.2-2 cc. Pressure, mm. Time of irrpdiaQuantum CHtI NO tion, mm. yield 78.5 20.5 1158 0.5 105.0 52.0 1367 0.84 109 85.0 931 1.2 119 87 3324 0.91 122 90 1101 1.1 102 95 4184 1.14 122 100 948 1.2 101 154 917 0.9 -(5) Bates and Spence. Trans. Faraday SOC., 17, 468 (1931). (6) B l d e l , Ogg and Lcighton. Trns JOURNAL. 64, 2500 (1942). (7) Bowen, 1. C h m . Soc., 76 (1035). (8) Leighton and Forbes, Tars JOURNAL, 14, 3139 (1930). described.g One centimeter d d d o n on the galvanometer scale corresponded to 1.014 X lo+ cal./sec. The diameter of the light beam was adjusted so that the whole area of it (r sq. an.) fell on the thennopile elements. Corrections were applied for the non-uniformity of the beam, and for relection at the rear window of the photo-cetl.Results and Discussion.-The results are shown in Table I.When the-pressure of th...

The Isolation and Properties of Catechol From White Fir Bark

“…of conc'd HC1. The mixture was slowly brought to reflux temperature over a period of 8 10.8 [10] 6.02 [20] 9.60 [41] 7.89 [13] 6.91 [25] 10.0 [11] 5.50 [29] 8.11 [15] 7.49…”

“…[8] 6.28 [72] 9.50 [18] 4.90 [100] 7.37 [15] 5.79 [100] 4.92 [26] 8.50 [17] 4.57 [25] 6.32 [59] 5.01…”

“…[5] 4.72 [99] 7.49 [7] 4.23 [7] 5.79 [88] 4.60 [19] 4.11 [51] 6.60 [13] 3.86 [27] 5.37 [100] 4.44 [28] 3.93 [25] 6.28 [19] 3.74 3.55 [100] 5.71 [13] 3.56 [70] 4.53 [59] 3.97 [60] 3.26 [42] 5.43 [18] 3.35 [3] 4.31 [37] 3.80 [45] 3.05 [22] 5.18 [15] 3.25 [7] 4.11 [71] 3.66 [39] 3.00 [35] 5.04 [10] 3.14 [38] 4.02 [49] 3.60 [35] 2.88 [16] 4.90 [15] 3.07 [38] 3.83 [39] 3.46 [44] 2.75 [10] 4.74 [12] 2.98 [4] 3.70 [34] 3.34 [19] 2.55 [9] 4.53 [15] 2.74 [4] 3.57 [34] 3.25 [11] 2.44 [10] 4.31 [21] 2.68 [9] 3.42 [71] 3.08 [13] 2.27 2.22 [12] 1.71…”

“…Both forms show the same optical rotation and give identical pentaacetate derivatives, indicating that racemization is not responsible for the high melting point. The form reported by Keller and Berger (15) is apparently a mixture and not a result of using unwashed gambir as they have suggested, but rather a function of the concentration of the solution from which crystallization takes place. " Average age of three tree samples.…”

“…was due to racemization during drying at high temperature. Recently, Keller and Berger (15) reported a dimorphic form of cZ-catechol, m.p. 210-213°.…”