Ethylamine kinetics

The concentration of phenylacetate can be determined from the kinetics of its pseudo-first-order hydrolysis reaction in an ethylamine buffer. When a standard solution of 0.55 mM phenylacetate is analyzed, the concentration of phenylacetate after 60 s is found to be 0.17 mM. When an unknown is analyzed, the concentration of phenylacetate remaining after 60 s is found to be 0.23 mM. What is the initial concentration of phenylacetate in the unknown ... 

When diazomethane is slowly added to excess lactam, the anions formed can interact with unreacted lactam by means of hydrogen bonds to form ion pairs similar to those formed by acetic acid-tri-ethylamine mixtures in nonpolar solvents. The methyldiazonium ion is then involved in an ion association wdth the mono-anion of a dimeric lactam which is naturally less reactive than a free lactam anion. The velocity of the Sn2 reaction, Eq. (7), is thus decreased. However, the decomposition velocity of the methyldiazonium ion, Eq. (6a), is constant and, hence, the S l character of the reaction is increased which favors 0-methylation. It is possible that this effect is also involved in kinetic dependence investigations have shown that with higher saccharin concentrations more 0-methylsaccharin is formed. 

In practice the epoxide-amine cure is often accelerated by the addition of catalysts such as boron trifluoride complexes, and the boron trifluoride-ethylamine adduct (BFE) is widely used for this purpose. In addition to catalysing the epoxide-amine reactions, BFE can initiate homopolymerisation of epoxide. The accelerating effect of BFE is illustrated by DSC scans for the TGDDM/DDS/BFE system in Figure 12. The multiple-peaked exotherm associated with the BFE-catalysed TGDDM/DDS cure indicates that the kinetics of this system are more complex than those for the cure with amine alone. For this system the overall heat of reaction was found to decrease with increasing BFE concentration 89). For DDS alone Q0 was about 110 kJ per mole epoxide while the value for BFE alone was 75 kJ/mole, and the DDS/BFE values were between these limits. It appears that the proportion of epoxide homo-polymerisation relative to amine or hydroxyl addition increases with increasing BFE concentration. 

Mechanisms have been suggested for the N-bromosuccinimide (NBS) oxidation of cyclopentanol and cyclohexanol, catalysed by iridium(III) chloride,120 of ethanolamine, diethanolamine, and triethanolamine in alkaline medium,121 and for ruthenium(III)-catalysed and uncatalysed oxidation of ethylamine and benzylamine.122 A suitable mechanism has been suggested to explain the break in the Hammett plot observed in the oxidation of substituted acetophenone oximes by NBS in acidic solution.123 Oxidation of substituted benhydrols with NBS showed a C-H/C-D primary kinetic isotope effect and a linear correlation with er+ values with p = —0.69. A cyclic transition state in the absence of mineral acid and a non-cyclic transition state in the presence of the acid are proposed.124 Sulfides are selectively oxidized to sulfoxides with NBS, catalysed by ft-cyclodextrin, in water. This reaction proceeds without over-oxidation to sulfones under mild conditions.125... 

Kinetic measurements gave evidence for deprotonation of the spiro-Meisenheimer intermediate 35 as the rate-limiting step during the rearrangement of 2-(4-nitrophenoxy)ethylamine 32 into 33 in aqueous alkah [23] (Scheme 14, R = H). The kinetic effect of N-alkyl substitution [24-26] (Scheme 14, R = Me, Et, f-Pr) has also been investigated. 

The kinetics of the addition of ketene dimer to aromatio amines havo been mvostigated. The dimers of the higher alkylketenes do not react with secondary amines or with phmiyUiydraiine, but their quantitative reaction with ethylamine hae been used for their determination, 2,3-J)ihydro-A, A diiii thyl-p-tketene dimer to form 7.8-dihydio-2,6 dimethy1-chromone. 

