Propene, hydration

The reactions are reversible and the equilibrium is less favourable for the decomposition of a thiol to an alkene and H2S than of the corresponding alcohol to an alkene and H20 under the same conditions data on equilibria in the reactions of propene with water [245] and with hydrogen sulphide [246] indicate that the equilibrium constant of propene hydration is smaller than that for propene sulphidation by approximately two orders of magnitude. 

With ion exchangers as catalysts for olefin hydration, special attention was paid to transport problems within the resin particles and to their effects on the reaction kinetics. In all cases, the rate was found to be of the first order with respect to the olefin. The role of water is more complicated but it is supposed that it is absorbed by the resin maintaining it in a swollen state the olefin must diffuse through the water or gel phase to a catalytic site where it may react. The quantitative interpretation depends on whether the reaction is carried out in a vapour system, liquid-vapour system or two-phase liquid system. In the vapour system [284, 285], the amount of water sorbed by the resin depends on the H20 partial pressure it was found at 125—170°C and 1.1—5.1 bar that 2-methyl-propene hydration rate is directly proportional to the amount of sorbed water... 

CH3. OH. CH2HgI, might serve as that intermediate but that would be difficult to reconcile with relative reactivities. The rate-determining step for allylmercuric iodide cleavage could be written as shown in equation (58) if the carbonium ion were the intermediate. This is analogous to the rate-determining step for propene hydration (equation... 

The excellent octane blending properties of DIPE for reformulated gasoline are now well established (4,5). Alternative routes to diisopropyl ether synthesis include propene hydration followed by IPA dehydration - pioneered by Mobil Corporation (6). With low-cost, crude acetone feedstocks as the basic building block, we believe that this new, one-step, route to DIPE (equation 2) enjoys very attractive, long-term, economics (2). 

During the butene hydration on catalysts with 0.65 mm particle size, the reactions were retarded by internal diffusion occurring at temperatures above or equal to 115 C. Equilibrium constant values of butene hydration reactions beyond a 120-150 °C temperature range proved to be much lower than for propene hydration. 

Other processes include the alkylation of phenol using alkenes, and the manufacture of acrylate and methacrylate esters from alcohols and the corresponding acids. Olefin hydration reactions require more extreme conditions but Deutsche Texaco have developed a resin-catalysed propene hydration process to form isopropyl alcohol [125]. The reaction is run at 130 C near the upper limit for sulphonic acid resins, but a species with sufficient lifetime is available. There is even some evidence that butene hydration is now carried out similarly. Finally, B.P. Chemicals have recently disclosed [126] a new olefin isomerisation process yielding 2,3-dimethylbut-l-ene. Here the conditions required to favour the isomerisation versus rapid oligomerisation had to be identified to establish a viable process. 

Besides the above reactions, any kind of acid-catalyzed reactions such as cracking of cumene, alkylation of benzene with propene, hydration of olefins, isomerization of cyclopropane, esterification of acetic acid with ethanol, etc. can be used for the estimation of the acidic property of solid acids. Skeletal isomerization of li-butane to -butane is used to check whether a solid acid has superacidity, since the isomerization is known not to be catalyzed even by 100% sulfuric acid. However, it should be noticed that the differentiation between acid strength and acid amount is not easy from the measurement of catalytic activity for an acid-catalyzed reaction. Characterization of acid catalysts by use of model reactions has been reviewed recently by Guisnet. ... 

We say that propene has undergone hydration Overall H and OH have added across... 

Isopropyl alcohol is prepared from petroleum by hydration of propene With a boil mg point of 82°C isopropyl alcohol evaporates quickly from the skin producing a cool mg effect Often containing dissolved oils and fragrances it is the major component of rubbing alcohol Isopropyl alcohol possesses weak antibacterial properties and is used to maintain medical instruments m a sterile condition and to clean the skin before minor surgery... 

Arrange the following compounds in order of increasing rate of acid-catalyzed hydration ethylene, 2-cyclopropylpropene, 2-methylpropene, propene, 1-cyclopro-pyl-l-methoxyefliene. Explain the basis of your prediction. 

FIGURE 6.9 Mechanism of acid-catalyzed hydration of 2-methyl propene. 

