Benzene Sentence Examples
Benzene poisoning unlikely to be a factor in causing scrapie.
The ringed structure of benzene, C 6 H 61 was first suggested in 1865 by August Kekule, who represented the molecule by six CH groups placed at the six angles of a regular hexagon, the sides of which denoted the valencies saturated by adjacent carbon atoms, the fourth valencies of each carbon atom being represented as saturated along alternate sides.
A thiophenol, C 6 H 5 SH, is known, and is prepared by the action of phosphorus pentasulphide on phenol, or by distilling a mixture of sodium benzene sulphonate and potassium sulphydrate.
For example, ethylene, C2H4 j is formed with absorption of 16200 cal., acetylene, C 2 H 2, with absorption of 59100 cal., and liquid benzene, C 6 H 6, with absorption of 9100 cal.
Paraffins are found in all crude oils, and olefines in varying proportions in the majority, while acetylene has been found in Baku oil; members of the benzene group and its derivatives, notably benzene and toluene, occur in all petroleums. Naphthenes are the chief components of some oils, as already indicated, and occur in varying quantities in many others.Advertisement
It is almost insoluble in water, but mixes in all proportions with absolute alcohol, ether, benzene and various oils.
Thus, he interpreted the interaction of benzene and nitric acid as C6H61-HN03 = C 6 H 5 NO 2 +H 2 0, the "residues" of benzene being C 6 H 5 and H, and of nitric acid HO and N02.
Carbocyclic rings will next be treated, benzene and its allies in some detail; and finally the heterocyclic nuclei.
Polymethylenes can give only secondary and tertiary alcohols, benzene only tertiary; these latter compounds are known as phenols.
This formula, notwithstanding many attempts at both disproving and modifying it, has well stood the test of time; the subject has been the basis of constant discussion, many variations have been proposed, but the original conception of Kekule remains quite as convenient as any of the newer forms, especially when considering the syntheses and decompositions of the benzene complex.Advertisement
Other hydrocarbon nuclei generally classed as aromatic in character result from the union of two or more benzene nuclei joined by one or two valencies with polymethylene or oxidized polymethylene rings; instances of such nuclei are indene, hydrindene, fluorene, and fluoranthene.
We now proceed to consider the properties, syntheses, decompositions and constitution of the benzene complex.
It has already been stated that benzene derivatives may be regarded as formed by the replacement of hydrogen atoms by other elements or radicals in exactly the same manner as in the aliphatic series.
In general, the aliphatic residues in such mixed compounds retain the characters of their class, while the aromatic residues retain the properties of benzene.
The introduction of hydroxyl groups into the benzene nucleus gives rise to compounds generically named phenols, which, although resembling the aliphatic alcohols in their origin, differ from these substances in their increased chemical activity and acid nature.Advertisement
These observations may be summarized by saying that the benzene nucleus is more negative in character than the aliphatic residues.
Although Kekule founded his famous benzene formula in 1865 on the assumptions that the six hydrogen atoms in benzene are equivalent and that the molecule is symmetrical, i.e.
Orientation of Substituent Groups.-The determination of the relative positions of the substituents in a benzene derivative constitutes an important factor in the general investigation of such compounds.
Generally if any group be replaced by another group, then the second group enters the nucleus in the position occupied by the displaced group; this means that if we can definitely orientate three di-derivatives of benzene, then any other compound, which can be obtained from or converted into one of our typical derivatives, may be definitely orientated.
Such a series of typical compounds are the benzene dicarboxylic acids (phthalic acids), C 6 H 4 (000H) 2.Advertisement
Ladenburg (Ann., 1875, 179, p. 163) to be symmetrical trimethyl benzene; terephthalic acid, the remaining isomer, must therefore be the para-compound.
Substitution of the Benzene Ring.-As a general rule, homologues and mono-derivatives of benzene react more readily with substituting agents than the parent hydrocarbon; for example, phenol is converted into tribromphenol by the action of bromine water, and into the nitrophenols by dilute nitric acid; similar activity characterizes aniline.
