咪唑啉酰胺在含CO2溶液中的缓蚀机理

用电化学阻抗谱及极化测量，研究了在含ＣＯ２的ＮａＣｌ溶液中咪唑啉酰胺（ＩＭ）对铁的缓蚀性能研究，并探讨了它在铁表面的吸脱附行为．结果表明，ＩＭ的缓蚀作用是由它对铁的负催化所控制．它在铁表面的吸附服从Ｌａｎｇｍｕｉｒ吸附等温式．电位正移到脱附电位以上是ＩＭ阳极脱附的主要原因，这时它使表面电容Ｃｄ显著增加，传递电阻Ｒｔ明显减小     

一种模拟沸石分子筛扩散反应的Monte Carlo方法

在考虑了沸石分子筛中吸附、脱附、扩散和反应的特点的基础上，发展了一种模拟沸石分子筛中扩菜反应的ＭｏｎｔｅＣａｒｌｏ方法。用Ｌａｎｇｍｕｉｒ吸附等温式验证了该方法的合理性，并证明了轰击频率λ代表了反应物气相压力，而吸附、脱附几率之比即为吸附平衡常数。同时，通过改变轰击频率λ和反应几率Ｐｔ，得到了吸附等温线和有效因子随Ｔｈｉｅｌｅ模数变化的曲线。     

气相存在下过渡金属表面脱附动力学机理的研究

作者利用同位素跳跃技术来探讨气相压强促进过渡金属表面吸附分子脱附这一新现象的机理。获得了３５３Ｋ下饱和吸附Ｃ１６Ｏ的Ｒｅ（０００１）表面的超高真空等温脱附和不同气相压强的同位素Ｃ１８Ｏ交换的谱图。从相对覆盖度及其对数随时间的变化曲线可以看出,真空等温脱附过程为一级动力学过程。而在气相同位素存在下交换脱附过程可用一级加二级来近似,拟合的结果与实验符合很好。作者还发现了交换速率远大于真空等温脱附速率,而且随压强的增加而增加,这说明气相压强直接促进了表面吸附分子的脱附。并提出了协同吸附－脱附机理来解释这一新现象     

酸性溶液中β-苯胺基苯丙酮在铁上的吸脱附行为

用极化曲线法研究了０．５ｍｏｌ·Ｌ－１硫酸溶液中β－苯胺基苯丙酮（ＰＡＰ）在铁－溶液界面的吸脱附行为及Ｃｌ－,Ｉ－的影响．结果表明,ＰＡＰ的吸附遵循Ｆｌｏｒｙ－Ｈｕｇｇｎｓ等温式;在较正的极化电位区出现阳极脱附现象．讨论了两种粒子联合吸附方式与浓度的关系,提出可根据吸附粒子的脱附电位与其浓度关系来推断联合吸附的理论模型     

NO在Cu－ZSM－5分子筛上程序升温脱附研究

本文用等温动态吸附和程序升温脱附技术研究了ＮＯ与Ｃｕ－ＺＳＭ－５的相互作用，并根据还原预处理样品上ＮＯ吸、脱附循环的研究探讨了全过程样品所经历的氧化还原循环，在２５℃等温吸附时，ＮＯ与Ｃｕ￣＋和／或Ｃｕ￣０反应产生了Ｎ＿２、Ｎ＿２Ｏ和Ｃｕ￣（２＋）以及超晶格氧，同时在Ｃｕ￣＋上有许多可逆吸附的ＮＯ．ＮＯ吸附在Ｃｕ￣（２＋）上是稳定的，升高温度时，ＮＯ分为三种状态脱附，分别位于约１００，１８０和４００℃．后两种可能以Ｃｕ￣（２＋）－ＮＯ＿２和Ｃｕ￣（２＋）－ＮＯ＿３为中间态．第三种ＮＯ脱附同时伴随着Ｏ＿２脱附，对于还原预处理的样品，吸附和脱附的一个循环总体上会使样品部分氧化。     

NO在Cu—ZSM—5分子筛上程序升温脱附研究

本文用等温动态吸附和程序升温脱附技术研究了ＮＯ与Ｃｕ－ＺＳＭ－５的相互作用，并根据还原预处理样品上ＮＯ吸、脱附循环的研究探讨了全过程样品所经历的氧化还原循环。在２５℃等温吸附时，ＮＯ与Ｃｕ＾＋和／或Ｃｕ＾０反应产生了Ｎ２、Ｎ２Ｏ和Ｃｕ＾２＋以及超晶格氧，同时在Ｃｕ＾＋上有许多可逆吸附的ＮＯ．ＮＯ吸附在Ｃｕ＾２＋上是稳定的。升高温度时，ＮＯ分为三种状态脱附，分别位于约１００，１８０和４００℃。后两种     

凤眼莲对铜离子的生物吸附研究

为探讨滇池凤眼莲对水中重金属离子Cu2 的吸附特性,考察了pH、时间、吸附剂量、浓度等因素对吸附能力的影响,进行了实验室吸附试验,绘制出吸附等温线,并由Langmuir曲线求出相应参数.对凤眼莲进行了脱附-再生实验.分析了吸附机理.结果表明,在pH3.5～5.5范围内,凤眼莲对Cu"有吸附作用,饱和吸附量可达35.6mg/g,吸附等温式为Cf/q=0.027Cf 0.114.用0.5mol/LHCl和NaOH可使其脱附与再生.     

