阳离子表面活性剂溴代十六烷基吡胶束对2,4—二硝基氯苯…

阳离子表面活性剂溴代十六烷基吡啶（ＣＰＢ）胶束对不中ＯＨ和２，４－二硝基氯苯的反应有催化作用，随ＣＰＢ浓度的增大，反应速率常数开始时迅速增大，然后趋于常数，ＯＨ浓度的增大使胶束催化不解的二级速率常数减小，ＣＰＢ胶束对此反应的速率提高作用比十六烷基三甲基溴化铵胶束更有效，对这两种胶束催化作用差异进行了讨论。     

尿酸和抗坏血酸在CPB现场修饰碳糊电极上的电化学行为

研究了尿酸(UA)和抗坏血酸(AA)在裸碳糊电极(CPE)和溴化十六烷基吡啶CPB)现场修饰碳糊电极(CPB/CPE)上的电化学行为,研究结果表明在PBS(pH=6.8)缓冲溶液中,UA和AA在CPE和CPB/CPE电极上的氧化均为一不可逆过程,在CPB/CPE上UA和AA的氧化峰电位负移,氧化峰电流增大,CPB/CPE对UA和AA的电化学氧化产生了促进作用。用电化学方法测得了UA和AA在CPE和CPB/CPE上的动力学参数如电荷转移系数α,扩散系数D,反应级数和反应速率常数k1。     

分光光度法研究二羟基二过碘酸合镍(Ⅳ)氧化三乙醇胺的反应动力学及机理

在碱性介质中,用分光光度法研究了二羟基二过碘酸合镍(Ⅳ)配离子氧化三乙醇胺的动力学.结果表明,反应对Ni(Ⅳ)为准一级反应,速率常数kobs=(k₁+k₂[OH^-])K₁K₂[OH^-][TEA]/{[H₂IO₆^3-]+K₁[OH^-]+K₁K₂[OH^-][TEA]},对还原剂三乙醇胺为正非整数级,表观速率常数随[OH^-]的增加而增加,随[IO₄^-]的增加而减小.据此提出了Ni(Ⅳ)和还原剂所形成的活化配合物的内部电子转移的反应机理.并求得28℃时前期平衡常数和速控步骤的速率常数分别为K₁=2.063,K₂=36.471L·mol^-1;k₁=8.008×10^-2s^-1,k₂=0.2896mol^-1·L·s^-1.     

多巴胺和抗坏血酸在CPB现场修饰碳糊电极上的电化学及电化学动力学性质

用现场修饰方法制备了溴化十六烷基吡啶(CPB)修饰碳糊电极(CPB/CPE)。运用循环伏安法(cyclic voltammetry,CV)、电位阶跃计时电流法(chronoamperometry,CA)及电位阶跃计时库仑法(chronocoulometry,CC)法研究了多巴胺(DA)和抗坏血酸(AA)在裸碳糊(CPE)和CPB/CPE上的电化学行为,测得了动力学参数如电荷转移系数α,扩散系数D,反应级数和电极反应速率常数kf。研究结果表明CPB/CPE可用于AA和DA共存体系中DA的电化学选择性测定。     

新试剂1-(2-羟基-3,5-二硝基苯基)-3-[4-(苯基偶氮)苯基]-三氮烯的合成及与季铵盐型阳离子表面活性剂的显色反应

合成了新试剂1-(2-羟基-3,5-二硝基苯基)-3-[4(苯基偶氮)苯基]-三氮烯(HDNPAPT),研究了该试剂在NaOH介质中与阳离子表面活性剂漠化十六烷基三甲铵(CTMAB)、溴化十六烷基吡啶(CPB)、溴化十二烷基二苄铰(DDMBAB)形成1:3的紫红色离子缔合物显色体系.测定了显色体系表面活性剂的临界胶束浓度、表观摩尔吸光系数ε_(max)、符合比尔定律的范围.探讨了微量阳离子表面活性剂CMTAB、CPB和DDMBAB的测定方法,结果满意.     