Experience has shown that such mono-derivatives as nitro compounds, sulphonic acids, carboxylic acids, aldehydes, and ketones yield as a general rule chiefly the meta-compounds, and this is independent of the nature of the second group introduced; on the other hand, benzene haloids, amino-, homologous-, and hydroxy-benzenes yield principally a mixture of the orthoand para-compounds.
Of other syntheses of true benzene derivatives, mention may be made of the formation of orcinol or [3 s]-dioxytoluene from dehydracetic acid; and the formation of esters of oxytoluic acid (5-methyl3-oxy-benzoic acid), C6 H3 CH3.
Another hexa-substituted benzene compound capable of direct synthesis is mellitic acid or benzene carboxylic acid, C6(000H)6.Advertisement
Hitherto we have generally restricted ourselves to syntheses which result in the production of a true benzene ring; but there are many reactions by which reduced benzene rings are synthesized, and from the compounds so obtained true benzenoid compounds may be prepared.
If we accept Kekule's formula for the benzene nucleus, then we may expect the double linkages to be opened up partially, either by oxidation or reduction, with the formation of di-, tetra-, or hexa-hydro derivatives, or entirely, with the production of open chain compounds.
Strong oxidation breaks the benzene complex into such compounds, as carbon dioxide, oxalic acid, formic acid, &c.; such decompositions are of little interest.
Carius showed that potassium chlorate and sulphuric acid oxidized benzene to trichlorphenomalic acid, a substance afterwards investigated by Kekule and 0.
Zincke; and his researches have led to the discovery of many chlorinated oxidation products which admit of decomposition into cyclic compounds containing fewer carbon atoms than characterize the benzene ring, and in turn yielding openchain or aliphatic compounds.
Decompositions of this nature were first discovered in the naphthalene series, where it was found that derivatives of indene (and of hydrindene and indone) and also of benzene resulted; Zincke then extended his methods to the disintegration of the oxybenzenes and obtained analogous results, R-pentene and aliphatic derivatives being formed (Rsymbolizing a ringed nucleus).
The development of the " structure theory " in about 1860 brought in its train an appreciation of the chemical structure of the derivatives of benzene.
Applying this notion to benzene, let us consider the impacts made by the carbon atom (I) which we will assume to be doubly linked to the carbon atom (2) and singly linked to (6), h standing for the hydrogen atom.
Ladenburg, who devoted much attention to the study of the substitution products of benzene, and 's to the support of his own formula.
This implied that in the benzene complex there was at least one carbon atom linked to three others, thus rendering Kekule's formula impossible and Ladenburg's and Claus' possible.
Baeyer pointed out that although benzene derivatives were obtainable from hexamethylene compounds, yet it by no means follows that only hexamethylene compounds need result when benzene compounds are reduced.
To follow Baeyer's results we must explain his nomenclature of the reduced benzene derivatives.
The benzene nucleus presents a remarkable case, which must be considered in the formulation of any complete theory of valency.
When applied to benzene, a twofold conjugated system is suggested in which the partial valencies of adjacent atoms neutralize, with the formation of a potential double link.
The stability of benzene is ascribed to this conjugation.'
Physico-chemical properties have also been drawn upon to decide whether double unions are present in the benzene complex; but here the predilections of the observers apparently influence the nature of the conclusions to be drawn from such data.
A similar contradiction apparently exists with regard to the specific volume, for while benzene has a specific volume correspinding to Claus' formula, toluene, or methylbenzene, rather points to Kekule's.
Stohmann of Leipzig; and the new data and the conclusions to be drawn from them formed the subject of much discussion, Briihl endeavouring to show how they supported Kekule's formula, while Thomsen maintained that they demanded the benzene union to have a different heat of combustion from the acetylene union.
Thomsen then investigated heats of combustion of various benzenoid hydrocarbons - benzene, naphthalene, anthracene, phenanthrene, &c. - in the crystallized state.
But, at the same time, the constants in the above relation are not identical with those in the corresponding relation empirically deduced from observations on fatty hydrocarbons; and we are therefore led to conclude that a benzene union is considerably more stable than an ethylene union.
