Deuterium exchange with

Desensitizers, in photography. 78 Deuterium, exchange with proton-2 of thiazolium salts, 31 Deviation theory. 69 Dialkylacyiphosphonates. adducts with thiazolium salts. 35... 

The best insight into the relaxation behavior of star polymers in dilute solution can be expected if, in addition to the whole star system, different parts of the star are considered separately. This can be achieved easily by neutron scattering techniques on systems where not only the entity of arms, but also single arms, the core or shell parts are labelled by proton deuterium exchange. With respect to the core-shell labelling it is convenient to build up the arms as diblock copolymers of A-B type with protonated or deuterated but otherwise chemically identical A and B blocks. 

In the case of the synthesis of 10,19,19,19-2H4-vitamin A, the most useful for biological studies, three deuterium atoms were incorporated into /i-ionone 30, in >98% by deuterium exchange with excess D2O in the presence of Na02H (and pyridine). The tri-deuteriated 30, utilized in Wittig-Horner reaction with dideuterio triethyl phosphonate, provided tetradeuteriated ethyl /J-ionilidene acetate 31 with more than 98% 2H4 (by NMR). No deuterium loss in the subsequent synthetic steps was observed as evidenced by MS and NMR analysis. 

Deuterium exchange with DjO was used by Shuravlev and Kiselev (199) in the determination of surface hydroxyl groups of silica gel. Adsorption isotherms of HgO and DjO were determined gravi-metrically they agreed with each other within the limits of experimental error. 

This order of reactivity was observ for add dedeuteration, but for acetylation, formylation, and chlorination it was slightly different thieno[3,2-h]thiophene (2) > thieno[2,3-h]thiophene (1) > thiophene thieno[3,4-6]thiophene (3) was not studied. A substantially greater discrepancy between theoretical and experimental data was observed for nucleophilic substitution from the data on base dedeuteration and competitive metalation reactions/ the order of decreasing reactivity was as follows thieno[2,3-h]thiophene (1) > thieno[3,2-h]thiophene (2) > thiophene. To a certain extent this may be explained by differences in the mechanism of metalation and deuterium exchange with a base. A discrepancy between calculation and experiment was also found for free-radical substitution. ... 

Evidence that the presence of water is important in these reactions has been obtained by Hansford (82). Pretreatment of the catalyst with a stream of predried air at 500°C resulted in a marked decrease in the rate of cracking. Further, if deuterium oxide was substituted for the water in the catalyst a large percentage of the deuterium exchanged with hydrogen atoms contained in the hydrocarbon undergoing reaction. Hansford also pointed out that effective catalysts for cracking reactions are always prepared from one or more hydrous oxides. 

Consider the reaction in which deuterium exchanges with ordinary hydrogen in water ... 

Carbanion mechanisms may give either syn or anti elimination. For example, Hunter and Shearing studied the butoxide-catalyzed elimination of methanol from 35 and 36. Since deuterium exchange with solvent is in close competition with elimination, the mechanism is probably (EjcB)b. The ratio ofsyn/anti... 

The rate of hydrogen exchange depends on the protolytic properties of both the solvent and the substrate. In fact there is a correspondence between the magnitude of the rate constants for deuterium exchange with ND3 and the conventional ionization constants of hydrocarbons which were used by Conant and Wheland (1932) and by McEwen (1936) to obtain the first quantitative estimates of the acidity of hydrocarbons. To do this, they determined the equilibrium of metallation of hydrocarbons by organo-alkali metal compounds. This reaction was described by Shorygin (1910) and is represented by the equation... 

The acid properties of hydrocarbons, deduced from deuterium exchange with liquid ammonia, will be discussed in detail in the following sections. 

Partial Rate Factors for the Deuterium Exchange with NHj + KNH2 and the Values of ctj... 

Partial Rate Factors for Deuterium Exchange with Bases and Acids Relative to the Partial Rate Factors in the Para Position... 

While deuterium exchange between DGeCl3 and benzene and toluene does not occur at room temperature, trichlorogermane behaves as a strong acid with the more basic methylbenzenes, i.e., m-xylene, mesitylene and isodurene, by promoting rapid deuterium exchange. With mesitylene, for example, the equilibrium is established at 20 °C after 60 minutes. 

It was pointed out earlier that benzene and methylbenzenes do not add to HGeCl3 under normal conditions although some of them do participate in deuterium exchange with DGeCl3. The general hydrogermylation equation (equation 50) vividly reflects a sequence of heterolytic stages of exhaustive addition to the aromatic double bonds. 

Of great aid to the study of adsorption on zeolites will be spectroscopic methods used in conjunction with quantitative mass spectroscopic analysis of hydrogen concentration in the zeolite by deuterium exchange with D2O (21). 

DBU undergoes a slow deuterium exchange with CDCI3 to give a product deuterated in position 10 (81CC998). 

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