Thiohydantoins. XII. Secondary Deuterium Isotope Effects in the Acid- and Base-catalyzed Hydrolysis of 1-Acetyl-5,5-dimethyl-2-thiohydantoin

1972 ◽  
Vol 50 (23) ◽  
pp. 3921-3923
Author(s):  
Wayne I. Congdon ◽  
John T. Edward
Keyword(s):  
Sulfuric Acid ◽  
Temperature Effect ◽  
Sodium Hydroxide ◽  
Isotope Effects ◽  
Temperature Range ◽  
Dilute Sodium Hydroxide ◽  
Acid And Base ◽  
Deuterium Isotope Effects ◽  
Hydrolysis Of

The rates of hydrolysis of 1-acetyl-5,5-dimethyl-2-thiohydantoin and of 1-acetyl-d3-5,5-dimethyl-2-thio-hydantoin in acid and base over the temperature range 11–58 °C have been measured. For the A-1 hydrolysis in 96.3% sulfuric acid, kH/kD decreased from 1.31 at 10.8° to 1.05 at 58.1°; these results accord with the proposed mechanism. For A-2 hydrolysis in 39.6% sulfuric acid and for base-catalyzed hydrolysis in dilute sodium hydroxide, kH/kD υs. temperature passed through a minimum at about 40 and 25° respectively. Some possible reasons for the temperature effect are discussed.

A comparison of the mechanisms of hydrolysis of benzimidates, esters, and amides in sulfuric acid media

2005 ◽  
Vol 83 (9) ◽  
pp. 1391-1399 ◽  
Author(s):  
Robin A Cox
Keyword(s):  
Sulfuric Acid ◽  
Isotope Effects ◽  
Ester Hydrolysis ◽  
Water Molecules ◽  
Acid Media ◽  
Tetrahedral Intermediate ◽  
Amide Hydrolysis ◽  
Solvent Isotope ◽  
Reaction Media ◽  
Hydrolysis Of

The mechanisms given in textbooks for both ester and amide hydrolysis in acid media are in need of revision. To illustrate this, benzimidates were chosen as model compounds for oxygen protonated benzamides. In aqueous sulfuric acid media they hydrolyze either by a mechanism involving attack of two water molecules at the carbonyl carbon to give a neutral tetrahedral intermediate directly, as in ester hydrolysis, or by an SN2 attack of two water molecules at the alkyl group of the alkoxy oxygen to form the corresponding amide, or by both mechanisms, depending on the structure of the benzimidate. The major line of evidence leading to these conclusions is the behavior of the excess acidity plots resulting from the rate constants obtained for the hydrolyses as functions of acid concentration and temperature. The first of these mechanisms is in fact very similar to one found for the hydrolysis of benzamides, as inferred from: (1) similar excess acidity plot behaviour; and (2) the observed solvent isotope effects for amide hydrolysis, which are fully consistent with the involvement of two water molecules, but not with one or with three (or more). This mechanism starts out as essentially the same one as that found for ester hydrolysis under the same conditions. Differences arise because the neutral tetrahedral intermediate, formed directly as a result of the protonated substrate being attacked by two water molecules (not one), possesses an easily protonated nitrogen in the amide and benzimidate cases, explaining both the lack of 18O exchange observed for amide hydrolysis and the irreversibility of the reaction. Protonated tetrahedral intermediates are too unstable to exist in the reaction media; in fact, protonation of an sp3 hybridized oxygen to put a full positive charge on it is extremely difficult. (This means that individual protonated alcohol or ether species are unlikely to exist in these media either.) Thus, the reaction of the intermediate going to product or exchanged reactant is a general-acid-catalyzed process for esters. For amide hydrolysis, the situation is complicated by the fact that another, different, mechanism takes over in more strongly acidic media, according to the excess acidity plots. Some possibilities for this are given.Key words: esters, amides, benzimidates, hydrolysis, excess acidity, mechanism, acid media.

Latex Battery Separators. Preparation and Properties

1937 ◽  
Vol 10 (2) ◽  
pp. 346-351
Author(s):  
H. W. Greenup ◽  
L. E. Olcott
Keyword(s):  
Sulfuric Acid ◽  
Sodium Hydroxide ◽  
Electrical Resistance ◽  
Sodium Hydroxide Solution ◽  
Storage Battery ◽  
Preliminary Treatment ◽  
Actual Contact ◽  
Dilute Sodium Hydroxide ◽  
Port Orford Cedar ◽  
Highly Porous

Abstract THE commonly used electrical storage battery consists of alternate negative plates of sponge lead and positive plates of lead peroxide immersed in an electrolyte, sulfuric acid; the whole is enclosed in a hard rubber or bituminous composition case. These plates are ordinarily separated from one another by ribbed sheets of wood called “separators.” The separators prevent short circuiting of the plates caused by actual contact of the plates with each other or by “treeing” (formation of lead crystals between the plates). The separators must be thin, in order to make the battery as compact as possible, and yet must be durable. It is necessary that they be highly porous so that their electrical resistance will be low, but the pores must be sufficiently fine so that “treeing” does not take place. Wood separators are ordinarily made of Port Orford cedar. They are usually given a preliminary treatment in warm, dilute sodium hydroxide solution to swell them, thus increasing their porosity, and to remove injurious substances which cause self-discharge and corrosion of the plates. Wood separators have the advantage of being inexpensive and of having fairly low electrical resistance, but they are not so resistant to the action of sulfuric acid and the oxidizing action in the cell as is desirable. They are, in many cases, the first part of the storage battery to fail and must then be replaced if the battery is to give further service.

Neighboring ortho carboxyl group participation and .alpha.-deuterium isotope effects in the hydrolysis of benzyl bromides

1979 ◽  
Vol 101 (9) ◽  
pp. 2320-2322 ◽  
Author(s):  
V. P. Vitullo ◽  
S. Sridharan ◽  
L. P. Johnson
Keyword(s):  
Isotope Effects ◽  
Carboxyl Group ◽  
Group Participation ◽  
Deuterium Isotope Effects ◽  
Hydrolysis Of

scholarly journals Mixed Solvent Deuterium Isotope Effects on the Hydrolysis of UO22+and Be2+Ions

1972 ◽  
Vol 45 (8) ◽  
pp. 2464-2468 ◽  
Author(s):  
Masunobu Maeda ◽  
Toshihiko Amaya ◽  
Hitoshi Ohtaki ◽  
Hidetake Kakihana
Keyword(s):  
Mixed Solvent ◽  
Isotope Effects ◽  
Deuterium Isotope Effects ◽  
Hydrolysis Of

Catalytic Reaction Mechanism Based on α-Secondary Deuterium Isotope Effects in Hydrolysis of Trehalose by European Honeybee Trehalase

2009 ◽  
Vol 73 (11) ◽  
pp. 2466-2473 ◽  
Author(s):  
Haruhide MORI ◽  
Jin-Ha LEE ◽  
Masayuki OKUYAMA ◽  
Mamoru NISHIMOTO ◽  
Masao OHGUCHI ◽  
...  
Keyword(s):  
Reaction Mechanism ◽  
Catalytic Reaction ◽  
Isotope Effects ◽  
Deuterium Isotope Effects ◽  
Hydrolysis Of ◽  
European Honeybee ◽  
Catalytic Reaction Mechanism
Sign in / Sign up

Export Citation Format

Share Document