Other Reagents

Other Reagents. Cobalt(i) complexes have been proposed as intermediates in the chromium(ii) reduction of macrocyclic cobalt(m) complexes. The reaction [CoLd(NH8)2] + + Cr + [Ld=(22)] is autocatalytic, and it is also strongly catalysed by the addition of [CoLt(HaO)2] [Lt=ligand (23)]. In the proposed mechanism (44) 

Oxidation of a series of monochloroplatinum(ii) complexes by [AuClJ has been reported [equation (46)]. Presumably the two chloride ions added to the platinum 

The first kinetic data have been reported for a rhodium(ii) species with innocent ligands, namely [Rh(NH3)J +. This short-lived species is produced by interaction of hydrated electrons with penta-amminerhodium(ra) complexes [equation (48)]. The 

Nmi-gnmplgmentary Reactions.— Reactions in which the valence changes of oxidant and reductant differ can yield interesting new information on intermediates of unusual oxidation state. They also include some of the best known oxidants and reductants, with a long history of study and mechanistic speculation. Kinetic data for these reactions are summarized in Table 3, on p. 40. 

New data on the oxidation of VO + by permanganate ion show that in acidic solution with reductant in excess, the stoicheiometry conforms to equation (51). The kinetics when followed spectrophotometrically at A =526 nm lead to the rate law 

Additional nitrogen sources have been reported in the synthesis of metal nitrides. These include trichloramine, hydrazine, and N,/V-diphenylhydrazine (Table 5.4). Based on the details provided it is not clear how these may be categorized within the organizational classification discussed above 

In contrast to uridine,389 cytidine does not yield a 5 -chloro-5 -deoxy derivative on reaction with N,N-dimethyl(chlorometh-animinium) chloride instead 2,2 -anhydrocytidine is formed.395 However, thionyl chloride or bromide in hexamethylphosphor-amide at room temperature achieves this selective replacement of the primary hydroxyl group of halogen in cytidine, and also in adenosine, in respective yields of 80 and 75% for the chloro compounds, and 55 and 30% for the bromo analogs.396 

Reports by Mattocks397,398 that 2-acetoxy-2-methylbutanoyl chloride reacts with 1,2- and 1,3-diols to afford chloroacetates led to an investigation into use of this type of reagent for selective transformation of the vicinal diol grouping in ribonucleosides. Greenberg and Mof-fatt399 chose to use 2-acetoxy-2-methylpropanoyl chloride (which lacks the complication of a chiral center), and, firstly, found that cis- 

The fact that 3-chloro-and 3-acetoxy-l,2-propanediol give,398 respectively, 2-acetoxy-l,3-dichloropropane and l,2-diacetoxy-3-chloropropane with 2-acetoxy-2-methylbutanoyl chloride suggested that the regiospecificity is controlled by steric factors, but electronic factors may assume a dominant role in certain cases. Thus, 1-phenyl- 

The reaction of adenosine with 2-acetoxy-2-methylpropanoyl chloride or the corresponding bromide is less regioselective than that of uridine,400 and gives 9-(2-0-acetyl-3-deoxy-3-halo-/3-D-xylofuranosyl)-and9-(3-0 - acetyl - 2 - deoxy - 2 - halo - /3 - D - arabinofuranosyl) - adenine, 

On treatment with concentrated halogen acids, certain hexitols yield 1,6-dideoxy-l,6-dihalo compounds. The structure of the compound so obtained from galactitol, first reported by Bouchardat,404 was later verified by synthesis.405 Allitol is transformed406 into 1,4-anhydro-6-chloro-6-deoxy-DL-allitol and l,4-anhydro-5,6-dichloro-5,6-dideoxy-DL-talitol on treatment with fuming hydrochloric acid at 100°. 

Dehydration of N,N -bis(2-vinyloxyethyl)urea 1743 with p-toluenesulfonyl chloride (TsCl) gives bis(2-vinyloxyethyl)carbodiimide 1744 in 23% yield. The compound is a prospective cross-linking agent [1280]. 

