Isopropoxide Ion Research Articles

Synthesis, characterization and reactivity of iron–olefin complexes of the type [CpFe(CO) 2(η 2-CH 2CHR)] +X − (Cp=η 5-C 5H 5; R=CH 3 to n-C 14H 29; X=PF 6 or BF 4)

A series of iron–olefin complexes of the type [CpFe(CO) 2(η 2-CH 2CHR)] + (R=CH 3 to n-C 14H 29) have been prepared using various synthesis methods. In addition, the complexes [Cp*Fe(CO) 2(η 2-CH 2CHR)] + (Cp*=η 5-C 5(CH 3) 5; R=CH 3, n-C 3H 7 and n-C 14H 29) and [CpRu(CO) 2(η 2-CH 2CHR)] + (R=CH 3, n-C 3H 7 and n-C 14H 29) have been synthesized by reacting the iron–alkyl complexes Cp*Fe(CO) 2(CH 2CH 2R) or ruthenium–alkyl complexes CpRu(CO) 2(CH 2CH 2R) with Ph 3CPF 6. A number of these complexes are new and have been fully characterized by analytical and spectroscopic methods. The reaction of [CpFe(CO) 2(η 2-CH 2CHR)] + with the isopropoxide ion gave the new ether derivatives [CpFe(CO) 2(CH 2CH{OCH(CH 3) 2}R)] (R=CH 3, n-C 2H 5, n-C 4H 9 and n-C 13H 27).

The site-specific reactivity of isopropanol in aqueous silicon etching: Controlling morphology with surface chemistry

The site-specific rates of isopropanol reaction on Si(111) were studied by kinetic competition with an etchant of known anisotropy and quantified using concentration-dependent changes in the etched surface morphology using a combination of STM measurements and kinetic Monte Carlo simulations. The isopropoxide ion was identified as the active species.

Reactions of the ambident super-electrophile series: the 2-(nitroaryl)-4,6-dinitrobenzotriazole 1-oxides with isopropoxide ion. Pathways of decomposition of the anionic σ-adducts

To elucidate the reactivity of super-electrophiles such as 4,6-dinitrobenzofuroxan as compared to normal electrophiles such as 1,3,5-trinitrobenzene, reaction of isopropoxide ion (iPrO−) with a series of ambident super-electrophiles was studied by 400 MHz 1H nuclear magnetic resonance spectroscopy. The 2-(nitroaryl)-4,6-dinitrobenzotriazole 1-oxides, 1–3, possess both a super-electrophilic (C-7) site and a normal electrophilic (C-1′) site. Nucleophiles can demonstrate selectivity for attack at C-7, which leads to formation of persistent anionic σ-adducts (Meisenheimer complexes), as compared to C-1′, which leads to N-2:C-1′ bond scission. The most reactive substrate, 2-(2′,4′,6′-trinitrophenyl)-4,6-dinitrobenzotriazole 1-oxide (Pi-DNBT, 1) was found to be the least selective substrate in C-7 adduct formation, while 2-(2′,4′-dinitrophenyl)- and 2-(4′-nitrophenyl)-4,6-dinitrobenzotriazole 1-oxides (DNP-DNBT, 2, and NP-DNBT, 3, respectively) showed increasing selectivity towards iPrO−, in turn. These results are discussed on the basis of overall selectivity for C-7 adduct formation and the relative selectivity of iPrO− as compared to methoxide and tert-butoxide ions. The conclusions are illustrated using comparative energy profiles. In terms of pathways for decomposition of the adducts, the C-7 adducts decompose via dissociation back to substrate and nucleophile and, thence, through C-1′ adduct formation to the scission products. However, for 1, the C-7 adduct 1a has now been found to decompose to 7-isopropyl-2-picryldinitrobenzotriazole, 1c. The possible mechanism of this formal internal redox will be discussed.

Isopropoxide ion — a novel depolarizer for aluminium batteries

The effect of isopropoxide as a depolarizer in aluminium cells/batteries is reported. The open-circuit potential, short-circuit current and discharge behaviour of both Al-polypyrrole and AlMnO 2 cells are improved significantly in the presence of isopropoxide. Isopropoxide ions are a better depolarizer than hydroxide ions. Galvanostatic polarization studies indicate that aluminium ions discharge at a higher potential in the presence of isopropoxide salt. The results indicate the possible use of isopropoxide ion as a depolarizer in practical aluminium batteries.

Effect of foreign ion additives on ceria surface reactivity towards isopropanol adsorption and decomposition: An infrared investigation

Infrared spectroscopy was employed to investigate reactions of isopropanol vapour on pure and doped ceria catalysts. The results obtained reveal that isopropanol is irreversibly adsorbed (at 298 K) on strongly dehydroxylated pure ceria surfaces in the form of coordinated molecules and, probably, two different types of isopropoxide ions (terminal and bridge-bonded). The coordinated molecules are suggested to be of importance in the alcohol dehydration (at > / 573 K) to give propene, whereas the bridging isopropoxides to be the surface intermediate of the dehydrogenation (at > /423 K) to give acetone. At > 573 K, the acetone takes part in a surface-mediated bimolecular reaction to produce isobutene and methane, and acetate surface species. The dehydration and dehydrogenation activities of ceria are seen to reside at eus Ce 4+- 2− pair sites. The secondary reaction of acetone, however, is suggested to occur on Ce 4+-OH − surface sites. Doping of ceria with Na + ions suppresses alcohol dehydration as well as further reactions of acetone. Cr 3+- and Al 3+-doping improve the surface selectivity towards dehydrogenation and dehydration reactions respectively.

