José M. Riveros

Bio: José M. Riveros is an academic researcher from University of São Paulo. The author has contributed to research in topics: Ion & Ion cyclotron resonance. The author has an hindex of 25, co-authored 119 publications receiving 3006 citations. Previous affiliations of José M. Riveros include Massachusetts Institute of Technology & University of Florida.

The Cluster−Continuum Model for the Calculation of the Solvation Free Energy of Ionic Species

Abstract: A hybrid approach using a combination of explicit solvent molecules and the isodensity polarizable continuum model (IPCM) method is proposed for the calculation of the solvation thermodynamic prope...

Theoretical Calculation of pKa Using the Cluster−Continuum Model

Abstract: The pKa's of 17 species from −10 to 50 were calculated using the ab initio MP2/6-311+G(2df,2p) level of theory and inclusion of solvent effects by the cluster−continuum model, a hybrid approach that combines gas-phase clustering by explicit solvent molecules and solvation of the cluster by the dielectric continuum. In addition, the pure continuum methods SM5.42R and PCM were also used for comparison purposes. Species such as alcohols, carboxylic acids, phenol, acetaldehyde and its hydrate, thiols, hydrochloric acid, amines, and ethane were included. Our results show that the cluster−continuum model yields much better agreement with experiment than do the above-mentioned pure continuum methods, with a rms error of 2.2 pKa units as opposed to 7 pKa units for the SM5.42R and PCM methods. The good performance of the cluster−continuum model can be attributed to the introduction of strong and specific solute−solvent interactions with the molecules in the first solvation shell of ions. This feature decreases the...

Gibbs energy of solvation of organic ions in aqueous and dimethyl sulfoxide solutions

Abstract: The Gibbs energy of solvation of several ions in water and dimethyl sulfoxide (DMSO) solutions was obtained through the use of thermodynamic equations relating ΔGsolv* of the ion with gas phase basicity, pKa, ΔGsolv* of neutral species and the Gibbs energy of solvation of the proton. We have used the most accurate and recent values for these properties, and this report provides 56 Gibbs energy of solvation values in aqueous solution and 30 in DMSO solution. Our results support the general view that anions are much better solvated in aqueous solution than in DMSO. An important example is the hydroxide ion for which the Gibbs energy of transfer from water to DMSO is 26 kcal mol−1. The majority of anions have a Gibbs energy of transfer in the range 10 to 15 kcal mol−1. In the case of cations, DMSO has a larger solvation ability but the difference in the Gibbs energy of solvation between water and DMSO is not greater than 5 kcal mol−1. The present data can be very useful for the development of continuum solvation models.

Microwave Spectrum and Structure of Nitric Acid

Abstract: The microwave spectra of five further isotopic species of nitric acid, H18ONO2, cis‐HON18OO, trans‐HONO18O, cis‐HO15N18OO, and D15NO3, have been investigated. The data have been used to refine the previous structural determination of Millen and Morton. In the calculation of structure, particular consideration has been given to the use of ground‐state moments of inertia in Kraitchman's equations for near‐oblate planar molecules. The structure was calculated using several different methods, including the double‐substitution method due to Pierce, in order to substantiate the following structural parameters: O–H=0.964, (H)O–N=1.406, cis–N–O=1.211, trans‐N–O=1.199 A, ∠HON=102°9′, ∠cis‐ONO=115°53′, ∠trans‐ONO=113°51′, and O···O (NO2 group)=2.184 A.This determination clearly demonstrates a 2° tilt of the NO2 group away from the hydrogen atom. The NO2 parameters are close to those found in a number of related molecules, but there is some evidence that the cis‐NO bond in HNO3 is slightly longer than the trans‐NO b...

Gas-phase Nucleophilic Displacement Reactions

Abstract: Publisher Summary This chapter reviews that gas-phase nucleophilic displacement reactions constitute a mature field of physical organic chemistry. It is a field that provides some unusual insights into the world of solvent-free chemistry, although many experiments remain to be rationalized on a more quantitative basis. The extent to which the understanding of gas-phase reactivity provides an insight into solution behavior by appropriate extrapolation of salvation effects has been under attack recently, and it is a subject of lively discussion. The chapter discusses that the most important lesson that can be derived from these examples is that significantly different chemistry can be generated in ionic reactions in the gas phase. This aspect is one which most theoretical and experimental chemists find intellectually stimulating and a challenge to be pursued.

Quantum mechanical continuum solvation models.