Typical procedure. Bis(2-vinyloxyethyl)carbodiimide 1744 [1280] To a vigorously stirred solution of the urea 1743 (4.99 g) in pyridine (50 mL) and triethylamine (14 mL), p-toluenesuUbnyl chloride (9.52 g) was added in small portions. (Spontaneous heating of the reaction mixture to 41 °C was observed.) Stirring was continued for a further 40 min. The precipitated salts, i.e. triethylammonium tosylate and triethylammonium chloride, were filtered off, the solvent was removed from the filtrate, and the residue was distilled in vacuo to give 1.02 g (23%) of the carbodi-imide 1744 bp 82 °C (0.5 mmHg) IR v ax = 2130 cm h On storage under normal conditions, carbodiimide 1744 is stable for several months. 

A method has been described for the preparation of carbodiimides 1699 by dehydration of ureas 1696 with p-tosyl chloride under solid-liquid phase-transfer catalytic (PTC) conditions using solid potassium carbonate as a base and a lipophilic quaternary ammonium salt as a catalyst. The method is generally applicable for the synthesis of disubstituted carbodiimides, but is especially useful for un-symmetrically substituted carbodiimides. Yields of the resulting carbodiimides 1699 vary depending on the solvent (usually used at reflux temperature) in benzene or toluene yields of 66-98% are achieved, while in chloroform they are only 30-50% [1281]. 

General procedure. Carbodiimides 1699 fiom ureas [1281] A solution of disubstituted urea 1696 (10 mmol) and p-toluenesulfonyl chloride (10 mmol) in benzene or toluene (70 mL) is stirred at reflux temperature for 1-5 h in the presence of potassium carbonate (3.53 g, 40 mmol) and benzyltriethylammonium chloride (TEBAC) (0.23 g, 1 mmol). 

The reaction is monitored by TLC. The resultant precipitate is filtered off, and the filtrate is washed with water (2 x 10 mL). The organic layer is dried with magnesium sulfate and concentrated to give the carbodiimide 1699 as an oily residue (66-98% yield), which is generally pure or can be distilled in vacuo. 

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The alkylidene dimethone (dimedone) (I) upon boiling with glacial acetic acid, acetic anhydride, hydrochloric acid and other reagents frequently loses water and passes into a substituted octahydroxanthene or the anhydride (II), which often serves as another derivative. The derivatives (I) are soluble in dilute alkali and the resulting solutions give colourations with ferric chloride solution on the other hand, the anhydrides (II) are insoluble in dilute alkali and hence can easily be distinguished from the alkylidene dimedones (I). 

If an unknown compound gives a positive test with the 2 4-dinitrophenylhydrazine reagent, it then becomes necessary to decide whether it is an aldehyde or a ketone. Although the dimedone reagent (Section 111,70,2) reacts only with aldehydes, it is hardly satisfactory for routine use in class reactions. It is much simpler to make use of three other reagents given below, the preparation and properties of which have already been described (Section 111,70). 

Step 3. The neutral components. The ethereal solution (E remaining after the acid extraction of Step 2 should contain only the neutral compounds of Solubility Groups V, VI and VII (see Table XI,5). Dry it with a little anhydrous magnesium sulphate, and distil off the ether. If a residue is obtained, neutral compounds are present in the mixture. Test a portion of this with respect to its solubility in concentrated sulphuric acid if it dissolves in the acid, pour the solution slowly and cautiously into ice water and note whether any compound is recovered. Examine the main residue for homogeneity and if it is a mixture devise procedures, based for example upon differences in volatility, solubility in inert solvents, reaction with hydrolytic and other reagents, to separate the components. 

N. Trachtenberg, 1969). products or even as the major 1958). The reaction sequence with SeOj, except that the C—< the dehydrogenation of C—C other reagents have also been quinones. 

There are other reagent gases, e.g., hydrogen (H2), butane (C4H,o), methanol (CH3OH), ammonia (NHj), and so on. 

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. 

Hafnium Boride. Hafnium diboride [12007-23-7] HfB2, is a gray crystalline soHd. It is usually prepared by the reaction of hafnium oxide with carbon and either boron oxide or boron carbide, but it can also be prepared from mixtures of hafnium tetrachloride, boron trichloride, and hydrogen above 2000°C, or by direct synthesis from the elements. Hafnium diboride is attacked by hydrofluoric acid but is resistant to nearly all other reagents at room temperature. Hafnium dodecaboride [32342-52-2] has been prepared by direct synthesis from the elements (56). 