孔雀石绿在CPB胶束介质中的电化学行为

以玻碳电极(GCE)为工作电极,用循环伏安法(CV)研究了孔雀石绿(MG)在溴代十六烷基吡啶(CPB)胶束介质中的电化学行为,并与其在磷酸盐缓冲溶液(PBS)中的电化学行为进行了比较。在20～300mV/s范围内MG的氧化峰电流Ip与扫描速度平方根成正比,表明MG在GCE上的电化学氧化反应是一个受扩散控制的电化学过程。通过介质pH值对MG电化学氧化反应的影响研究发现,在pH值为4～8范围内MG的电化学氧化过程没有质子参与。用计时库仑法(CC)、计时电流法(CA)测定了有无CPB存在时MG的扩散系数D分别为2.34×10-6和2.51×10-6cm2/s,电荷转移系数α分别为0.56和0.72,电极反应速率常数kf为3.95×10-4和9.12×10-4s-1。结果表明,在PBS浓度较大的体系中,CPB更早的到达CMC且MG平台部分的氧化峰电流Ip较低;MG在2.0×10-2～8mmol/L浓度范围内,其氧化峰峰电流Ip随浓度增大降低,峰电位Ep正移。     

碱性介质中二过碘酸合银(Ⅲ)配离子氧化四氢糠醇的反应动力学及机理

用分光光度法研究了碱性介质中二过碘酸合银(Ⅲ)配离子于27～42℃区间氧化四氢糠醇(THFA)的反应动力学。结果表明,反应对Ag(Ⅲ)及四氢糠醇均为一级,准一级速率常数kobs随[OH^-]增大而增大,随[IO₄^-]增加而减小,并有微弱的正盐效应。在氮气保护下,反应体系不能引发丙烯腈或丙烯酰胺聚合。提出了含有前期平衡的反应机理,求出了平衡常数、速控步骤的速率常数及相应的活化参数。     

亮绿褪色反应用于微量季铵盐型阳离子表面活性剂的分光光度法测定研究

在 p H 7.0 0 Tris- HCl缓冲介质中 ,微量季铵盐型阳离子表面活性剂溴化十六烷基三甲胺 ( CTMAB)和溴化十六烷基吡啶 ( CPB)能使亮绿 ( Brilliant Green,简称 BG)产生灵敏的褪色反应 ,发现其褪色程度ΔA (ΔA =A0 - Ai)与 CTMAB及 CPB用量存在定量关系。研究了该褪色反应的最佳条件 ,探讨了反应机理 ,拟定了利用该反应用于微量 CTMAB和 CPB的测定方法 ,CTMAB和 CPB的浓度分别在0～ 6× 1 0 - 5mol/ L ,0～ 8× 1 0 - 5mol/ L范围内符合比耳定律。拟定的方法用于电镀废液样品中微量 CTMAB的测定 ,结果满意     

胶束增稳荷移反应紫外分光光度法测定洛美沙星

提出了一种基于胶束增稳荷移反应测定洛美沙星的紫外分光光光度法 ,研究了在阳离子表面活性剂溴化十六烷基吡啶 (CPB)胶束体系中电子给体洛美沙星与电子受体四氯对苯醌之间的荷移反应产物的紫外光谱性质。发现CPB对洛美沙星与四氯对苯醌的荷移反应络合物有显著的增稳效应。洛美沙星的浓度在0 .8～ 5 4mg L范围内符合比尔定律 ,r =0 .9994。在测定波长 32 3nm处 ,络合物的表观摩尔吸光系数为 3.5 6×10 - 4L·mol- 1 ·cm- 1 。本方法用于片剂中洛美沙星含量的测定 ,其回收率为 97.8%～ 10 0 .5 % ,相对标准偏差为0 .9%～ 2 .4 %。     

抗坏血酸和尿酸在CPB现场修饰碳糊电极上的电化学行为及其选择性测定应用

研究了抗坏血酸(AA)和尿酸(UA)在裸碳糊电极(CPE)和溴化十六烷基吡啶(CPB)现场修饰碳糊电极(CPB/CPE)上的电化学行为.研究结果表明,在PBS水溶液中,AA和UA在CPB/CPE上氧化峰电流增加,峰电位负移,CPB/CPE对AA,UA电化学氧化反应产生了催化作用.微分脉冲法研究表明,在AA和UA共存体系中,AA和UA的氧化峰电位相差约220 mV,以此建立了AA和UA的电化学选择性测定方法.AA和UA的微分脉冲伏安氧化峰电流和其相应浓度分别在7.0×10-6～6.0×10-3 mol/L和5.0×10-7～6.0×10-4 mol/L的范围内呈良好的线性关系.在200倍AA共存时UA的检出限为5.0×10-6 mol/L,CPB修饰的碳糊电极直接应用于实际尿样中UA的测定.     

