Adipic acid from cyclohexene

The entrapped complexes are known to catalyze selective oxidation or hydrogenation reactions, depending mainly on the complexed transition metal cation [4, 82, 84]. Recently, two exciting examples have been published describing the synthesis of adipic acid from cyclohexene [93] or even from cyclohexane [94], respectively (cf Figure 6). 

The RuOa-catalyzed (NaI04 as oxidant) synthesis of adipic acid from cyclohexene in the two-phase system CO2- H2O, has been reported [57],... 

Catalytic oxidation in a two-phase water-C02 medium has been investigated for the synthesis of adipic acid from cyclohexene [2b]. The substrate and products were dissolved in the supercritical fluid while the oxidant (e.g. NaI04) resided in the aqueous phase. The catalyst RUO2 was oxidized to RUO4 in the aqueous phase which in turn oxidized the substrate, presumably at the liquid-supercritical interface. This is an example of a Type Ilia process. Unfortunately, catalyst efficiency was fairly low (five catalytic cycles), probably due to deactivation by formation of carbonates in the aqueous phase. 

Using chemistry presented in this and previous chapters, propose a synthesis for adipic acid from cyclohexene. 

The PW4O2J anion turned out to be a valuable catalyst for a number of oxidations of organic substrates with hydrogen peroxide, including the epoxidation of olefins and their cleavage, e.g. to get adipic acid from cyclohexene or from the intermediate 1,2-cyclohexanediol. " ... 

Cyclohexene will undergo an ozonolysis reaction to yield adipic acid upon oxidative workup. Cyclohexene is produced from cyclohexanol by a dehydration (elimination) reaction. The synthesis of adipic acid from cyclohexanol is... 

Environmental Aspects. Airborne particulate matter (187) and aerosol (188) samples from around the world have been found to contain a variety of organic monocarboxyhc and dicarboxyhc acids, including adipic acid. Traces of the acid found ia southern California air were related both to automobile exhaust emission (189) and, iadirecfly, to cyclohexene as a secondary aerosol precursor (via ozonolysis) (190). Dibasic acids (eg, succinic acid) have been found even ia such unlikely sources as the Murchison meteorite (191). PubHc health standards for adipic acid contamination of reservoir waters were evaluated with respect to toxicity, odor, taste, transparency, foam, and other criteria (192). BiodegradabiUty of adipic acid solutions was also evaluated with respect to BOD/theoretical oxygen demand ratio, rate, lag time, and other factors (193). 

Isophorone usually contains 2—5% of the isomer P-isophorone [471-01-2] (3,5,5-trimethyl-3-cyclohexen-l-one). The term a-isophorone is sometimes used ia referring to the a,P-unsaturated ketone, whereas P-isophorone connotes the unconjugated derivative. P-lsophorone (bp 186°C) is lower boiling than isophorone and can be converted to isophorone by distilling at reduced pressure ia the presence of -toluenesulfonic acid (188). Isophorone can be converted to P-isophorone by treatment with adipic acid (189) or H on(Ill) acetylacetoate (190). P-lsophorone can also be prepared from 4-bromoisophorone by reduction with chromous acetate (191). P-lsophorone can be used as an iatermediate ia the synthesis of carotenoids (192). 

The epoxidation method developed by Noyori was subsequently applied to the direct formation of dicarboxylic acids from olefins [55], Cyclohexene was oxidized to adipic acid in 93% yield with the tungstate/ammonium bisulfate system and 4 equivalents of hydrogen peroxide. The selectivity problem associated with the Noyori method was circumvented to a certain degree by the improvements introduced by Jacobs and coworkers [56]. Additional amounts of (aminomethyl)phos-phonic acid and Na2W04 were introduced into the standard catalytic mixture, and the pH of the reaction media was adjusted to 4.2-5 with aqueous NaOH. These changes allowed for the formation of epoxides from ot-pinene, 1 -phenyl- 1-cyclohex-ene, and indene, with high levels of conversion and good selectivity (Scheme 6.3). 

Diol (7) can dehydrate only to (6) it is a 1,6-difunctionalised compound which can be made from an adipic diester (8), and hence from cyclohexene. Dehydration occurs readily in acid solution to give a high yield of TM (6),... 

Wacker oxidation of styrene has also been performed in [bmim][BF4] and [bmim][PF6], at 60 °C with H2O2 and PdCF as a catalyst [19]. This system gave yields of acetophenone as high as 92 % after 3 h. Hydrogen peroxide may also be used under phase transfer conditions for alkene bond cleavage, to produce adipic acid (an intermediate in the synthesis of nylon-6) from cyclohexene (Scheme 9.9). 

