3- hydroxyl groups

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. 

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... 

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

Van Oss and Good [148] have compared solubilities and interfacial tensions for a series of alcohols and their corresponding hydrocarbons to determine the free energy of hydration of the hydroxyl group they find -14 kJ/mol per —OH group. 

Figure Bl.25.9(a) shows the positive SIMS spectrum of a silica-supported zirconium oxide catalyst precursor, freshly prepared by a condensation reaction between zirconium ethoxide and the hydroxyl groups of the support [17]. Note the simultaneous occurrence of single ions (Ff, Si, Zr and molecular ions (SiO, SiOFf, ZrO, ZrOFf, ZrtK. Also, the isotope pattern of zirconium is clearly visible. Isotopes are important in the identification of peaks, because all peak intensity ratios must agree with the natural abundance. In addition to the peaks expected from zirconia on silica mounted on an indium foil, the spectrum in figure Bl. 25.9(a)...

Figure C2.4.13. Thiol-tenninated hexasaccharide, where acetoxy groups can be replaced by hydroxyl groups, botlr before and following adsorjDtion [221],...

Heilweil E J, Casassa M P, Cavanagh R R and Stephenson J C 1984 Piooseoond vibrational energy relaxation of surfaoe hydroxyl groups on oolloidal silioa J. Chem. Phys. 81 2856-8... 

Hydroxylamine is derived from ammonia by replacing one hydrogen atom by a hydroxyl group. It is prepared by the electrolytic reduction of nitric acid, using a lead cathode ... 

Similar reactions occur with organic compounds which contain hydroxyl groups, thus... 

A somewhat similar reaction is the power of sulphur oxide dichloride to remove water of crystallisation from hydrated chlorides, the hydroxyl groups of the water molecule reacting as do those in the acid molecules in the above reaction. 

Golddll) chloride dissolves in hydrochloric acid to form tetra-chlorauric acid. HAUCI4. Here again, the gold(III) is 4-co-ordinate in the ion [AuCl4] . If alkali is added to this acid, successive replacement of chlorine atoms by hydroxyl groups occurs, forming finally the unstable tetrahydroxoaurate IlI) ion, [Au(OH)4] ... 

You can detect hydroxyl group transitions hy plotting dihedral an gles versn s lime over the course of th e sim n lation. This is the distance history. Grady investigated the distance history of water... 

The analyses which follow are arranged in the order in which they would be applied to a newly discovered substance, the estimation of the elements present and molecular weight deter-minations(f.e., determination of empirical and molecular formulae respectively) coming first, then the estimation of particular groups in the molecule, and finally the estimation of special classes of organic compounds. It should be noted, however, that this systematic order differs considerably from the order of experimental difficulty of the individual analyses. Consequently many of the later macro-analyses, such as the estimation of hydroxyl groups, acetyl groups, urea, etc. may well be undertaken by elementary students, while the earlier analyses, such as estimation of elements present in the molecule, should be reserved for more senior students. 

Estimation of the Number of Hydroxyl Groups in a given Polyhydric Alcohol or Phenol. 

The excess of unchanged acetic anhydride is then hydrolysed by the addition of water, and the total free acetic acid estimated by titration with standard NaOH solution. Simultaneously a control experiment is performed identical with the above except that the alcohol is omitted. The difference in the volumes of NaOH solution required in the two experiments is equivalent to the difference in the amount of acetic add formed, i.e., to the acetic acid used in the actual acetylation. If the molecular weight of the alcohol is known, the number of hydroxyl groups can then be calculated. 

I. DETERMINATION OF NUMBER OF HYDROXYL GROUPS IN PHENOL. CjHjOH. Molecular Weight, 94. 

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