A-DiHYDRoxY Compounds

Cleavage of an alkenoic acid can be carried out with permanganate, a permanganate—periodate mixture, periodate or with nitric acid, dichromate, ozone, or, if the unsaturation is first converted to a dihydroxy compound, lead tetraacetate (71,73). Oxidative ozonolysis is a process for the manufacture of azelaic acid [123-99-9] and pelargonic acid (74). 

Polycarbonates. Polyarjiates are aromatic polyesters commonly prepared from aromatic dicarboxylic acids and diphenols. One of the most important polyarylates is polycarbonate, a polyester of carbonic acid. Polycarbonate composite is extensively used in the automotive industry because the resin is a tough, corrosion-resistant material. Polycarbonates (qv) can be prepared from aUphatic or aromatic materials by two routes reaction of a dihydroxy compound with phosgene accompanied by Hberation ofHCl(eq. 5) ... 

An alternative technique is that of condensation polymerisation. A simple example of this is seen in the manufacture of linear polyesters. Here a dibasic acid is reacted with a dihydroxy compound, e.g. a glycol (Figure 2.5). 

Occasionally it happens that the oxo compound, produced by oxidation, forms a hydrate which is further oxidized to a dihydroxy compound. Attention must be given to the possibility (so far unreported) that when the hydrated species is in equilibrium with a trace of the ring-opened structure a sufficiently fast oxidation rate of the amino-aldehyde (i.e. the acyclic structure) could lead to the incorrect conclusion that the original material was not cyclic. 

L. P. Kuhn pointed out that, if hydroxyl groups of an a-dihydroxy compound are sufficiently close, they will form an internal hydrogen-bond. 

Unsaturated polyesters are prepared through a classical esterification process. Typically, a dihydroxy compound, or mixtures of dihydroxy compounds, are treated with maleic anhydride and/or together with other dicarboxylic acids such as aromatic or aliphatic dicarboxylic acids under elevated temperature to remove the water produced during esterification process. Although various catalysts will catalyze this esterification reaction, there is enough carboxylic acid in the mixture so that it is not necessary to add extra catalyst. 

The reaction between a dihydroxy compound (bisphenol) and phosgene, which is performed on an industrial scale, proceeds even at room temperature.The reaction is generally carried out in a biphasic medium consisting of methylene chloride (with dissolved phosgene) and aqueous sodium hydroxide (with dissolved bisphenol sodium salt) and a phase transfer catalyst (e.g.triethylamine).The procedure is termed interfacial polycondensation (see Sect.4.1.2.3 and Examples 4-5,4-12,and 4-13). 

Polymers formed by condensing epichlorohydrin with a dihydroxy compound, most often bisphenol A. (p. 657)... 

The second mole adds to the carbonyl group to give a dilithium salt, 3-5, which is stable under the reaction conditions. Sequential hydrolysis of each Old group in acid, during workup, gives a dihydroxy compound, 3-6, which is the hydrate of a ketone. A series of protonations and deprotonations transforms the hydrate into a species that can eliminate a molecule of water to form the ketone. 

The four structural units (a)-(d) form the bases of the structures of numerous inorganic compounds in which the bonds are covalent or covalent-ionic. It is also convenient to represent diagrammatically, by means of 3-connected nets, the structures of certain crystals in which the structural units (which may be ions or molecules) form three hydrogen bonds. In the hydrates of some acids one H is associated with H2O to form H3O which is a unit of type (a). In certain hydroxy-compounds each OH group is involved in two hydrogen bonds, and accordingly a molecule of a dihydroxy-compound may be represented as at (e), it... 

Another objection to the theory may be based on the experimental data existing on alcohol oxidation. According to Bone, alcohols should oxidize through a dihydroxy compound by the addition of an oxygen atom. The work of Wieland 5 and others has shown that the formation of aldehydes from primary alcohols may take place by dehydrogenation rather than further hydroxylation. Experimental evidence is lacking for the formation of the simple glycols by alcohol oxidation. 