ChemInform Abstract: Kinetics and Mechanism of the Reaction of 2,3‐Dimethoxy‐1,4‐naphthoquinone with Alkoxide Ions in Alcoholic Solvents

The reaction of 2,3-dimethoxy-1,4-naphthoquinone with ethoxide, n-propoxide, n-butoxide, and isopropoxide ion in the respective alcohols as solvents has been subjected to kinetic study. The reaction leads to 2,3-dialkoxy-1,4-naphthoquinones (2a–d) through 2-alkoxy-3-methoxy-1,4-naphthoquinones (3a–d) as intermediates. Catalytic behaviour by the alkoxide ions is observed. Rate constants and activation parameters have been measured for the two steps. The nucleophilic rate constants are related to the acidity of the respective alcohols, leading to linear behaviour in log k–ET(30) plots. Activation parameters of the two steps are discussed in terms of stabilization of reactants and transition states and the differences between the first and second substitution in terms of the effect of the sustituent in the vicinal position.

Kinetics and mechanism of the reaction of 2,3-dimethoxy-1,4-naphthoquinone with alkoxide ions in alcoholic solvents

The reaction of 2,3-dimethoxy-1,4-naphthoquinone with ethoxide, n-propoxide, n-butoxide, and isopropoxide ion in the respective alcohols as solvents has been subjected to kinetic study. The reaction leads to 2,3-dialkoxy-1,4-naphthoquinones (2a–d) through 2-alkoxy-3-methoxy-1,4-naphthoquinones (3a–d) as intermediates. Catalytic behaviour by the alkoxide ions is observed. Rate constants and activation parameters have been measured for the two steps. The nucleophilic rate constants are related to the acidity of the respective alcohols, leading to linear behaviour in log k–ET(30) plots. Activation parameters of the two steps are discussed in terms of stabilization of reactants and transition states and the differences between the first and second substitution in terms of the effect of the sustituent in the vicinal position.

Infrared study of the adsorption of propene and di-isopropyl ether on rutile

Infrared spectra are reported of propene and di-isopropyl ether adsorbed on rutile which had been preheated at 400 K. Propene was involved in hydrogen-bonding interactions with surface hydroxyl groups at 306 K and was probably also adsorbed through π-complex formation at Lewis-acidic surface sites. Chemisorption to give adsorbed isopropoxide ions occurred at higher temperatures and preceded subsequent oxidation to surface carboxylate species. Interactions between rutile and di-isopropyl ether were similarly dependent on temperature and involved hydrogen-bond formation, adsorption on Lewis-acidic sites and the appearance of infrared bands due to chemisorbed isopropoxide and carboxylate ions.

Kinetic studies of the reactions of 4-nitrobenzofuroxan with cyanide ion and isopropoxide ion in isopropanol

Kinetic studies of the reactions in isopropanol of 4-nitrobenzofuroxan with cyanide ion and isopropoxide ion have been carried out over the temperature range 15.0 to 35.0 °C. For both bases, the first species identifiable using stopped-flow reaction techniques is postulated to be a C-7 σ-complex of 4-nitrobenzofuroxan and base. Specific rate constants and activation parameters for the formation of these σ-complexes are compared to corresponding data relating to the formation of cyanide ion and isopropoxide ion—σ-complexes of 1,3,5-trinitrobenzene in isopropanol.

1H NMR studies of proton transfer and σ‐complex formation in the reactions of N‐substituted picramides with oxygen and nitrogen bases

Abstract1H NMR measurements of N‐substituted picramides in dimethyl sulphoxide‐methanol containing sodium methoxide show that the two major modes of 1:1 interaction involve transfer of an amino proton to give the conjugate base or methoxide attack at the 3‐position to give a σ‐adduct. The proportion of parent reacting by the latter pathway increases as the proportion of methanol in the solvent increases. Some comparative measurements in isopropanol‐dimethyl sulphoxide show that relative to methoxide the isopropoxide ion has a greater propensity for proton abstraction than for base addition. Reaction of the substrates with amide ions derived from piperidine or from benzylamine gives σ‐complexes by attack at unsubstituted ring positions. In the benzylamide adducts spin coupling is observed between the amino proton and the adjacent ring and methylene protons.

