Aldehydes sentence example

aldehydes
  • By the action of dehydrating agents they are converted into aldehydes or ketones.
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  • In the presence of a dehydrating agent (such as acetic anhydride), it combines with aldehydes to form compounds of the type R CH: C(COOH) 2, or their decomposition products (formed by loss of C02) R CH: CH COOH.
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  • Taking as types hydrogen, hydrochloric acid, water and ammonia, he postulated that all organic compounds were referable to these four forms: the hydrogen type included hydrocarbons, aldehydes and ketones; the hydrochloric acid type, the chlorides, bromides and iodides; the water type, the alcohols, ethers, monobasic acids, acid anhydrides, and the analogous sulphur compounds; and the ammonia type, the amines, acid-amides, and the analogous phosphorus and arsenic compounds.
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  • Compounds containing the group - CH: O are known as aldehydes (q.v.), while the group >C: O (sometimes termed the carbonyl or keto group) characterizes the ketones (q.v.).
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  • This group may be considered as resulting from the fusion of a carbonyl (:CO) and a hydroxyl (HO-) group; and we may expect to meet with compounds bearing structural resemblances to the derivatives of alcohols and aldehydes (or ketones).
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  • 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.
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  • Recent researches have shown that the law originally proposed by Kopp - " That the specific volume of a liquid compound (molecular volume) at its boiling-point is equal to the sum of the specific volumes of its constituents (atomic volumes), and that every element has a definite atomic value in its compounds " - is by no means exact, for isomers have different specific volumes, and the volume for an increment of CH 2 in different homologous series is by no means constant; for example, the difference among the esters of the fatty acids is about 57, whereas for the aliphatic aldehydes it is 49.
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  • Thus in the normal fatty alcohols, acids, esters, nitriles and ketones, the increment per CH 2 is 19°-21°; in the aldehydes it is 26°-27°.
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  • The same difference attends the introduction of the methyl group into many classes of compounds, for example, the paraffins, olefines, acetylenes, aromatic hydrocarbons, alcohols, aldehydes, ketones and esters, while a slightly lower value (157.1) is found in the case of the halogen compounds, nitriles, amines, acids, ethers, sulphides and nitro compounds.
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  • Those derived from aldehydes are known as aldoximes, those from ketones as ketoximes.
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  • They are prepared by condensing thio-amides with a-haloid ketones or aldehydes, the thio-amide reacting as the tautomeric thio-imino acid.
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  • In the vegetable kingdom glucose occurs, always in admixture with fructose, in many fruits, especially grapes, cherries, bananas, &c.; and in combination, generally with phenols and aldehydes belonging to the aromatic series, it forms an extensive class of compounds termed glucosides.
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  • The aldehydes may be prepared by the careful oxidation of primary alcohols with a mixture of potassium dichromate and sulphuric acid,-3R�CH OH+K Cr 07+4H SO = K2S04+ Cr (SO) +7H O+3R�CHO; by distilling the calcium salts of the fatty acids with calcium formate; and by hydrolysis of the acetals.
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  • The aldehydes are characterized by their great chemical reactivity.
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  • With hydrocyanic acid aldehydes form the cyanhydrins R�CH(OH)�CN.
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  • The hydrazones are crystalline substances which are of value in the characterization of the aldehydes.
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  • Aldehydes are converted into resins by the action of caustic alkalies.
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  • The reaction is a general one for all aldehydes with zinc methyl and zinc ethyl, but not with the higher zinc alkyls.
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  • Grignard (Comptes Rendus, 1900 et seq.) showed that aldehydes combine with magnesium alkyl iodides (in absolute ether solution) to form addition products, which are decomposed by water with the formation of secondary alcohols, thus from acetaldehyde and magnesium methyl iodide, isopropyl alcohol is obtained.
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  • The chief aldehydes are shown in the following table: - For formaldehyde see Formalin.
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  • Unsaturated aldehydes are also known, corresponding to the olefine alcohols; they show the characteristic properties of the saturated aldehydes and can form additive compounds in virtue of their unsaturated nature.
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  • The aromatic aldehydes resemble the aliphatic aldehydes in most respects, but in certain reactions they exhibit an entirely different behaviour.
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  • These compounds may be considered as 5-triazolones, a series of isomeric 3-triazolones resulting from the condensation of phenylsemicarbazide with aromatic aldehydes in the presence of an oxidant.