Mention may be made of the absorption spectrum of benzene.
These bands are due to molecular oscillations; Hartley suggests the carbon atoms to be rotating and forming alternately single and double linkages, the formation of three double links giving three bands, and of three single links another three; Baly and Collie, on the other hand, suggest the making and breaking of links between adjacent atoms, pointing out that there are seven combinations of one, two and three pairs of carbon atoms in the benzene molecule.
Experiments showed that the second acid was much more difficult to esterify than the first, pointing to the conclusion that Claus' formula for benzene was more probable than Kekule's.
Restricting ourselves to compounds resulting from the fusion of benzene rings, we have first to consider naphthalene, C10H8, which consists of two benzene rings having a pair of carbon atoms in common.
The next members are the -isomers anthracene and phenanthrene, C14H,0, formed from three benzene nuclei.
Here we shall only discuss the structure of these compounds in the light of the modern benzene theories; reference should be made to the articles Naphthalene, Anthracene and Phenanthrene for syntheses, decompositions, &c.
The third formula is based on Dewar's benzene formula, which we have seen to be incorrect.
In 1882 Claus suggested a combination of his own and Dewar's benzene formulae.
This is obviously unsymmetrical, consisting of an aliphatic and an aromatic nucleus; Claus explained the formation of the same phthalic acid from the oxidation of either nucleus by supposing that if the aromatic group be oxidized, the aliphatic residue assumes the character of a benzene nucleus.
The former, based on Kekule's symbol for benzene, explains the decompositions and syntheses of the ring, but the character of naphthalene is not in keeping with the presence of five double linkages, although it is more readily acted upon than benzene is.
Then, on account of the relatively slight - because divided - influence which would be exercised upon the two rings by the two affinities common to both, the remaining four centric affinities of each ring would presumably be less attracted into the ring than in the case of benzene; consequently they would be more active outwards, and combination would set in more readily.
On the other hand, if substitution be effected in the one ring, and the affinities in that ring become attracted inwards, as apparently happens in the case of benzene, the adjoining ring should become relatively more active because the common affinities would act less into it.
The centric formula proposed by Bamberger represents naphthalene as formed by the fusion of two benzene rings, this indicates that it is a monocyclic composed of ten atoms of carbon.
The formula has the advantage that it may be constructed from tetrahedral models of the carbon atom; but it involves the assumption that the molecule has within it a mechanism, equivalent in a measure to a system of railway points, which can readily close up and pass into that characteristic of benzene.
Bamberger, on the other hand, extends his views on benzene and naphthalene and assumes the molecule to be (1).
During recent years an immense number of ringed or cyclic compounds have been discovered, which exhibit individual characters more closely resembling benzene, naphthalene, &c. than purely aliphatic substances, inasmuch as in general they contain double linkages, yet withstand oxidation, and behave as nuclei, forming derivatives in much the same way as benzene.
By reduction, the double linkages become saturated, and compounds result which stand in much about the same relation to the original nucleus as hexamethylene does to benzene.
In general, therefore, it may be considered that the double linkages are not of exactly the same nature as the double linkage present in ethylene and ethylenoid compounds, but that they are analogous to the potential valencies of benzene.
Thus benzene, (CH) gives thiophene, (CH) S, from which it is difficultly distinguished; pyridine, (CH) N, gives thiazole, (CH) N S, which is a very similar substance; naphthalene gives thionaphthen, C 11 S, with which it shows great analogies, especially in the derivatives.
Similarly a CH group may be replaced by a nitrogen atom with the production of compounds of similar stability; thus benzene gives pyridine, naphthalene gives quinoline and isoquinoline; anthracene gives acridine and a and 3 anthrapyridines.
The more important types are derived from aromatic nuclei, benzene, naphthalene, &c.; the ortho-di-derivatives of the first named, lending themselves particularly to the formation of condensed nuclei.
This is comparable with the reduction of the benzene nucleus into hexamethylene, a substance of an aliphatic character.
One or two benzene nuclei may suffer condensation with the furfurane, thiophene and pyrrol rings, the common carbon atoms being vicinal to the hetero-atom.
