Halogen derivatives

The derivatives of the benzene series of hydrocarbons may be grouped in very nearly the same classes as the derivatives of the aliphatic hydrocarbons, as follows  

In considering these different classes it will be found that they bear the same relationship to the hydrocarbons from which they are formed as do the corresponding derivatives of the aliphatic series to their respective hydrocarbons. 

Study whereas in the aliphatic series only a few compounds of the class are known. The hydroxyl derivatives of the benzene series are of two distinct classes one of which includes true alcohols analogous to those of the aliphatic series, the other includes compounds known as phenols, which are acid compounds. The aldehydes and ketones of the two series are in general formed by similar reactions and are of similar character though in the benzene series a new class, known as quinones, are entirely distinctive. The acids of the benzene series while they may-be prepared by the oxidation of aldehydes as in the aliphatic series are often prepared by the oxidation of a methyl group to carboxyl. 

On the other hand, the ammoniacal character of the ammonia derivatives, the alcoholic character of the true benzene alcohols and the general reactions of aldehydes and acids are alike in the two series of derivatives. What has just been said applies in most cases to those derivatives of the benzene series in which the compound is formed by substitution in the benzene ring. As we shall find later the derivatives of this series are of two kinds (a) those in which substitution is in the ring, and b) those in which substitution is in the side chain of the benzene homologues. These latter compounds are wholly analogous to corresponding aliphatic compounds as in the case of the true alcohols of the benzene series just mentioned. The order of taking up the different classes varies in the two series because of the ease of preparation and the importance of the sulphuric and nitric acid derivatives of the benzene series. 

Halogen derivatives, also called halides, result from the replacement of one or more hydrogen atoms of a hydrocarbon by a halogen X, which can be chlorine, bromine, iodine and, less frequently, fluorine. They, therefore, contain at least one carbon-halogen bond C-X. 

There is a great variety of halogen derivatives, and their chemical reactivity depends on whether they are saturated or unsamrated, acyclic or benzenic, monohalogenated or polyhalogenated. 

Fluorine derivatives form a separate class. Unlike chlorinated, brominated or iodinated derivatives, they are chemically inert under normal conditions of temperature and pressure. They are very stable up to temperamres much higher than their homologous chlorine, bromine or iodine compounds. This behaviour is due to the peculiar namre of the C-F 

Halogen derivatives of aliphatic and aromatic hydrocarbons form a class of compounds with many applications, because they can dissolve many different products fats, varnish, cellulose, polymers, etc. They are intermediates in the synthesis of numerous compounds, such as dye stuffs or pharmaceuticals, plant care products, and insecticides. Certain halogen derivatives are used as coolants in refrigerators. 

In general, the higher the chemical stability of a compound, the lower the risk that it will attack aluminium. 

Halogen Derivatives. Structural studies of CCl2=CF2, (CF3)3CCF (both by electron diffraction), and CH2DF (by microwave) have been reported. A detailed vibrational study of four isotopic species of BrClFCH has been presented, and used to calculate a generalized valence force field, employing structural parameters from the electron-diffraction study.  

Direct bromination of indigo results in bromine derivatives, which have a certain value as colorants [32], 

7 -Tetrabromindigo is prepared by brominating indigo in glacial acetic acid. It has a brilliant, bathochromically shifted shade. 

Brominated indigo with a lower degree of bromination is also commercially available. 

In contrast to the 3-substituted products above, 4-chloro-, 4-bromo- and 4-iodo-isoxazoles are readily prepared by direct halogenation of the corresponding isoxazoles, from 4-isoxazolediazonium salts by the Sandmeyer reaction, or by reaction of hydroxylamine with a-halo- 8-dicarbonyl compounds (62HC(l7)l, p. 66, 63AHC(2)365). 3,5-Bis(dimethyl-amino)-4-fluoroisoxazole has been synthesized by reaction of (Me2NCO)2CHF with hydroxylamine (78BSB391). 

