Isopropyl alcohol, reduction

Acetone is reduced by amalgamated magnesium largely to a bimolecu lar reduction product, tetramethylethylene glycol or plnacol (CHjjjClOHjClOHjiCHj), some isopropyl alcohol is also formed ... 

For many reductions it is not necessary to distil the reagent. Dilute the dark solution, prepared as above to the point marked with an asterisk, to 1 htre with dry isopropyl alcohol this gives an approximately one molar solution. Alternatively, prepare the quantity necessary for the reduction, using the appropriate proportions of the reagents. 

Place 35 ml. of a M solution of aluminium tsopropoxide or 7 g. of solid aluminium tsopropoxide, 450 ml. of dry isopropyl alcohol and 21 g. of purified benzaldehyde (Section IV,115) in a 1 litre round-bottomed flask. Fit a short reflux condenser (no water in the cooling jacket) or better a Hahn condenser (2) (containing a 1 cm. layer of ethyl alcohol in the iimer tube) to the flask and arrange for slow distillation from a water bath at the rate of 3-6 drops per minute. Continue the heating until a negative test for acetone is obtained after 5 minutes of total reflux (6-9 hours) if the volume of the mixture falls below 200 ml. during the reduction, add more isopropyl alcohol. Remove the reflux or Hahn condenser and distil off (Fig. II, 13, 3) most of the isopropyl alcohol under atmospheric pressure from a suitable oil bath. Hydrolyse the... 

The vapor-phase reduction of acrolein with isopropyl alcohol in the presence of a mixed metal oxide catalyst yields aHyl alcohol in a one-pass yield of 90.4%, with a selectivity (60) to the alcohol of 96.4%. Acrolein may also be selectively reduced to yield propionaldehyde by treatment with a variety of reducing reagents. 

In the former USSR, there reportedly are two technologies in use one is old anthrahydroquinone autoxidation technology and the other is closed-loop isopropyl alcohol oxidation technology. Production faciUties include several smaller, 100-150-t/yr isopropyl alcohol oxidation plants and a larger, 15,000-t/yr plant, which reportedly is being expanded to 30,000-t/yr. Differences in this technology as compared to the Shell Chemical Co. process are the use of oxygen-enriched air in the oxidation step and, catalytic reduction of the coproduct acetone back to isopropyl alcohol per equation 21. 

A second process has two steps. The first step is oxidation of propylene [115-07-1] to acrolein and the second step is reduction of acrolein to ahyl alcohol by a hydrogen transfer reaction, using isopropyl alcohol (25). 

Amination. Isopropyl alcohol can be aminated by either ammonolysis ia the presence of dehydration catalysts or reductive ammonolysis usiag hydrogeaatioa catalysts. Either method produces two amines isopropylamine [75-31-0] and diisopropylamine [108-18-9]. Virtually no trisubstituted amine, ie, triisopropyl amine [122-20-3], is produced. The ratio of mono- to diisopropylamine produced depends on the molar ratio of isopropyl alcohol and ammonia [7664-41-7] employed. Molar ratios of ammonia and hydrogen to alcohol range from 2 1—5 1 (35,36). 

Other Processes. Isopropyl alcohol can be prepared by the Hquid-phase oxidation of propane (118). It is produced iacidentaHy by the reductive condensation of acetone, and is pardy recovered from fermentation (119). Large-scale commercial biological production of isopropyl alcohol from carbohydrate raw materials has also been studied (120—123). 

Isopropyl Alcohol and Aluminum Isopropoxide. This is called the Meer-wein-Ponndotf-Verley reduction It is reversible, and the reverse reaction is known as the Oppenauer oxidation (see 19-3) ... 

An unusual reaction is used to form a KRe 4 HjO. The reduction of potassium perrhenate in en-H20 solutions by potassium metal yields a white solid containing the Rh ion mixed with KOH. Extraction with isopropyl alcohol gives a colloidal brown liquid containing a mixture of KOH, isopropyl alcohol and the rhenidc. Fractional extraction of the liquid gives a gray solid that contains 5.5-60% KRe 4 HjO... 

The pioneering work of Posner, on the reduction of carbonyl compounds with isopropyl alcohol and alumina [116], has now been adapted to an expeditious solvent-free reduction procedure that utilizes aluminum alkoxides under microwave irradiation conditions (Scheme 6.37) [117]. 

