热动力学的研究 XV.分数级反主尖的热动力学法

根据热动力学基础理论和n级反应通用的势动力学方程,本文建立了各种分数级反应的热动力学研究法.应用M-340计算机编制了研究法基本公式中有关无量纲参数的各种函数表,并深入讨论了有关函数的基本性质及其图象.同时将本文建立的分数级反应研究法应用于整数级反应的热动力学研究,所得结果与文献报道的一、二级反应的无量纲参数法基本公式完全相同,该研究法还可用于判断化学反应的级数.     

Pyridazines. LI. On the Reactivity of Pyridazine-carbaldehydes towards Selected Active-Hydrogen Compounds

Reactions of 3-pyridazinecarbaldehyde and 4-pyridazinecarbaldehyde with various active methylene carbanions were studied. The products obtained in Knoevenagel reactions, Wittig-Horner-Emmons reactions, and Hantzsch-type reactions are presented.     

Flash vacuum pyrolysis over solid catalysts. 1. Pyrazoles over zeolites

Flash vacuum pyrolysis (fvp) reactions of 1H-pyrazole (1), 3,5-dimethylpyrazole (2), and 3,5-diphenylpyrazole (3) were carried out over zeolites. Reactions were performed using ZCOY-7, NH(4)-Y, and Na-Y zeolites. Reaction temperatures of heterogeneous reactions were lower than the corresponding temperatures in the homogeneous system, showing a catalytic effect of the zeolites. Compounds 1-3 afforded nitrogen extrusion in homogeneous fvp reactions while in the heterogeneous ones different reactions were present. Compounds 1 and 2 also afforded nitrogen extrusion; products arising from ring fragmentation were found in reactions of 2 and 3 while an isomeric imidazole was isolated in reactions of 3. Isomerization of 3 is attributed to a transition-state selectivity by the catalyst due to the relation between the size of the molecule and the cavity of the zeolite. This isomerization reaction was present only when zeolites with active Br?nsted sites were used.     

Solid-supported nitroso hetero Diels-Alder reactions. 1. Acylnitroso dienophiles: scope and limitations

Polymer-supported acylnitroso dienophiles were prepared and used in hetero Diels-Alder (HDA) reactions with a variety of dienes. The transient acylnitroso dienophiles were prepared in situ from immobilized hydroxamates, which were attached to solid supports via several linkers each cleavable by different cleavage reagents, and served for the synthesis of both N-unsubstituted and N-derivatized HDA adducts. Model compounds were used to (i) optimize reaction conditions for solid-supported HDA reactions, (ii) evaluate the outcome of the reactions with various dienes, (iii) compare relative reactivities of dienes, and (iv) assess the stability of HDA adducts toward cleavage conditions typically used in solid-phase syntheses. Cleaved products were submitted to biological assays, and the results are reported. The accompanying paper, focused on complementary arylnitroso HDA reactions, includes a comparison of both HDA reactions.     

Detailed mechanism generation. 2. Aldehydes, ketones, and olefins

Generalized reaction classes for the consumption and decomposition of aldehydes, ketones, and olefins are described. These classes are important for generating not only reactions for the consumption of the branching agents of low-temperature hydrocarbon combustion but also reactions of the oxidation of alkenes and the decomposition of cyclic ethers. These reaction classes have been extrapolated from specific reactions of existing validated mechanisms. The reaction patterns making up the class were derived by identifying the reactive center of the specific reactions and the important surrounding functional groups. The rates used currently are definitely "first guesses" based on these specific reactions. The reaction classes in this paper supplement the reaction classes derived from accepted reaction types in the previous paper in this series. The purpose of this paper is to outline a complete (with very few exceptions) set of reaction classes which describe the C(5) and C(6) products of the low-temperature and cyclic ether path in the heptane and isooctane mechanisms.     