5-Chloro- and 5-bromo-isoxazoles have been prepared by reaction of 5-isoxazolones with the appropriate phosphoryl halide (77JMC934). 3-Phenyl-5-trifluoromethylisoxazole has been synthesized by reaction of benzonitrile iV-oxide with 3,3,3-trifluoropropyne (77JMC934). 

A range of m- and p-phenylenebis[trifluoro(phenyl)silicates] result from the 

Mc3SiCI/phenol provides for the selective deprotection of the N-t-butyloxycarbonyl group in solid phase peptide synthesis, and Mc3SiQ/DMSO converts benzylic alcohols to styrenes and the oximes and semicarbazones of a,P-unsaturated ketones and aldehydes to the 

Nfe3SiCl/NaI provides for the selective preparation of (dichloromethylene)bi hosphonate partial esters, Me3SiI gives vinyl iodides from the phosphate, while it ring ns chiral 4- 

These include carbamates and thiosemicarbazides of Si, with Sn deiivadves of phosphate, RO2CCH2, mercapto, and dithiocarbonate and carbazate, Schiff base, N-heterocycles including pyrazoles, azobenzene, aminophenyl sulphides, and N-macrocycles, pyridine carboxylates and N-subsdtuted phenols, aminobenzoates, alkoxides, esters and salicylates, sulphur and nitrogoi subsdmted carboxylic acids, amino acids, steroids and lead-soine complexes.  

Aminonaphthylsilanes with CsF/imidazole discriminates 1 and 2 OH groups of serine n-butylamide to give fluorescent 3 silyl ethers which can be cleaved by HP t6 form fluorescent silyl fluorides. Photolysing ketene in the presence of methylfluorosilanes gives 

Cp2Mo(Me2SnCl)2 occurs in the crystal as 2 independent molecules with different Mo-Sn bond lengths due to single weak Sn—Cl 

MeSnX3(H0PM62)2 ( Cl or Br) show cis-trans dynamic equilibrium in solution and EtSnX3.20P(NMe2)3 (X=C1,I). FAB and El mass spectra of phenyl Ge, Sn and Pb halides are very similar except that FAB 

Plotting C shift against J. Me SnCl gives a straight 

This section lists complexes with Journal reference. Schiff base and 

Organolead tri-iodides have been prepared from Pbl and an alkyl iodide in the presence of MegSb as catalyst. They are low melting yellow-orange solids and the Pb—C bond is stable to protic reagents. Triphenyl-lead chloride and bromide both possess a five-co-ordinate bridged structure.  

Conditions are described for the direct synthesis of MeSnClj and XCCHj) -SnXs from SnCla and MeCl or X(CH2) X and of the organotin biocide (F,-CCH2CH2)3SnCl from metallic tin, while labelled Bu aSnOAc and Bu 2SnCl2 

A novel method for the anti-Mark onikoff hydrohalogenation of olefins involves hydrosilylation followed by conversion into the organofluorosilicate. Halogenation gives the organic halide in good yield, whereas MCPBA affords the alcohol [equation (95)]. Copper(ii) chloride and bromide similarly cleave 

The stereochemistry of alkylation of mixed chlorofluorosilanes cannot be explained purely in terms of the stability of the five-co-ordinate intermediate, though the hydrolysis (or alcoholysis) of chlorosilanes in the presence of base (HMPT, DMSO, or DMF) gives retention of configuration, as would be expected with nucleophilic attack on five-co-ordinate silicon. The equilibrium for the formation of HMPT-MeaSi+X (X=C1, Br, or 1) lies towards the reactants for X=C1, but well over to the products for the heavier halogens.  

The sequence follows that of last year and also includes sections on substituted carbaboranes and peroxides. 

