Pure species

IUPAC (1993) Nomenclature of Organic Chemistry. Revised Nomenclature, Ions, Radical Ions, and Related Species, Pure Appl. Chem. 65, 1357 [1.2]. 

The first step in analyzing an aqueous equilibrium is to identify the major species. Pure water contains H2 O molecules at a concentration of 55.5 M, so an aqueous solution always contains H2 O as a major species. In pure water, H2 O is the only major species, but an aqueous solution contains two or more major species H2 0 and those solute species that are present at highest concentration. 

Phenylbutenoid dimers from the rhizomes of Zingiber cassumunar. Phytochemistry 1993 32(2) 357-363. ZO082 Ayafor, J. F., M. H. K. Tchuendem, B. Nyasse, F. Tillequin, and H. Anke. Aframodial and other bioactive diterpenoids from Aframomum species. Pure Appl Chem 1994 66(10/11) 2327-2330. 

Chemical reactions are those in which elements are added or removed from a chemical species. Purely chemical reactions are those in which none of the species undergoes a change in its valence, i.e., no species is either oxidized or reduced. Electrochemical rections are chemical reactions in which not only may elements be added or removed from a chemical species but also at least one species undergoes a change in the number of valence electrons. For example, the precipitation of iron hydroxide, Fe(OH)2, is a pure chemical reaction ... 

We should note that all sequences to separate a mixture will have the same set of binary splits. For example, each alternative sequence for the separation of ABCDE into five single-species pure products will have a split between A and B, another between B and C, etc. The difference among the alternative sequences is the presence or absence of other species when carrying out each of these binary splits. The total of the vapor flows for a sequence is the base set of vapor flows V(i/j), where / and j are A/B, B/C, C/D, and D/E, plus its marginal vapor flows. Thus, the difference in marginal vapor flows is the difference in total vapor flows among the sequences. The sequence with the minimum marginal vapor flows is the sequence with the minimum total vapor flows. 

Derivation A glucoside found in the leaves of the cranberry, blueberry, and manzanita shrubs, and in the roots, trunks, and leaves of most pear species. Pure arbutin can be prepared synthetically from ace-tobromoglucose and hydroquinone in the presence of alkali. 

One can only tell if the protein is really free of other proteins by trying to go on fractionating it. IF it doesn t split into several components under ultracentrifugation or electrophoresis or chromatography, it is probably a single molecular species. Pure proteins can normally be crystallized, but even this is not an absolute indication of purity there may still be five or ten per cent of another protein present that cannot be removed without great difficulty. But only when one is sure that the protein is pure can any attempt be made to determine its structure. 

In an elegant recent work, Loos et al. [51, 52] reported the synthesis of polydialanine) via lipase-catalyzed ring-opening of 2-azetidinone (Scheme 5.4) (see Chapter 14 for details on the polymerization mechanism). After removal of cyclic side products and low-molecular-weight species, pure linear poly(P-alanine) was obtained. The average DP of the polymer obtained was limited to 8 because of the solubility of the polymer in the reaction medium. Control experiments with P-alanine as substrate confirmed that the ring structure of the 2-azetidinone was necessary to obtain the polymer. 

Speci. pure 921 — a, - 1I36-0.I74-T(K)(I300—2200 K Bubble pressure 1968 26... 

Nature of deposit Pure metal (or definite alloy) Usually M contaminated by 0/R derived species Pure metal, but may be porous and poorly adherent... 

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