Weak alkalis

Except in the case of the 4,5-diphenyl derivatives, these compounds are obtained as their hydrohalide salts tvith yields of 70 to 90% the free heterocyclic base is obtained by treatment with weak alkali. 

Dibromotetrafluoroethane [124-73-2] M 259.8, b 47.3 /760mm. Washed with water, then with weak alkali. Dried with CaCl2 or H2SO4 and distd. [Locke et al. J Am Chem Soc 56 1726 1934.] Also purified by gas chromatography on a silicone DC-200 column. 

The reaction of the iV-acetylenanime with perbenzoic acid at low temperature is much faster than attack at a A -double bond, so the latter can be preserved without prior protection. In addition, the A-acetyl compound is relatively stable to weak alkali and to Oppenauer conditions permitting, e.g., hydrolysis of a 3-acetate group and conversion to a 3-keto-A" function. These latter compounds also react selectively with perbenzoic acid at the A -double bond. 

A problem with studies on inert gas is that the interactions are so weak. Alkali halides are important commercial compounds because of their role in extractive metallurgy. A deal of effort has gone into corresponding calculations on alkali halides such as LiCl, with a view to understanding the structure and properties of ionic melts. Experience suggests that calculations at the Hartree-Fock level of theory are adequate, provided that a reasonable basis set is chosen. Figure 17.7 shows the variation of the anisotropy and incremental mean pair polarizability as a function of distance. 

Absorption of carbon dioxide in weak alkali 3. Absorption of chlorine in water... 

Stoneware and porcelain are attacked only by hydrofluoric acid and hot concentrated caustic alkalis and are almost completely unaffected by all concentrations of mineral and organic acids, acid salts and weak alkalis. The degree of susceptibility depends upon composition, firing temperature and porosity. 

T. R. French and C. B. Josephson. Surfactant-enhanced alkaline flooding with weak alkalis. US DOE Rep NlPER-507, NIPER, February 1991. 

The low-substituted hydroxyethylcellulose which, like methyl- and ethylcellulose, is soluble in alkali, particularly when cooled, has much to recommend it from an industrial point of view. It can be formed by the action of only small quantities (0.25 to 0.5 moles) of ethylene oxide on alkali cellulose.47 The reaction product need not be isolated since there are no salts formed, but may be diluted with water or weak alkali to give a spinning solution. The product should therefore be quite cheap. Preparation and properties of hydroxyethylcellulose have been discussed by Schorger and Shoemaker.47... 

Several tri(cyclopentadienyl)tin(ll) and lead(ll) complexes have been prepared with alkali metal cations. The arrangement of Cp rings around the metal is in a paddle wheel configuration the alkali cation is bound to Cp and not Sn or Pb, further supporting the view of a weak alkali metal group 14 bond. Representative examples of these compounds include (77S-Cp)2E(/r-Cp)-Na(PMDTA) (E = Sn 230, Pb 231).239 240... 

The process of treating cold-cured proofings with a weak alkali to neutralise any remaining acid and so prevent subsequent tendering of the fabric. Swelling... 

If a weak acid or weak alkali is used (or both are weak), the standard enthalpy of neutralisation is generally less exothermic. This is because heat energy is required to ionise a weak acid or base. 

Mechanical pulp bleaching, 21 48-51 chelation in, 21 49 new developments in, 21 50-51 using weak alkali sources in, 21 50-51 Mechanical pulping, 21 20-21 Mechanical pulps, in papermaking, 18 93-94... 

This method is particularly useful for aromatic aminocarboxylic and aminosulfonic acids, which are often only sparingly soluble in dilute acid. The amino compound is dissolved in water or in weak alkali and combined with a stoichiometric amount of sodium nitrite, upon which the resulting solution is poured into a mixture of acid and ice. Alternatively, the process may be reversed by pouring the acid into the amine-nitrite mixture. 

These reversible polymerisations of aldehydes are to be distinguished from the condensations which they can also undergo. Thus formaldehyde is converted by quite weak alkalis (Ca(OH)2, CaC03) into glycollic aldehyde and glyceraldehyde, and further into a mixture of hexoses (Butlerow, 0. Loew) from which E. Fischer isolated the so-called... 

