CH(A^2Δ)自由基被醇类分子猝灭动力学的温度效应研究

用266nm激光光解CHBr3产生CH自由基, 利用精密控温仪控制反应温度, 测定CH(A→X)荧光的时间分辨信号, 测量了290K至653K范围内CH(A)被乙醇、丙醇、丁醇猝灭的速率常数, 利用修正的碰撞配合物模型, 定性解释了在多极吸引势与活化势垒的双重影响下, 猝灭截面与温度间的关系。     

CH(A^2△和B^2∑^-)和醇类分子碰撞过程动力学研究

本文报道用四倍频YAG激光(266nm)光解CHBr3产生电子激发态CH(A,B)自由基和测量自发辐射CH(A,B→X)的时间分辨信号的方法测定了室温(290K)下CH(A,B)被醇类分子(乙醇、异丙醇、正丁醇、异戊醇和叔戊醇)猝灭的速率常数, 实验测定的CH(A)和CH(B)猝灭速率常数k~q^A和k~q^B(单位为10^-^1^0cm^3.molecule^-^1.s^-^1)值如下(误差为线性拟合的标准偏差):此外, 还从碰撞配合物模型出发, 就醇分子中OH基对猝灭速率常数的影响作了讨论。     

CH(A^2△和B^2∑^-)和醇类分子碰撞过程动力学研究

本文报道用四倍频YAG激光(266nm)光解CHBr_3产生电子激发态CH(A,B)自由基和测量自发辐射CH(A,B→X)的时间分辨信号的方法测定了室温(290K)下 CH(A,B)被醇类分子(乙醇、异丙醇、正丁醇、异戊醇和叔戊醇)猝灭的速率常数,实验测定的CH(A)和 CH(B)猝灭速率常数K_q~A和K_q~B(单位为10~(-10)cm~3·molecule~(-1)·s~(-1))值如下(误差为线性拟合的标准偏差):此外,还从碰撞配合物模型出发,就醇分子中OH基对猝灭速率常数的影响作了讨论.     

(CX~3)~2CO,CF~3COX和CXCl~3(X=H或D)对CH(A,B)自由基的猝灭

本文报道室温下用266nm激光光解-荧光猝灭方法测定CH_3COCH_3,CD_3COCD_3,CF_3CO_2H,CF_3CO_2D,CHCl_3和CDCl_3分子猝灭电子激发态CH(A,B)自由基的速率常数,考察了含不同同位素原子的猝灭剂分子对CH(A,B)猝灭的同位素效应.实验发现,含D的分子比相应含H的分子对CH(A,B)的猝灭具有更大的速率常数.     

(CX~3)~2CO,CF~3COX和CXCl~3(X=H或D)对CH(A,B)自由基的猝灭

本文报道室温下用266nm激光光解-荧光猝灭方法测定CH~3COCH~3,CD~3COCD~3,CF~3CO~2H,CF~3CO~2D,CHCl~3和CDCl~3分子猝灭电子激发态CH(A,B) 自由基的速率常数,考察了含不同同位素原子的猝灭剂分子对CH(A,B)猝灭的同位素效应. 实验发现,含D的分子比相应含H的分子对CH(A,B)的猝灭具有更大的速率常数     

荧光光谱法研究青蒿素类抗疟药与CYP2B6酶的相互作用

在模拟人体生理条件下,采用荧光光谱法及同步荧光法研究了抗疟药青蒿素(ART)和双氢青蒿素(DHA)与药物代谢酶CYP2B6之间的相互作用.结果表明,在温度为296～303 K时,ART和DHA对CYP2B6的猝灭机制均以静态猝灭为主,当温度由303 K升高至310 K时,则为静态猝灭和动态猝灭共同作用的混合猝灭机制;在...     

