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Ketones improvements

Refiners will turn to reformulated motor fuels where the octane number will be increased by alkylate or oxygenated compounds. It has indeed been shown for a long time that oxygenated compounds, alcohols, ethers and ketones Improved the octane number of hydrocarbon-based blends (Whitcomb, 1975). [Pg.352]

The control of reactivity to achieve specific syntheses is one of the overarching goals of organic chemistry. In the decade since the publication of the third edition, major advances have been made in the development of efficient new methods, particularly catalytic processes, and in means for control of reaction stereochemistry. For example, the scope and efficiency of palladium- catalyzed cross coupling have been greatly improved by optimization of catalysts by ligand modification. Among the developments in stereocontrol are catalysts for enantioselective reduction of ketones, improved methods for control of the... [Pg.970]

Aldehydes and ketones could be asymmetrically a-amino-oxylated [36, 37] or a-aminated [38] to corresponding poly-functional compounds 8 and 9 by proline-catalyzed reactions with nitrosobenzene or diethyl azodicarboxylate in molten imidazoUum salts (Scheme 22.5). As compared to those in common solvents, the yields of a-aminoxylation products 8 of both aldehydes and ketones improved significantly in the IL medium and the enantioselectivity was excellent Yields and enantiomeric enrichment of hydrazino-aldehydes 9 were somewhat lower. The ionic environment considerably accelerated the processes and the (S)-proline/IL system could be quantitatively recovered after completion of the aminoxylation reaction and reused (5-6 times) without any loss of catalytic performance. Aldehyde-derived products 8 and 9 (R = H) could be reduced to chiral 1,2-diol derivatives 10 or configurationally stable heterocycles 11, which are valuable intermediates in asymmetric synthesis. [Pg.621]

All the yields given refer to one circulation of the acid (or acids) over the catalyst, but can be improved by recirculating the product, from which the water layer has bmn removed, over the catalyst. With the higher ketones, the second circulation may result in carbonisation of the catalyst, thus rendering it inefficient. [Pg.340]

The conversion of a carbonyl compound by ammonium polysulphide solution into an amide with the same number of carbon atoms is known as the Willgerodt reaction. The procedure has been improved by the addition of about 40 per cent, of dioxan or of pyridine to increase the mutual solubility of the ketone and aqueous ammonium polysulphide the requisite temperature is lowered to about and the yield is generally better. [Pg.923]

A further improvement is embodied in the Klndler variation of the Willgerodt reaction this consists in heating the ketone with approximately equal amounts of sulphur and a dry amine instead of aqueous ammonium polysulphide. The principal product is a thioamide, and hydrolysis with acid or alkali affords the carboxylic acid, usually in good yield. [Pg.923]

A new method of synthesizing 2-aminothiazoles from thiourea and ketones has been developed by Dodson (225, 261, 280). It was improved by King and Lavacek (328) and later taken up by several other workers (328, 779, 798) (Method B). [Pg.213]

The yield can be raised to 28% if the Hofmann elimination is conducted in the presence of a water-soluble copper or iron compound (19). Further improvements up to 50% were reported when the elimination was carried out in the presence of ketone compounds (20). Further beneficial effects have been found with certain cosolvents, with reported yields of greater than 70% (8). [Pg.430]

Since adipic acid has been produced in commercial quantities for almost 50 years, it is not surprising that many variations and improvements have been made to the basic cyclohexane process. In general, however, the commercially important processes stiU employ two major reaction stages. The first reaction stage is the production of the intermediates cyclohexanone [108-94-1] and cyclohexanol [108-93-0], usuaHy abbreviated as KA, KA oil, ol-one, or anone-anol. The KA (ketone, alcohol), after separation from unreacted cyclohexane (which is recycled) and reaction by-products, is then converted to adipic acid by oxidation with nitric acid. An important alternative to this use of KA is its use as an intermediate in the manufacture of caprolactam, the monomer for production of nylon-6 [25038-54-4]. The latter use of KA predominates by a substantial margin on a worldwide basis, but not in the United States. [Pg.240]