Nickel plays a role in the Reppe polymeriza tion of acetylene where nickel salts act as catalysts to form cyclooctatetraene (62) the reduction of nickel haUdes by sodium cyclopentadienide to form nickelocene [1271 -28-9] (63) the synthesis of cyclododecatrienenickel [39330-67-1] (64) and formation from elemental nickel powder and other reagents of nickel(0) complexes that serve as catalysts for oligomerization and hydrocyanation reactions (65). 

Halogenation. Normally, 2-halopropane derivatives are prepared from isopropyl alcohol most economically by reaction with the corresponding acid haUde. However, under appropriate conditions, other reagents, eg, phosphoms haUdes and elemental halogen, also react by replacement of the hydroxyl group to give the haUde (46). 

Silicate Grouts. Sodium silicate [1344-09-8] h.3.s been most commonly used in the United States. Its properties include specific gravity, 1.40 viscosity, 206 mPa-s(=cP) at 20°C Si02 Na20 = 3.22. Reaction of sodium silicate solutions with acids, polyvalent cations, such organic compounds as formamide, or their mixtures, can lead to gel formation at rates, which depend on the quantity of acid or other reagent(s) used. 

Other reagents can be employed in a wet scmbbing process, but appHcation is typically limited by the higher costs. 

Other 2,3-Diphosphoglycerate Pocket Cross-Linkers. The reactivity of the valine NAl(l)a and lysine EF6(82)p residues in the 2,3-DPG pocket shown by NFPLP and (bis-PL)P4 has stimulated the search for other reagents that react similarly but have potential for greater efficiency and ease of scaleup. The systematic study of four different dicarboxyhc acid derivatives, cross-linked in both oxygenated and deoxygenated conditions, has been reported (92). Each of these derivatives presents problems in purification, and proof of the sites of reaction is tedious. 

Reduction. 2,2-Dimeth5lpropanal [630-19-3] can be prepared by the reduction of neopentanoic acid usiag various catalysts, such as iroa (14), tin or zirconium oxides (15,16), iron—chromium (17), and other reagents (18,19). The reduction of neopentanoic acid to 2,2-dimeth5lpropaaol [75-84-3]... 

Chlorate Analysis. Chlorate ion concentration is determined by reaction with a reducing agent. Ferrous sulfate is preferred for quaHty control (111), but other reagents, such as arsenious acid, stannous chloride, and potassium iodide, have also been used (112). When ferrous sulfate is used, a measured excess of the reagent is added to a strong hydrochloric acid solution of the chlorate for reduction, after which the excess ferrous sulfate is titrated with an oxidant, usually potassium permanganate or potassium dichromate. 

Chlorination with Other Reagents. Chlorotoluenes can also be obtained in good yields by the reaction of toluene with stoichiometric proportions of certain Lewis acid chlorides such as inon(III) chloride, as the chlorinating agent (51). Generally, the product mixture contains /)-chlorotoluene as the principal component. Several modifications have been proposed to improve product yields (52,53). 

Flotation reagents are selected to produce a stable froth and adjust the affinity of target minerals to collect in the froth. Other reagents depress the collection of minerals in the froth. The froth containing the copper minerals overflows into collection launders. 

Again, as with pyridopyrimidines, the main reaction is oxidation of di- or poly-hydro derivatives to fully aromatic structures, often merely by air or oxygen. In some cases the reagent of choice is mercury(II) oxide, whilst other reagents used include sulfur, bromine, chloranil, chromium trioxide-acetic acid, hydrogen peroxide, and potassium ferricyanide, which also caused oxidative removal of a benzyl group in the transformation (306) (307)... 

Various other reagents have been used to trap the intermediate sulfenic acid, and Scheme 14 shows some of these (74JCS(P1)1459, 74TL725, 74JCS(P1)1456, 77JCS(P1)1477, 70TL4897, 78TL4167). 

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