螺吡喃激发态的反应活性

研究了6′-硝基-1,3,3-三甲基吲(口乃木)苯骈螺吡喃,Ⅰ,和6′-硝基-1-苯基-3,3-二甲基吲(口乃木)苯骈螺吡喃,Ⅱ,的光化学,Ⅰ的直接光解和敏化光解均得到份菁结构的光解产物Ⅲ,量子产率分别是0.42和0.32.Ⅱ直接光解时生成相应的有色光解产物Ⅳ,量子产率是0.40,氮杂蒽酮为敏化剂的敏化光解量子产率是0.58,无疑地,单线态和三线态均参予螺吡喃的发色反应,用这些结果和折算关系式得到,在Ⅰ的直接光解中,Ⅲ主要来自单线态,而在Ⅱ的直接光解中,Ⅳ主要来自三线态.从Ⅰ或Ⅱ的敏化联乙酰燐光实验中求得三线态参数.它们是:φ_ISC^Ⅰ＝0.11,φ_ISC^Ⅱ＝0.48;³K_dt^Ⅰ＝3×10⁴秒^-1,³K_dt^Ⅱ＝9×10⁴秒^-1,类似地,³K_r^Ⅰ＝0.12×10⁴秒^-1,³K_r^Ⅱ＝2.52×10⁴秒^-1,这样,³φ_r^Ⅰ值较小是由于³φ_ISC^Ⅰ值较小,而三线态寿命随结构变动不大.最后,取苯乙烯为模型,用它的电子能量与乙烯双键扭曲角度关系图推断出,来自单线态的双离子具有螺环构型,而来自三线态者具有平面状构型.     

带有四个不同芳基的环丁烷的合成、结构及光化学性质

通过不同杂芳基乙烯分子间的交叉光二聚反应在硫酸溶液中和中压汞灯照射下,合成了4种含7个不同取代芳基的环丁烷衍生物.用紫外和红外光谱及¹H和¹³CNMR谱确定其结构为顺式头尾相对型二聚体.     

HCNO分子裂解机理的理论研究

实验提示应用248 nm UV波长对HCNO分子进行直接光解, 该分子可能发生裂解, 得到某些产物. 为了揭示HCNO分子的裂解机理, 选择HCNO分子的一组相对能级作为理论研究的起始点, 即¹A' (0.00 kJ/mol), ³A' (255.01 kJ/mol), ³A" (282.37 kJ/mol)和¹A" (341.59 kJ/mol), 进而找到了合理的反应路径, 阐明了相应的裂解机理, 得到的主要产物为H＋NCO, HCN＋O和NH＋CO, 与实验提示的结果相符合.     

激光诱导的亚硝酸与二苯醚的反应机理

355 nm光照下利用瞬态吸收光谱技术进行了有氧、无氧条件下二苯醚与亚硝酸体系的反应机理研究, 考察了其中瞬态物种的衰减行为, 并对其光解产物进行了GC-MS分析. 研究表明, HNO₂在355 nm紫外光的照射下产生的OH自由基和二苯醚反应生成C₁₂H₁₀O-OH 加合物, N₂条件下C₁₂H₁₀O-OH衰减的速率常数为(1.86±0.14)×10⁵ s^－1, 在有氧条件下, C₁₂H₁₀O-OH可转化为C₁₂H₁₀O-OHO₂, 衰减的速率常数为(6.6±0.4)×10⁶ s^－1. N₂条件下最终产物为苯酚、2-羟基二苯醚、4-羟基二苯醚、4-硝基二苯醚.     

用共振增强多光子电离方法研究几种含溴化合物的光解

利用飞行时间质谱仪(TOF)和共振增强多光子电离(REMPI)方法, 研究了两种正一溴代烷烃(C₂H₅Br, n-C₃H₇Br)和溴苯(C₆H₅Br)在234及267 nm附近的光解. 测出了这几种含溴化合物在不同波长下光解产物Br^*和Br的分支比N(Br*)/N(Br), 并根据从头计算结果, 解释了这几种含溴化合物光解产物的分支比随光解波长变化的趋势及几个低激发态势能面之间的关系.     