In connection with a synthesis of the hydroazulenic sesquiterpene kessanol (304), Knoevenagel condensation of photocitral-A (302) with ethyl cyanoacetate was found to give (303) as a single isomer. The following sequence includes an intramolecular Prins reaction initiated with SnCU. In Isobe s synthesis of vemolepin (307) the two carbons of the -y-iactone are introduced by a Knoevenagei condensation. Reaction of ketone (305) with di-f-butyl maionate followed by treatment with DBU affords (306), which is transformed to the a,a -dihydroxy compound (308). Hydrolysis of the esters foliowed by decarboxy-iation, formation of the y-lactone, Mannich reaction and elimination yields vemolepin (307 Scheme 58).3"... 

Polycarbonates based on 2-cyclohexen-l,4-diol and a dihydroxy compound liberate benzene through aromatization, a dihydroxyl compound, and carbon dioxide, upon acidolysis [343]. The low volatility of the dihydroxyl compound hampers complete development by heating alone and necessitates wet development. 

Benzylidene acetals are generally prepared following two standard procedures that is, by reacting a dihydroxy compound (i) with benzaldehyde in tetrahydrofuran in the presence of stoichiometric amounts of Lewis acid and (ii) with benzaldehyde dimethylacetal in dime-thylformamide in the presence of a catalytic amount of PTSA [39]. 

Epoxy resins are complex network polyethers usually formed in a two-staged process. The first stage involves a base-catalyzed step-growth reaction of an excess epoxide, typically epichlorohydrin with a dihydroxy compound such as bisphenol A This results in the formation of a low-molecular-weight prepolymer terminated on either side by an epoxide group. 

By the hydrolysis of ruberythric acid, it was concluded that alizarin must be a dihydroxy-compound. Distillation over zinc dust gave anthracene. 

These are usually prepared from epichlorhydrin and a dihydroxy compound. The latter is usualy a diphenol - in particular the compound called bisphenol A - though it can be a dihydric alcohol... 

Write a condensed structural formula for each of the following (a) an acid with the formula C4H8O2, (b) a cyclic ketone with the formula CsHsO, (c) a dihydroxy compound with the formula C3H8O2, (d) a cychc ester with the formula C5H8O2. 

Polyesters are macromolecules made by reacting a diacid or dianhydride with a dihydroxy compound (diols). To make unsaturated polyesters, maleic anhydride or fumeric acid is used in addition to a saturated acid, which provides unsaturation in the structure. The most commonly used anhydrides are maleic anhydride (unsaturated) and phthalic anhydride (saturated). The commonest diols are ethylene glycol or propylene glycol. Use of an unsaturated anhydride is very critical to provide unsaturation in the structure, which is utilised to cure the resin by free-radical polymerisation. The chemical reaction for the synthesis of UPE is shown in Figure 2.13. 

Several polymerization routes can be employed for the synthesis of suifone polymers. The synthesis route that is most practical and that is used almost exclusively today for the production of these polymers is the aromatic nucleophilic substitution polymerization route. This synthesis route involves the condensation polymerization of 4,4 -dihalodiphenylsulfone with a dihydroxy compound in the presence of a base to convert the phenolic hydroxyl group to a nucleophilic aromatic phenoxide group. The polymerization takes place in a dipolar aprotic solvent that will solvate aU components of the reaction medium. This suifone polymer chemistry was pioneered by Johnson and Famham in the early 1960s [1, 2]. 

When two hydroxyl units are incorporated into the same molecrde, it is a dihydroxy compound (two alcohol units) this type of molecule is called a diol (two OH diol). When there are three hydroxyl units, it is a triol tetraols, pen-taols, etc. are known. The nomenclature for a diol identifies the longest chain that bears both OH units, and gives the two carbon atoms that bear the OH units the lowest possible number. Typically, the name of the hydrocarbon chain precedes the term diol, with numbers to identify the positions of the hydroxyl groups. For example, HOCH2CH2CH2CHOH is 1,4-butanediol and CHgCHlOH) CH2CH(CH3)CH2CH2CH20H is 4-methyl-2,7-heptanediol. 

Brief mention should be made of a specific sub-class of polyesters, the polycarbonates. These are prepared by reacting a dihydroxy compound with a derivative of carbonic acid such as phosgene or a carbonic acid ester such as diphenyl carbonate ... 

Glycidyl epoxies are prepared via a condensation reaction of a dihydroxy compound, dibasic acid or a diamine and epichlorohydrin. 

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