荧光光谱法研究大豆甙元与牛血清白蛋白的相互作用

采用荧光光谱技术研究了大豆甙元与牛血清白蛋白(BSA)的相互作用.研究结果表明:290 K、303 K、310K、315 K温度下大豆甙元对BSA的猝灭速率常数Ksv随着温度升高逐渐降低,且均大于最大动态猝灭速率常数2×1010 L·mol -1·s-1,表明大豆甙元对BSA的荧光猝灭属静态猝灭过程.根据F(o)rst...     

烷烃和胺类分子对电子激发态CH(A~2Δ和B~2Σ~-)自由基猝灭

用266nm激光光解CHBr_3分子产生CH(A,B)态自由基,通过测量CH(A,B→X)自发辐射的时间分辨信号测定室温下(CH_3)_2NH、(C_2H_5)_2NH、(C_2H_5)_3N、n-C_5H_(12)、n-C_6H_(14)和n-C_7H_(16)对CH(A,B,v'=0)的猝灭速率常数.发现猝灭速率常数与猝灭剂烷烃分子中的C-H键数近似成线性关系,但对大的烷烃分子,这种增加逐渐趋缓.用碰撞络合物模型计算胺类分子及烷烃分子与CH形成碰撞络合物时的生成截面,结果表明,在电子激发态CH自由基的猝灭过程中,碰撞对子间的多极相互吸引势和色散力作用势可能起重要作用.     

荧光光谱法研究原花青素与牛血清白蛋白的相互作用

在pH=7.40的Tris-HCl缓冲体系中,采用荧光光谱技术研究了原花青素与牛血清白蛋白(BSA)的相互作用.根据295 K、303 K、310 K、315 K温度下的猝灭常数,表明原花青素对BSA的荧光猝灭为静态猝灭过程,由热力学参数焓变(△rHm)和熵变(△rSm)均大于零,推断出原花青素与BSA之间主要靠疏水作...     

烷烃类分子对NCO(A2∑+)自由基的猝灭

采用激光光解-激光诱导荧光(LP-LIF)的方法,用266 nm激光光解CHBr3分子产生CH自由基,再与N2O继续反应作为NCO自由基的产生源,用438.6 nm激光将电子基态X2∏i(0010)的NCO激励到激发态A2∑+(00°0)上,通过检测激发态NCO时间分辨荧光信号,测得室温(298 K)下NCO(A2∑+)被烷烃类分子猝灭的实验结果,获得了A2∑+(00°0)态猝灭速率常数.实验发现,随着烷烃分子中C-H键数增加,其猝灭截面也近线性增加,但随着分子体积增大,这种增加趋缓.     

Experimental and computational investigation of gas-phase reaction of chlorine with n-propanol: observation of chloropropanol conformational isomerization at room temperature

FTIR smog chamber techniques were used to measure k(Cl+n-C3H7OH) = (1.74 +/- 0.15) x 10-10 and k(Cl+CH2ClCH2CH2OH) = (7.54 +/- 0.73) x 10-11 cm3 molecule-1 s-1 in 700 Torr of N2 at 296 K. The reaction of Cl with n-C3H7OH gives CH3CH2CHOH, CH3CHCH2OH, and CH2CH2CH2OH radicals in yields of 60 +/- 5, 25 +/- 8, and 15 +/- 3%, respectively. Neither CH3CH2CHClOH nor CH3CHClCH2OH is available commercially, and infrared spectra for the three chlorides CH3CH2CHClOH, CH3CHClCH2OH, and CH2ClCH2CH2OH were calibrated experimentally. MP2/6-31G(d,p) calculations were used to corroborate the experimental vibrational assignments. Analysis reveals that each geometric isomer possesses several structurally and spectroscopically distinct conformers arising from intramolecular hydrogen bonding and, in the case of CH3CH2CHClOH, negative hyperconjugation. These conformers interchange slowly enough to be distinguished within the room-temperature vibrational spectrum. The experimentally observed vibrational spectra are well described by a Boltzmann-weighted superposition of the conformer spectra. As is typical of alpha-halogenated alcohols, CH3CH2CHClOH readily decomposes heterogeneously to propanal and HCl.     

