Selective alcohols

Acid mixtures are used to oxidize and remove the dark materials. Proper control gives a series of bleached waxes. A white wax requires double refining and reduces the yield to about 30% of the cmde wax input. A series of synthetic waxes is prepared by separating the acids and alcohols produced during saponification of the wax and reesterifying them with acids or alcohols selected to give desired properties of hardness, solubiHty, emulsification, and gloss. 

Triphenylmethyl ethers (trityl ethers) have been used to protect primary alcohols selectively [see (14)] , and unhindered secondary alcohols. 

The reaction of an alcohol with an acid chloride is strongly affected by steric hindrance. Bulky groups on either partner slow down the reaction considerably, resulting in a reactivity order among alcohols of primary > secondary > tertiary. As a result, it s often possible to esterify an unhindered alcohol selectively in the presence of a more hindered one. This can be important in complex syntheses... 

Reduction of ketone 85 with NaBkLt in THF formed the a-alcohol selectively (98, >23 1 dr, 55 % yield) which was then protected as the mesylate... 

Recent work done by Xiong et al.84 on Co/AC (activated carbon) catalysts showed that a Co2C species formed during the catalyst reduction in hydrogen at 500°C. Evidence for the carbide in the Co/AC catalysts was obtained by x-ray diffraction and XPS measurements, and the formation of this Co2C species reduced the FTS activity over the Co-based catalysts. The presence of bulk carbide also seems to enhance alcohol selectivity.85... 

Increasing pressure affects alcohols selectivity (Figure 9.21). The contents of alcohols in product carbon number fractions generally increase, and the shape of the distribution curve changes, exhibiting a second maximum at higher reaction pressure.29 At Nc = 2 the alcohol content increases drastically from ca. 3 to ca. 55 mole% when the pressure is raised from 1.2 to 33 bar. 

Selective oxidation of allylic alcohols.1 This zircononcene complex when used in catalytic amount can effect an Oppenauer-type oxidation of alcohols, including allylic ones, in the presence of a hydrogen acceptor, usually benzaldehyde or cyclohexanone. This system oxidizes primary alcohols selectively in the presence of secondary ones. Thus primary allylic alcohols are oxidized to the enals with retention of the configuration of the double bond in 75-95% yield. The method is not useful for oxidation of propargylic alcohols. 

Ferrate salts have been used under phase-transfer catalytic conditions for the oxidation of alcohols. Selective oxidation of allylic and benzylic alcohols to the corresponding aldehydes occurs under mild conditions [4],... 

Fig. 15.15 Cinnamyl alcohol selectivity as a function of conversion in the selective hydrogenation of cinnamaldehyde over differently supported Ru catalysts. Reactions conditions as listed in Tab. 15.4. Data compiled from literature [120,122,123,126], HSAG high-surface area graphite AC activated carbon.

Some selective serotonin re-uptake inhibitors are powerful inhibitors of cytochrome P450 enzymes and the metabolism of e.g. tricyclic antidepressants can be inhibited resulting in serious toxicity. Additive sedation can be expected when given in combination with CNS depressants such as benzodiazepines but also with alcohol. Selective serotonin re-uptake inhibitors should not be used in combination with monoamine oxidase inhibitors as fatal reactions have been reported. 

A similar chain-growth mechanism was said to occur with the first molybdenum-sulfur-potassium based catalysts of table I (15). For such a chain-growth mechanism, the heavier the average molecular weight of alcohols, the greater the formation of heavy compounds and, more often than not, the lower the alcohols selectivity. Furthermore, in Fischer-Tropsch type catalysts (24,25) diffusion limitations, mostly due to the presence of liquid products condensed in the micro porosity, increase with the size of diffusing molecules. These molecules are capable of... 

Here we report on a new TEMPO based catalyst system for the oxidation of primary and secondary alcohols selectively to aldehydes and ketones using NaOCl as a terminal oxidant. 

Substrate [NEtj] (M) r " (min ) Saturated alcohol Selectivity Aldeyde %T E -isomer Other product... 

Myers RD, Borg S, Mossberg R. Antagonism by naltrexone of voluntary alcohol selection in the chronically drinking macaque monkey. Aicohoi 1986 3 383-388. 

