Azo-compounds can be obtained by reduction of nitro-compounds, or by oxidation of hydrazo-compounds. They are usually prepared, however, by reacting a phenol or amine with a diazonium salt. The coupling usually takes place in the position para to the hydroxyl or amino group, but if this position is occupied it goes to the ortho position, e.g.  [c.49]

They form salts with metals and with organic bases, and form esters with alcohols. Anhydrides containing —C(0) 0 C(0) — groups are formed from most acids by elimination of a molecule of water between two carboxyl groups. This elimination may be either inter- or intra-molecular. The hydroxyl (-OH) group is replaceable by halogens (with, e.g. PClj) to give acyl halides. The acids are formed by oxidation of the corresponding alcohol or aldehyde by heating nitriles with alkalis or by treating Grignard reagents with carbon dioxide and decomposing the product with sulphuric acid. Many of these acids occur naturally in plants and animals, either free or as salts or esters.  [c.83]

It couples readily with diazotized bases to give extensive series of azo dyes, and may also couple on the fibre to give ingrained dyes. These azo dyes have a hydroxyl group ortho to the azo group which is of special value for after-treatment with co-ordinating metals, e.g. after-chroming with dichromate. It gives rise to important series of dyestuff intermediates obtained by sulphonation and nitration.  [c.270]

Phenols formed by the substitution of a hydrogen atom by a hydroxyl group, OH, in an aromatic ring ( I t)  [c.11]

Chromium(IJI) oxide. CrjOj (heat on (NH2)2Cr207, hydrolysis and ignition of chromium(lll) compounds). Green compound with the corundum structure. Gives chrom-ates(Ill) in solid stale reactions, anionic species with hydroxyl ions and [Cr(H20)t,P with acids. Used as a green pigment (viridian) and to give green colours in glass and porcelain.  [c.99]

The diazonium salts usually decompose when warmed with water to give a phenol and nitrogen. When treated with CuCl, CuBr, KI, the diazo group is replaced by chlorine, bromine or iodine respectively (Sandmeyer reaction). A diazonium sulphate and hydroxyl-amine give an azoimide. The diazonium salt of anthranilic acid (2-aminobenzoic acid) decomposes to give benzyne.  [c.133]

For ketoximes, the group which is syn or anti to the hydroxyl group must be specified. Difficulty in assigning the terms cis and trans arises when there is no pair of identical, or similar, groups substituting an alkene. Then the terms (E) [German entgegen = slCTOSs] and (Z) [German zusammen = together] replace the terms iransjcis. In many cases, but not all, the term cis corresponds to (Z) and trans to (E). Under this new system the two ligands attached to each olefinic carbon atom are put in order of precedence by application of sequence rules and the symbols (E) and (Z) are then used to describe those isomers in which the ligands of higher precedence are on the opposite side (E), etc. Maleic acid is then referred to as the (Z)-isomer and fumaric acid  [c.225]

CfiHsNjOs. Red needles m.p. 168-169°C. Soluble in dilute acids and alkalis. Prepared by reduction of picric acid with sodium hydrogen sulphide, ft is used for the preparation of azodyes, which can be after-chromed by treatment with metallic salts owing to the presence of a hydroxyl group ortho to the amino-group.  [c.313]

C21H36O2. M,p. 238°C. There are four isomeric pregnane-3,20-diols differing only in the orientation of the hydroxyl groups at positions 3 and 20 and with the 5/ configuration. Only the 3a,20a occurs naturally. It is formed by reduction of progesterone in the liver and is the chief urinary metabolite of it, being  [c.326]

Prepared by condensing p-chlorophenol with phlhalic anhydride in sulphuric acid solution in the presence of boric acid. The chlorine atom is replaced by hydroxyl during the condensation. It can also be prepared by oxidation of anthraquinone or 1-hydroxyanthraquinone by means of sulphuric acid in the presence of mercury(ll) sulphate and boric acid.  [c.338]

The initial step in the pathway is the condensation of erythrose-4-phosphale with phosphoenolpyruvate, yielding dehydroquinic acid, which by elimination of the elements of water affords dehydroshikimic acid reduction of the 3-keto group to hydroxyl gives shikimic acid.  [c.357]

See pages that mention the term Heterocoagulation : [c.12]    [c.18]    [c.48]    [c.52]    [c.58]    [c.63]    [c.80]    [c.84]    [c.124]    [c.129]    [c.158]    [c.165]    [c.167]    [c.177]    [c.192]    [c.193]    [c.193]    [c.203]    [c.206]    [c.209]    [c.211]    [c.211]    [c.212]    [c.212]    [c.212]    [c.221]    [c.221]    [c.224]    [c.233]    [c.260]    [c.261]    [c.283]    [c.293]    [c.304]    [c.304]    [c.314]    [c.316]    [c.373]    [c.376]    [c.426]   
Physical chemistry of surfaces (0) -- [ c.192 ]