- THE SOLUTION-STATE CONFORMATIONS OF IODOACETONE AND ω-IODOACETOPHENONE
-
A comparison of the experimental dipole moments of iodoacetone and ω-iodoacetophenone in n-hexane, carbon tetrachloride and benzene solution at 30.0 deg C with the values calculated (with inclusion of induced moments through space) for both cis and gauche conformers gives estimates of their (cis):(gauche) conformational ratios in these media.Molecular mechanics calculations show that the cis conformers of iodoacetone and ω-iodoacetophenone are nearly uniplanar, whereas the gauche-conformers of these compounds are characterized by (O=C-CH2-I) dihedral angles of 100.5 and 98.5 deg, respectively.
- Lumbroso, H.,Liegeois, Ch.,Guerrero, S. A.,Olivato, P. R.,Hase, Y.
-
-
Read Online
- Reaction kinetics and critical phenomena: Iodination of acetone in isobutyric acid + water near the consolute point
-
The rate of iodination of acetone has been measured as a function of temperature in the binary solvent isobutyric acid (IBA) + water near the upper consolute point. The reaction mixture was prepared by the addition of acetone, iodine, and potassium iodide to IBA + water at its critical composition of 38.8 mass % IBA. The value of the critical temperature determined immediately after mixing was 25.43 °C. Aliquots were extracted from the mixture at regular intervals in order to follow the time course of the reaction. After dilution of the aliquot with water to quench the reaction, the concentration of triiodide ion was determined by the measurement of the optical density at a wavelength of 565 nm. These measurements showed that the kinetics were zeroth order. When at the end of 24 h the reaction had come to equilibrium, the critical temperature was determined again and found to be 24.83 °C. An Arrhenius plot of the temperature dependence of the observed rate constant, kobs, was linear over the temperature range 27.00-38.00 °C, but between 25.43 and 27.00 °C, the values of kobs fell below the extrapolation of the Arrhenius line. This behavior is evidence in support of critical slowing down. Our experimental method and results are significant in three ways: (1) In contrast to in situ measurements of optical density, the determination of the optical density of diluted aliquots avoided any interference from critical opalescence. (2) The measured reaction rate exhibited critical slowing down. (3) The rate law was pseudo zeroth order both inside and outside the critical region, indicating that the reaction mechanism was unaffected by the presence of the critical point.
- Hu, Baichuan,Baird, James K.
-
-
Read Online
- A New Chemical Oscillator in a Novel Open Reactor: The ClO2-I2-Acetone System in a Membrane Fed Stirred Tank Reactor
-
The title reaction was carried out in a new type of semibatch reactor, where iodine or both iodine and chlorine dioxide are fed to the stirred bulk of the reactor through thin and selective silicon rubber membranes.For model calculations the iodine inflow rate and the pseudo-first-order rate constant of the iodide production from iodine were determined experimentally.All other reactions and rate constants were taken from the literature.The period and the duration of the experimentally found and theoretically predicted oscillations agree rather well.An exact electrochemical interpretation of the amplitude of the electrode potential oscillations requires further research.
- Marlovits, Gabor,Wittmann, Maria,Noszticzius, Zoltan,Gaspar, Vilmos
-
-
Read Online
- THE MECHANISM FOR NUCLEOPHILIC SUBSTITUTION OF α-CARBONYL DERIVATIVES. APPLICATION OF THE VALENCE-BOND CONFIGURATION MIXING MODEL.
-
The valence-bond configuration mixing model (VBCM) is applied to the nucleophilic substitution reactions of α-carbonyl derivatives.The model appears to resolve satisfactorily a number of features of these reactions that current mechanisms have not dealt with.These include: (i) the dependence of the rate-enchancing effect of the carbonyl upon the nucleophilic strenght of the entering group, (ii) the unusually large Hammett ? value for the reaction of PhCOCH2Br with substituted pyridines, and (iii) the mechanism by which the rate-enhancing effect of the carbonyl group is transmitted to the reaction centre.
