Standard laboratory reagents

Identify the materials used and give information on the degree of and criteria for purity, but do not reference standard laboratory reagents. Give the chemical names of all compounds and the chemical formulas of compounds that are new or uncommon. Use meaningful nomenclature that is, use standard systematic nomenclature where specificity and complexity require, or use trivial nomenclature where it will adequately and unambiguously define a well-established compound. 

Purity is usually expressed as a percentage, e.g. 99.9% pure. Chemicals for experiments can normally be purchased in two grades. The standard laboratory reagents will be about 99% pure, sometimes less, depending on the chemical and how it has been made and purified. The impurities and their concentrations are listed on the bottle. The analytical reagents, when available, will be of the order of 99.9 or 99.99% pure they are much more expensive, and may only be used for specialist purposes such as spectroscopy and analysis. 

Standards for food-grade chemicals in the United States are set by the Committee on Eood Chemicals Codex of the National Academy of Sciences (NAS) which pubHshes them in the Food Chemicals Codex (ECC) (6) (see also Eood additives). Standards for laboratory reagents are set by the American Chemical Society (ACS) Committee on Analytical Reagents and are pubHshed in Feagent Chemicals—A.CS Specifications (7). Standards for electronic-grade chemicals, which have extremely low limits for trace ions, are pubHshed aimually in The Book of SEMI Standards (BOSS) by Semiconductor Equipment and Materials International (SEMI) (8). 

All reagents and chemicals were commercially available materials purified by standard laboratory procedures. 

The preparation described here of 3-cyclopentene-1-carboxylic acid from dimethyl malonate and cis-1,4-dichloro-2-butene is an optimized version of a method reported earlier3 for obtaining this often used and versatile building block.6 The procedure is simple and efficient and requires only standard laboratory equipment. 3-Cyclopentene-1-carboxylic acid has previously been prepared through reaction of diethyl malonate with cis-1,4-dichloro(or dibromo)-2-butene in the presence of ethanolic sodium ethoxide, followed by hydrolysis of the isolated diethyl 3-cyclopentene-1,1-dicarboxylate intermediate, fractional recrystallization of the resultant diacid to remove the unwanted vinylcyclopropyl isomer, and finally decarboxylation.2>7 Alternatively, this compound can be obtained from the vinylcyclopropyl isomer (prepared from diethyl malonate and trans-1,4-dichloro-2-butene)8 or from cyclopentadiene9 or cyclopentene.10 In comparison with the present procedure, however, all these methods suffer from poor selectivity, low yields, length, or need of special equipment or reagents, if not a combination of these drawbacks. 

The HPMC was manufactured by Dow Chemicals (USA) as Methocel K15M and Methocel 100 grades. All solutes were of laboratory reagent standard obtained from British Drug Houses (Poole, UK) and all drugs were BP standard or better. 

Parts B and C exemplify efficient procedures for the stereoselective reduction of acetylenic ethers to the corresponding Z- and E-enol ethers, synthetically useful intermediates.5 These procedures, which are optimized versions of previously described methods,3 6 also require only common reagents and standard laboratory... 

Chemicals Used. Listed below are the specifications of the chemicals used in this study. Common laboratory reagents used for the various standard analyses met with the specifications prescribed in the cited methods and are not listed. All gases were supplied by the Matheson Company, East Rutherford, N. J. 

Intermediate precision is defined by ICH as the longterm variability of the measurement process, and is determined by comparing the results of a method run within a single laboratory over a number of weeks. A method s intermediate precision may reflect disagreement in results obtained by different operators, from different instruments, with standards and reagents from different suppliers, with columns from different batches, or a combination of these. The objective of intermediate precision validation is to verify that, in the same laboratory, the method will provide the same results after finishing the method development. 

Use Standard for octane-rating determinations (pure normal heptane has zero octane number), anesthetic, solvent, organic synthesis, preparation of laboratory reagents. 

Workers at NIST and elsewhere have used cells without liquid junctions to study primary-standard buffers extensively. Some of the properties of these buffers are discussed in detail elsewhere. Note that the NIST buffers are described by their molal concentrations (mol solute/kg solvent) for accuracy and precision of preparation. For general use, the buffers can be prepared from relatively inexpensive laboratory reagents for careful work, however, certified buffers can be purchased from the NIST. 

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