Naphthyridines and naphthinolines result from the condensation of two pryridine and two quinoline nuclei respectively; and quino-quinolines are unsymmetrical naphthyridine nuclei condensed with a benzene nucleus.
By actual observations it has been shown that ether, alcohol, many esters of the normal alcohols and fatty acids, benzene, and its halogen substitution products, have critical constants agreeing with this originally empirical law, due to Sydney Young and Thomas; acetic acid behaves abnormally, pointing to associated molecules at the critical point.
Hydrocarbons of similar structure have been prepared by Thiele, for example, the orange-yellow tetraphenyl-para-xylylene, which is obtained by boiling the bromide C6H4[CBr(C6H5)2]2 with benzene and molecular silver.
Other substituent groups exercise morphotropic effects similar to those exhibited by the alkyl radicles; investigations have been made on halogen-, hydroxy-, and nitro-derivatives of benzene and substituted benzenes.
To Jaeger is due the determination of the topic parameters of certain haloid-derivatives, and, while showing that the morphotropic effects closely resemble those occasioned by methyl, he established the important fact that, in general, the crystal form depended upon the orientation of the substituents in the benzene complex.
It is decomposed, on dry distillation, into carbon dioxide and pyromellitic acid, C i oH 6 0 8 i when distilled with lime it gives carbon dioxide and benzene.
Piperic acid differs from piperonylic acid by the group C4H 4, and it was apparent that these carbon atoms must be attached to the carbon atom which appears in the carboxyl group of piperonylic acid, for if they were directly attached to the benzene ring polycarboxylic acids would result in oxidation.
In 1877, with Crafts, he made the first publication of the fruitful and widely used method for synthesizing benzene homologues now generally known as the "Friedel and Crafts reaction."
Benzene is manufactured from the low-boiling fractions of the coal-tar distillate.
Benzene is a colourless, limpid, highly refracting liquid, having a pleasing and characteristic odour.
Benzene is of exceptional importance commercially on account of the many compounds derivable from it, which are exceedingly valuable in the arts.
The constitution of the benzene ring, the isomerism of its derivatives, and their syntheses from aliphatic or openchain compounds, are treated in the article Chemistry.
Passed through a red-hot tube, benzene vapour yields hydrogen, diphenyl, diphenylbenzenes and acetylene; the formation of the last compound is an instance of a reversible reaction, since Berthelot found that acetylene passed through a red-hot tube gave some benzene.
Benzene is very stable to oxidants, in fact resistance to oxidation is a strong characteristic of the benzene ring.
Sulphuric acid gives a benzene sulphonic acid.
Those substituted in the benzene nucleus are obtained by condensing two molecules of a substituted benzyl and benzal chlorides.
Prior to 1830, little was known of the process other than that organic compounds generally yielded tarry and solid matters, but the discoveries of Liebig and Dumas (of acetone from acetates), of Mitscherlich (of benzene from benzoates) and of Persoz (of methane from acetates and lime) brought the operation into common laboratory practice.
Aqueous alcohol becomes turbid when mixed with benzene, carbon disulphide or paraffin oil; when added to a solution of barium oxide in absolute alcohol, a white precipitate of barium hydroxide is formed.
It may be diluted with benzene or toluene.
Methylene iodide, CH 2 I 2, has a density of 3.33, and may be diluted with benzene.
In the "diffusion column" method, a liquid column uniformly varying in density from about 3.3 to I is prepared by pouring a little methylene iodide into a long test tube and adding five times as much benzene.
The solubility of the gas in various liquids, as given by different observers, is zoo Volumes of Brine Water Alcohol Paraffin Carbon disulphide Fusel oil Benzene Chloroform Acetic acid Acetone It will be seen from this table that where it is desired to collect and keep acetylene over a liquid, brine, i.e.
Dorp (Ber.,1874,7,P.578) obtained orthobenzoyl benzoic acid by heating phthalic anhydride with benzene in the presence of aluminium chloride.
It can be readily diazotized, and the diazonium salt when boiled with alcohol yields aposafranine or benzene induline, C18H12N3.