- McLennan, Duncan J.,Pross, Addy
-
-
Read Online
- Facile Access to an Active γ-NiOOH Electrocatalyst for Durable Water Oxidation Derived From an Intermetallic Nickel Germanide Precursor
-
Identifying novel classes of precatalysts for the oxygen evolution reaction (OER by water oxidation) with enhanced catalytic activity and stability is a key strategy to enable chemical energy conversion. The vast chemical space of intermetallic phases offers plenty of opportunities to discover OER electrocatalysts with improved performance. Herein we report intermetallic nickel germanide (NiGe) acting as a superior activity and durable Ni-based electro(pre)catalyst for OER. It is produced from a molecular bis(germylene)-Ni precursor. The ultra-small NiGe nanocrystals deposited on both nickel foam and fluorinated tin oxide (FTO) electrodes showed lower overpotentials and a durability of over three weeks (505 h) in comparison to the state-of-the-art Ni-, Co-, Fe-, and benchmark NiFe-based electrocatalysts under identical alkaline OER conditions. In contrast to other Ni-based intermetallic precatalysts under alkaline OER conditions, an unexpected electroconversion of NiGe into γ-NiIIIOOH with intercalated OH?/CO32? transpired that served as a highly active structure as shown by various ex situ methods and quasi in situ Raman spectroscopy.
- Menezes, Prashanth W.,Yao, Shenglai,Beltrán-Suito, Rodrigo,Hausmann, J. Niklas,Menezes, Pramod V.,Driess, Matthias
-
supporting information
p. 4640 - 4647
(2021/02/05)
-
- 1,2-Dibromoethane and KI mediated α-acyloxylation of ketones with carboxylic acids
-
The 1,2-dibromoethane- and KI-mediated α-acyloxylation of ketones is reported in moderate to good yield without the use of transition metals and strong oxidants. Various acids are well tolerated with wide functional group compatibility. An 1,2-dibromoethane- and KI-catalysed reaction mechanism is proposed based on the results of control experiments.
- Wang, Xujie,Li, Gangsheng,Yang, Yanan,Jiang, Jianshuang,Feng, Ziming,Zhang, Peicheng
-
supporting information
p. 711 - 714
(2019/09/30)
-
- Reaction of 4-hydroxycoumarin or its O-substituted derivatives with diatomic interhalogens: ICl and IBr
-
Herein, we present some aspects regarding the iodination/bromination of 4-hydroxycoumarin or its O-methyl or O-acetyl derivatives with iodine monochloride or iodine monobromide as halogenation reagents. Also, the investigation of photochemical transformation of the three 3-iodocoumarins was investigated for the first time.
- Popa, Marcel Mirel,Draghici, Constantin,Barbu, Loredana,Dumitrescu, Denisa E.,Dumitrascu, Florea
-
supporting information
p. 344 - 350
(2017/02/10)
-
- Synthesis and antiviral evaluation of 4′-(1,2,3-triazol-1-yl) thymidines
-
Non-obligate chain terminating nucleosides with a linear substituent (azido or ethynyl group) at the 4′ position represent an important class of compounds in antiviral discovery, particularly against hepatitis C virus (HCV) and human immunodeficiency virus (HIV). We have previously shown that 3′-azidothymidine (AZT)-derived 1,2,3-triazoles can be potent inhibitors of HIV-1. To gauge the medicinal chemistry impact of functionalizing the 4′-linear substituent and possibly generate novel antiviral nucleoside scaffolds, we have explored azide-alkyne cycloaddition reactions with 4′-azidothymidine (ADRT). The Ru-mediated reaction failed and the Cu-catalyzed variant generated 1,2,3-triazoles (9a-y) with only modest yields and efficiencies, indicating a substantial steric barrier around the 4′-azido group. Antiviral screening identified a few triazole analogues moderately active against HIV-1 (18-62% inhibition at 10 μM) and/or influenza A virus (15-50% inhibition at 10 μM), and none active against West Nile virus (WNV) or HCV. These results suggest that the linear 4′ azido group of ADRT may be essential for target binding and that its chemical manipulation could largely compromise antiviral potency. This journal is the Partner Organisations 2014.
- Vernekar, Sanjeev Kumar V.,Qiu, Li,Zacharias, Jeana,Geraghty, Robert J.,Wang, Zhengqiang
-
supporting information
p. 603 - 608
(2014/05/06)
-
- New simple synthesis of quinoline-4-carbonitriles
-
Alkylation of 2-nitrobenzyl cyanides with α-halomethyl ketones furnishes ketonitriles which upon reduction with tin(II) chloride form quinoline-4-carbonitriles in good yields.