Effects of remote unsaturated bonds at C-2 on nucleophilic aromatic substitution of fluorine in 6,7-difluoro-1,2,3,4-tetrahydro-3,3-dimethyl-1,4-methanonaphthalenes

Approximate values of the second-order rate constant for fluorine replacement by isopropoxide ion in propan-2-ol–dimethyl sulphoxide (1 : 1 v/v) have been determined for a series of 6,7-difluoro-1,2,3,4-tetrahydro-3,3-dimethyl-1,4-methanonaphthalenes containing unsaturated groups at C-2. A factor of 13 separates the most reactive system [the 2-oxo compound (10)] from the least reactive [the 2-methylene compound (13)] but the lack of product regiospecificity excludes homoconjugation as a possible effect in stabilising the transition state for attack at C-6; the (E)-2-benzylidene compound (14) gave identical product ratios at 100 and at 150° in propan-2-ol.

Effects of remote unsaturated bonds on nucleophilic aromatic substitution in polyfluoroaromatic compounds. Profound effect of a remote carbonyl group

Approximate values of the second-order rate constants for fluorine replacement by isopropoxide ion in a series of unsaturated and related saturated 5,6,7,8-tetrafluoro-1,4-bridged naphthalenes have been determined. For 5,6,7,8-tetrafluoro-1,4-dihydro-3,3-dimethyl-1,4-methanonaphthalen-2(3H)-one, the rate constant (extrapolated to 25 °C) is greater than that for 5,6,7,8-tetrafluoro-1,2,3,4-tetrahydro-endo-2-methoxy-3,3-dimethyl-1,4-methanonaphthalene by a factor of 100 with similar rates of reactions at C-6 and -7, rationalised in terms of the field effect of the carbonyl group and the exclusion of regiospecific homoconjugation in the transition state for reaction at C-6. All other systems examined reacted with similar rate constants, irrespective of remote unsaturated or saturated bonds.

The ortho:para ratio in aromatic nucleophilic substitution. Part I

ortho:para Ratios have been measured for the reaction of o- and p-fluoro- and -chloro-nitrobenzenes with methoxide, ethoxide, and isopropoxide ions. The rates of substitution at the 2- and 4-positions of 2,4-difluoro- and 2,4-dichloro-1-nitrobenzenes by these anions have also been determined. The results are discussed in terms of steric exclusion of solvation in the transition states of the reactions, and for 2,4-dichloro-1-nitrobenzene, the effect of rotation of the nitro-group out of the plane of the benzene ring is examined.

Kinetics of Proton Transfer Reactions of Carbon Acids. II. Reaction of Di-(4-nitrophenyl)methane with Alkoxide Bases

The second-order rate constants have been measured over a range of temperatures for the proton-transter reactions from di-(4-nitrophenyl)methane to ethoxide, isopropoxide, and t-butoxide ions in solvents consisting of the corresponding alcohols containing 10% toluene by volume. The activation parameters ΔH≠ and ΔS≠ have been calculated and an interpretation of them is given in terms of solvation effects during the activation process. A comparison between the activation parameters for proton transfers and E2 olefin-forming β-elimination reactions is made and discussed with respect to transition state character of the latter reactions.

Aromatic nucleophilic replacement. Part XVI. Reactions of o-fluoro- and p-fluoro-nitrobenzene and 1-fluoro-3,5-dinitrobenzene with sulphite ions, and of o- and p-fluoronitrobenzene with isopropoxide ions

Rate constants and Arrhenius parameters for the reactions of o- and p-fluoronitrobenzenes and of 1-fluoro-3,5-dinitrobenzene with sulphite ions in 60% aqueous ethanol and for the reactions of o- and p-fluoronitrobenzene with isopropoxide ions in absolute isopropyl alcohol have been measured. The results for the sulphite ion reactions have been interpreted in terms of a transition state lying closer to the reactants than to the Wheland intermediate, and those for the isopropoxide ion in terms of differential solvation of initial and transition states, with steric exclusion of solvation occuring in the transiton state of the ortho-isomer.

A theoretical investigation of α-hydrogen abstraction from some organic anions

The process of α-hydrogen abstraction from methoxide, formate and isopropoxide ions has been examined, using an SCMO method, by calculating changes in electronic charge on αH and CαH bond orders, as the CαH bond orders, as the CαH bond was extended with the residual moiety retaining its equilibrium geometry. In all cases negative charge accumulates on αH with increasing CαH separation and the systems yield H − at sufficiently large CαH distances. Possible implications for the mechanisms of oxidation of the anions by dehydrogenation are discussed.

Cation and Anion Influence in the Alfin Reagent for the Polymerization of Butadiene

Abstract A mixture of allylsodium, sodium isopropoxide and sodium chloride causes a very rapid polymerization of butadiene to a soluble polymer of unusually high molecular weight which has largely a 1,4-structure. The present work is a study of the influence of the sodium cation and of various halide salts, and of the isopropoxide ion as contrasted with the n-propoxide, upon the proportion of 1,4-polymerization. A proper combination of ions will favor greatly the end-to-end polymerization and any given reagent may cause either 1,4 or 1,2-polymerization to take place, depending on the composition of the reagent. An explanation based on adsorption and orientation of diene molecules on the surface of the insoluble aggregate of ions is suggested.