This paper presents a review of the organic Rankine cycle and supercritical Rankine cycle for the conversion of low-grade heat into electrical power, as well as selection criteria of potential working fluids, screening of 35 working fluids for the two cycles and analyses of the influence of fluid properties on cycle performance. The thermodynamic and physical properties, stability, environmental impacts, safety and compatibility, and availability and cost are among the important considerations when selecting a working fluid. The paper discusses the types of working fluids, influence of latent heat, density and specific heat, and the effectiveness of superheating. A discussion of the 35 screened working fluids is also presented.

A review of thermodynamic cycles and working fluids for the conversion of low-grade heat

Fluorine has received great attention in all fields of science. “Small atom with a big ego” was the title of the Symposium at the ACS meeting in San Francisco in 2000, where a number of the current scientific and industrial aspects of fluorine chemistry made possible by the small size and high electronegativity of the atom were discussed. This small atom has provided mankind with significant benefits in special products such as poly(tetrafluroethylene) (PTFE), freon, fluoro-liquid crystals, optical fiber, pharmaceutical and agrochemical compounds, and so on, all of which have their own unique properties that are otherwise difficult to obtain.1 For instance, at present, up to 30% of agrochemicals and 10% of pharmaceuticals currently used contain fluorine atoms. Therefore, organic fluorine compounds have received a great deal of interest and attention from the scientists involved in diverse fields of science and technology. Now, not only C-F bond formation but also selective C-F bond activation have become current subjects of active investigation from the viewpoint of effective synthesis of fluoroorganic compounds. The former is highlighted by designing a sophisticated fluorinating reagent for regioand stereocontrolled fluorination and developing versatile multifunctional and easily prepared building blocks. C-F bond formation has been treated extensively in several reviews2 and books.3 The latter is a subject that has been less explored but would be promising for selective defluorination of aliphatic fluorides, cross-coupling with aryl fluorides, and * To whom correspondence should be addressed. Phone: 81-78-803-5799. Fax: 81-78-803-5799. E-mail: amii@kobe-u.ac.jp and uneyamak@cc.okayamau.ac.jp. † Kobe University. ‡ Okayama University. Chem. Rev. 2009, 109, 2119–2183 2119

C-F bond activation in organic synthesis.

A simple and mild strategy for the direct trifluoromethylation of unactivated arenes and heteroarenes that acts via a radical-mediated mechanism and uses commercial photocatalysts. Premature metabolic decomposition can stop potentially promising drugs from reaching their intended targets. One way of blocking this metabolism involves the addition of a trifluoromethyl (CF3) group to aromatic or heteroaromatic moieties in a candidate drug molecule. David Nagib and David MacMillan report a new method for this synthesis that is more economical than current methods in terms of both raw materials and energy input. They use an energy-saving compact fluorescent light bulb to excite a variety of commercially available photocatalysts, which promote the addition of CF3 to unactivated arenes and heteroarenes through a radical-mediated mechanism. The potential of the method is demonstrated by the trifluoromethylation of three molecules: a uracil analogue, a precursor of the acetylcholinesterase inhibitor donepezil and a vitamin (flavone). Modern drug discovery relies on the continual development of synthetic methodology to address the many challenges associated with the design of new pharmaceutical agents1. One such challenge arises from the enzymatic metabolism of drugs in vivo by cytochrome P450 oxidases, which use single-electron oxidative mechanisms to rapidly modify small molecules to facilitate their excretion2. A commonly used synthetic strategy to protect against in vivo metabolism involves the incorporation of electron-withdrawing functionality, such as the trifluoromethyl (CF3) group, into drug candidates3. The CF3 group enjoys a privileged role in the realm of medicinal chemistry because its incorporation into small molecules often enhances efficacy by promoting electrostatic interactions with targets, improving cellular membrane permeability, and increasing robustness towards oxidative metabolism of the drug4,5,6. Although common pharmacophores often bear CF3 motifs in an aromatic system, access to such analogues typically requires the incorporation of the CF3 group, or a surrogate moiety, at the start of a multi-step synthetic sequence. Here we report a mild, operationally simple strategy for the direct trifluoromethylation of unactivated arenes and heteroarenes through a radical-mediated mechanism using commercial photocatalysts and a household light bulb. We demonstrate the broad utility of this transformation through addition of CF3 to a number of heteroaromatic and aromatic systems. The benefit to medicinal chemistry and applicability to late-stage drug development is also shown through examples of the direct trifluoromethylation of widely prescribed pharmaceutical agents.

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Trifluoromethylation of arenes and heteroarenes by means of photoredox catalysis

Good Partnership between Sulfur and Fluorine: Sulfur-Based Fluorination and Fluoroalkylation Reagents for Organic Synthesis

https://hal.archives-ouvertes.fr/hal-00528081/document

Fluid selection for a low-temperature solar organic Rankine cycle

CFC phase-out: have we met the challenge?

The hydrofluorocarbon 1,1,1,2-tetrafluoroethane (HFC-134a) as a ready source of trifluorovinyllithium

Free radical chemistry. Part 5. [1] A new approach to the synthesis of perfluorinated ethers

The reactivity of the hydrofluorocarbon 1,1,1,2-tetrafluoroethane (HFC-134a) and related compounds towards base attack. The generation and stability of the tetrafluoroethyl, trifluorovinyl and related anions

The reactions of XeF2 with a variety of organic solvents are described. XeF2 is foundto undergo both hydrogen- and chlorine-fluorine exchange over a relatively short timescalewith chloroform, dichloromethane and dibromomethane. XeF2 reacts very slowly withtetrachloromethane and fluorotrichloromethane, although the addition of a catalytic amountof HF increases the rate of reaction considerably. XeF2 dissolves in acetonitrile withnegligible reaction to the extent of 2.25 mol kg−1.

Richard L. Powell

Papers

CFC phase-out: have we met the challenge?

The hydrofluorocarbon 1,1,1,2-tetrafluoroethane (HFC-134a) as a ready source of trifluorovinyllithium

Free radical chemistry. Part 5. [1] A new approach to the synthesis of perfluorinated ethers

The reactivity of the hydrofluorocarbon 1,1,1,2-tetrafluoroethane (HFC-134a) and related compounds towards base attack. The generation and stability of the tetrafluoroethyl, trifluorovinyl and related anions

The reactions of xenon difluoride with inert solvents