高聚合度聚磷酸铵中特征磷的31P核磁共振分析

采用一维³¹P核磁共振(³¹P NMR)、 二维J分解谱(J-resolved)和扩散核磁(³¹P DOSY)等方法, 研究了高聚合度聚磷酸铵(APP)和多聚磷酸盐的特征磷及其偶合常数. 研究表明, 多聚磷酸盐及其中所含的二聚磷酸盐端基磷分别呈双峰和单峰特征, 多聚磷酸盐自旋偶合裂分的端基磷共振峰的偶合常数为19.4 Hz. APP中含有小分子二聚磷酸铵和正磷酸铵, 用³¹P NMR定量表征APP聚合度时需排除二聚体端基磷峰的面积. 在100 ℃水中溶解APP制备的APP水溶液中, 部分高聚合度APP发生断链, 中间磷共振峰处出现短链APP的磷共振峰.     

硝酸根存在下冰相中苯酚的光转化

通过室内模拟实验, 采用125 W高压汞灯作为光源, 在低温条件下(-14～-12 ℃)研究了冰相中硝酸根存在下苯酚的光解. 考察了苯酚的浓度、硝酸根的浓度、pH值以及光强度等因素对冰相中苯酚光化学转化的影响. 研究结果表明, 在冰相中苯酚光转化速率随着光强度和NO₃^-初始浓度的增加而加快, 随着苯酚初始浓度的增加而减慢; 在强酸或强碱条件下均抑制苯酚的光转化速率; 苯酚的光解速率符合一级动力学模式. 利用GC-MS和LC-MS分析了苯酚的光解产物, 据此推测了苯酚在硝酸根体系中可能的光解反应历程.     

铁卟啉与氟尿嘧啶轴向配位热力学性质研究

氟尿嘧啶(Fu)是一种常用的抗代谢药物,在体内可转变为脱氧尿嘧啶核苷酸,抑制胸腺嘧啶核苷酸合成酶,从而阻止尿嘧啶脱氧核苷酸转变成胸腺嘧啶脱氧核苷酸,它的结构与肿瘤细胞所必需的尿嘧啶相类似,在同一系统酶中互相竞争,阻断代谢环节,影响DNA的生物合成,从而抑制了肿瘤细胞的生长.它对多种癌症都有较好的疗效,但具有一定的毒副作用^[1].这些毒副作用产生的机理目前尚不清楚.卟啉类化合物是人体中不可缺少的物质,具有许多特殊的生物效应^[2～11].若它们的含量异常,则会引发多种病变.     

锅炉腐蚀产物的穆斯堡尔谱研究

本文测定了高、中压锅炉腐蚀产物的穆斯堡尔谱^[1,2]并鉴定其相组成。(一)实验部分1.中压锅炉腐蚀产物锈样A、B、C取自广州发电厂2^#锅炉水冷壁管内壁,管内压力40kg/cm²,温度250℃。锈样D、E分别取自过热器管(425℃)和省煤器管(150℃)内壁.2.高压锅炉腐蚀产物锈样F、G、H取自广东韶关发电厂3^#锅炉的水冷壁管内壁,管内压力110kg/cm²,温度320℃。     

通过实验和理论验证Pt0/SrTiO3-δ复合催化剂双反应路径促进CO2还原(英文)

在以H₂O为质子源的光催化二氧化碳还原反应(CO₂RR)过程中,光解H₂O产氢气(H₂)被认为是一个竞争反应.因此,光催化CO₂RR过程需要抑制H₂的产生,以提高碳氢产物的选择性和产率.以CO₂和H₂为反应物的逆水气变换反应(RWGS)是常见的CO₂加氢反应,在较高的温度和催化剂作用下生成CO和H₂O.目前,光催化CO₂RR研究主要聚焦于产物的选择性,而有关光解H₂O产生的还原性气体H₂在光热效应的促进下成为CO₂RR中新的质子源研究较少.光热催化是一种新的高效催化反应方式,在反应过程中需要光照和加热.光照能够促进半导体光生载流子的激发,热效应则能降低反应物分子的活化势垒,并能够促进中间产物的表面迁移以及生成物的脱附.利用光热催化热力学和动力学上的有利条件,为以H₂     

