Sonochemistry is the use of ultrasound to enhance or alter chemical reactions. Sonochemistry in the true sense of the term occurs when ultrasound induces “true” chemical effects on the reaction system, such as forming free radicals which accelerate the reaction. However, ultrasound may have other mechanical effects on the reaction, such as increasing the surface area between the reactants, accelerating dissolution, and/or renewing the surface of a solid reactant or catalyst. This comprehensive review summarizes several topics of study in the sonochemical literature, including bubble dynamics, factors affecting cavitation, the effects of ultrasound on a variety of chemical systems, modeling of kinetic and mass-transfer effects, the methods used to produce ultrasound, proposed cavitation reactors, and the problems of scaleup. The objective of this paper is to present a critical review of information available in the literature so as to facilitate and inspire future research in the field of sonochemistry.

Sonochemistry: Science and Engineering

The article discusses the mechanisms and the applications in organic synthesis, materials, supramolecular, and polymer synthesis of most organic reactions mediated by single electron transfer. Each reaction or class of reactions will be discussed by starting with the original discovery publication, followed by a summary of all or most review articles published in the field, and a discussion of the mechanism(s) and of the most important methodologic and synthetic developments since the most recent review was published. The mechanisms of most organic reactions are considered to proceed by two-electron transfer pathways, even though both biology and radical chemistry rely extensively on one-electron transfer processes. Radicals generated by homolytic cleavage at high temperature were traditionally employed in the industrial production of polymers and to a lesser extent in the synthesis of organic molecules.

Single electron transfer in radical ion and radical-mediated organic, materials and polymer synthesis.

Carbon—hydrogen spin—spin coupling constants

The analysis of the 13C NMR spectra of polycyclic aromatics is discussed briefly. Basic trends of chemical shifts are mentioned, but the emphasis is placed on substituent-induced chemical shifts (SCS). Semi-empirical approaches and regressional analysis are treated. The factors controlling SCS are discussed and steric, mesomeric and π-inductive effects are analysed.



CH, CF, CC, CP and C, Metal coupling constants are investigated and the influence of steric effects, bond order, mesomerism and angle distortions in relation to some of these coupling constants is discussed. Relaxation times are described in a series of compounds. The effects of dissolved oxygen or radicals are shown and the use of T1 as a monitor of molecular tumbling is depicted. The impact of 13C NMR on the understanding of charged aromatic species, both positive and negative ions, is mentioned and new information about reaction intermediates in electrophilic aromatic substitution is outlined. The possibility of using 13C NMR to investigate charge transfer complexes is also discussed. Among other subjects treated are automerization, deuterium exchange and biosynthetic incorporation of labelled materials and, finally, quantitative analysis is briefly touched upon.

13C NMR of polycyclic aromatic compounds. A review

The traditional Ullman reaction is the homocoupling of aromatic halides mediated by copper at elevated temperatures. Ullman first reported this reaction in 1901. Although the coupling conditions first reported are still widely used, a host of modifications have been made to these reactions. Some of these modifications include the use of activated and alternative metals, often resulting in much lower coupling temperatures. Nickel and palladium are the most utilized source of alternative metals, Periodic reviews have been published. This chapter covers the literature on copper, nickel, and palladium mediated homocoupling reactions in biaryl synthesis from 1901 to 2000. The focus of this chapter is the scope and limitation of these processes, preparation of the activated metal, and mechanism of the homocoupling process


Keywords:

Ullman reaction;
copper-mediated homocouplings;
palladium-mediated homocouplings;
polymerization;
axially chiral biaryls;
experimental procedures;
scope;
limitation;
mechanism;
biaryls;
bipyridyls;
bipyrimidyls;
biquinolines;
bifurans;
bithienyls;
bibenzothoiphenes;
metallocenes

Cu, Ni, and Pd Mediated Homocoupling Reactions in Biaryl Syntheses: The Ullmann Reaction

Long range 13C1H coupling constants are reported for a number of methylquinoline derivatives. The results have been compared with those observed in the pyridine series and correlated with 1H1H coupling constants.

NMR spectral studies of quinoline derivatives. Long range 13C1H coupling constants in methylquinoline derivatives

Ultrasound - promoted coupling of heteroaryl halides in the presence of lithium wire. Novel formation of isomeric bipyridines in a Wurtz - type reaction

The 13C n.m.r. spectra of a series of 2- and 4-quinolone derivatives are presented and discussed. A characteristic high field signal for C-8 was observed which should prove useful for the identification of substituted quinolones.

N.M.R. Spectral Studies of Some Quinolone Derivatives. Part III.1 Carbon-13 Magnetic Resonance Spectral Studies of 2- and 4-Quinolone Derivatives

Organotin(IV) derivatives of the ambidentate ligand 2-thiouracil. Infrared, Mössbauer, 1H and 13C NMR studies

The chemical shift of the NH protons for a series of monomethyl-, dimethyl- and trimethyl- substituted 2- and 4- quinolones has been studied. Compounds with an 8-methyl substituent exhibit a characteristic upfield shift which is considered to be due to a reduction in hydrogen bonding as a result of steric effects. The application of this effect to the identification of alkyl substituted quinolones and some natural products is discussed.

Alan G. Osborne

Papers

NMR spectral studies of quinoline derivatives. Long range 13C1H coupling constants in methylquinoline derivatives

Ultrasound - promoted coupling of heteroaryl halides in the presence of lithium wire. Novel formation of isomeric bipyridines in a Wurtz - type reaction

N.M.R. Spectral Studies of Some Quinolone Derivatives. Part III.1 Carbon-13 Magnetic Resonance Spectral Studies of 2- and 4-Quinolone Derivatives

Organotin(IV) derivatives of the ambidentate ligand 2-thiouracil. Infrared, Mössbauer, 1H and 13C NMR studies

N.M.R. Spectral Studies of Some Quinolone Derivatives. Effect of Substitution on the Degree of Hydrogen Bonding