Head-to-tail regioregular oligothiophene-functionalized 9,9'-spirobifluorene derivatives. 1. Synthesis

Two series of novel fully conjugated oligomers, oligothiophene-functionalized 9,9'-spirobifluorene derivatives, have been developed in this contribution. First, four 9,9'-spirobifluorene bromide derivatives (compounds 1a-d) are prepared through various synthetic routes. Oligothiophene derivatives with or without substituents are synthesized through the Grignard and Suzuki coupling reactions. The Negishi coupling reactions between oligothienylzinc chloride and various 9,9'-spirobifluorene bromides with Pd(PPh(3))(4) as catalyst successfully produce the desired compounds, unsubstituted oligothiophene-functionalized 9,9'-spirobifluorene derivatives, compounds 2 to 4a-d. Since the Negishi coupling reactions afford regioregularly head-to-tail (H-T) oligo(4-n-hexylthiophene)-functionalized 9,9'-spirobifluorene derivatives in poor yields, the Suzuki coupling reactions between sodium 4-n-hexylthienyl-2-boronate 8, and various 9,9'-spirobifluorene-based bromides 1a-d and 9-16 are employed to produce highly regioregular head-to-tail oligothiophene-functionalized 9,9'-spirobifluorene derivatives (compounds 5 to 7a-d) in very high yields. We also investigate the effect of solvents on the Suzuki coupling reactions. The structure and purity of all compounds are verified by FT-IR, (1)H and (13)C NMR, MS, and elemental analysis.     

Calorimetric investigation of polymerization reactions. III. Curing reaction of epoxides with amines

The curing reactions of epoxy resin with aliphatic diamines and the reaction of phenyl glycidyl ether with butylamine as a model for the curing reactions were investigated with a differential scanning calorimeter (DSC) operated isothermally. The heat of reaction of phenyl glycidyl ether with butylamine is equal to 24.5 ± 0.6 kcal/mole. The rate of reaction was followed over the whole range of conversion for both model and curing reactions. The reactions are accelerated by the hydrogen-bond donor produced in the system. The rate constants based on the third-order kinetics were determined and discussed for the model reaction and for the chemically controlled region of curing reactions. The activation energies for these rate constants are 13-14 kcal/mole. At a later stage of conversion, the curing reactions become controlled by diffusion of functional groups. The final extent of conversion is short of completion for most isothermally cured and even for postcured samples because of crosslinking. It was quantitatively indicated that the final conversion of isothermal cure corresponds to the transition of the system from a viscous liquid to a glass on the basis of the theory of glass transition temperature of crosslinked polymer systems.     

Reactions of gaseous ions. I. Methane and ethylene

At elevated pressures in a mass spectrometer ion source reactions occur between certain ions and the neutral species present. We have studied the various secondary ions formed in methane and ethylene at elevated pressures and have determined the reactions by which they are formed and the rates of these reactions. The rates are all extremely fast. The reaction rates have been treated by classical collision theory and it has been shown that to a fair approximation the cross-sections and reaction rate constants can be predicted from a simple balance of rotational and polarization forces. [Reprinted from J. Am. Chem. Soc. 1957; 79: 2419.] Copyright 1957 by the American Chemical Society and reprinted by permission of the copyright owner.     

Organic Stereochemistry. Part 8

This review terminates our general presentation of the principles of stereochemistry with special reference to the biomedicinal sciences. Here, we discuss and illustrate the principles of prostereoisomerism, and apply these to product and substrate? product stereoselectivity in drug metabolism. The review begins with an overview of the concept of prostereoisomerism, discussing such aspects as homotopic, enantiotopic, and diastereotopic groups and faces. The main part of this review is dedicated to drug and xenobiotic metabolism. Here, the concept of prostereoisomerism proves particularly helpful to avoid confusing metabolic reactions in which an existing stereogenic element (e.g., a stereogenic center) influences the course of the reaction (substrate stereoselectivity), with metabolic reactions which create a stereogenic element (almost always a stereogenic center; product stereoselectivity). Specifically, examples of product stereoselectivity will be taken from functionalization reactions (so‐called phase‐I reactions) and conjugation (so‐called phase‐II reactions). Cases where stereoisomeric substrates show distinct product stereoselectivities (substrate? product stereoselectivity) will also be presented.     

Sulfostyrils. IV. Reactions of 4-keto-3,4-dihydrosulfostyril

The ketone group in 4-keto-3,4-dihydrosulfostyril (I) displays anomalous properties. Its reactions are described; in some reactions it behaved normally, in others it proved quite inert. Attempted oximination of I led to extrusion of the sulfone group with formation of isatin derivatives. Compound I was converted to a tetracyclic indole derivative.     