丙酮在吸附树脂上的真空脱附性能研究

以超高交联吸附树脂为吸附剂,在固定床中研究了真空度、脱附温度、吸附初始浓度等因素对丙酮真空脱附性能的影响。实验结果表明,丙酮的脱附率随脱附温度和真空度增加而增加;丙酮初始吸附进气浓度越高,脱附率越高;在脱附温度60℃、真空度98kPa时,丙酮的脱附率可达85.3%。此外,开展了程序升温脱附实验,结果表明,超高交联吸附树脂吸附丙酮量越多其脱附速率越快,且最大脱附峰向低温区移动,这主要是因为微孔比中孔具有更大的吸附势,吸附在中孔内的丙酮更容易脱附。     

还原型和氧化型谷胱甘肽在磁性Fe3O4纳米粒子上的吸附组装

研究了Fe3O4磁性纳米粒子在水溶液中对还原型谷胱甘肽(GSH)和氧化型谷胱甘肽(GSSG)的吸附。分别测定了两种物质在不同温度下的吸附等温线,比较了研究结果,并用Freundlich吸附等温式对数据进行拟合,根据公式计算出相关的吸附热力学函数值,研究了碳化二亚胺含量和pH对吸附结果的影响,并从吸附量和脱附实验结果探讨了其可能的吸附机理。结果表明,还原型谷胱甘肽和氧化型谷胱甘肽在Fe3O4表面的吸附是不可逆的,加入强电解质基本不能够脱附,两者间形成了部分共价键。     

聚丙烯纤维预辐照接枝制备弱碱性离子交换纤维及其对链霉素的吸附

以γ-射线预辐照,在聚丙烯(PP)纤维上接枝丙烯酰胺(AAm),再经过Hofmarm降解反应制备弱碱性离子交换纤维(PP-g-YAm)交换容量达到5.47mmol/g干纤维.研究了PP-g-VAm纤维对链霉素的吸附和解吸性能.其吸附等温曲线符合Langmiur吸附等温式.静态吸附试验表明,PP-g-AAm纤维对链霉素的吸附量可以达到446.96mg/g千纤维,脱附率达到98.9%.     

Thermal desorption of the PO radical from polycrystalline Pt surfaces

The PO radical was detected to desorb from polycrystalline Pt surfaces during the catalytic decomposition of dimethyl methyl phosphonate and trimethyl phosphite above 1100 K using the laser-induced fluorescence technique. The activation energy for the desorption of adsorbed PO radicals, PO(a) → PO(g), was determined to be 59±2 kcal/mol in the temperature range 1100–1350 K at different radical source pressures. The mechanisms for PO production from these two catalytic reactions are briefly discussed.     

A Straightforward Synthesis of Six‐Membered‐Ring Heterocyclic α‐Aminophosphonic Acids from N‐Acyliminium Ions

A convenient synthesis of phosphonic analogues of pipecolic acid and its heterocyclic analogues is reported. The major step of the elaborated procedure is the introduction of the phosphonate group into the skeleton of the appropriate cyclic amide through N‐acyliminium ions. The former ones were obtained by preparation of the hemiaminals or their methyl ethers from the N‐protected cyclic amides. Finally, the reaction with trimethyl phosphite in the presence of BF₃·OEt₂ afforded the desired phosphonates, which were converted into phosphonic acids by the hydrolysis of phosphonate moiety with simultaneous cleavage of the nitrogen protecting groups.     

Cyclisation reactions of 2-substituted benzoylphosphonates with trialkyl phosphites via nucleophilic attack on a carbonyl-containing ortho substituent

Dimethyl 2-acetoxy- and dimethyl 2-benzoyloxy-benzoylphosphonate undergo cyclisation and deoxygenation in the presence of excess trimethyl phosphite to give dimethyl (3-methyl-1-benzofuran-2-yl)phosphonate and dimethyl (3-phenyl-1-benzofuran-2-yl)phosphonate, respectively. The reaction pathway has been shown to involve phosphite attack on initially formed tricyclic dioxaphospholane intermediates with the subsequent loss of two molecules of trimethyl phosphate. In the absence of additional trimethyl phosphite the initially formed tricyclic dioxaphospholane intermediates lose one molecule of trimethyl phosphate and then undergo a novel rearrangement to give β-ketophosphonates. The mechanism for this reaction helps explain some previously reported epoxide rearrangements. In contrast, the initially formed anionic intermediate from the reaction of dimethyl 2-benzoyloxymethylbenzoylphosphonate with trimethyl phosphite undergoes decomposition to give a carbene intermediate which is trapped by the trimethyl phosphite to give an ylidic phosphonate.     

