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Methylene glycol, dehydration

It has been shown by H naff (1963) that the rate of reaction of several carbonyl reagents (bisulphite, hydrazine, phenylhydrazine, semi-carbazide and hydroxylamine) with aqueous formaldehyde solutions is independent of the nature and concentration of the reagent, and is therefore determined by the rate of dehydration of methylene glycol. He obtained catalytic constants for hydrogen and hydroxide ions, and a detailed study of acid-base catalysis has been made by the same method by Bell and Evans (1966). [Pg.21]

In addition to the small amount of formaldehyde originally present in the aqueous solution, a little more is formed from the methylene glycol. However, formaldehyde component reacts very slowly with cellular proteins, and then it is slowly exhausted. This means that the interior of the tissue block after fixation for 4-6 hr at room temperature is exposed mainly to methylene glycol therefore, this portion of the tissue is fixed by ethanol during dehydration, resulting in the coagulation of proteins. [Pg.54]

Paradoxically, it is reactions which follow the Br0nsted law too well which now require explanation. The best example is the dehydration of methylene glycol, which gives a linear plot of logi 0 k against pK of catalyst for a range in pK of 16 units [41]. The reaction is subject to both acid and base catalysis, and can be considered as proceeding by the mechanisms... [Pg.218]

Although most of the installed solvent dehydration systems have been for ethanol dehydration, dehydration of other solvents including 2-propanol, ethylene glycol, acetone, and methylene chloride, has been considered. [Pg.87]

Materials. Methylene 4,4 -diphenyldiisocyanate (MDI, Mobay) was recrystallized from cyclohexane. Toluenediisocyanate (TDI— represents mixture of 2,4- and 2,6-isomers in 80/20 ratio), p-toluidine (Aldrich) and aniline (Aldrich) were purified by vacuum distillation before use. Diphenylmethane, tert-butyl peroxide (TBP), 4-bromoaniline, butyl lithium in hexane, and ethyl chloroformate, were obtained from Aldrich and used as received. Spectrograde tetrahydrofuran (THF) and benzene from Burdick and Jackson were used as received. Poly(tetramethylene ether glycol) with MW 1000 was obtained from polysciences and dehydrated under a rough vacuum at 50 °C for 24 h. [Pg.45]


See other pages where Methylene glycol, dehydration is mentioned: [Pg.449]    [Pg.342]    [Pg.23]    [Pg.26]    [Pg.23]    [Pg.26]    [Pg.75]    [Pg.185]    [Pg.148]    [Pg.213]    [Pg.1232]    [Pg.430]    [Pg.432]    [Pg.137]    [Pg.137]    [Pg.281]    [Pg.2988]   
See also in sourсe #XX -- [ Pg.218 ]




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