More recent research efforts have focused on the development of other possible catalysts such as promoted Raney copper,371,403 catalysts prepared from intermetal-lic precursors,362,371 386 404-406 and catalysts that tolerate high C02 content.407 Catalyst modifications allowed to shift the selectivity to the formation of higher alcohols.208,408 110 For example, in a process developed by IFP, a multicomponent oxide catalyst is applied with copper and chromium as the main components 410 By this method, 70-75% total alcohol selectivities and 30-50% of C2 and higher alcohol selectivities can be achieved at 12-18% conversion levels (260-320°C, 60-100 atm). 

Yeast Disorders. Many genera and species of yeasts are found on grapes. Undesirable yeasts must be inhibited as soon as the grapes are crushed, and the primary fermentation must be controlled by inoculating the must with pure strains of yeast. This ensures a clean fermentation in a reasonable time with efficient conversion of the grape sugars to alcohol. Selecting pure yeasts is a matter of preference for individual wineries, but the preference in the United States has been for yeasts which do not produce undesirable by-products. 

PS-PB-PS 33-80% Dioxane + ethanol THF + allyl alcohol (selective for PS) Solubilization of PB and PS-PB-PS triblock Micellar structure with solubilizate SLS Tuzar et ai (1982)... 

Kspecially interesting is the fact that the epoxide ring is activated by intramolecular chelation" <37). Pnor to this discovery, 18 standard reagents had tailed in opening the epoxide.7 The reducing agent attacks activated epoxide 37 selectively from the sterically more accessible side and produces a tertiary alcohol Selective protection of the secondary alcohol leads to compound 16... 

Hydrogenation of a-acylamino or a-halogeno (3-keto phosphonates with a BINAP-Ru complex gives the corresponding syn alcohols selectively with >98% ee (Scheme 1.58) [243a,251]. The sense of enantio- and diastereoface discrimination is the same as that in the case of ot-substituted [3-keto carboxylic esters (see Table of Scheme 1.57). 

Later, the chiral bicyclic phosphine catalyst 5a was also used for kinetic resolution of allylic alcohols with isobutyric anhydride [8, 9]. The best results were obtained for trisubstituted allylic alcohols - selectivity factors ranged from 32 to 82 at -40 °C. 

The DMAP derivative 19a was tested for kinetic resolution of a variety of mono esters of cyclic cis diols (rac-20a-i) (Scheme 12.5) [15]. Catalyst 19a afforded selectivity factors up to 12.3 and highly enantioenriched mono esters 20 with conversions of 65-73%. For this type of reaction the selectivity of the Campbell catalyst 19b was similar (selectivity factor 13.2, Scheme 12.5) [16a], The latter catalyst was identified by screening of a 31-mer library prepared from the parent N-(4-pyridyl)-a-methylproline and a variety of amines [16a], The solid-phase-bound forms of N-(4-pyridyl)-a-methylproline, as reported by Anson et al. [16b], are easily recyclable acylation catalysts affording selectivity factors up to 11.9 in the kinetic resolution of the secondary alcohol rac-20b (Scheme 12.5). In the kinetic resolution of N-acylated amino alcohols, selectivity factors up to 21 were achieved by use of the Kawabata-Fuji catalyst 19a, and up to 18.8 by use of the Campbell system 19b (Scheme 12.5) [15, 16a]. 

While there is little evidence to suggest that alcohol produces its pharmacological effect via a specific "alcohol receptor", some lipids do show a particular vulnerability to the disorganizing effects of the drug. For example, alcohol selectively inhibits monoamine oxidase-B, and not the A form, in human platelets and brain similarly, it inhibits sodium/ potassium-dependent adenosine triphosphatase in the neuronal membrane but not in the glial membrane. 

From a functional point of view, Nguyen et al. examined the pervapora-tion characteristics of CA/P(VP-co-VAc) blends for application as alcohol-selective membrane materials [107]. The blend membranes were shown to be very efficient in the removal of ethanol from its mixture with ethyl tert-butyl ether (ETBE). ferf-butyl ethers are octane-value enhancers for gasoline, and the synthesis requires an excess of alcohol in the reaction to reach high... 

---