Deuterium ammonia

The log—log plot of the adsorption isotherm, which can possibly be correlated to the pressure-dependency of the catalytic reaction rate, is very flat. The adsorption of ethylene on nickel increases only by 10% for an increase of the equilibrium pressure by a factor of 10, although the surface is still far from being covered by a monolayer. The work of Laidler et al. (3), who studied the ammonia-deuterium exchange reaction on a promoted iron catalyst by means of the microwave method, also throws doubt on the zero-order kinetics with respect to observations made by Farkas (4). 

Schuit, van Reijen, and Sachtler (470) have also calculated the volcanoshaped curves for other reactions according to the data of a number of authors the ammonia-deuterium exchange [Fig. 64, Kemball (471)], the hydrogenation of ethylene [Fig. 65, Schuit and van Reijen (472)-, Beeck... 

As a starting material for other deuterocompounds. For example deuterium oxide, on magnesium nitride, gives deutero-ammonia, NDj with calcium dicarbide, deuteroethyne, C2D2, is obtained. 

Fluorine reacts with ammonia in the presence of ammonium acid fluoride to give nitrogen trifluoride, NF. This compound can be used as a fluorine source in the high power hydrogen fluoride—deuterium fluoride (HF/DF) chemical lasers and in the production of microelectronic siUcon-based components. 

There are ample precedents for reductions of double bonds in conjugated enones with lithium in deuterioammonia (see section V-C). Examples of the reduction of saturated ketones in deuterated media appear only as side reactions (over reductions) during the above mentioned conversions. For experimental details, therefore, one should consult the literature for the analogous reductions in protic medium (see also chapter 1). The use of deuterioammonia is essential for labeling purposes since by using liquid ammonia and methanol-OD the resulting alcohol contains no deuterium. For the preparation of deuterioammonia see section IX-D. 

While keeping the collected deuterioammonia at dry ice-isopropyl alcohol temperature, lithium wire (10 mg) is added, followed by a solution of 3/3-hydroxy-5a-cholest-7-en-6-one (161 50 mg) in anhydrous tetrahydrofuran (4 ml). The reaction mixture is stirred for 20 min, the cooling bath is then removed and the ammonia is allowed to boil under reflux for 40 min. A saturated solution of ammonium chloride in tetrahydrofuran is added dropwise until the deep blue color disappears and then the ammonia is allowed to evaporate. The residue is extracted with ether and the organic layer washed with dilute hydrochloric acid and sodium bicarbonate solution and then with water. Drying and evaporation of the solvent gives a semicrystalline residue which is dissolved in acetone and oxidized with 8 N chromic acid solution. After the usual workup the residue is dissolved in methanol containing sodium hydroxide (0.2 g) and heated under reflux for 1 hr to remove any deuterium introduced at C-5 or C-7. (For workup, see section II-B). 

This investigation was undertaken to establish the ionic mechanism responsible for exchange reactions occurring at pressures ranging from 0.85 to 0.98 atm. in irradiated deuterium, hydrocarbon and deuterium, ammonia gaseous mixtures at 25 °C. and lower temperatures. New tech-... 

Electrolysis continued to be used for primary enrichment in countries with abundant electric power, such as Iceland and Norway, where the H2 is used in ammonia manufacture [9]. Molecular deuterium, D2, is produced in Norway by the electrolysis of DzO. For heavy water production, the method has, for the most part, been replaced by steam-H2S exchange columns for heavy water enrichment ... 

Halcinonide dissolved in either methanol, deutero-methanol, aqueous ammonia-methanol, or deuterium oxide deuter-ated ammonia-methanol solvents appears stable after storage for six days at 50°, using nuclear magnetic resonance and mass spectrometry.70... 

Recently, this view of secondary a-deuterium KIEs has had to be modified in the light of results obtained from several different theoretical calculations which showed that the Ca—H(D) stretching vibration contribution to the isotope effect was much more important than previously thought. The first indication that the original description of secondary a-deuterium KIEs was incorrect was published by Williams (1984), who used the degenerate displacement of methylammonium ion by ammonia (equation (4)) to model the compression effects in enzymatic methyl transfer (SN2) reactions. 

The calculations were performed at the semiempirical level using AMI parametrization. The results for the methyl chloride reaction (Table 8) supported Williams earlier findings for the methylammonium ion-ammonia reaction (p. 147) and the results by Wolfe and Kim in that the inverse secondary a-deuterium KIE arose from an increase in the C —H stretching force constants which accompanied the change from sp3 hybridization at the a-carbon in the reactant to the spMike hybridization in the transition state. More important, however, were the observations that (i) the total KIE is dominated by the vibrational (ZPE) component of the KIE with which it correlates linearly, and (ii) that the inverse contribution from the C —H(D) stretching vibrations is almost constant for all the reactions. Ibis suggests that the contribution from the other vibrations, i.e. the rest in Table 8, determines the magnitude of the KIE. In fact, Barnes and Williams stated that the... 

The ONSH reaction of the carbanion of 2-phenylpropionitrile (45 c) with nitrobenzene in liquid ammonia at -70 °C involves rate-limiting Carom—H bond breaking, as evidenced by the 9.8 times faster rate than for reaction of the analogous substitution of deuterium in 4-<7-nitrobenzene and perdeuterionitrobenzene. Reactions of the carbanion derived from (45c) with 4-chloro-3-trifluoromethylnitrobenzene and 4-chloronitrobenzene in toluene under phase transfer catalysis has also been studied." ... 

As already reported in Section II,A, the amination of 6-bromo-5-deuterio-4-phenylpyrimidine with potassium amide in liquid ammonia provides a produet in which deuterium is no longer present. Based on the work deseribed previously, it seems reasonable to conclude that this easily occurring deuterium-hydrogen exchange takes place in the intermediary imidoyl bromide (17a, X = Br) (Scheme 11.18) and not in the cyanoazadiene (17b). In the strong basie medium a fast equilibrium can be formulated between these open-ehain intermediates (17a, X = Br, 29, and 30) (Scheme 11.18). 

Analogous parahydrogen conversion and deuterium exchange reactions, catalyzed by NH2, have been observed in liquid ammonia (Wilmarth and Dayton, 61). The kinetics are of the same form as those of the OH -cat-alyzed reaction in water and the mechanism is open to similar interpretations. The NH2 -catalyzed reaction is much faster, its rate constant at —50° being 10 times that of the OH -catalyzed reaction at 100°. The assumption of equal frequency factors for the two reactions leads to a calculated activation energy for the NH2 -catalyzed reaction of about 10 kcal. This low value has been attributed to the much greater base strength of NH2 relative to OH . The results provide some support for the hydride ion mechanism. 

In connection with the interpretation of these trends it should be noted that in some reactions (e.g., ethylene hydrogenation) the activation energy remains substantially constant and the frequency factor changes as the metal is varied, while in other reactions (e.g., deuterium-ammonia exchange) the reverse is the case. In the exchange of deuterium with saturated hydrocarbons, a compensation effect (Cremer, 128) has been noted. The significance of these different patterns is not clear. 

It should be noted that the correlations being discussed here are far from perfect and exceptions can be found in nearly each of the reaction series. (For the ethylene-hydrogen and deuterium-ammonia reactions, the correlation between catalytic activity and per cent d-character is nearly quantitative.) This is to be expected in view of the experimental difficulties involved in preparing clean and reproducible metal surfaces, particularly where different metals are being compared. In any attempt to correlate catalytic properties with work functions, it should also lie recognized that the work function is affected by adsorption, and therefore that the work functions of metals under catalytic conditions, or even their relative order, may be somewhat different than those of the clean metals. 

---