Reaction with Halogen Acids

The reactions of the cyclitols with halogen acids may be divided into two groups, halohydrin formation and aromatization. 

There appears to be only one example of halohydrins obtained by direct action of halogen acids on the cyclitols d-quercitol was heated at 100° with a solution of HCl (saturated at 10°), and a very small amount of substance, m.p. 198-200°, was obtained which had an analysis corresponding to a monochlorohydrin 100) and also one, m.p. 155°, that appeared to be a trichlorohydrin, C6H7Cl3(OH)2. 

A number of such derivatives have been obtained from cyclitol esters through the action of HCl or HBr on the ester 46) or by reacting an acyl halide 106a, b) with a cyclitol. Considerable isomerization occurs, since the same dibromohydrin tetraacetates are obtained from mi/o-inositol, scyllo-inositol, and pinitol 61b). Debromination to known cyclohexanepentols and -tetrols has enabled McCasland 61b, 65) to assign tentative structures, and, in some cases, configurations to the mono- and dibromohydrins. 

In addition to the conversion of the three cyclitols to the same bromohy-drins, Muller 46) found further evidence for isomerization. When the reaction mixture from mi/o-inositol or scyllo-mositol was treated with Ba(OH)2, he was able to isolate iso-inositol, which has since been shown to be DL-inositol 107). It is to be noted that inversion of any two adjacent carbon atoms of scyllo-inositol would give DL-inositol, while inversion of any one carbon atom would give m /o-inositol. Inversion of the stereochemically equivalent carbon atoms (number 1) of m /o-inositol would give DL-inositol. Muller also isolated an ill-characterized pseudo-inositol.  

Hydrochloric acid has been used for the aromatization of shikimic acid to p-hydroxybenzoic acid 71), and of Z-quinic acid to hydroquinone and p-hy-droxybenzoic acid 111). Conduritol was transformed in part to catechol by 12.5 to 25 % HCl 66). Fuming hydrobromic acid converted Z-quinic acid to hydroquinone, 3,4-dihydroxybenzoic, and benzoic acids 112). Muller 46) 

Simple aliphatic oxiranes can be converted to fluorohydrin with hydrogen fluoride only with great difficulty, but the reaction can be carried out in systems with rigid conformations (e.g., steroids, 9,10-epoxydecalin). Good yields can be attained from cyclopentene and cyclohexene oxides with 42% pyridine-polyhydrogen fluoride and in a series of terpene oxides with an amine-hydrogen fluoride complex.  

The reactions can be performed more simply with hydrochloric acid and hydro-bromic acid. The reaction between terpene oxides and hydrochloric acid has been examined, for example, in the cases of p-mentadiene dioxide, a-3,4-epoxy-carane, and a-4,5-epoxycarane. Studies have been made of the reactions of steroid oxiranes with hydrochloric acid and hydrobromic acid. The acidic opening of compounds containing two oxirane rings can be carried out selectively and in good yield (Eq. 309).  

The selectivity is influenced considerably by the nature and stereochemistry of the substituents. For instance, under conditions similar to those used in Eq. 309, 130 does not react. °  

The stereospecific synthesis of trisubstituted olefins has been described in the concerted ring-opening reaction of cyclopropyloxirane (Eq. 310) ° as a novel adaption of the Julia-Johnson olefin synthesis.  

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The monosubstituted adduct offers the ready synthesis of a whole range of monosubstituted adducts (see Scheme 6) it is often possible to isolate in these reactions intermediates that are not readily obtained by alternative methods. Thus, in the reaction with halogen acids to yield the bridged hydrido complexes HOs3(CO)10X, it is possible to identify the intermediate HOs3(CO)uX complex in which the halogen functions as a one-electron donor bonding to only one metal center (158). 

Alcohols are converted to alkyl halides by SN1 and S 2 reactions with halogen acids. 

Addition reactions with halogen acids to give haloalkanes ... 

Reaction with Other Inorganic Halogen Compounds. Anhydrous HCl forms addition compounds at lower temperatures with halogen acids such as HBr and HI, and also with HCN. These compounds are stable at room temperature. 

Reaction with Halogen Nucleophiles. Hydrochloric acid [7647-01-0] hydrobromic acid [10035-10-6] and hydroiodic acid [10034-85-2] react readily with ethyleneimine (3) to give the corresponding P-halogenoethylamines (20,21). 

Nor can there be any question of real tautomerism in the case of phenol. In its chemical properties phenol resembles the aliphatic enols in all respects. We need only recall the agreement in the acid character, the production of colour with ferric chloride, and the reactions with halogens, nitrous acid, and aromatic diazo-compounds (coupling), caused by the activity of the double bond and proceeding in the same way in phenols and aliphatic enols. The enol nature of phenol provides valuable support for the conception of the constitution of benzene as expressed in the Kekule-Thiele formula, since it is an expression of the tendency of the ring to maintain the aromatic state of lowest energy. In this connexion the hypothetical keto-form of phenol (A)—not yet obtained—would be of interest in comparison with... 

Alcohols can react in several ways, depending on the reactants and on the conditions of the reaction. For example, alcohols can undergo substitution with halogen acids, elimination to form alkenes, and oxidation to form aldehydes, ketones, or carboxylic acids. 

Barium reacts violently with dilute acids, evolving hydrogen. Reactions with halogens give barium halides ... 

Heating with metal oxides at elevated temperatures produces anhydrous borates. Reactions with halogens in the presence of carbon at temperatures above 500°C give boron trdialides. Heating a mixture of boric acid, ammonia and calcium phosphate in an electric furnace produces boron nitride. 

Plutonium reacts with hydrogen at high temperatures forming hydrides. With nitrogen, it forms nitrides, and with halogens, various plutonium hahdes form. Halide products also are obtained with halogen acids. Reactions with carbon monoxide yields plutonium carbides, whde with carbon dioxide, the products are both carbides and oxides. Such reactions occur only at high temperatures. 

Sodium azide is a toxic as well as an explosive substance (Patnaik, P. 1999. A Comprehensive Guide to the Hazardous Properties of Chemical Substances, 2nd e(j New York John Wdey Sons). Although inert to shock, violent decomposition can occur when heated at 275°C. Contact of solid or solution with lead and copper must be avoided. Reactions with halogens, carbon disulfide, or chromyl chloride can be explosive. Dissolution in water produces toxic vapors of hydrazoic acid. The salt is an acute poison causing headache, hypotension, hypothermia, and convulsion. 

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