Deuterium oxides reactions with

B. Reactions of Benzene with Deuterium Oxide and with Deuterium-... 

The fact that an isotope effect of 1.7 0.1 is observed 38) in the benzene/deuterium oxide reaction at 30°C indicates that this reaction is the rate-determining step of the dissociative n complex substitution mechanism. In this respect the result agrees with the direct observations made by other investigators 41, 42), namely that unsaturated hydrocarbons chemisorb at a faster rate than their subsequent interactions with chemisorbed hydrogen. 

The reaction of the lithiated species with deuterium oxide proceeds with retention of configuration due to the coordination of the electrophile to the lithium cation. However, the corresponding ate complex is formed with inversion because no coordination of the Lewis acid is possible at the lithium cation and, therefore, the protonolysis of the ate complex proceeds with inversion of configuration. Among the Lewis acids examined, triethylaluminum gives the best result. 

However, under somewhat different conditions (aqueous acetonitrile at 85°), no evidence for the free carbonium ion could be found (Bethell et al., 1965). Moreover, the invariance of the product proportions when water is replaced by deuterium oxide, coupled with the observation of a large tritium isotope effect on the formation of diphenylmethanol, is consistent only with the ylid mechanism (equation 21) (Bethell et al., 1969). For reaction of diarylmethylenes with alcohols, substantial hydrogen-isotope effects are observed, consistent with both equations 21 and 22. 

An indication of the importance of the steric inhibition of resonance in aromatic substitution reactions has been gained by a study of the exchange reaction of dialkylanilines with deuterium oxide.21 With di-methylaniline, for example, the ortho and para hydrogen atoms equilibrate readily with deuterium oxide. This reaction, like most aromatic substitution reactions (see Chapter 13), is believed to proceed by the attack of a positively charged fragment (in this case a hydrogen or deuterium ion) at a point of high electron density. Consequently, the ease with which equilibration occurs can be taken as an approximate measure of the contribution of forms such as XLV or XLVI to the structure of the... 

Topper and Stetten s work involved (1) the reaction of n-glucose-l-d in ordinary water saturated with calcium hydroxide, and (2) the reaction of D-glucose in deuterium oxide saturated with calcium hydroxide-d2. These isomerizations were carried out at both 25° and 35°. In the experiments with D-glucose-l-d at 35°, the n-mannose isolated (as the phenylhydrazone) contained 44 % of the deuterium in the starting substance, all of which was retained at Cl, whereas the n-fructose isolated (as the phenylosazone) retained 94% of the deuterium. A similar result (100% retention of deuterium) was reported for the n-fructose isolated from the reaction at 25°. These figures for n-fructose were based on the assumption that 50 % of the... 

This oxidation reaction with water is understood by the sequence hydroxypalladation followed by carbonyl generation via 1,2-hydride shift (eq 4). It has been confirmed that no incorporation of deuterium occurs when the reaction is carried out in D2O and that all hydrogens of the alkene are retained in the carbonyl compound, which is clearly indicative of the hydride shift. 

The slightly different physical properties of deuterium allow its concentration in ordinary hydrogen (or the concentration of a deuterium-containing compound in a hydrogen compound) to be determined. Exchange of deuterium and hydrogen occurs and can be used to elucidate the mechanism of reactions (i.e. the deuterium is a non-radioactive tracer). Methanol exchanges with deuterium oxide thus ... 

White Phosphorus Oxidation. Emission of green light from the oxidation of elemental white phosphoms in moist air is one of the oldest recorded examples of chemiluminescence. Although the chemiluminescence is normally observed from sotid phosphoms, the reaction actually occurs primarily just above the surface with gas-phase phosphoms vapor. The reaction mechanism is not known, but careful spectral analyses of the reaction with water and deuterium oxide vapors indicate that the primary emitting species in the visible spectmm are excited states of (PO)2 and HPO or DPO. Ultraviolet emission from excited PO is also detected (196). 