Kinetics of radiation-induced grafting reactions. II. Cellulose acetate–styrene systems

Kinetics of grafting reactions of styrene to preirradiated cellulose acetate have been studied by labeling the active sites with bromine atoms. The dilution of styrene monomer with methanol affected grafting reactions remarkedly: e.g., as the concentration of methanol in monomer solutions increased, the growth rates of individual graft radicals decreased while the average lifetimes increased. The integrated amounts of active sites which participated in grafting reactions were also affected by the constitution of monomer solutions and varied roughly in proportion to the extents of swelling of cellulose acetate. Grafting yields for styrene/methanol = 1/1 were higher than for 3/1 and 1/3 throughout the duration of grafting reactions, which is due not only to the high molecular weight of graft chains but also to the large number of graft chains for the 1/1 system compared to the other systems.     

2-Polyfluoroalkylchromones. 7. Reactions of 6-substituted 2-tetra- and 2-pentafluoroethylchromones with 2-aminoethanol

The reactions of 2-aminoethanol with 6-methyl-2-tetra- and 6-methyl-2-pentafluoroethylchromones involve the carbonyl group to give imines; the reactions with 6-nitro-2-tetra- and 6-nitro-2-pentafluoroethylchromones involve the C(2) atom, resulting in the pyrone ring opening. This also occurs in the reactions of 2-(1,1,2,2-tetrafluoroethyl)chromone with ammonia and benzylamine.     

The effect of heating rate upon the coupling of complex reactions. I. Independent and competitive reactions

Theoretical curves of the rate of conversion vs. temperature at constant heating rate for first-order reactions with activation energies of 80, 160, 240 and 320 kJ mole^?1 are compared over a range of heating rates from 10^?9 to 10⁵ K s^?1 for independent and competitive reactions. Independent reactions with different activation energies may be separated from one another by either increasing or decreasing the rate of heating. The spectrum of derivative peaks for two competing reactions at various heating rates has a dispersion effect in the region of change from low to high activation energy reactions. The practical range of heating rates in thermal analytical experiments and the application of these model cases to the understanding of the kinetics of complex systems at high and low temperatures are discussed.     

Chemo-differentiating ABB' multicomponent reactions. Privileged building blocks

Multicomponent reactions (MCRs) designated as ABB' are defined as those reactions that introduce into the final product one molecule of component A and two molecules of component B in a chemo-differentiating manner. This ability to discriminate the incorporation of component B ensures that these processes maintain the advantages of using multicomponent reactions in diversity-oriented molecular construction. Furthermore, they benefit from the fact that only two reagents need to be mixed together. Component B can be therefore considered to be a privileged building block, and the reactions in which it participates, chemo-differentiating multicomponent reactions. Among the reduced set of compounds capable of acting as such building blocks, we discuss the use of ketenes, terminal conjugated alkynoates, enolisable carbonyl compounds, cyclic enol ethers and cyclic enamines.     

Thermally reversible polymer linkages. II. Linear addition polymers

The stepwise addition polymerization reactions of bisazlactones [bis(2-oxazolin-5-one)s] and a variety of 4,4′-bisphenols have been studied for the purpose of making thermally reversible linear polymers. Thus polymerization occurs at or near room temperature, while depolymerization yielding the two monomer species occurs at elevated temperatures. The synthesis of oligomers in solution without the use of catalyst occurs for the reaction of bisazlactones with bisphenols containing an electron-withdrawing moiety between the two phenol groups of the bisphenol. These oligomers regenerate the bisphenol and bisazlactone monomers upon heating to 165–200°C for several hours under dry box conditions. In many cases, these reactions follow the same patterns of reactivity observed in model studies. This chemistry may be useful for forming degradable or recyclable polymers, where shortchain prepolymers, or macromonomers, endcapped with azlactone and phenol moieties could be used to form high molecular weight polymers that are thermoreversible. Such a reaction system might also be used for preventing reactions of bisphenols and/or bisazlactones at low temperatures, with the desired reaction initiated by formation of the reactive species at elevated temperatures. Envisioned uses in this case might be thermally triggered crosslinking or polymerization reactions, or temperature controlled drug release. © 1993 John Wiley & Sons, Inc.     

Pyrolysis of aminonitriles,cyanohydrazones, and cyanoacetamides. Part II. Elimination reactions of arylacetylhydrazone,arylcyanoacetylhydrazone, and substituted cyanoacetamides

Rates of pyrolytic reactions of arylacetylhydrazone and arylcyanoacetylhydrazone (1–4) of the general formula GCH₂CONHNCHAr (G = H,CN) have been measured. The increase in the acidity of the hydrogen atom involved in the six-centered elimination process suggested for these reactions causes a significant increase in rates and thus appears to be the limiting factor in these pyrolytic reactions. The implication of this conclusion for the pyrolytic reactions of substituted cyanoacetamides (5–8), NCCH₂CONHAr are considered. The mechanism of pyrolytic reactions of compounds (5–8) appears to proceed through a 4-membered cyclic transition state. © 1996 John Wiley & Sons, Inc.     

