Saturated ketone

Isolated double bonds do not interfere with this reaction sequence, but other ketones (saturated or a, -unsaturated) will also form enol acetates, which in turn are capable of further reaction with 7V-iodosuccinimide. 

Ketones Saturated open-chain ketones and six-membered cyclic ketones absorb at 1715 cm-1., five-membered cyclic ketones absorb at 1750 cm J, and ketones next to a double bond or an aromatic ring absorb at 1690 cm-1. 

Reduction of carbon-carbon double bond Microalgae easily reduce carbon-carbon double bonds in enone. Usually, the reduction of carbonyl group and carbon-carbon double bond proceeds concomitantly to afford the mixture of corresponding saturated ketone, saturated alcohol, and unsaturated alcohol because a whole cell of microalgae has two types of reductases to reduce carbonyl and olefinic groups. The use of isolated reductase, which reduces carbon-carbon double bond chemoselectively, can produce saturated ketones selectively. 

Substrate Conversion [%] Saturated ketone [%] Saturated alcohol [%] Unsaturated Selectivity alcohol [%] [%] ... 

Catalyst P lr ratio % Conversion (h) % Unsaturated alcohol % Saturated aldehyde/ ketone % Saturated alcohol... 

The curves for log(kK/s ) and log(kK/s ) of acetophenone are parallel in the range pAT << PH << pAT and the vertical distance between them then equals pAtE = log(kK/s 1) — log /s-1). Most ketones are very weak bases, pAt < 0, so that the parameter does not affect the shape of the pH-rate profiles in the range pH > 1. Base catalysis of ketonization saturates at pH = pAr , while the rate of enolization continues to rise, so that the curves for kE and kK eventually cross at higher pH. At still higher pH, the rate constant kE exceeds that of kK = k o and kobs follows kK. The crossing point, for which kE = kK, lies at pH = pAT = 18.3 for acetophenone (Fig. 3), which is outside the accessible pH range when ionic strength I is limited to 0.1 m, but pA is readily calculated from Equation (2). 

Kieselguhr G impregnated with 0.1M EDTA ethyl methyl ketone saturated 164, 165 with Mcllvaine buffer pH 4.7 or alcohol later plates exposed to ammonia TC 56 ETC 30 ... 

Reduction of ketones. Saturated and conjugated ketones can be reduced by the reagent to alcohols, probably by a mechanism similar to electrochemical reduction (as illustrated for acetophenone in scheme I). In some cases, ptnacols are formed as well. Thus acetophenone is reduced to the alcohol (45 % yield) and the pinacol (45% yield). Generally the alcohol is the predominant product. For example, benzophenonc is reduced to benzhydrol in 98 % yield. a,)3-Unsaturated ketones are reduced to saturated alcohols. Reduction of camphor gives predominantly the exo-alcohol note that reduction with sodium in alcohol or with potassium, in the presence of graphite (not intercalated), gives predominantly the endo-alcohol. 

Niobium and tantalum can also be separated by solvent extraction (p. 572) Nb is extracted almost quantitatively from HCl solution by methyldioctyl-amine in xylene while Ta remains in the acid. (Leddicotte and Moore, 1952). Chromatographic methods (p. 570) are also possible. Thus Mercer and Williams (1952) separated Nb and Hf from ores containing Ti and other metals. The fluorides were adsorbed on paper pulp elution with methyl ethyl ketone saturated with water extracted the tantalum equilibration of the column with a 1% solution of HF in the ketone arrested the movement of Ti, Zr... 

Activated manganese dioxide (MnO2) reliably oxidizes acetylenic, allylic, and benzylic alcohols to aldehydes and ketones. Saturated primary and secondary alcohols are also oxidized, albeit more slowly. The two main concerns are the activity of the manganese dioxide and the slow filtration of salts after the reaction. Activated MnOi is available commercially or may be prepared. 

MEMBERED RINfe KETONESi 4-MEMBERED RINO KETONES SATURATED ALDE YDES... 

In 2002, Snapper and Hoveyda reported a chiral peptide 15-Al(OiPr)3 complex for the cyanosilylation of ketones (Scheme 19.9). This catalyst system exhibited excellent results (67->98% peld and 80-95% enantiomeric excess) for aromatic (cyclic and acyclic) and aliphatic ketones (saturated and unsaturated). Notably, the first example of catalytic enantioselective cyanide addition to an alkynyl ketone was developed. Meanwhile, the chiral ligand 15 was recyclable, readily modifiable and easily synthesised in six steps with 75% overall yield. 

The easily prepared, stable solid reagent diphenylamine-borane (Ph2NH BH8) has been shown to be more reactive than aliphatic amine-boranes and almost as reactive as borane-THF for the reduction of ketones acids are also reduced to alcohols. Polyethylene glycols (PEG) catalyse the reduction of ketones by sodium borohydride under phase-transfer (PT) conditions, for example in solid-liquid PT with PEG as solvent. The solid zinc borohydride-dimethylformamide complex reduces aldehydes and ketones to alcohols, but only one hydrogen atom from each tetrahydridoborate unit is utilized. The different rates of reduction of various classes of ketone (saturated aliphatic faster than aromatic, and a -unsaturated very slow) suggest a possible selectivity between ketones. The corresponding cadmium complex, prepared in situ, reacts similarly. Lithium methylborohydride, LiMeBHj, prepared as shown in equation (1), where... 

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