First-order kinetics does not necessarily indicate an E mechanism. For example, the decomposition of the quaternary salt of dimethyl-0-(p-nitrophenyl)-ethylamine is first order in aqueous solution. Nevertheless, the transformation undoubtedly occurs by an E2 process, since a large increase in the rate of reaction is observed when a base stronger than water is present. When the hydrogen atoms in the 0-position are particularly sensitive to attack as they are here, even the weak base, water, must be able to initiate the reaction 9... 

From this study the following reaction scheme describing the transformation of ethylamine to the main product DMEA and by-products was established. From a kinetic point of view, steps 2 and 3 are the rate determining reactions. It follows that the DMEA selectivity is increased by modifying the acido-basicity of copper chromite used as a catalyst. In fact, the change of the catalyst basicity can decrease the MEA condensation to form DEA without modification of the hydro-dehydrogenating properties of the catalyst which are necessary for the methylation of ethylamine with methanol (steps 1 and 3). 

The lipase catalyzes the kinetic resolution of racemic amines, e.g. 1-phenyl-ethylamine (Fig. 19-21)[11. Products are intermediates for pharmaceuticals and pesticides. They can also be used as chiral synthons in asymmetric synthesis. As acylating agent ethylmethoxyacetate is used, because the reaction rate is more than 100 times faster than that with butyl acetate. Probably an enhanced carbonyl activity induced by the electronegative a-substituents accounts for the activating effect of the methoxy group. The lipase is immobilized on polyacrylate. The lowered activity caused by use of in organic solvent (tert-methylbutylether = MTBE) can be increased... 

An amination reaction was performed using dg-ethanol. A kinetic isotope effect with r = 6 was observed. Analysis of the ethylamine revealed that the major product was CD3CH2NH2. 

Smit, M. H. Gass, A. E. G. Gyanide detection using a substrate-regenerating, peroxidase-based biosensor. Anal. Chem. 1990, 62, 2429-2436. Gooper, J. M. Bannister, J. V. McNeil, G. J. A kinetic study of the catalysed oxidation of 1, 3-dimethylferrocene ethylamine by cytochrome... 

In conclusion, we propose a specific research program for deaminations in aqueous systems based on ideas mentioned in this section, namely to investigate (a) deamination kinetics and products of a series of simple aliphatic amines in water with sodium nitrite and perchloric acid at various acidities, (b) decompositions of diazenolates of the same amines in water and (c) decompositions of a standard type of N-nitroso amides, again of the same amines and all in the same aprotic solvent. The reaction conditions should be as similar as possible in the experiments of all three series. The series of amines should include methyl-, ethyl-, 1-methylethyl-, 1-methylpropyl-, and ( cr butyl)amine and [l- H]ethylamine, but not amines with longer aliphatic chains, as the very informative work of Southam and Whiting (1982) demonstrated clearly that, in deaminations of such amines, many mechanistically complex products are formed. In addition, micellar effects increase the complexity of reactions with such amines (see Sect. 7.3). It is obvious from the series of amines that we have proposed that this program is based on the work of Brosch and Kirmse (1991), Hovinen and Fishbein (1992), Hovinen et al. (1992), Finneman et al. (1993), and Ho and Fishbein (1994). Work with chiral 1-methylpropyl- and [l- H]ethyl-amine will provide information on the stereochemistry of these reactions. 

Kinetic resolution of secondary allylic alcohols by Sharpless asymmetric epoxidation using fert-butylhydroperoxide in the presence of a chiral titanium-tartrate catalyst has been widely used in the synthesis of chiral natural products. As an extension of this synthetic procedure, the kinetic resolution of a-(2-furfuryl)alkylamides with a modified Sharpless reagent has been used . Thus treatment of racemic A-p-toluenesulphonyl-a-(2-furfuryl)ethylamine [( )-74] with fert-butylhydroperoxide, titanium isopropoxide [Ti(OPr-/)4], calcium hydride (CaHa), silica gel and L-(+)-diisopropyl tartrate [l-(+)-DIPT] gave (S)-Al-p-toluenesulphonyl-a-(2-furfuryl)ethylamine [(S)-74] in high chemical yield and enantiomeric excess . Similarly prepared were the (S)-Al-p-toluenesulphonyl-a-(2-furfuryl)-n-propylamine and other homologues of (S)-74 using l-(+)-D1PT. When D-(—)-DIPT was used, the enantiomers were formed . ... 