Details of his work, especially in connexion with benzene derivatives, are given in 6.53, 55 and 942; 11.21 5; 20.430; 25.892 and 21.635.
Most of the azoximes are very volatile substances, sublime readily, and are easily soluble in water, alcohol and benzene.
The residue is treated with a warm concentrated solution of soda, and the oil which separates is removed by shaking with benzene.
It is readily soluble in alcohol, ether and benzene.
Diazoimino benzene, C 6 H 5 N 3, is also known.
The fact that benzene and its derivatives are remarkable for their powerful absorption of the most refrangible rays, and for some characteristic absorption bands appearing on dilution, led Hartley to a more extended examination of some of the more complicated organic substances.
He determined that definite absorption bands are only produced by substances in which three pairs of carbon atoms are doubly linked together, as in the benzene ring.
If that line be connected with a band we may feel certain that some derivative of benzene is present.
It will be advantageous if the spectra of ammonia, benzene, aniline and dimethyl aniline be compared, when the re-' markable coincidences will at once become apparent, as also the different weighting of the molecule.
The spectrum of nitrobenzene is also worth comparing with benzene and nitric acid.
Tschelinzeff (Ber., 1904, 37, p. 4534) showed that the ether may be replaced by benzene containing a small quantity of ether or anisole, or a few drops of a tertiary amine.
Equally good comparisons have been obtained for solutions in other solvents such as acetic acid 3.88, formic acid 2.84, benzene 5.30, and nitrobenzene 6.95.
Berthelot that under the influence of the silent electric discharge, a mixture of benzene vapour and argon underwent contraction, with formation of a gummy product from which the argon could be recovered.
A large number of these acids, which are mostly benzene derivatives, have been isolated and more or less closely investigated.
As a synthetical agent in organic chemistry, aluminium chloride has rendered possible more reactions than any other substance; here we can only mention the classic syntheses of benzene homologues.
Potassium benzene diazotate, C 6 H 5 N 2 OK, crystallizes in colourless silky needles.
By the addition of the diazonium salts to a hot concentrated solution of a caustic alkali, C. Schraube and C. Schmidt(Ber., 18 94, 2 7, p. 520)obtained an isomer of potassium benzene diazotate.
Potassium benzene iso-diazotate resembles the normal salt, but is more stable, and is more highly ionized.
Benzene diazonium hydroxide, although a strong base, reacts with the alkaline hydroxides to form salts with the evolution of heat, and generally behaves as a weak acid.
Weith (1844-1881), professor of chemistry at Zurich University, he undertook to continue the lectures on benzene derivatives, and this led him to the discovery of thiophen.
This conception led Kekule to his "closed-chain" or "ring" theory of the constitution of benzene which has been called the "most brilliant piece of prediction to be found in the whole range of organic chemistry," and this in turn led in particular to the elucidation of the constitution of the "aromatic compounds," and in general to new methods of chemical synthesis and decomposition, and to a deeper insight into the composition of numberless organic bodies and their mutual relations.
Japp, in the Kekule memorial lecture he delivered before the London Chemical Society on the 15th of December 1897, declared that three-fourths of modern organic chemistry is directly or indirectly the product of Kekule's benzene theory, and that without its guidance and inspiration the industries of the coal-tar colours and artificial therapeutic agents in their present form and extension would have been inconceivable.
He investigated the relation of benzene to benzoic acid and to other derivatives.
Cements such as marine glue are solutions of shellac, india-rubber or asphaltum in benzene or naphtha.
It may be synthetically prepared by the fusion of cymol sulphonic acid with caustic potash; by the action of nitrous acid on 1-methyl-2-amino-4-propyl benzene; by prolonged heating of 5 parts of camphor with r part of iodine; or by heating carvol with glacial phosphoric acid.
Lagodzinski (Berichte, 1895, 28, p. 1427) has synthesized alizarin by condensing hemipinic acid [(CH30)2C6H2(COOH)2] with benzene in the presence of aluminium chloride.
It separates from benzene and thiophene with one molecule of the "solvent of crystallization."