Kinetics of the reactions of Cl*(2P(1/2)) and Cl(2P(3/2)) atoms with CH3OH, C2H5OH, n-C3H7OH, and i-C3H7OH at 295 K

The title reactions were studied using laser flash photolysis/laser-induced-fluorescence (FP-LIF) techniques. The two spin-orbit states, Cl*(2P(1/2)) and Cl(2P(3/2)), were detected using LIF at 135.2 and 134.7 nm, respectively. Measured reaction rate constants were as follows (units of cm3 molecule(-1) s(-1)): k(Cl(2P(3/2))+CH3OH) = (5.35 +/- 0.24) x 10(-11), k(Cl(2P(3/2))+C2H5OH) = (9.50 +/- 0.85) x 10(-11), k(Cl(2P(3/2))+n-C3H7OH) = (1.71 +/- 0.11) x 10(-10), and k(Cl(2P(3/2))+i-C3H7OH) = (9.11 +/- 0.60) x 10(-11). Measured rate constants for total removal of Cl*(2P(1/2)) in collisions with CH3OH, C2H5OH, n-C3H7OH, and i-C3H7OH were (1.95 +/- 0.13) x 10(-10), (2.48 +/- 0.18) x 10(-10), (3.13 +/- 0.18) x 10(-10), and (2.84 +/- 0.16) x 10(-10), respectively; quoted errors are two-standard deviations. Although spin-orbit excited Cl*(2P(1/2)) atoms have 2.52 kcal/mol more energy than Cl(2P(3/2)), the rates of chemical reaction of Cl*(2P(1/2)) with CH3OH, C2H5OH, n-C3H7OH, and i-C3H7OH are only 60-90% of the corresponding Cl(2P(3/2)) atom reactions. Under ambient conditions spin-orbit excited Cl* atoms are responsible for 0.5%, 0.5%, 0.4%, and 0.7% of the observed reactivity of thermalized Cl atoms toward CH3OH, C2H5OH, n-C3H7OH, and i-C3H7OH, respectively.     

脂族酰基过氧化物分解动力学的研究X: 过氧化酰热分解反应的自旋捕获ESR研究

用亚硝基丁烷(TNB)、亚硝基苯和C-苯基-N-叔丁基硝酮作为自旋捕获剂来捕获和检出一些二酰基过氧化物类化合物分解时形成的短命烷基自由基. 报导了烷基自由基对自旋捕获剂加成的氮氧化物自由基的电子自旋共振谱, 并观察到2,4,4-三甲基戊基自由基中α-CH2的氢是非对映和非等价的. 据此, 认为与这一类自由基的加合物产生的电子自旋共振谱与其它类型自由基是不同的.     

A novel cationic heteropolyoxovanadium(IV) cluster functionalized with organic ligands: synthesis and characterization of the fully reduced species [Mn(II)V(IV)6O6[(OCH2CH2)2N(CH2CH2OH)]6]Cl2

The solvothermal reaction of (HOCH2CH2)3N with [(n-C4H9)4N]3[H3V10O28] and MnCl2 x 4H2O in CH3CN and CH3OH yields a novel cationic heteropolyoxovanadium(IV) cluster, [Mn(II)V(IV)6O6[(OCH2CH2)2N(CH2CH2OH)]6]2+, containing a fully reduced new cyclic [MnV6N6O18] core with the Anderson structure.     

Esterification and Chemoselective Synthesis of R-Tetrahydrothiazo-2- thione-4-carboxylic Esters Catalyzed by TiCl4

A series of esters of R-tetrahydrothiazo-2-thione-4-carboxylic acid[R-TTCA] was synthesized by direct esterification of R-TTCA with alcohols(CH3OH,C2H5OH,n-C3H7OH,i-C3H7OH,n-C4H9OH,sec-C4H9OH)in the presence of TiCl4 as the catalyst at room temperature without using any other solvent or dehydrant in high yields,91.6%-99.1% for primary alcohols and 55%- 80% for secondary alcohols.The catalyst has a strong chemoselective activity for the esterification of primary alcohols with R-TTCA in the presence of secondary alcohols.Owing to high yield,high chemoselectivity,and mild conditions used,this is an efficient method for the esterification of primary alcohols with R-TTCA.     

