Alcohols, oxygenates

Methanol reforming (decomposition) over Cu/Zn/Al catalysts [83] [258] [343] is a well-established technology [61] [260], mainly used for small hydrogen plants (less than 1000 Nm /h). Since the amount of heat required per mole of hydrogen is far less than for steam reforming of natural gas, the equipment becomes much cheaper than the tubular reformer. On the other hand, the heat of evaporation on a mass basis of methanol is about four times higher than that of naphtha. 

A methanol reformer is typically a reactor heated by electricity or indirectly by circulating heating oil [61]. A more advanced and compact scheme [183] applies steam condensing on the outside of catalyst tubes. 

The optimum choice of operating conditions [63] is around a steam-to-methanol ratio of 1.5 and a temperature in the range 250 to 300°C. The pressure does not influence the reaction rate, but very high pressures limit the equilibrium conversion, which otherwise is above 99%. 

Methanol may be a suitable alternative in areas with expensive hydrocarbons considering the simplicity of the methanol reforming unit 

DME is easily converted over Cu/Zn/Al catalysts [32] [191] [483] with little change in the layout of the plant [63]. Without water addition, decomposition of DME over a Cu/Al/Zn catalyst results in a syngas with H2/C0=2. This route has been applied for small-scale supply of S5mgas, eliminating storage of carbon monoxide. By using methyl formate as feed, a syngas with H2/CO=l is achievable. 

---

Each carbon has four bonds in ethyl alcohol oxygen and each carbon are surrounded by eight electrons... 

An advantage that sulfonate esters have over alkyl halides is that their prepara tion from alcohols does not involve any of the bonds to carbon The alcohol oxygen becomes the oxygen that connects the alkyl group to the sulfonyl group Thus the configuration of a sulfonate ester is exactly the same as that of the alcohol from which It was prepared If we wish to study the stereochemistry of nucleophilic substitution m an optically active substrate for example we know that a tosylate ester will have the same configuration and the same optical purity as the alcohol from which it was prepared... 

The reaction of alcohols with acyl chlorides is analogous to their reaction with p toluenesulfonyl chloride described earlier (Section 8 14 and Table 15 2) In those reactions a p toluene sulfonate ester was formed by displacement of chloride from the sulfonyl group by the oxygen of the alcohol Carboxylic esters arise by displacement of chlonde from a carbonyl group by the alcohol oxygen... 

The values 1/V(dj dj) are for the atoms i and j, which make up this bond, and the connectivity index, x, is obtained as the sum of the bond connectivities. In molecules containing heteroatoms, the d values were considered to be equal to the difference between the number of valence electrons (E") and the number of hydrogen atoms (hi). Thus, for an alcoholic oxygen atom, d = 1, and d = 5. The valence connectivity-index, y can then be calculated the use of removes redundancies that can occur through the use of y alone. The calculation of connectivity indices and for the case of two isomeric heptanols is as follows. 

The alcohol oxygen attacks the sulfur atom of the sulfonyl chloride. 

The varying participation of the alcohol functions in metal coordination in these complexes is undoubtedly a reflection of both the moderate donor capacity of alcohol oxygens and the different coordination preferences of the respective metal ions involved. 

The two more stable structures jomo and ietero are characterized by a double hydrogen bond between Ej and Pj or P. The Ej molecule acts as proton donor towards the nitrogen of prolinol, and as acceptor towards the alcoholic proton of P . In the two less stable structure IIhomo and Utetero. the prolinol maintains an intramolecular H-bond between the alcoholic oxygen and nitrogen and, thus, only one hydrogen bond with the Ej molecule is possible, in which the oxygen of Pr/s accepts a proton. 

The miscibility of ethers with water resembles those of alcohols of the same molecular mass. Both ethoxyethane and butan-l-ol are miscible to almost the same extent i.e., 7.5 and 9 g per 100 mb water, respectively while pentane is essentially immiscible with water. Can you explain this olDservation This is due to the fact that Just like alcohols, oxygen of ether can also form hydrogen bonds with water molecule as shown ... 

While in most reported cases the nucleophiles were amines, there were few examples involving heterocyclic nitrogens [40], alcoholic oxygens [27] or carbon nucleophiles [42, 43] too. Figure 4 shows a recent example of tandem Ugi-Dieckmann protocol [42]. Ugi convertible isocyanide 2, which requires a basic activation, was used, allowing a domino activation-cyclization of the intermediate 20 to give pyrrolidinediones (tetramic acids) 22. 

This section is about diaUcylethers, aldehydes, ketones and alcohols. Oxygen net charges deduced from standard STO-3G calculations are indicated in Table 6.7 (see also Fig. 6.9), along with their NMR shifts (ppm from water) for dialkylethers [140] and carbonyl compounds [140], as well as selected ionization potentials [147]. 

The use of organomagnesium reagents as bases leads to complexation of the nitrile imines (e.g., 141), which has been found to have a strong effect in promoting syn selectivity in reactions with methyl 2-(l-hydroxyalkyl)acrylates via coordination of the metal atom with the alcoholic oxygen (e.g., leading to the formation of 142). Lithium complexation had little effect (78). 

Oxidation of Potassium Peroxide. Determination of Potassium Superoxide. Potassium peroxide was prepared by the addition of a tert-butyl alcohol solution of 90% hydrogen peroxide to potassium tert-butoxide in DMSO or tert-butyl alcohol. Oxygen absorption was followed in the standard manner (20). Analysis of solid precipitates for potassium superoxide followed exactly the method of Seyb and Kleinberg (23). Potassium superoxide formed in the oxidation of benzhydrol was determined in a 15-ml. aliquot of the oxidation solution. To this aliquot 10 ml. of diethyl phthlate was added to prevent freezing of the solution. The mixture was cooled to 0°C., and 10 ml. of acetic acid-diethyl phthlate (4 to 1) added over a period of 30 minutes with stirring. The volume of the evolved oxygen was measured. 

In a general base catalysis, the pyridine forms a hydrogen bond to an alcohol function (56). This causes a polarization and increases the nucleophi-licity of the alcohol oxygen thus accelerating the reaction [46c]. The second mechanism postulates a betain intermediate 57 which is formed by a nucleophilic attack of the pyridine on the ketene 59 [46d]. 

The ethylzinc alcoholate (149) prepared from racemic a-terr-butyl-6-phenyl-2-pyridyl-methanol and Et2Zn exists in the solid state as a hetero chiral dimer (Figure 78). Also in this case the alcoholate oxygen atoms bridge between two zinc atoms, affording a central Zn—O—Zn—O plane. The pyridyl nitrogen atoms are coordinated in such a way to the zinc atoms [Zn—N 2.185(2) A] that they are in awfi-position with respect to this plane. 

Now let us consider esters in which the alcohol portion is the predominant portion of the molecule. Esters of fatty alcohols (except methyl esters) eliminate a molecule of acid in the same manner that alcohols eliminate water. A scheme similar to that described earlier for alcohols, involving a single hydrogen transfer to the alcohol oxygen of the ester, can be written. An alternative mechanism involves a hydride transfer to the carbonyl oxygen (McLafferty rearrangement). 

---