- Bujok, Robert,Wrobel, Zbigniew,Wojciechowski, Krzysztof,Trawczyski, Adam
-
p. 2682 - 2686,5
(2012/12/12)
-
- Diethyl [Nitro(diazo)methyl]phosphonate: Synthesis and reactivity towards alkenes
-
A novel and convenient synthesis of diethyl [nitro(di-azo)methyl] phosphonate and its reactions with various alkenes are described. The reactivity of diethyl [nitro(diazo)methyl]phosphonate is shown to be dependent on the structure of the alkene. A number of cyclopropyl-nitrophosphonates were obtained. Georg Thieme Verlag Stuttgart.
- Chemagin, Andrey V.,Yashin, Nikolai V.,Grishin, Yuri K.,Kuznetsova, Tamara S.,Zefirov, Nikolai S.
-
scheme or table
p. 259 - 266
(2010/03/24)
-
- Synthesis of the Bestmann-Ohira reagent
-
The conversion of an aldehyde to a terminal alkyne by means of a one-carbon chain extension is a key reaction in organic synthesis. By using dimethyl 1-diazo-2-oxopropylphosphonate, the Bestmann-Ohira reagent, the transformation can be achieved in one pot. A reliable, convenient sequence for the preparation of the Bestmann-Ohira reagent is described. Georg Thieme Verlag Stuttgart.
- Pietruszka, Joerg,Witt, Andreas
-
p. 4266 - 4268
(2008/03/28)
-
- Re-examination of nucleophilic substitution in chlorokojic acid
-
Chlorokojic acid was reacted with S2O23 , NO-3 , N-3 , I- , and SCN- . Only the three latter nucleophiles substituted the chlorine atom in the 2-CH2/s
- Uher, Michal,Szymońska, Joanna,Korenova, Anna,Tomasik, Piotr
-
p. 301 - 307
(2007/10/03)
-
- Iodomethane oxidation by dimethyldioxirane: A new route to hypoiodous acid and iodohydrines
-
matrix presented The oxidation of iodomethane with dimethyldioxirane allows the generation of stable neutral solutions of hypoiodous acid in the absence of any trapping agent for iodide anion. Hypoiodous acid is trapped in situ by addition to representative olefins to give iodohydrines in good yields. The stereochemical study of the products shows the anti-stereospecific nature of the iodohydroxylation reaction.
- Asensio, Gregorio,Andreu, Cecilia,Boix-Bernardini, Carmen,Mello, Rossella,Gonzalez-Nunez, Maria Elena
-
p. 2125 - 2128
(2008/02/09)
-
- Contrasting behavior of pentafluorophenoxyacetone and pentafluorobenzyloxyacetone in electron impact and electron capture mass spectrometry
-
Towards the goal of finding new ketone electrophores suitable as molecular labels for electrophoric release tags, pentafluorophenuxyacetone (1) and pentafluorbenzyloxyacetone (2) were prepared. Both ketones were evaluated by electron capture (EC) and electron impact (EI) modes of mass spectrometry (MS). By EC-MS, 1 nearly gave a single ion (as desired), whereas 2 gave many ions. This behavior was completely reversed in EI-MS. To account for certain ion fragments in the EC mass spectrum of 2, an anion radical MCLafferty-type rearrangement and loss of a carbene neutral were postulated. Electron impact of 1 gave an abundant ion at m/z 117 (C5F3+), which was suggested to be a diyne cation.
- Xu, Linxiao,Huang, Yulin,Giese, Roger W.
-
p. 615 - 620
(2007/10/03)
-
- Preparation of 1-aminoalkylphosphonic acids and 2-aminoalkylphosphonic acids by reductive amination of oxoalkylphosphonates
-
By reacting dialkyl 1-oxo- or 2-oxoalkylphosphonates with benzhydrylamine followed by reduction with triacetoxyborohydride and acid hydrolysis gave corresponding aminoalkylphosphonic acids with satisfactory yields. The use of benzylamine, α-methylbenzylamine and tritylamine was unsuccessful in the case of dialkyl 1-oxoalkylphosphonates whereas conversion of 2-oxoalkylphosphonates was also achieved although with lower yields.