On oxidation it gives triphenylcarbinol, (C 6 H 5) 3 C OH, and reduction with hydriodic acid and red phosphorus gives benzene and toluene.
Considerable interest is attached to the remarkable series of hydrocarbons obtained by Gomberg (Ber., 1900, 33, p. 3150, et seq.) by acting on triphenylmethane chloride (from triphenylmethane carbinol and phosphorus pentachloride, or from carbon tetrachloride and benzene in the presence of aluminium chloride) and its homologues with zinc, silver or mercury.
Thus by using benzene, benzaldehyde and anthracene are obtained.
In these latter cases the reaction may proceed in different directions; thus, with the aromatic hydrocarbons, chlorine in the cold or in the presence of a carrier substitutes in the benzene nucleus, but in the presence of sunlight or on warming, substitution takes place in the side chain.
Cochineal also contains a fat and wax; cochineal wax or coccerin, C30H60(C31H6103)2, may be extracted by benzene, the fat is a glyceryl myristate C3H5(C14Hz702)3.
Many ortho and, para-compounds of the aromatic series (for example, the brom-phenols, benzene para-disulphonic acid) also yield resorcin on fusion with caustic potash.
Thioresorcin is obtained by the action of zinc and hydrochloric acid on the chloride of benzene meta-disulphonic acid.
It may be prepared by distilling calcium benzoate; by condensing benzene with benzoyl chloride in the presence of anhydrous aluminium chloride; by the action of mercury diphenyl on benzoyl chloride, or by oxidizing diphenylmethane with chromic acid.
Potash fusion converts it into benzene and benzoic acid.
On distillation with sulphuric acid, it is converted into mesitylene C 9 H 12 (symmetrical trimethyl benzene).
It crystallizes readily from benzene or acetic acid and explodes when subjected to shock or when heated.
Blom found that on brominating orthoacetamido-acetophenone in presence of water or acetic acid, the bromine goes into the benzene nucleus, whilst in chloroform or sulphuric acid or by use of bromine vapour it goes into the side chain as well.
Phosphorus is nearly insoluble in water, but dissolves in carbon bisulphide, sulphur chloride, benzene and oil of turpentine.
Those with the hydroxyl group in the benzene nucleus are prepared from the aminophenols by the Skraup reaction.
It is a liquid with an odour like that of benzene.
Benzene hexachloride, C 6 H 6 C1 61 is formed by the action of chlorine on benzene in sunlight.
The /3 form results by chlorinating boiling benzene in sunlight, and may be separated from the a variety by distillation in a current of steam.
Ethane, when heated to this degree, splits up into ethylene and hydrogen, whilst ethylene decomposes to methane and acetylene, and the acetylene at once polymerizes to benzene, styrolene, retene, &c. A portion also condenses, and at the same time loses some hydrogen, becoming naphthalene; and the compounds so formed by interactions amongst themselves build up the remainder of the hydrocarbons present in the coal tar, whilst the organic substances containing oxygen in the coal break down, and cause the formation of the phenols in the tar.
Of the first class, the light paraffin oils and pitch may be taken as examples; whilst benzene, naphthalene and retort carbon represent the second.
The formation of the second class of bodies is a great loss to the gas manufacturer, as, with the exception of the trace of benzene carried with the gas as vapour, these products are not only useless in the gas, but one of them, naphthalene, is a serious trouble, because any trace carried forward by the gas condenses with sudden changes of temperature, and causes obstructions in the service pipes, whilst their presence in the tar means the loss of a very large proportion of the illuminating constituents of the gas.
In 1876 M.P.E.Berthelot came to the conclusion that the illuminating value of the Paris coal gas was almost entirely due to benzene vapour.
But here again another mistaken idea arose, owing to a faulty method of estimating the benzene, and there is no doubt that methane is one of the most important of the hydrocarbons present, when the gas is burnt in such a way as to evolve from it the proper illuminating power, whilst the benzene vapour, small as the quantity is, comes next in importance and the ethylene last.
Its derivatives and its relation to benzene had been previously studied by the above and other experimenters, its relation to benzene being first proved experimentally by Cannizzaro and its constitution settled by Fittig and Tollens's synthesis from sodium and a mixture of methyl iodide and brombenzene.