Chemical/Physical. Gaseous products formed from the reaction of cyclohexene with ozone were (% yield) formic acid (12), carbon monoxide (18), carbon dioxide (42), ethylene (1), and valeraldehyde (17) (Hatakeyama et al., 1987). In a smog chamber experiment conducted in the dark at 25 °C, cyclohexane reacted with ozone. The following products and their respective molar yields were oxalic acid (6.16%), malonic acid (6.88%), succinic acid (0.63%), glutaric acid (5.89%), adipic acid (2.20%), 4-hydroxybutanal (2.60%), hydroxypentanoic acid (1.02%), hydroxyglutaric acid (2.33%), hydroxyadipic acid (1.19%), 4-oxobutanoic acid (6.90%), 4-oxopentanoic acid (4.52%), 6-oxohexanoic acid (4.16%), 1,4-butandial (0.53%), 1,5-pentanedial (0.44%), 1,6-hexanedial (1.64%), and pentanal (17.05%). 

Adipic acid historically has been manufactured predominantly from cyclohexane and, to a lesser extent, phenol. During the 1970s and 1980s, however, much research has been directed to alternative feedstocks, especially butadiene and cyclohexene, as dictated by shifts in hydrocarbon markets. All current industrial processes use nitric acid in the final oxidation stage. Growing concern with air quality may exert further pressure for alternative routes as manufacturers seek to avoid NO, abatement costs, a necessary part of processes dial use nitric acid. 

No atoms are lost in the cleavage reaction so that cheap cyclohexene 6 is used to make adipic acid 7 for nylon manufacture. Any of the oxidative cleavage methods from the last chapter could be used Vogel1 has a recipe using concentrated nitric acid on cyclohexanol 8 that presumably goes by dehydration to the alkene 6 followed by oxidation, and other methods are probably used industrially. 

Although aldehydes are obtained from the cleavage of double bonds by ruthenium tetroxide under neutral conditions (Section 3.8.3.4), carboxylic acids are produced under alkaline or acidic conditions. For example, the oxidation of cyclohexene by Ru04 under alkaline conditions has been reported to give adipic acid in yields of 86-95%. ... 

The literature of this reaction to 1940 has been adequately reviewed. The emphasis up to that time was placed on obtaining higher yields of carbonyl compounds by hydrolysis of the ozonides. Several methods have been described for the oxidative cleavage of ozonides to acids. These procedures may prove valuable in the synthesis of certain acids. By adding the ozonide of 1-tridecene to an alkaline silver oxide suspension at 95°, a 94% yield of lauric acid is obtained. Decomposition of ozonides with 30% hydrogen peroxide is described for the preparation of 5-methyl-hexanoic acid (67%) from 6-methyl-l-heptene and of adipic acid (60%) from cyclohexene. A study of solvents for ozonolysis has been made. ... 

Caprolactam (world production of which is about 5 million tons) is mostly produced from benzene through three intermediates cyclohexane, cyclohexanone and cyclohexanone oxime. Cyclohexanone is mainly produced by oxidation of cyclohexane with air, but a small part of it is obtained by hydrogenation of phenol. It can be also produced through selective hydrogenation of benzene to cyclohexene, subsequent hydration of cyclohexene and dehydrogenation of cyclohexanol. The route via cyclohexene has been commercialized by the Asahi Chemical Company in Japan for adipic acid manufacturing, but the process has not yet been applied for caprolactam production. 

The environmental impact of the cyclohexane oxidation could also be reduced. An alternative is to start from benzene and make a selective hydrogenation to form cyclohexene. Ru-based supported catalysts working in the liquid phase and in the presence of a co-catalysts such as Zn (Asahi Chemical Industry process) are selective in the reaction, with yields up to about 60% [247], but with cyclohexane as the main by-product. Cyclohexene is hydrated in the liquid phase with an MFI zeolite as catalyst at moderate temperature (100-130 °C). This reaction is very selective (>99%). This route was primarily developed for the synthesis of adipic acid, but could be used also to reduce the number of products and separation costs in the production of cyclohexanone. 

Reconnection is the usual strategy for synthesising 1,6 dlfunctlonallsed compounds since the cyclohexenes required for the oxidative cleavage are easily made. Adipic acid (1) is available from cyclohexene Itself and Is a source of five-membered rings by condensation reactions Chapter 19). 

To convert olefins into carboxylic acids in this way it is preferable to oxidize the primary fission products of the ozonide in a subsidiary reaction. Particularly good results were obtained by Asinger using a hot suspension of silver oxide116 and by Wilms using peracetic acid 117 Wilms thus obtained adipic acid in yields of about 90% from cyclohexene ... 

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