Studies on Phosphate Effect of Cytosine and Its Novel Photoproduct

ＩｎｔｒｏｄｕｃｔｉｏｎＩｎ１９６３，ＭｏｏｒＡ．Ｍ．［１］ｆｉｒｓｔｌｙｒｅｐｏｒｔｅｄｔｈｅｐｈｏｓｐｈａｔｅｅｆｅｃｔ，ｉ．ｅ．，ｉｎｔｈｅＵＶｉｒｒａｄｉａｔｉｏｎ（２５３．７ｎｍ）ｏｆａｑｕｅｏｕｓｓｏｌｕｔｉｏｎｓｏｆ４－ａｍｉｎｏ－２－...     

A Novel Photoproduct of Uracil in Phosphate-Buffered Saline

Under UV irradiation the photoreaction of pyrimidine bases in aqueous solution hasdisclosed three mpes of reactions, namely: (a) nucleophilic addition ofwateT, ethanol, orhydrogen cyanide at the 5,6-double bond; (b) dimerization by addition at the samedouble bond; (c) ring cleavage. It has been reported' that the presence of phosphatesaltered the course of the photolysis process of pyrimidine bases and derivatives under theirradiation of low pressure mercury lamp (LPML, 254 "m), but the role…     

Enhancement of the Photolysis of Nucleic Acid Monomers by Phosphates

Abstract— In the tentative simulation of prebiotic synthesis, it was found that the photolysis yield of nucleic acid bases, nucleosides and nucleotides (NA) undergoing UV irradiation was sharply enhanced by added orthophosphate. Filter experiments demonstrated that the enhancement is due to UV quanta of wavelength less than 215 nm in the emission spectrum of a medium pressure mercury lamp. The phosphate-induced enhancement of the photolysis of NA constitutes an additional channel of nucleic acid monomer degradation through their interaction with photoionized phosphate radicals.     

A Novel Photoproduct of 1, 3-Dimethyluracil in Phosphate Buffered-saline

1, 3-Dimethyluracil （DMU） in phosphate buffered-saline （PBS, pH=8） was irradiated by a medium pressure mercury lamp （MPML） and produced a novel compound C6H9N2O6P. The composition and structure of the compound has been identified by elemental analysis, EIMS, UV, IR, ^1H and ^31P-NMR.     

A Novel Photoproduct of Thymine in Phosphate-buffered Saline under Far UV Irradiation

The photolysis of thymine in phosphate-buffered saline (PBS, pH 8.0) under the irradiation of medium pressure mercury lamp (MPML) produces a novel compound C5H7N206P. The composition and structure of the compound have been identified by elemental analysis, EI-MS,UV, IR, ^1H, ^13C, ^31P-NMR.     

A Novel Photoproduct of 2-Methoxycytosine in Phosphate Solution Under Far UV Irradiation

Theph0tolysis0f2-meth0xycytosineinph0sphate-buffersoluti0nunderl0wpressuremercurylamp(LPML,254nm)wasrep0rtedasearlyasl963byMoor"wh0foundthatthepresence0fin0rganic0rthoph0sphatealteredthec0urse0ftheph0toIysispr0cess0f2-methoxycytosineandpr0ducedannewc0mp0undI(Schemel).Pith2andShawjconfirmedtheresultofM00r.butthereactionmechanismhadnotbeenelucidated.Inparticular,theroleofph0sphateinthemechanismwasn0tclear.Inaprevi0uspaper'wefoundthatthephot0lysisyieldofnucteobases'nucle0sidesandnucleotides(N…     

