Diols ethanediol

Vicinal diols are diols that have their hydroxyl groups on adjacent carbons Two commonly encountered vicinal diols are 1 2 ethanediol and 1 2 propanediol... 

Diols that bear two hydroxyl groups m a 1 2 or 1 3 relationship to each other yield cyclic acetals on reaction with either aldehydes or ketones The five membered cyclic acetals derived from ethylene glycol (12 ethanediol) are the most commonly encoun tered examples Often the position of equilibrium is made more favorable by removing the water formed m the reaction by azeotropic distillation with benzene or toluene... 

Alkaline hydrolysis of the crude adduct formed with benzaldehyde, followed by treatment with diazomethane and column chromatography, affords methyl (2R,3S)-3-hydroxy-2-methyl-3-phenylpropanoate in 96% ee. Reduction of the crude products formed in the reactions with 2-inethylpropanal and 2,2-dimethylpropanal leads to the corresponding 1,3-diols with >96% ee. In both the hydrolysis and the reduction procedures, the chiral auxiliary reagent, 1,1,2-triphenyl-1,2-ethanediol, can be recovered and reused72. 

Recently, Lin17 270 271 found a 3rd-order for the reaction of sucdnic and adipic adds with 1 -ethanediol in the presence of an excess of a diol. Surprisingly, he found orders 1 with respect to add and 2 with respect to alcohol. This was explained by the fact that acid... 

Japaridze et al.m 323 have studied the interface between Hg and a number of vicinal and nonvicinal diols such as 1,2-, 1,3-, 2,3- and 1,4-butanediol (BD), ethanediol (ED), and 1,3-propanediol. KF and LiC104 were used as surface-inactive electrolytes. The potential of zero charge was measured by the capacitance method against an SCE in water without correction for the liquid junction potential at the solvent/H20 contact (such a potential drop is estimated to be in the range of 20 to 30 mV). The potential of the capacitance minimum was found to be independent of the electrolyte concentration while capacitance decreased with dilution. Therefore, Emin was taken to measure E . These values are reported in Table 4. 

Ethylene glycol, or 1,2-ethanediol, HOCH2CH2OH (2), is an example of a diol, which is a compound with two hydroxyl groups. Ethylene glycol is used as a component of antifreeze mixtures and in the manufacture of some synthetic fibers. 

Other chiral diols, such as (1S,2S)-1,2-diphenyl-l,2-ethanediol and diethyl (1 /f,2/ )-l,2-di-hydroxybutanedioate offer only low atropdiastereoselectivity or, in the case of the 1,4-diol, (4.S, 55 )-4,5-bis(hydroxymcthyl)-2,2-dimethyl-1,3-dioxolane, no atropdiastereoselectivity at all28a. 

The stereochemical aspects of the fates of 1-phenyl-1,2-ethanediol and mandelic acid in rats have been examined by Drummond et al. (1990). The proportions of a dose of 1-phenyl-1,2-ethanediol converted to phenylglyoxylic and mandelic acids depend upon its stereochemistry. The i -diol is preferentially converted to i -mandelic acid (30% of the dose in 48 h) with 15% of the dose as phenylglyoxylic acid. In contrast, after administration of the 5 -diol, the major product is phenylglyoxylic acid (46% of the dose) with 16% as mandelic acid (JUS 80 20). 

Instead of two molecules of alcohols, a diol is often used. This produces cyclic acetals. 1,2-ethanediol (ethylene glycol) is usually the diol of choice, and the products are called ethylene acetals. 

Preparation of diols Acid-catalysed epoxides are easily cleaved by water. Water reacts as the nucleophile, and this is referred to as a hydrolysis. For example, hydrolysis of ethylene oxide in the presence of acid-catalyst produces 1,2-ethanediol (ethylene glycol). 

Ethanediol (ethylene glycol) is a familiar antifreeze. However, it also is used in automotive cooling systems in climates that rarely, if ever, reach temperatures at which water would freeze. What other function, as important as lowering the freezing point, does the diol serve when added to automotive cooling systems ... 

Included in this class of olefins is ( )-stilbene (entry 20), which throughout studies of AD has usually been the olefin dihydroxylated with the highest degree of enantioselectivity. Availability of (R,R) or (.5,5)-1,2-diphenyl-1,2-ethanediol (also referred to as stilbenediol or dihydrobenzoin) with high enantiomeric purities has led to reports of a number of applications, including incorporation into chiral dioxaphospholanes [50], chiral boronates [51], chiral ketene acetals [52], chiral crown ethers [53], and conversion into 1,2-diphenylethane-1,2-diamines [54]. Dihydroxylation of the substituted rran.r-stilbene 46 with Os04/NMO and DHQD-CLB gives the i ,/ -diol 47 with 82% ee in 88% yield [55]. 

Details for the large-scale synthesis of (R,R) 1,2-diphenyl-1,2-ethanediol by using the DHQD-CLB/NMO variation of catalytic AD have been published [47]. Under these conditions the crude diol is produced with 90% ee and upon crystallization, essentially enantiomerically pure diol is obtained in 75% yield. Subsequent improvements in the catalytic AD process now allow this dihydroxylation to be achieved with >99.8% ee (entry 20, Column 9) however, the Organic Synthesis procedure [47] is still an excellent choice for preparing large amounts of the... 

According to protonation thermochemistry of simple a,(0-diols (1,2-ethanediol, 1,3-propanediol, 1,4-butanediol), the diols show enhanced proton affinities in the gas phase compared with primary alcohols attributed to the formation of a strong intramolecular hydrogen bond.59 60... 

Acetaldehyde has been prepared in part (a). Recalling that vicinal diols are available from the hydroxylation of alkenes, 1,2-ethanediol may be prepared by the sequence... 

Some solvents are reluctant to crystallize before turning into a glass, including allyl alcohol (2-propen-l-ol), ethylene glycol (1,2-ethanediol), and hexylene glycol (2-methyl-pentane-2,4-diol). Some common solvents may be liquid below their freezing points if they contain impurities, in particular small amounts of water. Thus, /-butyl alcohol (2-methyl-2-propanol), acetic acid, and phenol can appear liquid at or below ambient temperatures (i.e., < Tm) due to this cause. 

Boronic esters of (R,R)-l,2-dicyclohexyl-l,2-ethanediol or pinanediol react with thionyl chloride and excess imidazole in acetonitrile on a borosilicate glass surface to form the corresponding cyclic sulfites of diols <20010M2920>. Similarly, cyclic sulfites and sulfates have been prepared from silicates of diols <1997TL4841>. 

Protein-chemical Properties of Apoenzyme. Adenosylcobalamin-dependent diol dehydrase was discovered and isolated first by Abeles and co-workers (3, 4) in the cells of Klebsiella pneumoniae (formerly known as Aerohacter aero genes) ATCC 8724 grown without aeration in a glycerol or glycerol-1,2-propanediol medium. This enzyme catalyzes the conversion of 1,2-propanediol, 1,2-ethanediol, and glycerol to propionaldehyde, acetaldehyde, and j3-hydroxypropionaldehyde, respectively (4, 5). Adenosylcobalamin and K+ or other monovalent cations of a similar size are required for catalysis. Recently, the au-... 

---