【摘要】 用三苯基锑作为氯气的吸收剂,研究了⁶⁰ Coγ射线对四氯化碳、三苯基锑-空气-四氯化碳体系的辐射效应.用氧化铝柱层析法分离辐解产物,分别求得■（可能为逆反应 CCl₃+Cl₂-→CCl₄+Cl 消耗的氯的 G 值）,并根据■值计算出自由基产额 G_R=24. 6,与 D.P.P.H 法测得的 G_R=25基本一致.当三苯基锑浓度大于每毫升24毫克时,三苯基锑能有效地抑制氯气与 CCl₃基之间的逆反应.由实验求得■和三苯基锑浓度间的关系曲线,并与用稳定态理论导出的理论曲线进行比较,发现两者基本一致.更多还原

【Abstract】 The radiolysis of air-free CCl₄ has been well investigated.Using D.P.P.H.Br₂or HI as “scavenger”,the G value of the radicals and the “molecular” products havebeen determined.But the mechanism of radiolysis of CCl₄ in the presence of air isstill not clarified.The main difficulty is that the G value of the back reaction CCl₃+Cl₂→CCl₄+Cl during irradiation has not been determined.It is impossible tocompare the yield of chlorine with G_R value obtained by D.P.P.H method,and tocarry out kinetic calculations.In order to eliminate the back reaction we havesuccessfully used tagged triphenyl antimony (¹²⁴ Sb) to remove Cl₂ formed duringirradiation according to the following reaction（C₆H₅） ₃Sb+Cl₂→（C₆H₅） ₃SbCl₂Thus,not only the G value of Cl₂ and CCl₄ can be determined but the kineticcalculation may also be performed.After the irradiation of the system,the radiolytic products were quantitativelyseparated by chromatography on an Al₂O₃ column.Elution with benzene,gave（C₆H₅） ₃Sb （m.p 52℃）,elution with ethanol gave （C₆H₅） ₃Sb（OH）₂ （m.p 218～219℃,containing Sb 31. 5%）,which is formed from the hydrolysis of （C₆H₅） ₃SbCl₂（C₆H₅） ₃SbCl₂（C₆H₅） ₃Sb（OH）₂+2HClG_{（C6H5） 3SbCl2} ,value （22. 0） obtained from the chromatographic method,is in agreementwith that （22. 3） obtained from the isotope dilution method.Finally,elution with 0. 01N aqueous NaOH gave a fraction which may be（C₆H₅） ₃Sb（C₆H₅） ₂SbO₂H or （C₆H₅） ₂SbOH.This component will be transferredinto the inorganic phase and the peak in NaOH will disappear in the chromatographyif the irradiated carbon tetrachloride is extracted with 12% HCl.We have determined G_Cl of CCl₄ in the presence of air,G_Cl2 =5. 3±0. 2.The radiolysis of （C₆H₅） ₃Sb-air-CCl₄ systems is an oxygen consuming process（see Fig 1 Chinese text）.Therefore,when the concentration effect of （C₆H₅） ₃Sb is investigated,the absorbed dose should be controlled under 7. 05×10¹⁸ eV/ml-CCl₄.From the dependence of G_{（C6H5） SbCl2} on the conecntrations of （C₆H₅） ₃Sb in thesystem of （C₆H₅） aSb-air-CCl₄ （see Fig.2 Chinese text）,it can be shown that:（1）G_{（C6H5） SbCl2} increases with the increasing concentration of （C₆H₅） ₃Sb and eventuallyapproachs a constant value (G_{（C6H5） SbCl2} ≈21. 7) .It means that the back reaction,CCl₃+Cl₂→CCl₄+Cl,is inhibited.G_-Cl of the back reaction is obtained by thesubtraction of G_Cl from G_{（C6H5） SbCl2} ,namelyG_-Cl2 =G_{（C6H5） SbCl2} -G_Cl2 =21. 7-5. 3=16. 4（2） The yield of unknown species in NaOH fraction is about 7 and is veryinsensitive to the variation of （C₆H₅） ₃Sb concentration.The unknown species may bethe reaction products of （C₆H₅） ₃Sb and Cl^*,thus:ororHence,G value （～7） in NaOH fraction probably represents the yield of Cl^* atoms.By using G value of triphenyl antimony dichloride and suggesting the followingmechanism for the production of chlorineCCl₃+O₂→CCl₃O₂CCl₃O₂→COCl₂+ClOClO+CCl₄→COCl₂+Cl₂+ClCl+Cl→Cl₂G_CCL and GCl+Cl^* could be evaluated.Assuming GCCl</sub> being approximately equal toGCl+Cl^*,then one molecule CCl4 will form two Cl2 molecules under gamma irradiation.Let x be the number of OCl4 molecules changed per 100 eV of energy absorbed,thenxCCl4→xCC13+xClThere are seven Cl^* atoms and x-7 Cl atoms in the x chlorine atoms.Hence,we havethe following relationsGCl2 =G(（C6H5） 3SbCl2-0. 