Me SiCL/Zn reduction of 1,2 riiketones gives siloxyalkenes using ultrasound, while alkenes result from ol, -unsaturated carbonyl compounds which can be 

RSiFc are assessed as organylating agents, while (13-crown-6)K complexes of 

Ke- SiI, tetrachlorocyclopropene gives the first ionic carbon halide, explosive 

Cy SnXj (X=Cl,3r) and MeSnlj show discrete tetrahedral molecules with some 

Crown ether complexes of ti SnX. (X=ClO, iiiCS) have been prepared and all are 

Miller and D. R. McKean, Tetrahedron Lett., 1980, 2639 W. Ando and M. Ikeno, Chemistry Lett., 1980, 1255 Z. Kosarych and T. Cohen, Tetrahedron Lett., 1980, 3959. 

The electrochemical reduction of halosilanes and germanes in aprotic solvents to give disilanes and digermanes is irreversible and takes place at a low potential. Bu MeCgFsSiCl forms volatile derivatives with alcohols, carboxylic acids, thiols, and amines. All show remarkable hydrolytic stability and are suitable for gas chromatography with electron capture detection.  

This is shorter than last year but follows the same pattern, with authors omitted from composite journal references for brevity. 

Bordeau, E. Frairmet, and C. Clement, J. Organomet. Chem., 1980, 202, 123 Molecular optical anistropy of alkenyl-, amino-, and alkoxysilanes. 

methanetetraylbis... trad. NyN -Diisopropylcarbodiimide new Methanedi(ylidene)bis(propan-2-ylazane) 

Halogen compounds should generally be named substitutively complete substitution can be indicated by the prefix per. 

For some simple halogen derivatives, however, radicofunctional names are still widely in use. 

C6H5-CHCI2 Benzylidene dichloride, traditionally also benzal 

In a few cases additive names still persist although they are strongly discouraged by now. 

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Halogen derivatives of silanes can be obtained but direct halogena-tion often occurs with explosive violence the halogen derivatives are usually prepared by reacting the silane at low temperature with a carbon compound such as tetrachloromethane, in the presence of the corresponding aluminium halide which acts as a catalyst. 

Picrates. Some halogen derivatives of the higher aromatic hydrocarbons form picrates (for experimental details, see under Aromatic Hydrocarbons, Section IV,9, 1), for example, a-chloronaphthalene (m.p. 137°), a-bromonaphthalene (m.p. 134°), and p-bromonaphthalene (m.p. 86°). 

Concentrated sulphuric acid. The paraffin hydrocarbons, cych-paraffins, the less readily sulphonated aromatic hydrocarbons (benzene, toluene, xylenes, etc.) and their halogen derivatives, and the diaryl ethers are generally insoluble in cold concentrated sulphuric acid. Unsaturated hydrocarbons, certain polyalkylated aromatic hydrocarbons (such as mesitylene) and most oxygen-containing compounds are soluble in the cold acid. 

Hydroxyalkylthiazoles are also obtained by cyclization or from alkoxyalkyl-thiazoles by hydrolysis (36, 44, 45, 52, 55-57) and by lithium aluminium hydride reduction of the esters of thiazolecarboxylic acids (58-60) or of the thiazoleacetic adds. The Cannizzaro reaction of 4-thiazolealdehyde gives 4-(hydroxymethyl)-thiazole (53). The main reactions of hydroxyalkyl thiazoles are the synthesis of halogenated derivatives by the action of hydrobroraic acid (55, 61-63), thionyl chloride (44, 45, 63-66), phosphoryl chloride (52, 62, 67), phosphorus penta-chloride (58), tribromide (38, 68), esterification (58, 68-71), and elimination that leads to the alkenylthiazoles (49, 72). 

Halogen Derivatives. Using substitutive nomenclature, names are formed by adding prefixes listed in Table 1.8 to the name of the parent compound. The prefix perhalo- implies the replacement of all hydrogen atoms by the particular halogen atoms. 

The most important of the halogenated derivatives of acetic acid is chloroacetic acid. Fluorine, chlorine, bromine, and iodine derivatives are all known, as are mixed halogenated acids. For a discussion of the fluorine derivatives see Fluorine compounds, organic. 

Halogenated and 4,5-halogenated derivatives of 1,8-naphthalenedicarboxyHc acid anhydride are useful intermediates for dyes, pigments, and fluorescent whiteners for polymers. 

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