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  • In organic chemistry, his study of the ketones and aldehydes, begun in 1857, provided him with the subject of his other doctoral thesis.
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  • It is found also that some monosaccharoses behave as aldehydes whilst others contain a keto group; those having the first character are called aldoses, and the others ketoses.
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  • Wallach, Ber., 1881, 14, P. 421); by the action of reducing agents on nitroparaffins; by the action of zinc and hydrochloric acid on aldehyde ammonias (German Patent 73,812); by the reduction of the phenylhydrazones and oximes of aldehydes and ketones with sodium amalgam in the presence of alcohol and sodium acetate (J.
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  • They form condensation products with aldehydes, benzaldehyde and aniline forming benzylidene aniline, C 6 H 5 N: CHC 6 H 5, and when heated with acids they form anilides.
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  • The calcium salts distilled with calcium formate yield aldehydes r distilled with soda-lime, ketones result.
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  • It condenses with aldehydes and ketones to produce semioxamazones.
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  • Aldehydes also combine directly with ammonia.
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  • It combines with aldehydes and ketones to form the nitriles of oxy-acids, for example, CH 3 CHO+HCN=CH 3 CH(OH)(CN).
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  • The calcium salt, when heated with the calcium salts of higher homologues, gives aldehydes.
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  • Hantzsch has shown that aldehydes condense with aceto-acetic ester and ammonia to produce the homologues of pyridine, thus: R R [[Rooc Ch 2 Cho Ch 2 Coor Rooc C - Ch - C Coor]] + + 1 = Ii II +3H20.
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  • For the formation of primary and secondary alcohols see Aldehydes and Ketones.
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  • This solution is frequently used as a test reagent for the detection of aldehydes, giving, in most cases, a red coloration on the addition of a small quantity of the aldehyde.
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  • They do not reduce silver solutions, and are not so readily oxidized as the aldehydes.
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  • It unites with aldehydes to form esters of ketonic acids, and with aniline yields anilido-acetic acid.
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  • And so, as a rule, from isomeric alcohols, those containing a group - CH 2.0H, yield by oxidation aldehydes and are distinguished by the name primary; whereas those containing CH OH, called secondary, produce ketones.
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  • Villiger (Be y ., 1901, 34, pp. 2679, 3612) showed that many organic compounds (ethers, alcohols, aldehydes, ketones, &c.) behave towards acids, particularly the more complex acids, very much like bases and yield crystallized salts in which quadrivalent oxygen must be assumed as the basic element.
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  • It condenses readily with aldehydes, yielding with formaldehyde, on the addition of.
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  • The reaction is apparently a R C / N general one for all aldehydes.
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  • The reaction is a perfectly general one, for the aniline may be replaced by other aromatic amines and the aldehyde by other aldehydes, and so a large number of quinoline homologues may be prepared in this way.
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  • It is a colourless liquid which boils at 247° C. The -CH 3 group is very reactive, condensing readily with aldehydes and with phthalic anhydride.
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  • Aldehydes and Ketones.-The aldehydes are prepared in the usual manner from primary alcohols and acids.
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  • With aldehydes and ketones it forms oximes.
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  • The primary alcohols are first oxidized to aldehydes, which, on further oxidation, yield acids containing the same number of carbon atoms as in the original alcohol.
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  • Tertiary alcohols yield neither aldehydes nor ketones, but a mixture of two or more acids.
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  • Primary alcohols are obtained by decomposing their sulphuric acid esters (from sulphuric acid and the olefines) with boiling water; by the action of nitrous acid on primary amines; or by the reduction of aldehydes, acid chlorides or acid anhydrides.
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  • Secondary alcohols result from the reduction of ketones; and from the reaction of zinc alkyls on aldehydes or formic acid esters.
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  • The aldehydes and ketones provided material for his earlier work.
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  • He observed that aldehydes and ketones may suffer reduction in neutral, alkaline, and sometimes acid solution to secondary and tertiary glycols, substances which he named pinacones; and also that certain pinacones when distilled with dilute sulphuric acid gave compounds, which he named pinacolines.
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  • They combine with aldehydes and ketones, with elimination of water and formation of mercaptals and mercaptols.
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  • The products of oxidation are not yet fully known; most likely they consist of lower fatty acids, such as formic and acetic acids, and perhaps also of aldehydes and ketones.
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  • The presence of that hydrogen atom makes aldehydes very easy to oxidize.