阳离子表面活性剂混合胶团对2,4-二硝基氯苯水解反应的 催化作用

研究了阳离子表面活性剂混合胶团对2,4-二硝基氯苯(DNCB)碱性水解反应的催化作用。结果表明：(1)在十六烷基三甲基溴化铵(CTAB)和十六烷基溴化吡啶(CPB)混合溶液中DNCB水解一级速率常数k1与混合胶团中CTAB或CPB的摩尔分数有直线关系,表面活性剂形成理想的混合胶团。(2)辛基三甲基省化铵(OTAB)与CTAB,CPB的cmc值相差很大,在它们的混合胶团中OTAB含量极少,DNCB水解k1与CPB/OTAB混合胶团中CPB摩尔分数的关系与直线呈负偏差。(3)在CTAB(或CPB)与OTAB混合体系中OTAB起溴盐作用,使催化活性降低。用假相离子交换(PIE)模型对所得结果给出了定量的处理和解释。     

Micellar effect upon the reaction of hydroxide ion with coumarin

Cationic micelles of cetyltrimethylammonium bromide, CTABr, speed attack of hydroxide ion upon coumarin by a factor of c.a-2, due to a concentration effect. The first-order rate constants, k_obs, at a given hydroxide ions concentration go through maxima with increasing surfactant concentration. The overall micellar effects in these cationic micelles can be treated in terms of the pseudo-phase ion exchange model. Analysis of the data shows that second-order rate constant at the micellar surface is smaller than the second-order rate constant in water. Anionic micelles of sodium dodecyi sulfate, SDS, inhibit the same reaction. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 273–276, 1998.     

Kinetics of alkaline fading of methyl violet in micellar solutions of surfactants: Comparing Piszkiewicz's,Berezin's,and pseudophase ion-exchange models

The micellar effect of surfactants of various types on the rate of the reaction between methyl violet and hydroxide ion is studied. The absorption spectra show that the cation of methyl violet is bound by micelles of all types at proper concentrations of surfactants. The observed rate constant in micellar systems containing nonionic Brij-35, zwitterionic 3-(dimethyldodecylammonio)-propanesulfonate, cationic cetyltrimethylammonium bromide and hydroxide surfactants is higher, whereas in solutions of the anionic surfactant sodium dodecylsulfate is lower than that one in the surfactant-free system. Piszkiewicz's, Berezin's, and pseudophase ion-exchange models of the kinetic micellar effect are used for the treatment of the dependences of the above-mentioned constants on the surfactant concentration. The values of the corresponding kinetic parameters are compared and discussed. The influence of nonionic, zwitterionic, and anionic micelles on the reaction rate is discussed on the basis of medium and concentration kinetic effects. The character of the cationic micelles effect is somewhat paradoxical. Although the observed pseudo–first-order reaction rate constant substantially increases in the presence of such micelles, the second order-rate constant in these micelles is lower than the corresponding value in surfactant-free aqueous solution. As a possible explanation, the decrease in the reactivity of the HO^– ions is proposed, owing to their electrostatic association with the cationic headgroups (“diverting effect”).     

Applicability of Positive Cooperativity Model of Enzyme Catalysis on Surfactant-Mediated Reaction of Pararosaniline Hydrochloride Carbocation with Hydroxide Ion

The reaction of hydroxide ion with stabilized pararosaniline hydrochloride carbocation was investigated in the presence of cationic micelles of cetyltrimethylammonium bromide (CTAB) and anionic micelles of sodium dodecyl sulfate (SDS). Pseudo-first-order kinetics were followed by the reaction system and rate constant depends on surfactant concentration. The reaction was strongly inhibited in the presence of SDS micelles whereas catalyzed in the presence of CTAB micelles. Micellar data were analyzed by applying positive cooperativity model of enzyme catalysis. The value of index of cooperativity (n) was greater than 1 for all reaction systems. Inhibitory and catalytic effect in the presence of micelles had been explained on the basis of hydrophobic and electrostatic interactions of various species present in the reaction systems. Presence of counterions in the reaction system inhibited the reaction rate.     

Kinetics of the acidic hydrolysis of fenuron in the aqueous and micellar media

The kinetics of the hydrolysis of fenuron by hydrochloric acid in aqueous methanol solution was studied spectrophotometrically. The influence of cationic micelles of cetyltrimethylammonium bromide and anionic micelles of sodium lauryl sulfate on the rate of hydrolysis of fenuron have also been studied. The anionic micelles increased the rate of reaction, while the cationic micelles decreased the rate of hydrolysis. The reaction followed first-order kinetics in [fenuron]. The rate of reaction was increased with increase in [HCl] in lower range, but become constant at higher concentration in aqueous and micellar pseudophases. The reaction starts with the protonation of amino group of fenuron followed by rate-determining attack of water. The results in micellar media are accounted for on the basis of distribution of substrate into micellar and aqueous pseudophases.     