Eigure 2 shows that even materials which are rather resistant to oxidation ( 2/ 1 0.1) are consumed to a noticeable degree at high conversions. Also the use of plug-flow or batch reactors can offer a measurable improvement in efficiencies in comparison with back-mixed reactors. Intermediates that cooxidize about as readily as the feed hydrocarbon (eg, ketones with similar stmcture) can be produced in perhaps reasonable efficiencies but, except at very low conversions, are subject to considerable loss through oxidation. They may be suitable coproducts if they are also precursors to more oxidation-resistant desirable materials. Intermediates which oxidize relatively rapidly (/ 2 / i — 3-50 eg, alcohols and aldehydes) are difficult to produce in appreciable amounts, even in batch or plug-flow reactors. Indeed, for = 50, to isolate 90% or more of the intermediate made, the conversion must... [Pg.337]

These reversible reactions are cataly2ed by bases or acids, such as 2iac chloride and aluminum isopropoxide, or by anion-exchange resias. Ultrasonic vibrations improve the reaction rate and yield. Reaction of aromatic aldehydes or ketones with nitroparaffins yields either the nitro alcohol or the nitro olefin, depending on the catalyst. Conjugated unsaturated aldehydes or ketones and nitroparaffins (Michael addition) yield nitro-substituted carbonyl compounds rather than nitro alcohols. Condensation with keto esters gives the substituted nitro alcohols (37) keto aldehydes react preferentially at the aldehyde function. [Pg.100]

Polymerization Solvent. Sulfolane can be used alone or in combination with a cosolvent as a polymerization solvent for polyureas, polysulfones, polysUoxanes, polyether polyols, polybenzimidazoles, polyphenylene ethers, poly(l,4-benzamide) (poly(imino-l,4-phenylenecarbonyl)), sUylated poly(amides), poly(arylene ether ketones), polythioamides, and poly(vinylnaphthalene/fumaronitrile) initiated by laser (134—144). Advantages of using sulfolane as a polymerization solvent include increased polymerization rate, ease of polymer purification, better solubilizing characteristics, and improved thermal stabUity. The increased polymerization rate has been attributed not only to an increase in the reaction temperature because of the higher boiling point of sulfolane, but also to a decrease in the activation energy of polymerization as a result of the contribution from the sulfonic group of the solvent. [Pg.70]

Appllca.tlons. MCA is used for the resolution of many classes of chiral dmgs. Polar compounds such as amines, amides, imides, esters, and ketones can be resolved (34). A phenyl or a cycloalkyl group near the chiral center seems to improve chiral selectivity. Nonpolar racemates have also been resolved, but charged or dissociating compounds are not retained on MCA. Mobile phases used with MCA columns include ethanol and methanol. [Pg.100]

Random copolymers of vinyl chloride and other monomers are important commercially. Most of these materials are produced by suspension or emulsion polymerization using free-radical initiators. Important producers for vinyl chloride—vinyUdene chloride copolymers include Borden, Inc. and Dow. These copolymers are used in specialized coatings appHcations because of their enhanced solubiUty and as extender resins in plastisols where rapid fusion is required (72). Another important class of materials are the vinyl chloride—vinyl acetate copolymers. Principal producers include Borden Chemicals Plastics, B. F. Goodrich Chemical, and Union Carbide. The copolymerization of vinyl chloride with vinyl acetate yields a material with improved processabihty compared with vinyl chloride homopolymer. However, the physical and chemical properties of the copolymers are different from those of the homopolymer PVC. Generally, as the vinyl acetate content increases, the resin solubiUty in ketone and ester solvents and its susceptibiUty to chemical attack increase, the resin viscosity and heat distortion temperature decrease, and the tensile strength and flexibiUty increase slightly. [Pg.185]