It may be obtained synthetically by Fittig and Tollens's method (above); by Friedel and Craft's process, devised in 1877, of acting with aluminium chloride on a mixture of benzene and methyl chloride; this reaction leads to the production of higher homologues which may, however, break down under the continued action of the aluminium chloride; or by heating the toluene carboxylic acids obtained by oxidizing the higher homologues of benzene.
It is soluble in alcohol, ether, benzene and chloroform.
It is a fuming liquid, which is soluble in benzene and in acetic acid; it dissolves in water to form a deep blue solution.
In 1855 Adolph Wurtz had shown that when sodium acted upon alkyl iodides, the alkyl residues combined to form more complex hydrocarbons; Fittig developed this method by showing that a mixture of an aromatic and alkyl haloid, under similar treatment, yielded homologues of benzene.
The tri-iodide, AsI3 prepared by subliming arsenic and iodine together in a retort, by leading arsine into an alcoholic iodine solution, or by boiling powdered arsenic and iodine with water, filtering and evaporating, forms brick-red hexagonal tables, of specific gravity 4.39, soluble in alcohol, ether and benzene, and in a large excess of water; in the presence of a small quantity of water, it is decomposed with formation of hydriodic acid and an insoluble basic salt of the composition 4AsOI.
Terephthalic acid, formed by oxidizing para-diderivatives of benzene, or best by oxidizing caraway oil, a mixture of cymene and cuminol, with chromic acid, as almost insoluble in water, alcohol and ether; it sublimes without melting when heated.
Ten volumes of the purest coal-tar benzene were shaken for four hours with one volume of sulphuric acid, the acid layer was removed and neutralized with lead carbonate, and the lead thiophen sulphonate obtained was distilled with an equivalent quantity of ammonium chloride.
The purity of the product depends upon the quality of the benzene from which the nitrobenzene was prepared.
They are completely soluble in ether, carbon bisulphide, chloroform, carbon tetrachloride, petroleum ether, and benzene.
Carbon tetrachloride, chloroform, acetone and benzene are far too expensive.
There is a committee on toxicology which we gather looks at the toxicology of chemicals such as benzene (and perhaps even pesticides ).
Various solvents, such as benzene, alcohol and chloroform, will dissolve out the pigment, leaving the plastid colorless.
It is the hydrogen compound corresponding to P. Greiss' diazoimino benzene, C 6 H 5 N 3, which is prepared by the addition of ammonia to diazobenzene perbromide.
An aromatic primary amine is one in which the -NH 2 group is attached directly to a benzene ring.
This produces an electron which adds to the benzene ring to generate a radical anion.
An aromatic is a organic compound that contains a benzene ring in is molecule or has very similar chemical properties to benzene.
Many individual compounds are carcinogenic, including benzene, which is added to unleaded gasoline.
The Environment Agency issued two new reports covering volatile organic compounds and new Soil Guidance Values covering contamination from toluene and ethyl benzene.
It does, however, provide a useful indication of the uncertainties of the overall estimates of roadside benzene concentrations.
If methyl benzene is reacted with chlorine in the presence of uv light, substitution takes place in the alkyl side chain.
Aliphatic any non-aromatic organic compound Aromatic any organic compound containing de-localised electrons in a ring structure - e.g. benzene, benzoic acid.
Lindane is also widely known as gamma hexachlorocyclohexane (gamma-HCH) or gamma benzene hexachloride (gammaBHC ).
Dry hydrogen chloride gas is used in some cases, but these tend to involve aromatic esters (ones containing a benzene ring ).
Probe has speeded up AN experienced chartered geologist says levels of benzene discovered in Muirfield Close have been played down.
An aryl halide has a halogen atom attached directly to a benzene ring.
Fears were expressed that other cancer causing chemicals including phenol and benzene are also polluting the site.
However, nitro groups make the ring much less reactive than the original benzene ring.
Well, this can be explained by the presence of three bulky benzene rings (see below ).