The rates of hydration of alkenes increase dramatically with increasing alkyl substitution (see table at left). This is usually attributed to the relative stabilities of carbocations formed as intermediates in the initial (and rate-hmiting) step of the reaction, e.g., for hydration of propene. 

The mechanism for the acid-catalysed hydration reaction is very similar to that for the hydrohalogenation of alkenes and also proceeds via a carbocatlon intermediate. It is outlined below using water and propene. 

Like the hydrohalogenation reaction, the hydration of unsymmetrlcal alkenes, such as propene, leads to two products. As well as propan-2-ol, propan-l-ol is also formed. 

Due to electron withdrawing effect of nitro group and electron releasing effect of methoxy group. 11.20 (i) Hydration of Propene. 

Acrolein (CHj=CHCHO, also known as 2-propenal) is a a,P-unsaturated aldehyde that can be transformed reducfively to saturated or unsaturated alcohols by reduction of the C = 0 or C = C double bonds (Claus 1998). In addition, a,P-unsaturated aldehydes may undergo hydration reactions in aqueous solutions. It was observed that, under acidic (pH12) conditions, acrolein is hydrated to 3-hydroxypropanal (Jensen and Hashtroudi 1976). In a natural subsurface environment, where pH may range from 6.5 to 8.5, the hydration rate of acrolein increases with the pH and its half-life decreases. Based on an experiment to analyze effects of iron on acrolein transformation, Oh et al. (2006) note that, under acidic conditions (e.g., pH = 4.4), acrolein disappears rapidly from solution in the presence of elemental iron (Fig. 16.1). Moreover, the formation of... 

Eine Losung aus Tetrabutylammoniumchlorid und Kaliumfluorid-Bis-hydrat kann eben-falls verwendet werden. So erhalt man z.B. aus l,3-Diphenyl-3-oxo-propen mit Nitro-methan 1,3-Diphenyl-4-nitro-l-oxo-butan zu 95%4... 

Propene is used as a starting material for numerous other compounds. Chief among these are isopropyl alcohol, acrylonitrile, and propylene oxide. Isopropyl alcohol results from the hydration of propylene during cracking and is the primary chemical derived from propylene. Isopropyl alcohol is used as a solvent, antifreeze, and as rubbing alcohol, but its major use is for the production of acetone. Acrylonitrile is used primarily as a monomer in the production of acrylic fibers. Polymerized acrylonitrile fibers are produced under the trade names such as Orion (DuPont) and Acrilan (Monsanto). Acrylonitrile is also a reactant in the synthesis of dyes, pharmaceuticals, synthetic rubber, and resins. Acrylonitrile production occurs primarily through ammoxidation of propylene CH3- CH = CH2 + NH3 + 1.5 02—> CH2 = CH - C = N + 3 H20. 

Propylene oxide is produced from the chlorohydrination of propene similar to the process used to make ethylene oxide (see Ethene). A major use of propylene oxide involves hydrating propylene oxide to produces propylene glycol, propylene polyglycols, and other polyether polyols. These products are used to produce both rigid and flexible polyurethane foams, but they are also used to produce polyurethane elastomers, sealants, and adhesives. 

The mechanisms of these reactions have much in common and have been studied extensively from this point of view. They also have very considerable synthetic utility. The addition of water to alkenes (hydration) is particularly important for the preparation of a number of commercially important alcohols. Thus ethanol and 2-propanol (isopropyl alcohol) are made on a very large scale by the hydration of the corresponding alkenes (ethene and propene) using sulfuric or phosphoric acids as catalysts. The nature of this type of reaction will be described later. 

Exercise 10-15 Arrange ethene, propene, and 2-methylpropene in order of expected ease of hydration with aqueous acid. Show your reasoning. 

Recently, there have been many new catalysts developed for the hydration of alkenes, although most are more suited for industrial purposes. These catalysts include zeolites such as pentasil,283 mordenite286 and ferrierite,183 as well as those containing heavy metals,287 heteropolyacids288 and sulfonic acid exchange resins.289 It is reported that some of these new catalysts perform as high as 99.6% conversions and 99.4% selectivity, as illustrated in the hydration of propene into 2-propanol (equation 192).290... 

---