Complexes of N-N bonded dinitrogen dioxide, such as depicted in pathway B of Scheme 5, would appear to be necessary in order to effect the formation of the N-N bond. This has been treated theoretically as a metal promoted reductive coupling of 2 NO to form a hyponitrite complex (79). The Cu Tp112) system was also shown to catalyze NO oxidations of benzyl and isopropyl alcohol to benzaldehyde and acetone (Eq. (37)). Electrospray mass spectrometry indicated that higher... 

The reaction which is carried out in presence of isopropyl alcohol is also called Meerwein-Pondorf-Verley reduction. An example is the reduction of crotonaldehyde to crotyl alcohol. 

In practice, the equivalent synthon of 2 was l-cyano-4,5-dimethoxybenzocyclobutene 22 (Scheme 3.7) which on heating generates a reactive o-quinodimethane by a conrotatory electrocyclic ring opening process (Cf. Scheme 3.7) and reacts, at 150-160 °C, with the 3,4-dihydroisoquinoleine 23 to give 80-88%yield of 13-cyanoprotoberberine 24. A simple reductive decyanation with lithium in liquid ammonia in the presence of isopropyl alcohol afforded xylopinine (19) in 84.6% yield [19]. 

Several reagents reduce aldehydes preferentially to ketones in mixtures of both. Very high selectivity was found in reductions using dehydrated aluminum oxide soaked with isopropyl alcohol and especially diisopropylcarbinol [755], or silica gel and tributylstamane [756]. The best selectivity was achieved with lithium trialkoxyalumimm hydrides at —78°. In the system hexanal/ cyclohexanone the ratio of primary to secondary alcohol was 87 13 at 0° and 91.5 8.5 at —78° with lithium tris(/er/-butoxy)aluminum hydride [752], and 93.6 6.4 at 0° and 99.6 0.4 at —78° with lithium tris(3-ethyl-3-pentyl-oxy)aluminum hydride [752],... 

Chemical reduction of aromatic aldehydes to alcohols was accomplished with lithium aluminum hydride [5i], alane [770], lithium borohydride [750], sodium borohydride [757], sodium trimethoxyborohydride [99], tetrabutylam-monium borohydride [777], tetrabutylammonium cyanoborohydride [757], B-3-pinanyl-9-borabicyclo[3.3.1]nonane [709], tributylstannane [756], diphenylstan-nane [114], sodium dithionite [262], isopropyl alcohol [755], formaldehyde (crossed Cannizzaro reaction) [i7i] and others. 

In nitro aldehydes both the nitro group and the aldehyde group are readily reduced by catalytic hydrogenation. It may be difficult, if not impossible to hydrogenate either function separately. More dependable methods are reduction by alane [787] or by isopropyl alcohol and aluminum isopropoxide Meerwein-Ponndorf) [788] to nitro alcohols, and by stannous chloride [789, 790], titanium trichloride [590] or ferrous sulfate [218] to amino aldehydes Procedure 38, p. 214). 

Different stereoselectivities caused by solvent effects are demonstrated in the reduction of dihydroisophorone (3,3,5-trimethylcyclohexanone) with sodium borohydride which gave less stable tranj-3,3,5-trimethylcyclohexanol (with axial hydroxyl) by reduction in anhydrous isopropyl alcohol (55-56%), in anhydrous tert-butyl alcohol (55%), in 65% aqeuous isopropyl alcohol (59.5%), in anhydrous ethanol (67%), and in 71% aqueous methanol (73%) (the balance to 100% being the more stable cis isomer with equatorial hydroxyl) [849]. 

Reduction of unsaturated ketones to unsaturated alcohols is best carried out Nit v complex hydrides. a,/3-Unsaturated ketones may suifer reduction even at the conjugated double bond [764, 879]. Usually only the carbonyl group is reduced, especially if the inverse technique is applied. Such reductions are accomplished in high yields with lithium aluminum hydride [879, 880, 881, 882], with lithium trimethoxyaluminum hydride [764], with alane [879], with diisobutylalane [883], with lithium butylborohydride [884], with sodium boro-hydride [75/], with sodium cyanoborohydride [780, 885] with 9-borabicyclo [3.3.1]nonane (9-BBN) [764] and with isopropyl alcohol and aluminum isopro-... 

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