- Ryglowski, Artur,Kafarski, Pawel
-
p. 10685 - 10692
(2007/10/03)
-
- Comparison of Several Substrates in the Briggs-Rauscher Oscillating System
-
Acetone, methylmalonic acid, malonic acid, iodomalonic acid, and phenylmalonic acid are compared under identical conditions in the Briggs-Rauscher oscillating system.Each of these five substrates consumes iodine to form an iodo product and produces iodide at the same time.The rates of iodine consumption have been measured for each of the substrates individually.To a first approximation, all of the substrates behave in a similar manner when compared at concentrations which react with iodine at similar rates.A skeleton model for the oscillatory system cannot quantitatively predict variations of the oscillatory period with concentration for any one of the substrates.Several reactions and processes are discussed which must be part of a complete description of the oscillator but which make only marginal improvements when compared to the skeleton model: reduction of iodate ion and iodine by hydroperoxy radical, reduction of iodate by the substrate enol, second-order reduction of iodate by iodide, next oxidation of iodine by hydrogen peroxide, continuous HOIO production, and decomposition of the iodo products.
- Furrow, Stanley D.
-
p. 11131 - 11140
(2007/10/02)
-
- THE CHEMISTRY OF PERFLUOROALKANESULFONYL IODIDES
-
The reaction between silver perfluoroalkanesulfinate (1) (RF=a, Cl(CF2)6; b, Cl(CF2)4) and iodine in dichloromethane at low temperature (e. g. -30 deg C) resulted in the formation of the corresponding perfluoroalkanesulfonyl iodide(2), which was identified by its 19F NMR spectra.The perfluoroalkanesulfonyl iodide generated in situ reacted with various olefins to form two series of adducts, namely the normal adducts, RFSO2CH2CHIR(3) and the adducts resulting from the loss of SO2, RFCH2CHIR(4) in yields ranging from moderate to good.A radical reaction mechanism is proposed and tested by e.s.r. experiments.Perfluoroalkanesulfonyl iodide reacted with acetone and other compounds containing active hydrogen to give iodinated products.
- Huang, Wei-Yuan,Hu, Li-Qing
-
-
- Syntheses de dioxolannes α-iodes
-
Three methods of iodination of cyclic ketals are described.Direct iodination by monoiodine chloride in ether leads to very good yields in monoiodo compounds.A high selectivity is obtained when one of the α-carbon atoms is tertiary.
- Daubie, Christophe,Bacquet-Einhorn, Cathy,Lelandais, Daniel
-
p. 1548 - 1551
(2007/10/02)
-
- Kinetics of Iodination of Ketones by N-Iodosuccinimide in Acid Medium
-
The kinetics of iodination of some ketones by N-iodosuccinimide (NIS) has been studied in aq. acetic acid medium in the presence of HClO4.The reaction is acid-catalysed exhibiting first order dependence with respect to acid.The reaction shows first order dependence with respect to and zero order dependence with respect to , indicating the acid-catalysed enolisation of ketones as the rate-determining step and reaction between enol and NIS as the fast step.The decrease in dielectric constant of the medium slightly enhances the reaction rate.The ρ, ?-relationship in the case of acetophenones is quite linear with ρ = -0.5 indicating the simultaneous operation of equilibrium protonation of ketones and deprotonation of the conjugate acid.The ρ, ?* plot of the different aliphatic ketones is also linear.The order of reactivity of different cyclic ketones studied is cyclohexanone ca. cyclooctanone > cyclopentanone > cycloheptanone.Arrhenius parameters have been computed and the observed isoenthalpic relationship has been discussed.A mechanism consistent with the results has been proposed.
- Radhakrishnamurti, P. S.,Mahapatro, D. K.
-
p. 207 - 210
(2007/10/02)
-
- Carbon-Halogen Bonding Studies. Halogen Redistribution Reactions between Alkyl or Acetyl Halides and Tri-n-butyltin Halides
-
The equilibrium positions have been determined for the halogen redistribution reactions of tri-n-butyltin halides with a variety of structurally different types of alkyl halides and with acetyl halides.These have been related through the reaction ΔGo values to carbon-halogen bond dissociation energy differences.It is suggested that the trends observed in the latter may provide evidence for the existence of a small steric bond weakening effect in the order C-I > C-Br > C-Cl bonds on going from methyl to primary, secondary, and tertiary alkyl halides.On the other hand, with the 2,3-? bond containing allyl, benzyl, and propargyl halides , α-haloacetones, and haloacetonitriles, there may be some type of electronic carbon-halogen bond strengthening effect which lies in order C-I > C-Br > C-Cl.Finally, for the acetyl halides, the data are in agreement with increases in bond strengths resulting from ? contributions being in the order C-Cl > C-Br > C-I.
- Friedrich, Edwin C.,Abma, Charles B.
-
p. 1367 - 1371
(2007/10/02)
-