A solution of 5a-pregn-9-en-12-one (36, 29 mg) in methanol-OD (5 ml) is saturated with 20% sodium deuterioxide in deuterium oxide and heated under reflux for 3 days. After cooling, the reaction mixture is diluted with ether... 

A solution of estradiol (38, 15 mg) in methanol-OD (4 ml) and one drop of 10% deuteriosulfuric acid in deuterium oxide is heated under reflux for 5 days. After cooling the reaction mixture is diluted with ether, washed with dilute sodium bicarbonate solution and water, then dried over anhydrous sodium sulfate. Evaporation of the ether gives crystalline 2,4-d2-estradiol (39, 15 mg, 99%), mp 173-175° (ether-hexane), exhibiting 82% isotopic purity and only one aromatic hydrogen by NMR. (For an experimental procedure describing the exchange of aromatic protons under Clemmensen conditions, see section III-D.)... 

The earliest attempts to prepare deuterated steroids were carried out by exchange reactions of aliphatic hydrogens with deuterium in the presence of a surface catalyst. Cholesterol, for example, has been treated with platinum in a mixture of deuterium oxide and acetic acid-OD, and was found to yield... 

A solution of the ketone (10 mg) in dry dioxane (5 ml) is placed in the cathode compartment of the cell. Then 10% deuteriosulfuric acid in deuterium oxide (5 ml) is added slowly with stirring. A small additional quantity of dioxane may be necessary to maintain a homogeneous solution. The anode compartment is filled with an identical solvent mixture and the electrode inserted. The current is adjusted to 1(X) milliamps and the electrolysis is continued for 6-10 hr with rapid stirring. The progress of the reaction is... 

During the course of these mechanistic studies a wide range of possible applications of this reaction have been revealed. When the reduction is carried out with lithium aluminum deuteride and the anion complex decomposed with water, a monodeuterio compound (95) is obtained in which 70% of the deuterium is in the 3a-position. Reduction with lithium aluminum hydride followed by hydrolysis with deuterium oxide yields mainly (70 %) the 3j5-di-epimer (96), while for the preparation of dideuterio compounds (94) both steps have to be carried out with deuterated reagents. ... 

Deuterioammonia (about 5 ml) is generated by adding deuterium oxide (14 ml) to a stirred suspension of magnesium nitride (20 g) in mineral oil (30 ml). Tlie deuterioammonia is collected directly in the reaction flask (equipped with a dry ice condenser) at —79° after passing through a trap which is kept at 0°. 

Displacement of aromatic halogen in 2,4-diiodo-estradiol with tritiated Raney nickel yields 2,4-ditritiated estradiol. Aromatic halogen can also be replaced by heating the substrate with zinc in acetic acid-OD or by deuteration with palladium-on-charcoal in a mixture of dioxane-deuterium oxide-triethylamine, but examples are lacking for the application of these reactions in the steroid field. Deuteration of the bridge-head position in norbornane is readily accomplished in high isotopic purity by treatment of the... 

Deuterio-3-iiitro-l,6-iiaphthyridiiie (168) was prepared from 4-chloro-3-iiitro-l,6-iiaphthyridiiie (166) by a reaction with tosyl hydrazide and subsequent hydrolysis of the 4-tosylhydrazino derivative (167) with Na2C03/ D2O solution (83RTC359). 7-Deuterio-l,8-naphthyridin-2(lH)-one was prepared by heating l,8-naphthyridin-2(lH)-one with deuterium oxide at 230°C for 35 h (85JHC761). Tliis deuterio compound could be converted into 2-chloro-(or 2-ethoxy-) 7-deuterio-3,6-dinitro-l,8-naphthyridine. 

In neutral and alkaline media, the rate of exchange at the 3 and 6 position of 4-aminopyridazine is independent of acidity but decreases markedly when the media become more acidic. This was interpreted in terms of a rate-determining removal of the 6-proton by deuteroxide ion to give the ylid (XXIV), which reacts with deuterium oxide in a fast step. A similar result for the 3 and 6 positions of py-ridazin-4-one suggests the same mechanism. For reaction at the 5 position, the rate-acidity profile indicated reaction on the free base as did that for the 5 position of pyridazin-3-one, though the appearance of a maximum in the rate at — HQ = 0.8 was anomalous and suggested incursion of a further mechanism. 