Co-oligomerization of ethylene and higher linear alpha olefins. II. Olefin reactivities in various reaction steps of co-oligomerization with nickel ylide-based system

Part I described co-oligomerization reactions of ethylene and various linear α-olefins (propylene, 1-butene, 1-hexene, 1-heptene, 1-octene, and 1-decene) in the presence of the homogeneous catalyst consisting of sulfonated nickel ylide and diethylaluminum ethoxide. The present article analyzes olefin reactivities in various reaction steps of the co-oligomerization reactions as well as reactivities of various catalytic species. Chain propagation reactions (insertion into the Ni? C bonds) with participation of α-olefins exhibit poor regioselectivity, primary insertion being ca. 60% more probable than the secondary insertion. Ethylene is significantly more reactive in chain propagation reactions: 50–70 times compared to olefin primary insertion and 100–120 times compared to olefin secondary insertion. Reactivities of α-olefins in chain propagation reactions decrease slightly for higher olefin alkyl groups. Reactivities of Ni? C bonds in chain propagation and chain termination reactions strongly depend on the structure of the alkyl group attached to the nickel atom. The Ni? CHR? CH₂? R bond has very low reactivity in ethylene insertion reaction and usually decomposes in the α-hydrogen elimination process. Kinetic analysis of olefin co-oligomerization reactions provides numerous analogies with olefin copolymerization reactions in the presence of Ziegler–Natta catalysts.     

The isokinetic relationship. V. Investigation of Bimolecular reaction systems

The appearance of the isokinetic relationship in bimolecular reaction series is examined. It is shown that the abscissa of the common point of intersection of the Arrhenius plots is governed by the interaction of the collision complex with the surrounding heat bath and the height of the potential barrier which this complex has to overcome. The appearance of negative isokinetic temperatures (i.e. “anticompensation”) is explained and demonstrated for second-order gas phase reactions. With increasing interactions between the reactants and the heat bath (for example in condensed phase reactions) the common point of intersection is shifted towards greater reciprocal isokinetic temperatures. The theory is applied to both gas phase and liquid phase reactions, the crucial heat-bath vibrational frequencies calculated from the isokinetic temperature are found to correspond to bands in the far-infrared spectra of the solvent used as the reaction medium.     

Fused s-triazino heterocycles. VIII. 1,3,4,6,9b-pentaazaphenalenes. Reactions of a methyl and bromomethyl side chain

Enhanced reactivity of the methyl group of 2-t-butyl-5-methyl-1,3,4,6,9b-pentaazaphenalene allowed acetic anhydride-catalyzed condensation reactions with several aromatic aldehydes, and base-catalyzed alkylation reactions with several alkyl halides to take place, albeit in low yields. Of the many nucleophiles tried, only salts of carboxylic acids, in the presence of 18-crown-6, were able to displace bromine from 2-(bromomethyl)-5-methyl-1,3,4,6,9b-pentaazaphenalene.     

Bisorthoesters as Polymer Intermediates. III. Oligomers Containing Purine Rings

Hexa-n-propyl orthoisophthalate, hexa-n-propyl orthoterephthal-ate, and in one case hexaethyl orthooxalate were condensed with aminomalondiamine dihydrochloride or aminomalonamideamidine dihydrochloride in DMSO or DMF between 100°C and the boiling point of DMF to oligomers containing adenine and hypoxanthine rings. For example, hexa-n-propyl orthoisophthalate and amino-malonamidamidine dihydrochloride in dimethyl sulfoxide at 100°C gave an oligomer of poly (2,8-hypoxanthinediyl-1,3-phenylene). The condensation was limited to oligomers of relatively low molecular weight, partly because of the low solubility of the oligomers under reaction conditions and partly also because the four reactive amino groups of the aminomalonamideamidine and the aminomalondiamidine did not react simply as difunc-tional tetramines to form linear aromatic polymers; this unequal reactivity of the amine functions caused side reactions to occur. Such side reactions have not been observed in the reactions of bisorthoesters with tetrafunctional aromatic orthodiamines, such as 3,3′,4,4′-tetraaminobiphenyl.