REAGENTS USE

C22H23N3O9. An organic reagent used for the detection and estimation of aluminium. It is a brownish-red powder, soluble in water which gives a red lake with aluminium which can be estimated colorimetrically. It can also be used for detecting scandium and indium. 

Dinitrophenylhydra2ones usually separate in well-formed crystals. These can be filtered at the pump, washed with a diluted sample of the acid in the reagent used, then with water, and then (when the solubility allows) with a small quantity of ethanol the dried specimen is then usually pure. It should, however, be recrystallised from a suitable solvent, a process which can usually be carried out with the dinitrophenylhydrazones of the simpler aldehydes and ketones. Many other hydrazones have a very low solubility in most solvents, and a recrystallisation which involves prolonged boiling with a large volume of solvent may be accompanied by partial decomposition, and with the ultimate deposition of a sample less pure than the above washed, dried and unrecrystal-lised sample. 

Although phenol gives these marked colour changes, the test is unsatisfactory with many other phenols, the precise tint obtained varying with the purity of the phenol, amount of reagents used, and temperature and time of heating. 

Give characteristic reduction products depending upon reagent used. 

Dissolve 0-5 g. of the substance in 10 ml. of 50 per cent, alcohol, add 0-5 g. of solid ammonium chloride and about 0 -5 g. of zinc powder. Heat the mixture to boiling, and allow the ensuing chemical reaction to proceed for 5 minutes. Filter from the excess of zinc powder, and teat the filtrate with Tollen s reagent Section 111,70, (i). An immediate black or grey precipitate or a silver mirror indicates the presence of a hydroxyl-amine formed by reduction of the nitro compound. Alternatively, the filtrate may be warmed with Fehling s solution, when cuprous oxide will be precipitated if a hydroxylamine is present. Make certain that the original compound does not aflfect the reagent used. 

Nitration can be effected under a wide variety of conditions, as already indicated. The characteristics and kinetics exhibited by the reactions depend on the reagents used, but, as the mechanisms have been elucidated, the surprising fact has emerged that the nitronium ion is preeminently effective as the electrophilic species. The evidence for the operation of other electrophiles will be discussed, but it can be said that the supremacy of one electrophile is uncharacteristic of electrophilic substitutions, and bestows on nitration great utility as a model reaction. 

Cydopentane reagents used in synthesis are usually derived from cyclopentanone (R.A. Ellison, 1973). Classically they are made by base-catalyzed intramolecular aldol or ester condensations (see also p. 55). An important example is 2-methylcydopentane-l,3-dione. It is synthesized by intramolecular acylation of diethyl propionylsucdnate dianion followed by saponification and decarboxylation. This cyclization only worked with potassium t-butoxide in boiling xylene (R. Bucourt, 1965). Faster routes to this diketone start with succinic acid or its anhydride. A Friedel-Crafts acylation with 2-acetoxy-2-butene in nitrobenzene or with pro-pionyl chloride in nitromethane leads to acylated adducts, which are deacylated in aqueous acids (V.J. Grenda, 1967 L.E. Schick, 1969). A new promising route to substituted cyclopent-2-enones makes use of intermediate 5-nitro-l,3-diones (D. Seebach, 1977). 

Triflates are used for the reaction[470]. The 5-phenyltropone 609 is prepared by coupling of the triflate with phenylzinc chloride[471]. Instead of the expensive triflale, phenyl fluoroalkanesulfonate as a triflate equivalent is used for coupling[472]. Phenyl fluorosulfonate (610) is another reagent used for cou-pling[473]. 

Thionyl chloride and phosphorus tribromide are specialized reagents used to bring about particular functional group transformations For this reason we won t present the mechanisms by which they convert alcohols to alkyl halides but instead will limit our selves to those mechanisms that have broad applicability and enhance our knowledge of fundamental principles In those instances you will find that a mechanistic understand mg IS of great help m organizing the reaction types of organic chemistry... 

Thionyl chloride is a synthetic reagent used to convert alcohols to alkyl chlorides... 

Azide ion ( N=N=N ) Sodium azide IS a reagent used for carbon-nitrogen bond formation The product IS an alkyl azide... 

Replacement of the proton on nitrogen in succinimide by bromine gives N bromo succinimide a reagent used for allylic and benzylic brominations (Sections 10 4 and 1112)... 

Carboxypeptidase catalyzed hydrolysis can be used to identify the C terminal ammo acid The N terminus is determined by chemical means One reagent used for this purpose is Sanger s reagent 1 fluoro 2 4 dimtrobenzene (see Figure 27 9)... 

This table includes the more common reagents used in gravimetric determinations. The lists of elements precip-... 

The accuracy of a method depends on its selectivity for the analyte. Even the best methods, however, may not be free from interferents that contribute to the measured signal. Potential interferents may be present in the sample itself or the reagents used during the analysis. In this section we will briefly look at how to minimize these two sources of interference. 

The reagent used to bind the species to be masked in an unreactive complex. 

A reagent used to reduce the analyte before its analysis by a redox titration. 

Uses. Although cyanoacetic acid can be used in appHcations requiring strong organic acids, its principal use is in the preparation of malonic esters and other reagents used in the manufacture of pharmaceuticals, eg, barbital, caffeine, and B vitamins (see Alkaloids Hypnotics Vitamins). Cyanoacetic acid can be used for the preparation of heterocycHc ketones. 

Device Legislation. Regulations covering medical devices define reagents used in in vitro diagnostic tests as devices (see Medical diagnostic reagents Prosthetic and biot dicaldevices). 

Table 6. Organic Auxiliary Reagents Used in Froth Flotation Technology...

The basic flow sheet for the flotation-concentration of nonsulfide minerals is essentially the same as that for treating sulfides but the family of reagents used is different. The reagents utilized for nonsulfide mineral concentrations by flotation are usually fatty acids or their salts (RCOOH, RCOOM), sulfonates (RSO M), sulfates (RSO M), where M is usually Na or K, and R represents a linear, branched, or cycHc hydrocarbon chain and amines [R2N(R)3]A where R and R are hydrocarbon chains and A is an anion such as Cl or Br . Collectors for most nonsulfides can be selected on the basis of their isoelectric points. Thus at pH > pH p cationic surfactants are suitable collectors whereas at lower pH values anion-type collectors are selected as illustrated in Figure 10 (28). Figure 13 shows an iron ore flotation flow sheet as a representative of high volume oxide flotation practice. 

The reaction proceeds in a stepwise fashion and products with only one or two halogens can be produced by suitably limiting the reagent. Using alcohols, alkoxy groups are introduced. Either one or all three halogens can be replaced. 

Yields are best in the case of aromatic metallic reagents. Use of aUphatic reagents favors low molecular weight products. Products often are recovered by water addition, followed by separation and distillation of the organic layer. Such procedures inevitably lead to acidic by-products when there is incomplete replacement of the halogens on phosphoms. A modification of the Wurt2 reaction sometimes is used. 

There are two commercial PPS processes being practiced worldwide the Phillips process and the Kureha process. Although these processes contain some common steps, there are distinguishing features, most notably in the reagents used to faciUtate the synthesis of high molecular weight linear PPS. 

Flotation. Tallow amines contain small amounts of short-chain compounds, eg, the octyl, lauryl, and myristyl (C ) groups. These amines usually produce enough froth for the flotation. Small quantities of specialized synthetic alcohols, eg, Dowfroth P, are frequentiy added to the flotation system to supplement the natural frothers. The quantities of the reagents used ia potash flotation plants are Hsted ia Table 5. 

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