Acids, dehydration

Isobutyl alcohol, isobutanol, 2-methyl-propanol, isopropyl carbinol, Me2CHCH20H. B.p. 108°C. Occurs in fusel-oil. Oxidized by potassium permanganate to 2-methyl-propanoic acid dehydrated by strong sulphuric acid to 2-methylpropene. 

Prepared by stirring phthalimide with cold concentrated ammonia solution. Hydrolysed to phlhalic acid with dilute acids. Dehydration with ethanoic anhydride gives first n-cyano-benzamide and then phthalonitrile. 

Dimethyl Ether. Synthesis gas conversion to methanol is limited by equiUbrium. One way to increase conversion of synthesis gas is to remove product methanol from the equiUbrium as it is formed. Air Products and others have developed a process that accomplishes this objective by dehydration of methanol to dimethyl ether [115-10-6]. Testing by Air Products at the pilot faciUty in LaPorte has demonstrated a 40% improvement in conversion. The reaction is similar to the Hquid-phase methanol process except that a soHd acid dehydration catalyst is added to the copper-based methanol catalyst slurried in an inert hydrocarbon Hquid (26). 

Hydrated iron(III) fluoride [15469-38-2] is easily prepared from yeHow Fe202 and hydrofluoric acid. Dehydration of FeF 3H20 produces... 

Condensa.tlon, A variety of condensation reactions involving the hydroxyl or the carboxyl or both groups occur with lactic acid. The important reactions where products can be obtained ia high yields are esterificatioa (both iatramolecular and with another alcohol or acid), dehydration, and aminolysis. 

The decomposes spontaneously on standing for a few days. The acid dehydration reaction requires a day for completion at —10°C and explosions... 

R = alkyl, R = H) can be condensed, using acid, dehydrating agents (eg, phosphoms pentoxide), or vacuum to form polymeric peroxides (3). Most such polymeric peroxides decompose explosively. 

Phenylboric acid (benzeneboronic acid) [98-80-6] M 121.9, m -43", 215-216" (anhydride), 217-220", pKj 8.83. It recrystallises from H2O, but can convert spontaneously to benzeneboronic anhydride or phenylboroxide on standing in dry air. Possible impurity is dibenzeneborinic acid which can be removed by washing with pet ether. Heating in an oven at 110°/760mm Ih converts it to the anhydride m 214-216°. Its solubility in H2O is 1.1% at 0° and 2.5% at 25° and in EtOH it is 10% (w/v). [Gilman and Moore J Am Chem Soc 80 3609 1958.] If the acid is required, not the anhydride, the acid (from recrystallisation in H2O) is dried in a slow stream of air saturated with H2O. The anhydride is converted to the acid by recrystallisation from H2O. The acid gradually dehydrates to the anhydride if left in air at room temperature with 30-40% relative humidity. The melting point is usually that of the anhydride because the acid dehydrates before it melts [Washburn et al. Org Synth Coll Vol IV 68 7965]. 

In 1869 Berthelot- reported the production of styrene by dehydrogenation of ethylbenzene. This method is the basis of present day commercial methods. Over the year many other methods were developed, such as the decarboxylation of acids, dehydration of alcohols, pyrolysis of acetylene, pyrolysis of hydrocarbons and the chlorination and dehydrogenation of ethylbenzene." ... 

The acid catalyzed elimination of acylated amines has recently been described and is said to resemble the acid dehydration of alcohols in character ... 

Yields are in the order of 50%. A more convenient sequence, but involving two extra steps, requires prior preparation of the 2,4-dinitrophenyl-hydrazone or semicarbazone followed by an acidic dehydration, and finally removal of the protecting group. 

The 2,4-dinitrophenylhydrazone is formed in ethanolic hydrochloric acid dehydration will then take place on heating only if the ketol dinitrophenyl-hydrazone remains soluble in the reaction mixture. 

Nitromifene (85) is such an agent. A Grignard reaction of aryl ether and ketone leads to tertiary carbinol Tosic acid dehydration leads to a mixture of 1 and stilbenes which constitute the antiestrogen, nitromi fene (85)... 

Compound A, C H O, was found to be an optically active alcohol. Despite its apparent unsaturation, no hydrogen was absorbed on catalytic reduction over a palladium catalyst. On treatment of A with dilute sulfuric acid, dehydration occurred and an optically inactive alkene B, Q iH14, was produced as the major product. Alkene B, on ozonolysis, gave two products. One product was identified as propanal, CH3CH2CHO. Compound C, the other product, was shown to be a ketone, CgHgO. How many degrees of unsaturation does A have Write the reactions, and identify A, B, and C. 

When 2-methyl-2<5-pentanedioJ is treated with sulfuric acid, dehydration occurs and 2,2-dimethyltetrahydrofuran is formed. Suggest a mechanism for this reaction. Which of the two oxygen atoms is most likely to be eliminated, and why ... 

HCOOH C02 + 2H If the CO is formed from formic acid dehydration,... 

Because trifluoromethanesulfonic acid is a stronger acid than perchloric acid, under no circumstances should perchlorate salts be used with the neat acid, because the hot anhydrous perchloric acid so formed represents an extreme explosion hazard, especially in contact with transition metal complexes (or with organic materials). See Perchloric acid Dehydrating agents See other ORGANIC ACIDS... 

Hydrogen peroxide Phosphorus(V) oxide Oxygen difluoride Phosphorus(V) oxide Perchloric acid Dehydrating agents... 

Figure 4. Correlation between infrared data and model reaction, (a) Basicity Hydrogen transfer activity versus surface area of 1230 cm 1 band of adsorbed C02 species after RT evacuation, (b) Acidity Dehydration activity versus quantity of Bronsted acid sites able to retain DMP at 150°C.

Poly(vinyl alcohol) and polyacrylamide (PAAM) blends, obtained by the different methods described above, can also be used for acetic acid dehydration, due to its capacity to swell in mixtures of acetic acid/water. 

Another, industrially relevant foUow-up reaction of isomaltulose comprises its ready conversion into 5-(a-D-glucosyloxymethyl)-furfural ( a-GMF ) by acidic dehydration of its fructose portion under conditions (acidic resin in DMSO, 120°C ) that retain the intersaccharidic linkage (Scheme 2.17). As this process can also be performed in a continuous-flow reactor,a most versatile building block is available from sucrose in two steps, of which the first is already industrially realized, and the second simple enough to be performed on a large scale. 

D-xylose was converted into 2-furaldehyde in acidified, tritiated water, no carbon-bound isotope was detected. This suggested that the 1,2-enediol (2) reacted immediately, as otherwise, tritium would have been detected at the aldehydic carbon atom of 2-furaldehyde, as a result of aldose-ketose interconversion.An acidic dehydration performed with d-[2- H]xylose showed that an intramolecular C-2-C-1 hydrogen transfer had actually occurred. Thus, these data indicated that an intramolecular hydride shift is more probable than the previously accepted step involving a 1,2-enediol intermediate. 

Acidic dehydration of alcohols, to give an alkene is also associated with substitution reaction to give an ether. 

Write the mechanism of acid dehydration of ethanol to yield ethene. 

Preparation of ethers by acid dehydration of secondary or tertiaiy alcohols is not a suitable method. Give reason. 

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