Aliphatics acidic hydrogen

Carboxylic acids react with xenon difluoride to produce unstable xenon esters The esters decarboxylate to produce free radical intermediates, which undergo fluonnation or reaction with the solvent system Thus aliphatic acids decarboxylate to produce mainly fluoroalkanes or products from abstraction of hydrogen from the solvent Perfluoro acids decarboxylate in the presence of aromatic substrates to give perfluoroalkyl aromatics Aromatic and vinylic acids do not decarboxylate [91] (equation 51)... 

Cinnamic Acid.—The reaction, which takes place when an aldehyde (aliphatic or aromatic) acts on the sodium salt of an aliphatic acid in presence of the anhychide, is known as Perkin s reaction, and has a ery wide application. Accoid-ing to the result of Fittig s researches on the properties of the unsaturated acids described below, the reaction occurs in two steps. The aldeh) de forms first an additive compound with the acid, the aldehyde caibon attaching itself to the n-carbon ii.e.i nevt the carbovyl) of the acid. A saturated hydiOKy-acid is formed, which is stable, if the a-carbon is attached to only one atom of hydrogen, as in the case of isobutync acid,... 

Two different sets of experimental conditions have been used. Buu-Hoi et al. and Hansen have employed the method introduced by Papa et using Raney nickel alloy directly for the desulfurization in an alkaline medium. Under these conditions most functional groups are removed and this method is most convenient for the preparation of aliphatic acids. The other method uses Raney nickel catalysts of different reactivity in various solvents such as aqueous ammonia, alcohol, ether, or acetone. The solvent and activity of the catalyst can have an appreciable influence on yields and types of compounds formed, but have not yet been investigated in detail. In acetic anhydride, for instance, desulfurization of thiophenes does not occur and these reaction conditions have been employed for reductive acetylation of nitrothiophenes. Even under the mildest conditions, all double bonds are hydrogenated and all halogens removed. Nitro and oxime groups are reduced to amines. 

The Japp-Klingemann reaction is a special case of the aliphatic diazo coupling. For a successful reaction, the dicarbonyl substrate 2 should bear a sufficiently CH-acidic hydrogen. 

The procedure is modified for the reaction of preformed cyanohydrins with chiral amines39. I11 a further variation, Schiff bases of aliphatic aldehydes with optically active 1-arylalkyl-amines are transformed with liquid hydrogen cyanide to the corresponding a-aminonitrilcs, which, after acid hydrolysis, give the /V-aryUilkylamino acids. Hydrogenation then yields the a-amino acids40 41. 

In commercial-scale epoxidation of unsaturated organic compounds, 50-70% hydrogen peroxide is added dining 2-8 h to the stirred mixture of unsaturated compound, aliphatic acid and acid catalyst at 50-80°C, the rate of addition being... 

We note also that the schemes discussed until now only show the oxidation of the ethylene glycol moiety. In the PECT copolymer, the 1,4-cyclohexylenedi-methylene moiety is also available for oxidation. Indeed, given that the oxidizable hydrogens are tertiary, one reasonably expects a greater ease of production of a radical from that center. Grossetete et al. [11] reported such to be the case with the observation that photo-oxidation reactions occurred much faster with the PECT copolymer than with PET itself. The aliphatic acids that they reported, as identified by the SF4 treatment, could also account for previous aliphatic acid reports [25], This is also additional support that the photo-oxidation mechanism is operating as proposed (Scheme 18.4). 

The phase-transfer catalysed reaction of alkyl halides with potassium carbonate in dimethylacetamide, or a potassium carbonate/potassium hydrogen carbonate mixture in toluene, provides an excellent route to dialkyl carbonates without recourse to the use of phosgene [55, 56], An analogous reaction of acid chlorides with sodium hydrogen carbonate in benzene, or acetonitrile, produces anhydrides (3.3.29.B, >80%), although there is a tendency in acetonitrile for aliphatic acid chlorides to hydrolyse yielding the acids [57]. 

Electrochemical oxidation of aliphatic tertiary amines in acetonitrile together with compounds having weakly acidic hydrogens, such as dimethyl malonate, leads to addition of the malonate anion to the immonium cation intermediate. 2,4,6-Collidine is added to combine with protons, which are released during reaction [90],... 

The radical-anions of aliphatic nitrocompounds are detectable in aqueous solution as transient intermediates formed during continuous electrolysis in the cavity of the esr spectrometer [4], Decay of the species occurs by protonation and then further reactions. 2-Methyl-2-nitropropane has no acidic hydrogens so that it can be examined in aqueous alkaline solution where the radical-anion is not protonated. Over the pH range 9-11, this radical-anion decays by a first order process with k = 0.8 0.1 s at 26 C. Decay results from cleavage of the carbon-nitrogen bond to give a carbon centred radical and nitrite ion. Ultimately, the di-(ferr,-butyI)nitrone radical is formed in follow-up reactions [5],... 

The tetraiodide is slightly soluble in acetone and in ethanol (about 1 gm PoI4/liter) but is insoluble in dilute mineral acids and in ethers, aliphatic acids and hydrocarbons. It is slowly hydrolyzed by water and by concentrated alkali, the white product presumably being a basic iodide, and is decomposed by chlorine, hypochlorite, nitrite, and hot concentrated nitric acid. It does not react with ammonia gas but is reduced to the metal on heating in hydrogen sulfide. Suspensions of the tetraiodide in 0.1 N hydriodic acid are unaffected by hydrazine or sulfur dioxide, even on boiling, and there is no evidence for a diiodide. 

The carboxylic dimer has a center of symmetry only the asymmetrical C=0 stretching mode absorbs in the IR. Hydrogen bonding and resonance weaken the C=0 bond, resulting in absorption at a lower frequency than the monomer. The C=0 group in dimerized saturated aliphatic acids absorbs in the region of 1720-1706 cm1. 

Aromatic carboxylic acids are, in general, less reactive towards sulfur tetrafluoride than aliphatic acids. The reactivity strongly depends on the nature of the aromatic ring substituents. Benzoic, 4-methylbenzoic and particularly 4-methoxybenzoic acid (la-c) give poor yields of the respective (trifluoromethyl)benzenes 2a-c, but the yields of 2 increase with increasing electron-withdrawing power of the substituents.122 Yields of (trifluoromethyl)benzenes substantially increase, even under milder conditions, in the presence of an excess of anhydrous hydrogen fluoride.123... 

The method described here, discovered by Newman and Beal,6 employs triethylamine (1 equivalent) to react with the hydrogen chloride thus only one equivalent of diazomethane is necessary. This modification is restricted to the preparation of aromatic diazoketones-aliphatic acid chlorides give a mixture of products. ... 

Reactions have been described for RH = amines, alcohols, aromatics, aliphatics, perfluoroalkyls, hydrogen halides, and thiols (167). Another recent use of S2OfiF2 in organic chemistry has been in the synthesis of lactones by the remote oxidation of carboxylic acids using a... 

In 1939 it was observed16 that anhydrous liquid hydrogen fluoride is an excellent agent for effecting intramolecular acylation of aryl substituted aliphatic acids. Since that time a number of cyclizations have been performed with this reagent (Table VIII). 

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