Specific Features of Reactions of Halomethyl Derivatives of Alkyl 5-Isobutylfuran-3-carboxylates with Trimethyl Phosphite and Sodium Diethyl Phosphite

Ethyl 5-isobutyl-2-methylfuran-3-carboxylate is selectively brominated with N-bromosuccin-imide by the methyl group to give an unstable bromide. The latter on heating or in the presence of bases un-dergoes dehydrobromination accompanied by rearrangement, leading to a (2'2-dimethylvinyl)furan derivative.Phosphorylation of this bromide with trimethyl phosphite gives a 2-dimethoxyphosphorylmethyl derivativeand a product containing the phosphonate group to the isobutyl radical. Chloromethylation of the startingester proceeds in the 4 position of the furan ring. The resulting chloride undergoes phosphorylation underconditions of the Michaelis-Becker reaction to give the corresponding 4-(dialkoxyphosphorylmethyl)furan'and under the action of trimethyl phosphite a mixture of the same phosphonate, a dehalogenation producthaving a dimethylvinyl fragment. Bromination of the 4-chloromethyl derivative with N-bromosuccinimideinvolves the 2-methyl group. The dihalide reacts with trimethyl phosphite by way of reduction of the bromomethyl group to give 4-chloromethyl- or 4-dimethoxyphosphorylmethyl derivatives, as well as analogous dehydrohalogenation products containing a 5-dimethylvinyl fragment. A scheme describing the sequence of formation of these products in the course of the reaction is offered.     

Infrared study of UV-irradiated tungsten trioxide powders containing adsorbed dimethyl methyl phosphonate and trimethyl phosphate

The photodecomposition of dimethyl methylphosphonate (DMMP) and trimethyl phosphate (TMP) adsorbed on monoclinic WO₃ powders when irradiated by ultraviolet light (UV) in air, oxygen, and under evacuation was investigated using infrared spectroscopy (IR). The IR spectra show that DMMP decomposes into methyl phosphonate upon exposure to 254 nm UV for 2 h at room temperature in air. The same decomposition of DMMP occurs only at temperatures above 300°C without UV illumination. TMP differs from DMMP in that the photodecomposition product is not the same as the decomposition product obtained by heating above 300°C. Thermal decomposition leads to formation of a phosphate on the surface, whereas photodecomposition leads to the same adsorbed methyl phosphonate as found for the thermal or photodecomposition of DMMP. Since TMP does not contain a P-CH₃ bond, the formation of a methyl phosphonate on the surface after UV illumination involves a mechanism where CH₃ groups migrate from the methoxy group to the phosphorous central atom. No decomposition is observed at room temperature when DMMP or TMP adsorbed on WO₃ is irradiated under vacuum or in nitrogen atmosphere. Therefore, the photodecomposition of either DMMP or TMP adsorbed on WO₃ at room temperature does not involve a reaction with the lattice oxygen but rather a reaction with the oxygen radicals produced by the decomposition of ozone.     

Gas-phase ion-molecule reactions in organophosphorus esters

Self-condensation ion-molecule reactions of trimethyl phosphite, triethyl phosphite, dimethyl phosphonate, trimethyl phosphate and 2, 2-dichlorovinyl dimethyl phosphate (dichlorvos) were investigated by ion trap mass spectrometry and Fourier transform ion cyclotron resonance mass spectrometry. Reaction paths for the main processes observed were elucidated by parent ion selection and for reaction times up to 500 ms. In parallel, high-resolution measurements were performed in order to determine the composition of the principal ions. Among the compounds under examination, trimethyl phosphite and triethyl phosphite mainly give [M + H](+) and [M + (RO)(2)P](+) (R = CH(3), C(2)H(5)) adduct ions, whereas trimethyl phosphate and dimethyl phosphonate display [2M + H](+) ions, as the only abundant products, formed by reaction of [M + H](+) and M. 2,2-Dichlorovinyl dimethyl phosphate mostly shows fragmentation processes. The reaction patterns of the compounds examined were related to their different structural features. Gas-phase basicities of the phosphoryl compounds were also determined or re-examined. Copyright 1999 John Wiley & Sons, Ltd.     

