Ethene hydration

The equilibrium constant for ethene hydration is considerably greater than for methanal hydration, largely because the carbon-carbon double bond is weaker. Even so, methanal adds water rapidly and reversibly at room temperature without need for a catalyst. The corresponding addition of water to ethene occurs only in the presence of strongly acidic catalysts (Section 10-3E, Table 15-2). 

As we saw earlier (Section 22.4), ethanol can be made from ethene by adding water in the presence of an acid catalyst. This process is referred to as hydration ... 

The catalyst is a mixture of copper, zinc oxide, and chromium(lll) oxide. Ethanol is produced in large quantities throughout the world by the fermentation of carbohydrates. It is also prepared by the hydration of ethene in an addition reaction ... 

The acid-catalyzed hydration of alkenes follows Markovnikov s rule => the reaction does not yield 1° alcohols except in the special case of the hydration of ethene. 

Most ethanol for industrial purposes is produced by the acid-catalyzed hydration of ethene. 

Fig. 1 compares the activities of vanadium-, cobalt- and nickel- based catalysts in ODH of ethane. Representative catalysts contained between 2.9 and 3.9 wt.% of metal. It is to be pointed out that metal oxide-like species was not present at any of the catalysts, as its presentation is generally the reason in the activity-selectivity decrease. The absence of metal oxide-like species was evidenced by the absence of its characteristic bands in the UV-Vis spectra of hydrated and dehydrated catalysts (not shown in the Figure). The activity of catalysts was compared (i) at 600 °C, (ii) using reaction mixture of 9.0 vol. % ethane and 2.5 vol. % oxygen in helium, and (iii) contact time W/F 0.12 g. i.s.ml 1. These reaction conditions represent the most effective reaction conditions for V-HMS catalysts [4] The ethane conversions, the ethene yields and the selectivity to ethene varied between 13-30 %, 5-16 %, and 37-78 %, respectively, depending on the type of metal species (Co, Ni, V) and support material (A1203, HMS, MFI). 

The larger hydrocarbon molecule has been broken down into a mixture of a shorter chain alkane plus an alkene. Both of these products are useful the alkane for the manufacture of petrol and the alkene for the manufacture of ethanol, by hydration, and plastics such as (poly)ethene. 

Much ethanol is manufactured by the hydration of ethene. The reaction is an addition reaction between steam and ethene at 300 °C, in the presence of a solid phosphoric acid catalyst, at a pressure of about 70 atmospheres. 

Hydrate to 273° alcohol (H+, H20) 1° from ethene can rearrange (Markovnikov)... 

Nowadays, large quantities of ethanol are obtained by hydration of ethene (Section 11.4). 

Write the mechanism of hydration of ethene to yield ethanol. 

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 Heck arylation of ethene with iodoarenes was investigated with a preformed [PdCl2(tppms)2] catalyst and gave the product styrenes in 60-100% yield (115). In contrast, when the in situ system Pd(OAc)2 -T 2tppms was used as a precursor, the conversion was less effective and yielded the hydration products. 

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. 

Some of the reactions we have mentioned are used for large-scale industrial production. For example, ethanol is made in quantity by the hydration of ethene, using an excess of steam under pressure at temperatures around 300° in the presence of phosphoric acid ... 

A dilute solution of ethanol is obtained, which can be concentrated by distillation to a constant-boiling point mixture that contains 95.6% ethanol by weight. Dehydration of the remaining few percent of water to give absolute alcohol is achieved either by chemical means or by distillation with benzene, which results in preferential separation of the water. Ethanol also is made in large quantities by fermentation, but this route is not competitive for industrial uses with the hydration of ethene. Isopropyl alcohol and tert-butyl alcohol also are manufactured by hydration of the corresponding alkenes. 

Ethanol is by far the most important of the alcohols and is often just called alcohol . Ethanol can be produced by fermentation (p. 236) as well as by the hydration of ethene (Chapter 14, p. 224). It is a neutral, colourless, volatile liquid which does not conduct electricity. 

Explain why the hydration of this alkene occurs 1015 times faster than the hydration of ethene ... 

ALLO-OCIMENE TENPIN HYDRATE TENPENE ETHENS PINE OIL MALEIC RESINS OIL ADDITIVES [Pg.1286]

In this context it is also worth mentioning that Showa Denko has developed a new process for the direct oxidation of ethene to acetic acid using a combination of palladium(II) and a heteropoly acid [104]. However, the reaction probably involves heteropoly acid-catalyzed hydration followed by palladium-catalyzed aerobic oxidation of ethanol to acetic acid rather than a classical Wacker mechanism. 

Pd-promoted H4SiWi204o/Si02 is effective for this reaction in a mixture of ethene, water, and oxygen this process has been commercialized since 1997. The reaction is proposed to proceed through hydration of ethene, followed by oxidation of ethanol. The selectivity toward acetic acid reaches 86% over Pd/H4SiWi2O40 Si02. 

Although alcohols can be relatively easily dehydrated to form an alkene, the reverse is not as easily done alcohols cannot be synthesised in a single simple step in an ordinary laboratory by the addition of water to an alkene. However, in industry it is very different. Most ethanol these days is manufactured by hydration of ethene using a catalyst at high temperature and pressure ... 

Hydration of ethene using ethene gas + steam at 600 K + pressure of 60 atm in the presence of phosphoric add... 

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