Photoreaction of benzofuroxan

Benzofuroxan 5 , upon irradiation using a high pressure mercury lamp with a Pyrex filter in acetonitrile containing a little water, afforded 1H-azepine-2,7-dione 6 . The initial stage of this reaction would be formation of a highly reactive intermediate possessing two nitrile oxide functions. On the other hand, when compound 5 was irradiated using a low pressure mercury lamp in acetonitrile containing a little water, it afforded 6H-furazano[4,5-c]carbazole 3-oxide 11 and compound 6 . The structure of compound 11 was determined by an X-ray structural analysis. In the presence of an aromatic hydrocarbon, the formation of compound 11 was decreased and that of compound 6 was increased. Mechanistic studies on the photoreaction suggest that the photosensitized formation of compound 6 with the aromatic hydrocarbon may be carried out by the reabsorption of the fluorescence of it near 365 nm and the presence of it may quench the formation of compound 11 .     

Photoassisted reaction of chemical warfare agent VX droplets under UV light irradiation

A photoassisted reaction of O-ethyl S-[2-(diisopropylamino) ethyl] methylphosphonothioate (VX) droplets in air was carried out. The experimental results indicated that VX droplets could be easily and chemically transformed into other compounds under irradiation of a germicidal lamp over sufficient time. Quantum chemical calculation results demonstrated that UV light less than 278 nm wavelength could possibly initiate photoreaction of VX and that both P-S and P=O bonds in the VX molecule were lengthened. The identification of reaction products by gas and liquid chromatography mass spectroscopy and NMR revealed that the VX molecule in air under UV light irradiation could undergo isomerization of S-esters to O-esters, cleavage of P-S, S-C, and C-N bonds, and ozonation of tertiary amines.     

On-fiber photodegradation after solid-phase microextraction of p,p'-DDT and two of its major photoproducts,p,p'-DDE and p,p'-DDD

The potential of performing photochemical studies in solid phase microextraction (SPME) fibers, "photo-SPME", to study the photodegradation of p,p'-DDT and two of its major degradation products, p,p'-DDE and p,p'-DDD, is shown. Analyses were carried out by gas chromatography mass spectroscopy detection. DDT was extracted from aqueous solutions using five different commercial coatings. The fibers were then exposed to UV light emitted by a low-pressure mercury lamp. After 30 min of irradiation, the degradation of DDT only occurred in polydimethylsiloxane fibers. The on-fiber degradation kinetics of p,p'-DDT was studied from 2 to 60 min. A large number of photoproducts were generated and their kinetic behavior was studied. In order to clarify the possible photoreaction pathways for DDT, individual water solutions containing p,p'-DDD or p.p'-DDE were prepared and photo-SPME was performed for each compound at different irradiation times. On the basis of the photoproducts identified, some photodegradation pathways are proposed. Finally, aqueous photodegradation studies followed by SPME were performed and compared to the photo-SPME. This work will show the enormous potential of photo-SPME to perform photodegradation studies.     

Photochemical cleavage reaction of 8-quinolinyl sulfonates that are halogenated and nitrated at the 7-position

Photochemical bond-cleavage reactions are potentially useful in chemistry, bioorganic chemistry and medicinal chemistry. We previously reported on a photochemical cleavage reaction of 8-quinolinyl sulfonate (8-QS) derivatives in aqueous solution at neutral pH, which we proposed to proceed via an excited triplet state. In this report, we report on the synthesis of some new photocleavable 8-QS derivatives, in which halogen atoms or a nitro group was introduced at the 7-position, in an attempt to improve photoreactive properties and to produce a red-shift in the irradiation wavelength. The introduction of bromine and iodine resulted in an acceleration in the photoreaction by about 1.5 times, possibly due to a heavy atom effect. It was also found that 7-nitro-8-QS absorbs at >360 nm, and, as a result, the S-O bond of this compound can be cleaved by photoirradiation with a fluorescent lamp in aqueous solution and on silicon surface.