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Book

Cover Physical Chemistry: Quanta, Matter, and Change

Peter Atkins, Julio de Paula, and Ronald Friedman

Physical Chemistry starts off by looking at the foundations of the subject and provides the reader with some mathematical background. It then looks at quantum mechanics, taking into consideration the quantum mechanics of motion, molecular structure, and molecular symmetry. It then considers Fourier transforms, molecular spectroscopy, magnetic resonance, statistical thermodynamics, probability theory, the first law of thermodynamics, and multivariate calculus. The final part of the book examines physical equilibria, chemical equilibria, molecular motion, chemical kinetics, reaction dynamics, and processes in fluid systems and solid states.

Chapter

Cover Atkins’ Physical Chemistry

Motion in liquids  

This chapter shows how molecular motion in liquids from is different to that that in gases on account of the presence of significant intermolecular interactions and the much higher density typical of a liquid. It explores the electrical resistance of electrolyte solutions and analyses it in terms of the response of the ions to an applied electric field. It discusses how solute molecules and ions move through liquid environments. The chapter demonstrates how ions reach a terminal velocity when the electrical force on them is balanced by the drag due to the viscosity of the solvent. It mentions inelastic neutron scattering, in which the energy neutrons collect or discard as they pass through a sample is interpreted in terms of the motion of its molecules.

Chapter

Cover Supramolecular Chemistry

Mechanically interlocked molecules  

This chapter explores mechanically interlocked molecules (MIMs), which belong to a category of structures containing two or more molecular sub-components that, despite not being chemically bonded, are inextricably connected due to the inability of bonds to pass through one another. This type of molecular entanglement is described as a mechanical bond. The chapter begins by outlining the formidable challenges presented in the syntheses of MIMs and the key strategies that have been developed to overcome them. It then considers cases in which the influence of the mechanical bond on chemical and physical properties, including supramolecular properties, delivers applications in sensing, catalysis, and materials. The control of molecular motion is one of the most prominent attributes of the mechanical bond. The chapter discusses how this facet serves as the foundation of modern-day molecular machinery and how dynamic MIMs are critical to future applications in nanotechnology.

Chapter

Cover Instrumental Analysis (International Edition)

Infrared Spectroscopy  

This chapter focuses on infrared (IR) spectroscopy, which is used to probe molecular vibrational modes and gives substantive insight into the molecular structure of the analyte. It explains that a vibrational mode is a unique vibration within a molecule in which all atoms involved in the vibration have a sinusoidal motion and the motion of all of the atoms shares the same phase. It also considers the determination of the types of bonds that exist within a molecule as one of the main uses of IR spectroscopy. The chapter highlights the three regions of the IR spectrum: near-IR, mid-IR, and far-IR, which are named based on their anthropocentric relationship to the human eye's lower detection limit. It draws attention to mid-IR radiation, which is used to probe the primary vibrational modes associated with the bonds within a molecule.

Chapter

Cover The Physicochemical Basis of Pharmaceuticals

The Theory of Disperse Systems  

This chapter focuses on the theory of disperse systems. Various types of disperse system can be formed depending on the state of the disperse phase and the continuous phase. The chapter then looks at the drug distribution in pharmaceutical disperse systems. Drug molecules usually partition between the disperse phase and the continuous phase and can be present in both phases, but the concentration of drug is usually much greater in one phase. Disperse systems can be classified as molecular, colloidal, and coarse dispersions, according to the properties exhibited. Dispersed entities move in dispersions due to Brownian motion, diffusion, and sedimentation. Viscosity describes the resistance of a liquid to flow and the higher the viscosity of a liquid the greater the resistance of the liquid to flow when shear stress is applied. Increases in interfacial tension and interfacial contact area increase interfacial free energy and can destabilize disperse systems.

Chapter

Cover Computational Chemistry

Dynamics Methods  

This chapter focuses on dynamics methods. Especially for complex systems, the ‘static’ inspection of features of the potential energy surface is not sufficient to predict the behaviour of the system described by it. Simulation techniques sample the range of structures that are visited under particular experimental conditions. Molecular dynamics simulations perform this sampling by applying Newton’s laws of motion to the atoms. On the other hand, Monte Carlo simulations use random changes of structure, with an algorithm for accepting or rejecting given changes that results in an overall Boltzmann distribution. Sampled structures can be analysed in terms of average properties, for example using radial distribution functions. The most common application of dynamical simulation methods is the study of biomolecules, their structural variability, and their interactions with other molecules.