These large rate enhancements are attributable to the copper(II) ion complexing with penicillin [26] because methylation of the free carboxylate group in benzylpenicillin reduces the rate of the copper(II) ion-trifluoro-ethylamine reaction by ca 10. There is no kinetic dependence upon the concentration of trifluoroethylamine which indicates that aminolysis does... 

Different kinetic behavior was observed when secondary hydroxy-alkylic amines, methyl-2-hydroxyethylamine and butyl-2-hydroxy-ethylamine, were employed as nucleophiles. Autoacceleration appeared in dioxane for both secondary amines however, normal second order kinetics were followed in DMF when the nucleophile is methyl-2-hydroxyethylamine which has less bulky substituents. In the reaction of butyl-2-hydroxyethylamine with CMPS in DMF, rate retardation began when the conversion reached about 75% owing to the steric hindance of the bulky butyl groupThus the sensitivity of the rate profiles to reaction media and nucleophile structure complicates assessment of "polymeric effects". 

DFT calculations combined with a distortion/interaction energy analysis showed that the anomalous Z selectivity observed in Wittig reactions of ( rt/j< -substituted benzalde-hydes is not caused by phosphoms-heteroatom interactions in the addition TS but is predominantly steric in nature. An efficient synthesis of olefins by the coupling of stabilized, semi-stabilized, and non-stabilized phosphorus ylides with various carbonyl compounds in the presence of silver carbonate has been reported. The first catalytic (in phosphane) Wittig reaction has been developed by utilizing an organosilane that chemoselectively reduces a phosphane oxide pre-catalyst to a phosphane. Sodium carbonate and A,A-diisopropyl-ethylamine have been employed as bases. The kinetic E/Z... 

The oxidation of aspirin by A-sodio-A-bromobenzenesulfonamide (bromamine-B, BAB) in aqueous HCIO4 is first order in BAB, fractional order in aspirin and inverse fractional order in H+. The reaction proceeds via decarboxylation, bromination, and AcOH loss, affording the product 2,4,6-Br3CeH20H. The oxidation of D-cycloserine (CS) by BAB in HCl is first order in BAB and fractional order each in CS and H+. The proposed mechanism assumes simultaneous catalysis by H+ and Cl ions and is consistent with the observed kinetic results. The oxidation of diethylamine by BAB catalysed by ruthenium(III) is first order in oxidant, catalyst and substrate, but inverse fractional order in H+. A mechanism in which the metal coordinates the nitrogen atom of the amine before a slow electrophilic attack on the nitrogen by BAB, elimination of HBr, attack by water, and disproportionation affords acetaldehyde and ethylamine, which undergoes a similar oxidation. " ... 

The kinetics of dissociation and of formation of the pentacyanofer-rate(II) complexes of cysteine, penicillamine, glutathione, and 2-mercapto-ethylamine have been established pyrazine was used as incoming ligand in the dissociation studies. The pH dependence of both dissociation and formation can be ascribed to protonation equilibria of the ligands. Kinetics both of dissociation and of formation have also been studied for the 2-methyl pyrazine complex [Fe(CN)s(2Mepz)] , 2. Dissociation was... 

Other instances of IHD are not so definitive because the evidence is not based iy>on kinetically stable and homogenously ligated complexes. The in VOCI3 is more highly shielded than in V0Br3, putting in the IHD category. Mixed ethylamine... 

Pt(dien)X] + are stated to occur by a two-step mechanism. It is argued, from reactivity trends for various compounds rather than from any direct evidence for an intermediate of significant lifetime, that it is the second step, the breakdown of a five-co-ordinate species [Pt(dien)X(SR2)] +, that is rate-determining. Kinetic parameters are also reported for the reaction of [Pt(dien)Br]+ with methylamine and with ethylamine. ... 

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