Atmospheric chemistry of a model biodiesel fuel, CH3C(O)O(CH2)2OC(O)CH3: kinetics, mechanisms, and products of Cl atom and OH radical initiated oxidation in the presence and absence of NOx

Relative rate techniques were used to study the kinetics of the reactions of Cl atoms and OH radicals with ethylene glycol diacetate, CH3C(O)O(CH2)2OC(O)CH3, in 700 Torr of N2/O2 diluent at 296 K. The rate constants measured were k(Cl + CH3C(O)O(CH2)2OC(O)CH3) = (5.7 +/- 1.1) x 10(-12) and k(OH + CH3C(O)O(CH2)2OC(O)CH3) = (2.36 +/- 0.34) x 10(-12) cm3 molecule-1 s-1. Product studies of the Cl atom initiated oxidation of ethylene glycol diacetate in the absence of NO in 700 Torr of O2/N2 diluent at 296 K show the primary products to be CH3C(O)OC(O)CH2OC(O)CH3, CH3C(O)OC(O)H, and CH3C(O)OH. Product studies of the Cl atom initiated oxidation of ethylene glycol diacetate in the presence of NO in 700 Torr of O2/N2 diluent at 296 K show the primary products to be CH3C(O)OC(O)H and CH3C(O)OH. The CH3C(O)OCH2O* radical is formed during the Cl atom initiated oxidation of ethylene glycol diacetate, and two loss mechanisms were identified: reaction with O2 to give CH3C(O)OC(O)H and alpha-ester rearrangement to give CH3C(O)OH and HC(O) radicals. The reaction of CH3C(O)OCH2O2* with NO gives chemically activated CH3C(O)OCH2O* radicals which are more likely to undergo decomposition via the alpha-ester rearrangement than CH3C(O)OCH2O* radicals produced in the peroxy radical self-reaction.     

Enantioselective self-assembly of bimetallic [Mn(II) (delta)-Cr(III)(C2O4)3]- and [Mn(II) (lambda)-Cr(III)(C2O4)3]- layered anionic networks templated by the optically active (Rp)- and (Sp)-[1-CH2N(n-C3H7)3-2-CH3-C5H3Fe-C5H5]+ ions

The ferrocenic ammonium (Rp)- and (Sp)-[1-CH2NR(3-)-2-CH3-C5H3Fe-C5H5] iodide salts with R=CH3, C2H5, n-C3H7, n-C4H9, were synthesized starting from the (Rp)- and (Sp)-[1-CH2N(CH3)2-2-CH3-C5H3Fe-C5H5] amines obtained in their optically active forms through asymmetric cyclopalladation of [C5H5Fe-C5H4CH2N(CH3)2]. 1H NMR studies of these planar chiral 1,2-disubstituted ferrocenic ammonium iodide salts in the presence of the (Delta)-(tris(tetrachlorobenzenediolato)phosphate(V) anion), [(Delta)-Trisphat] support the formation of specific diastereomeric ion pairs. Such intermolecular interactions can be related to the self-assembly of the two-dimensional optically active compounds [[(Sp)-1-CH2N(n-C3H7)3-2-CH3-C5H3Fe-C5H5][Mn (Delta)-Cr(C2O4)3]] and [[(Rp)-1-CH2N(n-C3H7)3-2-CH3-C5H3Fe-C5H5][Mn (Lambda)-Cr(C2O4)3]] starting from the resolved (Rp)- and (Sp)-[1-CH2N(n-C3H7)3-2-CH3-C5H3Fe-C5H5]+ ion associated to the racemic anionic building block rac-[Cr(C2O4)3]3- and Mn2+. Both enantiomeric forms of the networks behave as ferromagnets with a Curie temperature of 5.7 K.     