The oxidation of cyclohexane to a mixture of cyclohexanol and cyclohexanone, known as KA-od (ketone—alcohol, cyclohexanone—cyclohexanol cmde mixture), is used for most production (1). The earlier technology that used an oxidation catalyst such as cobalt naphthenate at 180—250°C at low conversions (2) has been improved. Cyclohexanol can be obtained through a boric acid-catalyzed cyclohexane oxidation at 140—180°C with up to 10% conversion (3). Unreacted cyclohexane is recycled and the product mixture is separated by vacuum distillation. The hydrogenation of phenol to a mixture of cyclohexanol and cyclohexanone is usually carried out at elevated temperatures and pressure ia either the Hquid (4) or ia the vapor phase (5) catalyzed by nickel. [Pg.425]

Based on this variety of properties, amorphous polybutadiene has found a niche in the mbber industry. Moreover, it appears that the anionicaHy prepared polymer is the only polymer that can be functionalized by polar groups. The functionalization is done by using aromatic substituted aldehydes and ketones or esters. Functionalization has been reported to dramatically improve polymer-filler interaction and reduce tread hysteresis (70—73). [Pg.534]

Polymers used for seat and plug seals and internal static seals include PTFE (polytetrafluoroeth ene) and other fluorocarbons, polyethylene, nylon, polyether-ether-ketone, and acetal. Fluorocarbons are often carbon or glass-filled to improve mechanical properties and heat resistance. Temperature and chemical compatibility with the process fluid are the key selec tion criteria. Polymer-lined bearings and guides are used to decrease fric tion, which lessens dead band and reduces actuator force requirements. See Sec. 28, Materials of Construction, for properties. [Pg.790]

An improved method for the preparation of A" -3-ketones from 4-bromo compounds was described by Mattox and Kendall. This procedure involves dehydrobromination of the 2,4-dinitrophenylhydrazone and subsequent cleavage of the hydrazone with pyruvic acid ... [Pg.288]

The bromination of 4,5-j -dihydrocortisone acetate in buffered acetic acid does not proceed very cleanly (<70%) and, in an attempt to improve this step in the cortisone synthesis, Holysz ° investigated the use of dimethylformamide (DMF) as a solvent for bromination. Improved yields were obtained (although in retrospect the homogeneity and structural assignments of some products seem questionable.) It was also observed that the combination of certain metal halides, particularly lithium chloride and bromide in hot DMF was specially effective in dehydrobromination of 4-bromodihydrocortisone acetate. Other amide solvents such as dimethylacetamide (DMA) and A-formylpiperidine can be used in place of DMF. It became apparent later that this method of dehydrobromination is also prone to produce isomeric unsaturated ketones. When applied to 2,4-dibromo-3-ketones, a substantial amount of the A -isomer is formed. [Pg.290]

Joly s method (or modifications) is the best procedure for preparing A " -3-ketones and can be extended to the elimination of hydrogen bromide from a-bromo ketones of all types. Rearrangement is sometimes observed but is not often serious. Selectivity can be improved in some instances by lowering the reaction temperature. The method has been found useful for the preparation of A" -3-ketones from 6-halo-A" -3-ketones ... [Pg.292]


See other pages where Ketones improvements is mentioned: [Pg.292]    [Pg.55]    [Pg.292]    [Pg.55]    [Pg.339]    [Pg.176]    [Pg.80]    [Pg.70]    [Pg.133]    [Pg.490]    [Pg.309]    [Pg.115]    [Pg.102]    [Pg.172]    [Pg.181]    [Pg.519]    [Pg.160]    [Pg.162]    [Pg.232]    [Pg.70]    [Pg.100]    [Pg.85]    [Pg.534]    [Pg.101]    [Pg.105]    [Pg.226]    [Pg.643]    [Pg.786]    [Pg.459]    [Pg.7]    [Pg.286]   
See also in sourсe #XX -- [ Pg.42 ]




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