Abstract: 6.2.2. Definition of Effective Properties 3064 6.3. Response Properties to Magnetic Fields 3066 6.3.1. Nuclear Shielding 3066 6.3.2. Indirect Spin−Spin Coupling 3067 6.3.3. EPR Parameters 3068 6.4. Properties of Chiral Systems 3069 6.4.1. Electronic Circular Dichroism (ECD) 3069 6.4.2. Optical Rotation (OR) 3069 6.4.3. VCD and VROA 3070 7. Continuum and Discrete Models 3071 7.1. Continuum Methods within MD and MC Simulations 3072

Chemistry with ADF

Abstract: We present the theoretical and technical foundations of the Amsterdam Density Functional (ADF) program with a survey of the characteristics of the code (numerical integration, density fitting for the Coulomb potential, and STO basis functions). Recent developments enhance the efficiency of ADF (e.g., parallelization, near order-N scaling, QM/MM) and its functionality (e.g., NMR chemical shifts, COSMO solvent effects, ZORA relativistic method, excitation energies, frequency-dependent (hyper)polarizabilities, atomic VDD charges). In the Applications section we discuss the physical model of the electronic structure and the chemical bond, i.e., the Kohn–Sham molecular orbital (MO) theory, and illustrate the power of the Kohn–Sham MO model in conjunction with the ADF-typical fragment approach to quantitatively understand and predict chemical phenomena. We review the “Activation-strain TS interaction” (ATS) model of chemical reactivity as a conceptual framework for understanding how activation barriers of various types of (competing) reaction mechanisms arise and how they may be controlled, for example, in organic chemistry or homogeneous catalysis. Finally, we include a brief discussion of exemplary applications in the field of biochemistry (structure and bonding of DNA) and of time-dependent density functional theory (TDDFT) to indicate how this development further reinforces the ADF tools for the analysis of chemical phenomena. © 2001 John Wiley & Sons, Inc. J Comput Chem 22: 931–967, 2001

Atomic and molecular electron affinities: photoelectron experiments and theoretical computations.

Abstract: I. Introduction and Scope 231A. Definitions of Atomic Electron Affinities 233B. Definitions of Molecular Electron Affinities 233II. Experimental Photoelectron Electron Affinities 235A. Historical Background 235B. The Photoeffect 236C. Experimental Methods 237D. Time-of-Flight Negative Ion PhotoelectronSpectroscopy239E. Some Thermochemical Uses of ElectronAffinities241F. Layout of Table 10: ExperimentalPhotoelectron Electron Affinities242III. Theoretical Determination of Electron Affinities 242A. Historical Background 2421. Theoretical Predictions of Atomic ElectronAffinities2422. Theoretical Predictions of MolecularElectron Affinities243B. Present Status of Theoretical Electron AffinityPredictions243C. Basis Sets and Theoretical Electron Affinities 244D. Density Functional Theory (DFT) andElectron Affinities245E. Layout of Tables 8 and 9: Theoretical DFTElectron Affinities247F. Details of Density Functional MethodsEmployed in Tables 8 and 9247IV. Discussion and Observations 248A. Statistical Analysis of DFT Results ThroughComparisons to Experiment and OtherTheoretical Methods248B. Theoretical EAs for Species with UnknownExperimental EAs251C. On the Applicability of DFT to Anions and theFuture of DFT EA Predictions251D. Specific Theoretical Successes 251E. Interesting Problems 2521. C

Advanced Organic Chemistry

Abstract: Organic Chemistry By Dr. I. L. Finar. Vol. 2: Stereochemistry and the Chemistry of Natural Products. Pp. xi + 733. (London and New York: Longmans, Green and Co., Ltd., 1956.) 40s. net.

Benchmarking the Conductor-like Polarizable Continuum Model (CPCM) for Aqueous Solvation Free Energies of Neutral and Ionic Organic Molecules.

Abstract: The conductor-like polarizable continuum model (CPCM) using several cavity models is applied to compute aqueous solvation free energies for a number of organic molecules (30 neutral molecules, 21 anions, and 19 cations). The calculated solvation free energies are compared to the available experimental data from the viewpoint of cavity models, computational methods, calculation time, and aqueous pKa values. The HF/6-31+G(d)//HF/6-31+G(d) and the HF/6-31+G(d)//B3LYP/6-31+G(d) with the UAKS cavities, in which radii are optimized with PBE0/6-31G(d), provide aqueous solvation effects in best agreement with available experimental data. The mean absolute deviations from experiment are 2.6 kcal/mol. The MP2/6-31++G(d,p)//HF/6-31+G(d) with the CPCM-UAKS(HF/6-31+G(d)) calculation is also performed for the base-catalyzed hydrolysis of methyl acetate in water.