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  • The aldol condensation (using aldehydes, ketones, two different carbonyl partners, and the intramolecular variant ).
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  • It does not contain aldehydes, phenols or chlorine.
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  • The dominance of sodium formate suggests corrosion was influenced by organic acids and/or aldehydes emitted by the old wooden storage cases.
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  • Members were asked whether any further information on other aldehydes was required, and their comments on the DH Toxicology Unit review welcomed.
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  • Aliphatic conjugated and aromatic aldehydes failed to produce urticarial skin reactions with the exception of acrolein.
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  • For example, methanal, ethanal and propanone - the common small aldehydes and ketones - are miscible with water in all proportions.
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  • It was further commented that the DETR paper indicated that other simple aldehydes were generally present at lower concentrations than formaldehyde and acetaldehyde.
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  • There are two functional group isomers of which you need to be aware: alcohols and ethers aldehydes and ketones What is here?
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  • Thus with hydroxylamine aldehydes yield aldoximes, R CH: N OH, and ketones, ketoximes, R 2 C: N OH (see Oximes), while phenyl hydrazine gives phenylhydrazones, R 2 C:N NH C 6 H 5 (see Hydrazones).
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  • Thus in the normal fatty alcohols, acids, esters, nitriles and ketones, the increment per CH 2 is 19°-21°; in the aldehydes it is 26°-27°.
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  • The aldehydes may be prepared by the careful oxidation of primary alcohols with a mixture of potassium dichromate and sulphuric acid,-3R�CH OH+K Cr 07+4H SO = K2S04+ Cr (SO) +7H O+3R�CHO; by distilling the calcium salts of the fatty acids with calcium formate; and by hydrolysis of the acetals.
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  • With hydrocyanic acid aldehydes form the cyanhydrins R�CH(OH)�CN.
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  • The aldehydes condense readily with acetoacetic ester in the presence of ammonia, to pyridines (see Pyridine), whilst 0.
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  • Citronellal, rhodinal and geranial are also unsaturated aldehydes (see Terpenes).
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  • In the case of aromatic aldehydes, acids are also obtained by means of " Cannizzaro's reaction " (see Benzaldehyde).
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  • About 1874 he abandoned the manufacture of coal-tar colours and devoted himself exclusively to research in pure chemistry, and among the discoveries he made in this field was that of the reaction known by his name, depending on the condensation of aldehydes with fatty acids (see Cinnamic Acid).
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  • Ketones do not polymerize in the same way as aldehydes, but under the influence of acids and bases yield condensation products; thus acetone gives mesityl oxide, phorone and mesitylene (see below).
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  • Soc. 18 9 3, 63, p. 469); and by passing hydrochloric acid gas into a mixture of aromatic aldehydes and their cyanhydrins (E.
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  • 1876, 9, p. 1524; 1877, 10, p. 1113), or by heating aldehydes and ortho-aminophenols to high temperature (G.
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  • It is a colourless liquid which boils at 247° C. The -CH 3 group is very reactive, condensing readily with aldehydes and with phthalic anhydride.
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  • They represent a large number of classes of substances of which the most important are: (1) Hydrocarbons, such as pinene in oil of turpentine, camphene in citronella oil, limonene in lemon and orange-peel oils, caryophyllene in clove oil and cumene in oil of thyme; (2) ketones, such as camphor from the camphor tree, and irone which occurs in orris root; (3) phenols, such as eugenol in clove oil, thymol in thyme oil, saffrol in sassafras oil, anethol in anise oil; (4) aldehydes, such as citral and citronellal, the most important constituents of lemon oil and lemon-grass oil, benzaldehyde in the oil of bitter almonds, cinnamic aldehyde in cassia oil, vanillin in gum benzoin and heliotropin in the spiraea oil, &c.; (5) alcohols and their esters, such as geraniol (rhodinol) in rose oil and geranium oil, linalool, occurring in bergamot and lavender oils, and as the acetic ester in rose oil, terpineol in cardamom oil, menthol in peppermint oil, eucalyptol in eucalyptus oil and borneol in rosemary oil and Borneo camphor; (6) acids and their anhydrides, such as cinnamic acid in Peru balsam and coumarin in woodruff; and (7) nitrogenous compounds, such as mustard oil, indol in jasmine oil and anthranilic methyl-ester in neroli and jasmine oils.
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  • The characteristic flavour and odour of wines and spirits is dependent on the proportion of higher alcohols, aldehydes and esters which may be produced.
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