FIGURE 6.22 Disulfide interchange.92 (A) Discovered in synthesis when hydrazinolysis of an unsymmetrical derivative of cystine gave two symmetrical products instead of the expected monohydrazide at the urethane-protected cysteine moiety of the derivative.95 (B) Mechanism for interchange catalyzed by strong acid,94 which is suppressed by thiols. (C) Mechanism for interchange catalyzed by weak alkali, which is enhanced by thiols. 

D-Erythrose undergoes self-aldolization in alkali solution, to form d- / co-L- /3 C6 TO-3-octulopyranose by combination of the 1,2-enediol and aldehyde forms. In weak alkali at 105°, syrupy D-erythrose yields d- /ycero-tetrulose, jS-D-a/tro-L-g/ycero-l-octulofuranose, and a-Ti-gluco-i -g/ycero-3-octulopyranose. At 300° in alkali, the major products from syrupy D-erythrose were 1-5% of butanedione (biacetyl) with smaller proportions of pyrocatechol, 33, 2,5-dimethyl-2,5-cyclohexadiene-l,4-dione (2,5-dimethylbenzoquinone), and 2,5-dimethyl-1,4-benzenediol (2,5-dimethylhydroquinone). It was assumed that D-erythrose is reduced to erythritol by a Cannizzaro type of reaction, followed by dehydration of erythritol to form biacetyl. However, very low proportions (<1%) of biacetyl are formed from erythritol compared with D-erythrose itself. Apparently, some other mechanism predominates in the formation of biacetyl. 

Polypropylene Polypropylene (PP) pipe and fittings have excellent resistance to most common organic and mineral acids and their salts, strong and weak alkalies, and many organic chemicals. They are available in sizes through 6 in, in Schedules 40 and 80, but are not covered as such by ASTM specifications. 

The gluability of the lignin-epoxy resin adhesives was found to be improved by the addition of calcium carbonate (50% by weight) to the liquid resin. This must be attributed to the nature of the weak alkali in calcium carbonate as a cure accelerator, and to the reinforcement effect of fillers. Since wood surfaces are acidic, the addition of alkaline fillers effectively alters the pH of the glue line. 

The most important industrial alkalis are the weak alkali ammonia (Section 9.3), caustic soda (sodium hydroxide), and lime (calcium oxide).1-6 For many industrial and agricultural purposes, the most economical source of alkali is lime, which is used in steelmaking and other metallurgical operations ( 45% of U.S. production of lime), in control of air pollution from smokestack gases (Chapter 8), in water and sewage treatment (Sections 9.6 and 14.5), in pulp and paper production (Section 10.4), in reduction of soil acidity, in cement and concrete manufacture (indirectly, as discussed later), and in many chemical processes such as paper making (Section 10.4). In short, lime is one of the most important of all chemical commodities. 

Cyclic esters show accelerated hydrolysis rates. Ethylene sulfate compared to dimethyl sulfate is twice as fast in weak acid (first order) and 20 times as fast in weak alkali (second order) (50). Catechol sulfate [4074-55-9] is 2 x 107 times faster than diphenyl sulfate in alkaline solution (52). Alcoholysis rates of several dialkyl sulfates at 35—85°C are also known (53). 

Washed with water, then with weak alkali. Dried with CaCl2 or H2SO4 and distd. [Locke et al. JACS 56 1726 1934. ... 

Aldols can be obtained as result of the so-called aldol condensation reaction. Hiis takes place between an aliphatic aldehyde and another aldehyde or ketone. The second aldehyde has at least one CHaCHO group. Formaldehyde is the most frequently used aldehyde for this reaction. A small amount of weak alkali serves as a catalyst. The reactions may be represented as follows RCHa. CHO + R CH2. CHO -> RCHa. CH(OH) CHR. CHO and RCHO + CH3. CO - CH3 - RCH(OH). CHa... 

Oxazepam (251) is reduced polarographically in acid solution in a four-electron wave and in alkaline solution in a two-electron wave 335 the four-electron reaction in acidic solution leads to a reductive removal of the hydroxyl group and a saturation of the C=N bond. In weak alkali, preparative reduction gives 4 > n > 2, and polarograms taken during the reduction show the presence of an intermediate more easily reducible than 251 and also oxidizable in an anodic reaction. Anodic oxidation of one form of the intermediates yields 251. 

Weak alkalies and acids aie employed to effect the condensation. 

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