Thermal decomposition mechanisms of the methoxyphenols: formation of phenol, cyclopentadienone, vinylacetylene, and acetylene

The pyrolyses of the guaiacols or methoxyphenols (o-, m-, and p-HOC(6)H(4)OCH(3)) have been studied using a heated SiC microtubular (μ-tubular) reactor. The decomposition products are detected by both photoionization time-of-flight mass spectroscopy (PIMS) and matrix isolation infrared spectroscopy (IR). Gas exiting the heated SiC μ-tubular reactor is subject to a free expansion after a residence time of approximately 50-100 μs. The PIMS reveals that, for all three guaiacols, the initial decomposition step is loss of methyl radical: HOC(6)H(4)OCH(3) → HOC(6)H(4)O + CH(3). Decarbonylation of the HOC(6)H(4)O radical produces the hydroxycyclopentadienyl radical, C(5)H(4)OH. As the temperature of the μ-tubular reactor is raised to 1275 K, the C(5)H(4)OH radical loses a H atom to produce cyclopentadienone, C(5)H(4)═O. Loss of CO from cyclopentadienone leads to the final products, acetylene and vinylacetylene: C(5)H(4)═O → [CO + 2 HC≡CH] or [CO + HC≡C-CH═CH(2)]. The formation of C(5)H(4)═O, HCCH, and CH(2)CHCCH is confirmed with IR spectroscopy. In separate studies of the (1 + 1) resonance-enhanced multiphoton ionization (REMPI) spectra, we observe the presence of C(6)H(5)OH in the molecular beam: C(6)H(5)OH + λ(275.1?nm) → [C(6)H(5)OH ?] + λ(275.1nm) → C(6)H(5)OH(+). From the REMPI and PIMS signals and previous work on methoxybenzene, we suggest that phenol results from a radical/radical reaction: CH(3) + C(5)H(4)OH → [CH(3)-C(5)H(4)OH]* → C(6)H(5)OH + 2H.     

Synthesis of acyclic quaternary ammonium compounds containing ω-alkoxyethyl and 2-hydroxyethyl substituents at the nitrogen atom

Russian Chemical Bulletin - A series of acyclic symmetric quaternary ammonium chlorides Me2(HOCH2CH2)N+(CH2CH2O)nR Cl– (n = 1, R = n-C9H19; n = 2, R = n-C6H13; n = 3, R = n-C3H7) was...     

Generation and reactivity of enantiomeric (BINOLato)Ni+ complexes with chiral secondary alcohols in the gas phase

In the presence of secondary alcohols, electrospray ionization of dilute methanolic solutions of nickel(II) salts and 1,1'-bis-2-naphthol (BINOL) leads to complexes of the formal composition [(BINOLato)Ni(CH3CH(OH)R)]+ (BINOLato refers to a singly deprotonated (R)- or (S)-1,1'-bis-2-naphthol ligand; R=CH3, C2H5, n-C3H7, n-C4H9, n-C5H11, n-C6H13, c-C6H11, and C6H5). Upon collision-induced dissociation, each mass-selected nickel complex either loses the entire secondary alcohol ligand or undergoes bond activation followed by elimination of the corresponding ketone, as revealed by deuterium labeling. When enantiomeric BINOLato ligands (R or S) are combined with chiral secondary alcohols (R or S), differences in the branching ratios between these channels for the two stereoisomers of the secondary alcohols provide insight into the chiral discrimination operative in the C--H- and O--H-bond activation processes. For saturated alkan-2-ols, the chiral discrimination is low, and if any preference is observed at all, ketone elimination from the homochiral complexes (R,R and S,S) is slightly favored. In contrast, the diastereomeric (BINOLato)Ni+ complexes of 1-phenylethanol exhibit preferential ketone losses for the heterochiral systems (S,R and R,S).