Surface modification of silica nanoparticles to reduce aggregation and nonspecific binding

In this article, a systematic study of the design and development of surface-modification schemes for silica nanoparticles is presented. The nanoparticle surface design involves an optimum balance of the use of inert and active surface functional groups to achieve minimal nanoparticle aggregation and reduce nanoparticle nonspecific binding. Silica nanoparticles were prepared in a water-in-oil microemulsion and subsequently surface modified via cohydrolysis with tetraethyl orthosilicate (TEOS) and various organosilane reagents. Nanoparticles with different functional groups, including carboxylate, amine, amine/phosphonate, poly(ethylene glycol), octadecyl, and carboxylate/octadecyl groups, were produced. Aggregation studies using SEM, dynamic light scattering, and zeta potential analysis indicate that severe aggregation among amine-modified silica nanoparticles can be reduced by adding inert functional groups, such as methyl phosphonate, to the surface. To determine the effect of various surface-modification schemes on nanoparticle nonspecific binding, the interaction between functionalized silica nanoparticles and a DNA chip was also studied using confocal imaging/fluorescence microscopy. Dye-doped silica nanoparticles functionalized with octadecyl and carboxylate groups showed minimal nonspecific binding. Using these surface-modification schemes, fluorescent dye-doped silica nanoparticles can be more readily conjugated with biomolecules and used as highly fluorescent, sensitive, and reproducible labels in bioanalytical applications.     

Four related diethyl [(arylamino)(4‐ethynylphenyl)methyl]phosphonates

Crystal structures are reported for four related diethyl [(arylamino)(4‐ethynylphenyl)lmethyl]phosphonate derivatives, namely diethyl [(4‐bromoanilino)(4‐ethynylphenyl)methyl]phosphonate, C₁₉H₂₁BrNO₃P, (I), diethyl ((4‐chloro‐2‐methylanilino){4‐[2‐(trimethylsilyl)ethynyl]phenyl}methyl)phosphonate, C₂₃H₃₁ClNO₃PSi, (II), diethyl ((4‐fluoroanilino){4‐[2‐(trimethylsilyl)ethynyl]phenyl}methyl)phosphonate, C₂₂H₂₉FNO₃PSi, (III), and diethyl [(4‐ethynylphenyl)(naphthalen‐2‐ylamino)methyl]phosphonate, C₂₃H₂₄NO₃P, (IV). The conformation of the anilinobenzyl group is very similar in all four compounds. The P—C bond has an approximately staggered conformation, with the aniline and ethynylphenyl groups in gauche positions with respect to the P=O double bond. The two six‐membered rings are almost perpendicular. The sums of the valence angles about the N atoms vary from 344 (2) to 351 (2)°. In the crystal structures, molecules of (I), (III) and (IV) are arranged as centrosymmetric or pseudocentrosymmetric dimers connected by two N—H...O=P hydrogen bonds. The molecules of (II) are arranged as centrosymmetric dimers connected by C_methyl—H...O=P hydrogen bonds. The N—H bond of (II) is not involved in hydrogen bonding.     

Aminium salts obtained from diethyl [(3,5-di-tert-butyl-4-oxo-2,5-cyclohexadienylidene)methyl]phosphonate

Russian Journal of Organic Chemistry - In reaction of diethyl [(3,5-di-tert-butyl-4-oxocyclohexa-2,5-diеn-1-ylidene)methyl]phosphonate with N 1,N 1-dimethylethane-1,2-diamine aminophosphonate...     

An efficient preparation of isosteric phosphonate analogues of sphingolipids by opening of oxirane and cyclic sulfamidate intermediates with alpha-lithiated alkylphosphonic esters

D-erythro-(2S,3R,4E)-Sphingosine-1-phosphonate (1), the isosteric phosphonate analogue of naturally occurring sphingosine 1-phosphate (1a), and D-ribo-phytosphingosine 1-phosphonate (2), the isosteric phosphonate analogue of D-ribo-phytosphingosine-1-phosphate (2a), were synthesized starting with methyl 2,3-O-isopropylidene-d-glycerate (4) and D-ribo-phytosphingosine (3), respectively. Oxirane 12 was formed in eight steps from 4, and cyclic sulfamidate 22 was formed in five steps from 3. The phosphonate group was introduced via regioselective ring-opening reactions of oxirane 12 and cyclic sulfamidate 22 with lithium dialkyl methylphosphonate, affording 13 and 23, respectively. The synthesis of 1 was completed by S(N)2 displacement of chloromesylate intermediate 14b with azide ion, followed by conversion of the resulting azido group to a NHBoc group and deprotection. The synthesis of 2 was completed by cleavage of the acetal, N-benzyl, and alkyl phosphonate ester groups.