The photo-Kolbe reaction is the decarboxylation of carboxylic acids at tow voltage under irradiation at semiconductor anodes (TiO ), that are partially doped with metals, e.g. platinum [343, 344]. On semiconductor powders the dominant product is a hydrocarbon by substitution of the carboxylate group for hydrogen (Eq. 41), whereas on an n-TiOj single crystal in the oxidation of acetic acid the formation of ethane besides methane could be observed [345, 346]. Dependent on the kind of semiconductor, the adsorbed metal, and the pH of the solution the extent of alkyl coupling versus reduction to the hydrocarbon can be controlled to some extent [346]. The intermediacy of alkyl radicals has been demonstrated by ESR-spectroscopy [347], that of the alkyl anion by deuterium incorporation [344]. With vicinal diacids the mono- or bisdecarboxylation can be controlled by the light flux [348]. Adipic acid yielded butane [349] with levulinic acid the products of decarboxylation, methyl ethyl-... 

The decarboxylation of carboxylic acid in the presence of a nucleophile is a classical reaction known as the Hunsdiecker reaction. Such reactions can be carried out sometimes in aqueous conditions. Man-ganese(II) acetate catalyzed the reaction of a, 3-unsaturated aromatic carboxylic acids with NBS (1 and 2 equiv) in MeCN/water to afford haloalkenes and a-(dibromomethyl)benzenemethanols, respectively (Eq. 9.15).32 Decarboxylation of free carboxylic acids catalyzed by Pd/C under hydrothermal water (250° C/4 MPa) gave the corresponding hydrocarbons (Eq. 9.16).33 Under the hydrothermal conditions of deuterium oxide, decarbonylative deuteration was observed to give fully deuterated hydrocarbons from carboxylic acids or aldehydes. 

The stereochemistry of dienes has been found to have a pronounced effect in the concerted cyclo-additions with benzyne 64>65h A concerted disrotatory cyclo-addition of tetrafluorobenzyne, leading for example with trans- (3-methylstyrene to (63, R = Me), is likely and in accord with the conservation of orbital symmetry 68>. However while the electro-cyclic rearrangement of (63, R = H) to (65, R = H) is not allowed, base catalysed prototropic rearrangement is possible. A carbanion (64, R = H) cannot have more than a transient existence in the reaction of tetrafluorobenzyne with styrene because no deuterium incorporation in (65) was detected when either the reaction mixture was quenched with deuterium oxide or when the reaction was conducted in the presence of a ten molar excess of deuteriopentafluorobenzene. 

When we allowed pentafluorophenyl-lithium to decompose in ether in the presence of an excess of N, ZV-dimethy laniline we obtained the compounds (92) 70, X = F), (94), the latter as the major compound, and a product which was shown to be (97). That this latter compound did not arise by metallation of 2V,lV-dimethylaniline followed by addition to tetrafluorobenzyne was shown by quenching the reaction mixture with deuterium oxide. No deuterium incorporation was detected. The compound (97) provides a rare example of a product derived by a Stevens rearrangement in which aryl migration has occurred b>. 

The mechanism of this unusual dimerization is not known. All the lithiumorganic compounds have been identified by the reaction with dimethyl sulfate as well as by deuterolysis with deuterium oxide. 

Let us now turn to a comparison of theory with experiment. Comparing (95), (84), and (68), we find that the dependence of the photocatalytic effect K on the position of the Fermi level at the surface s and in the bulk cv of an unexcited sample for the oxidation of water is the same as for the oxidation of CO or for the hydrogen-deuterium exchange reaction. For this reason, such factors as the introduction of impurities into a specimen, the adsorption of gases on the surface of the specimen, and the preliminary treatment of the specimen will exert the same influence on the photocatalytic effect in all the three reactions indicated above. The dependence of K on the intensity I of the exciting light must also be the same in all the three cases. 

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