The method of estimating future benzene roadside and background concentrations is similar to that used for calculating exceedances of the 5 ppb standard.
Phys., 1888 (6) 14, p. 435); by heating phenol carboxylic acids with baryta; and, in small quantities by the oxidation of benzene with hydrogen peroxide or nascent ozone (A.
Kekule was the forerunner of his celebrated benzene theory in particular, and of the universal application of structural formulae to the representation of the most complex organic compounds equally lucidly as the representation of the simplest salts.
Herrmann, Ann., 1882, 211, p. 306; also see below, Configuration of the Benzene Complex); the condensation of acetone dicarboxylic ester with malonic ester to form triketohexamethylene dicarboxylic ester (E.
Many diketo compounds suffer condensation between two molecules to form hydrobenzene derivatives; thus a, 7 -di-acetoglutaric ester, C 2 H S O 2 C(CH 3 CO) CH CH 2 CH(CO CH 3)CO 2 C 2 H 5, yields a methylketohexamethylene,whiles-acetobutyric ester,CH 3 CO (CH2)2C02C2N5, is converted into dihydroresorcinol or m-diketohexamethylene by sodium ethylate; this last reaction is reversed by baryta (see Decompositions of Benzene Ring).
The ring of this compound is ruptured by caustic soda with the formation of perchlorvinyl acrylic acid (5), which gives on reduction ethidine propionic acid (6), a compound containing five of the carbon atoms originally in the benzene ring (see Zincke, Ber., 18 94, 27, p. 33 6 4) (the carbon atoms are omitted in some of the formulae).
The pioneer in this field was August Kekule, who, in 1865 (Ann., 137, p. 129; see also his Lehrbuch der organischen Chemie), submitted his well-known formula for benzene, so founding the " benzene theory " and opening up a problem which, notwithstanding the immense amount of labour since bestowed upon it, still remains imperfectly solved.
The relative merits of the formulae of Kekule, Claus and Dewar were next investigated by means of the reduction products of benzene, it being Baeyer's intention to detect whether double linkages were or were not present in the benzene complex.
Wislicenus, Le Bel and van 't Hoff has resulted in the introduction of another condition which formulae for the benzene complex must satisfy, viz.
One of the most important applications of these values is found in the case of the constitution of benzene, where Thomsen decides in favour of the Claus formula, involving nine single carbon linkages, and rejects the Kekule formula, which has three single and three double bonds (see section IV.).
This holds for benzene and phenol, and is supported by the observations of Gossner on [1.3.5] trinitrobenzene and picric acid (1.3.5-trinitro, 2 oxybenzene); these last two substances assume rhombic forms, and picric acid differs from trinitrobenzene in having w considerably greater, with x and slightly less.
On distillation with zinc dust it forms cymene (1.4 methyl isopropyl benzene).
Benzene is manufactured from the low-boiling fractions of the coal-tar distillate '(see' Coal-Tar).
It sometimes separates with crystals of a solute as " benzene of crystallization," as for example with triphenylmethane, thio-p-tolyl urea, tropine, &c.
Bamberger, Ber., 1893.26, p. 49 6); by the oxidation of nitrosobenzene (below) with atmospheric oxygen; or by the decomposition of benzene diazonium nitrate mercury nitrite, Hg(NO 2) 2.2C 6 H 5 N 2 NO 3, with copper powder (A.
Well, this can be explained by the presence of three bulky benzene rings (see below).
There is a committee on toxicology which we gather looks at the toxicology of chemicals such as benzene (and perhaps even pesticides).
Exposure to ionizing radiation and to certain organic chemicals, such as benzene, is believed to increase the risk of developing leukemia.
People who are at an increased risk for developing leukemia because of proven exposure to ionizing radiation or exposure to the toxic liquid benzene, and people with Down syndrome, should undergo periodic medical checkups.
For example, exposure to ionizing radiation and to certain organic chemicals, such as benzene, is believed to increase the risks for getting leukemia.
Lindane-A benzene compound that is used to kill body and pubic lice.
Never pour water on the unit or use gasoline, benzene, paint thinner or other chemicals to try and clean the unit.