6=21. 7-0. 6=21. 1where.0. 6 is the G value of the “molecular” product of chlorineand 2x-7/2=21. 1solving for x,we get namely This value agrees well with the result obtained by D.P.P.H method.We have investigated the radiolysis kinetics of （C6H5） 3Sb-CCl4 in the presenceof air with steady state theory.The following nine main reactions were assumed.2CCl4（CCl3） 2+Cl2 （0）CCl4CCl3+Cl（Cl+Cl^*） （1）CCl3+ClCCl4 （2）CCl3+Cl2CCl4+Cl （3）CCl3+O2COCl2+ClO （4）ClO+CCl4COCl2+Cl2+Cl （5）Cl^*+CCl4CCl3+Cl2 （6）Cl+ClCl2 （7）（C6H5） 3Sb+Cl2（C6H5） 3SbCl2 （8）The true reaction For Eq.（4） would be written asCCl3+O2→CCl3O2→COCl2+ClOIn order to simplify the oomputation,the following conditions were assumed（1） Because the yields of the cemponent in NaOH fraction was unehanged withthe variation of the concentrations of （C6H5） 3Sb （G≈7） ,it was assumed that thiscomponent was the reaction products between Cl^* and （C6H5） 3Sb.Therefore,thereaction （6） was neglected in the following calculations.（2） Considering the consistence between the radical yields obtained by beth D.P.P.H method and （C6H5） 3Sb method,we oonoluded that the reaction,CCl3+O2→CCl3O2 was so fast in the presence of air that the recombination of radicals escapedfrom the track （CCl3-Cl→CCl4） can be neglected.（3） The yield of the “molecular” products in the spur reaction,is rather low(GCl2 =0. 47-0. 80,here taking as 0. 60) .The reaction （2CCl4→（CCl3） 2+Cl2） canbe neglected.So we have wherehere,taking G-CCl4 =12. 3,N0is Avogadro’s number.When steady state has been established.Solving Eqs.（1） to （5） ,we haveThe equation （6） represents the relation between Cl2 and the concentration of（C6H5） 3Sb in the irradiated system at steady state.This equation shows that Cl2concentration in the irradiated system is deereased gradually while the concentrationof （C6H5） 3Sb is increased.It means that （C6H5） 3Sb effectively inbibits Cl2 accumulation.Using equations （5） and （6） we get the desired expressionwhereThe solubility of O2 in CCl4 is 2×10^-3 M at 25℃.As the irradiation container wasleft with a sufficient space for air and a controlled dose was used,the comsumed oxygenwas practically negleoted.The O2 concentration can be approximately taken as aconstant.where N is the oonversion ooeffioient,and M（C6H5） 3Sb is the molecular weight of （C6H5） 3Sb（the concentration of triphenyl antinomy in equation （7） is expressed by mg/ml CCl4） .From equation （7） we can obtain the maximum of G（C6H5） 3SbCl being about 21. 0.The difference between it and the experimental value （21. 7） is 0. 7. This smalldifference may be due to the omission of the “molooular” yield,0. 6,in the deductionof equation （7） .If the “molecular” yield is considered,but the correction of theunknown species in the NaOH fraotion is omitted,then the equation will have thefollowing form whereUsing equation （7） and （10） and setting A′=3. 3 and A′=1. 7 correspondingly,thetheoretical curves of the variation of G（C4H5） 3SbCl</sub> with the concentrations of （C6H5） 3Sbare plotted in Fig.2 （Chinese text） Comparing these with the experimental curve （seeFig.2） ,it can be seen that except those points of which concentration in （C6H5） 3Sb isless than 16 mg/ml-CCl4 the experimental curve is in agreement with the theoreticalcurve within an error of 10%.On the basis of the agreement between the ourves obtained by the kineticcalculation and by experiments,it can be concluded that the above-mentioned ninereactions are main reactions in the radiolysis of the system （C6H5） 3Sb-air-CCl4.</sub>更多还原