Micellar‐accelerated hydrolysis of organophosphate and thiophosphates by pyridine oximate

Rate constants for the hydrolysis reaction of phosphate (paraoxon) and thiophosphate (parathion, fenitrothion) esters by oximate (pyridinealdoxime 2‐PyOx⁻ and 4‐PyOx⁻) and its functionalized pyridinium surfactants 4‐(hydroxyimino) methyl)‐1‐alkylpyridinium bromide ions (alkyl = C_nH_2n+1, n = 10, 12, 14, 16) have been measured kinetically at pH 9.5 and 27°C in micellar media of cationic surfactants cetyltrimethylammonium bromide (CTAB) and cetylpyridinium bromide (CPB). Acid dissociation constant, pK_a, of oximes has also been determined by spectrophotometric, kinetic, and potentiometric methods. The rate acceleration effects of cationic micelles have been explored. Cationic micelles of the pyridinium head group (CPB) showed a large catalytic effect than the ammonium head group (CTAB). The effects of pH, oximate concentration, and surfactants have been discussed.     

Kinetics of the alkaline hydrolysis of fenuron in aqueous and micellar media

The kinetics of the hydrolysis of fenuron in sodium hydroxide has been investigated spectrometrically in an aqueous medium and in cationic micelles of cetyltrimethylammonium bromide (CTAB) medium. The reaction follows first‐order kinetics with respect to [fenuron] in both the aqueous and micellar media. The rate of hydrolysis increases with the increase in [NaOH] in the lower concentration range but shows a leveling behavior at higher concentrations. The reaction followed the rate equation, 1/k_obs = 1/k + 1/(kK[OH^?]), where k_obs is the observed rate constant, k is rate constant in aqueous medium, and k is the equilibrium constant for the formation of hydroxide addition product. The cationic CTAB micelles enhanced the rate of hydrolytic reaction. In both aqueous and micellar pseudophases, the hydrolysis of fenuron presumably occurs via an addition–elimination mechanism in which an intermediate hydroxide addition complex is formed. The added salts decrease the rate of reaction. © 2007 Wiley Periodicals, Inc. Int J Chem Kinet 39: 638–644, 2007     

Solubilization of a water-insoluble dye in aqueous NaBr solutions of alkylpyridinium bromides and its relation to micellar size and shape

In order to investigate the effect of added salt on micelle size, shape, and structure the solubilization of Orange OT in aqueous NaBr solutions of decylpyridinium bromide (DePB), dodecylpyridinium bromide (DPB), tetradecylpyridinium bromide (TPB), and hexadecylpyridinium bromide (CPB) has been examined. The solubilization powers of DePB and DPB micelles increase with increasing NaBr concentration up to 2.86 and 3.07 mol dm^–3, respectively, but above these concentrations remain unaltered. This suggests that spherical micelles of DePB and DPB can have a maximum and constant size at NaBr concentrations higher than these threshold concentrations. On the other hand, the solubilization powers of TPB and CPB micelles increase in the whole range of NaBr concentration studied. The dependencies of the solubilization powers of their micelles on the counterion concentration change at 0.10 and 0.03 mol dm^–3 NaBr, respectively, as suggests that TPB and CPB micelles undergo the sphere–rod transition at those concentrations. Orange OT is a more suitable probe for detecting the presence of the maximum- and constant-size spherical micelle than Sudan Red B.     

Comparative study of the cationic surfactants and their influence on the alkaline hydrolysis of acetylsalicylic acid

A kinetic study of the reaction of acetylsalicylic acid (aspirin) with sodium hydroxide has been studied in the presence of some conventional and novel cationic surfactants. The pseudo‐first‐order rate constant increases with the surfactant concentration initially and then decreases. In comparison to conventional cationic surfactants, i.e., cetyltrimethylammonium bromide and cetylpyridinium bromide, novel alkyldiethylethanolammonium bromide (R = C₁₆) surfactant accelerated the alkaline hydrolysis significantly. The pseudophase ion‐exchange model has been applied to fit the experimental results. Activation parameters have also been evaluated. © 2010 Wiley Periodicals, Inc. Int J Chem Kinet 43: 1–8, 2011     

Effect of Cationic Micelles on the Kinetics of Interaction of Ninhydrin with l-Leucine and l-Phenylalanine

The effect of cationic micelles of cetyltrimethylammonium bromide (CTAB) and N-cetylpyridinium bromide (CPB) on the interaction of l-leucine and l-phenylalanine with ninhydrin have been studied at 70 degrees C. Both surfactants strongly catalyze the reactions. The reaction rates are higher in CTAB micelles than in CPB micelles. Quantitative kinetic analysis has been performed on the basis of a pseudo-phase model. The influence of different salts on the reaction rates has also been seen and it is found that tightly bound/incorporated counterions are the most effective. Copyright 1999 Academic Press.