Glycols, dehydration oxidation

The cis- 1,2-glycols, obtainable from the parent aromatic hydrocarbon by osmium tetroxide hydroxylation, can be converted to the corresponding trans-1,2-glycols by oxidation-reduction, using a mixture of dimethyl sulfoxide, sulfur trioxide, and pyridine, followed by lithium aluminum hydride reduction. The trans- 1,2-glycols can be dehydrated to arene oxides using DMF-DMA as mentioned above. Benzo[a]pyrene 4,5-oxide (28) and 7,12-dimethylbenz[a]anthracene 5,6-oxide (30) have been prepared by this method in 68 and 80% yields, respectively.18... 

Uses Defoamer for industrial and food-processing systems (fermentation, brine systems, wine, yeast, etc.), chemical processing (adhesive mfg., water-based ink mfg., latex processing, soap mfg., starch processing. paint additive, alcohol fennentation), wastewater treatment, petrochemical (resin polymerization, glycol dehydrators, ethylene oxide prod., urea prod.)... 

Although the selective oxidation reaction (8-1) is not reversible, the products of reaction 8-1 (S and H2O) can react by the reverse of reaction 8-3 to reduce overall sulfur recovery. Therefore, in the MODOP process, water is removed from the gas stream in the quench tower to improve the conversion of hydrogen sulfide to sulfur. Conversion can be further increased by removal of additional water in a glycol dehydration tower after the quenching... 

Corrosion can be a serious problem in the operation of glycol dehydration plants. Since the pure glycol solutions are themselves essentially non-corrosive to carbon steel, it is generally believed that the corrosion is accelerated by the presence of other compounds that may come from the oxidation or thermal decompcrsition of the glycol, or enter the system with the gas stream. The rate of corrosion will, of course, be influenced by the temperature of the solution, velocity of the fluid, and other factors. In general, the principles that have been employed in combating corrosion are... 

Two additional steps were taken to minimize corrosion downstream of the glycol dehydrator unit. One was the use of a product-gas scrubber to minimize glycol entrainment in the gas stream, and the other was the use of a second inhibitor that was added to the dried-gas stream. This material was of the polyethanolrosinamine-type consisting of 70% solution in isopropyl alcohol of a mixture of 90% ethoxylated rosinamine (II moles ethylene oxide with each mole of rosinamine) and 10% free rosinamine. This inhibitor was injected at the rate of 0.1 gal/day for a gas volume of 60 MMsef/day. As a result of the above measures, the corrosion rate of coupons suspended in the dried-gas line decreased from almost 30 mils ear to as low as 0.2 mil/year during about 4 years of testing. 

If a-phellandrene be oxidised by potassium permanganate, the principal body resulting is a-oxy-/3-isopropyl glutaric acid. If /3-phellandrene be oxidised, closely related acids result, but if a 1 per cent, solution of permanganate be used and the oxidation effected very carefully in the cold, with the terpene always in excess, a glycol, CjoHjg(OH)2, results, which when dehydrated with dilute sulphuric acid yields tetrahydro-cuminic aldehyde. 

Cyclohexadiene has been prepared by dehydration of cyclohexen-3-ol,3 by pyrolysis at 540° of the diacetate of cyclohexane-1,2-diol,4 by dehydrobromination with quinoline of 3-hromocyclohexene,6 by treating the ethyl ether of cyclohexen-3-ol with potassium bisulfatc,6 7 by heating cyclohexene oxide with phthalic anhydride,8 by treating cyclohexane-1,2-diol with concentrated sulfuric acid,9 by treatment of 1,2-dibromocyclo-hexane with tributylamine,10 with sodium hydroxide in ethylene glycol,10 and with quinoline,6 and by treatment of 3,6-dibromo-cyclohexene with sodium.6... 

The formation of 5-hydroxy-2 -deoxycytidine (22) and 5-hydroxy-2 -de-oxyuridine (23) that arise from dehydration of dCyd glycols 20 and related dUrd derivatives 21, respectively, was assessed by HPLC-electrochemical detection within calf thymus DNA upon exposure to photoexcited menadione and subsequent enzymatic hydrolysis [57]. The latter two oxidized nucleo-... 

Cyclopentanecarboxaldehyde has been prepared by the procedure described above 2 3 by the reaction of aqueous nitric acid and mercuric nitrate with cyclohexene 6 by the action of magnesium bromide etherate 6 or thoria 7 on cyclohexene oxide by the dehydration of frarei-l, 2-cyclohexanediol over alumina mixed with glass helices 8 by the dehydration of divinyl glycol over alumina followed by reduction 9 by the reaction of cyclopentene with a solution of [HFe(CO)4] under a carbon monoxide atmosphere 10 and by the reaction of cyclopentadiene with dicobalt octacarbonyl under a hydrogen and carbon monoxide atmosphere.11... 

The anion of this para form forms a cyclic intermediate with the glycol which may get hydrated (3) or dehydrated. (4) These then give the final oxidation product and liberate the anion. 

In a similar manner, coccinelline (99) and precoccinelline (100) have been synthesized from 2,6-lutidine (351) (336,450). Thus, treatment of the monolithium derivative (153) of 351 with P-bromopropionaldehyde dimethylacetal gave an acetal, which was converted to the keto acetal (412) by treatment with phenyllithium and acetonitrile. Reaction of 412 with ethylene glycol and p-toluenesulfonic acid followed by reduction with sodium-isoamyl alcohol gave the cw-piperidine (413). Hydrolysis of 413 with 5% HCl gave the tricyclic acetal (414) which was transformed to a separable 1 1 mixture of the ketones (415 and 416) by treatment with pyrrolidine-acetic acid. Reaction of ketone 416 with methyllithium followed by dehydration with thionyl chloride afforded the rather unstable olefin (417) which on catalytic hydrogenation over platinum oxide in methanol gave precoccinelline (100). Oxidation of 100 with m-chloroperbenzoic acid yielded coccinelline (99) (Scheme 52) (336,450). 

Ethanediol (ethylene glycol) [5g] Commercial products are pure enough for most purposes. In order to remove water of 2000 ppm, the ethanediol is dehydrated with sodium sulfate anhydride and distilled twice at reduced pressure in a dry nitrogen atmosphere in order to avoid oxidation to aldehyde. 

Prepared commercially either by dehydration of ethylene glycol with H2SO4 and heating ethylene oxide or bis(B-chloroethyl)ether with NaOH. 

Polymers usually are prepared by two different types of polymerization reactions — addition and condensation. In addition polymerization all of the atoms of the monomer molecules become part of the polymer in condensation polymerization some of the atoms of the monomer are split off in the reaction as water, alcohol, ammonia, or carbon dioxide, and so on. Some polymers can be formed either by addition or condensation reactions. An example is polyethylene glycol, which, in principle, can form either by dehydration of 1,2-ethanediol (ethylene glycol), which is condensation, or by addition polymerization of oxacyclopropane (ethylene oxide) 1... 

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